57 files changed, 23037 insertions, 39 deletions

diff --git a/documentation/ref-manual/examples/hello-autotools/hello_2.10.bb b/documentation/ref-manual/examples/hello-autotools/hello_2.10.bb
new file mode 100644
index 0000000000..aa2beb9a9b
--- /dev/null
+++ b/documentation/ref-manual/examples/hello-autotools/hello_2.10.bb
@@ -0,0 +1,9 @@
+DESCRIPTION = "GNU Helloworld application"
+SECTION = "examples"
+LICENSE = "GPLv3"
+LIC_FILES_CHKSUM = "file://COPYING;md5=d32239bcb673463ab874e80d47fae504"
+
+SRC_URI = "${GNU_MIRROR}/hello/hello-${PV}.tar.gz"
+SRC_URI[sha256sum] = "31e066137a962676e89f69d1b65382de95a7ef7d914b8cb956f41ea72e0f516b"
+
+inherit autotools-brokensep gettext
diff --git a/documentation/ref-manual/examples/hello-autotools/hello_2.3.bb b/documentation/ref-manual/examples/hello-autotools/hello_2.3.bb
deleted file mode 100644
index 5dfb0b30cf..0000000000
--- a/documentation/ref-manual/examples/hello-autotools/hello_2.3.bb
+++ /dev/null
@@ -1,8 +0,0 @@
-DESCRIPTION = "GNU Helloworld application"
-SECTION = "examples"
-LICENSE = "GPLv3"
-LIC_FILES_CHKSUM = "file://COPYING;md5=adefda309052235aa5d1e99ce7557010"
-
-SRC_URI = "${GNU_MIRROR}/hello/hello-${PV}.tar.bz2"
-
-inherit autotools
diff --git a/documentation/ref-manual/examples/libxpm/libxpm_3.5.6.bb b/documentation/ref-manual/examples/libxpm/libxpm_3.5.6.bb
index b58d4d7bd1..c0c8986405 100644
--- a/documentation/ref-manual/examples/libxpm/libxpm_3.5.6.bb
+++ b/documentation/ref-manual/examples/libxpm/libxpm_3.5.6.bb
@@ -1,4 +1,4 @@
-require xorg-lib-common.inc
+require recipes-graphics/xorg-lib/xorg-lib-common.inc
 
 DESCRIPTION = "X11 Pixmap library"
 LICENSE = "X-BSD"
diff --git a/documentation/ref-manual/faq.rst b/documentation/ref-manual/faq.rst
new file mode 100644
index 0000000000..2d2aaad0a9
--- /dev/null
+++ b/documentation/ref-manual/faq.rst
@@ -0,0 +1,451 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+***
+FAQ
+***
+
+**Q:** How does Poky differ from `OpenEmbedded <http://www.openembedded.org/>`__?
+
+**A:** The term ``Poky`` refers to the specific reference build
+system that the Yocto Project provides. Poky is based on
+:term:`OpenEmbedded-Core (OE-Core)` and :term:`BitBake`. Thus, the
+generic term used here for the build system is the "OpenEmbedded build
+system." Development in the Yocto Project using Poky is closely tied to
+OpenEmbedded, with changes always being merged to OE-Core or BitBake
+first before being pulled back into Poky. This practice benefits both
+projects immediately.
+
+**Q:** My development system does not meet the required Git, tar, and
+Python versions. In particular, I do not have Python 3.5.0 or greater.
+Can I still use the Yocto Project?
+
+**A:** You can get the required tools on your host development system a
+couple different ways (i.e. building a tarball or downloading a
+tarball). See the "`Required Git, tar, Python and gcc
+Versions <#required-git-tar-python-and-gcc-versions>`__" section for
+steps on how to update your build tools.
+
+**Q:** How can you claim Poky / OpenEmbedded-Core is stable?
+
+**A:** There are three areas that help with stability;
+
+-  The Yocto Project team keeps :term:`OpenEmbedded-Core (OE-Core)` small and
+   focused, containing around 830 recipes as opposed to the thousands
+   available in other OpenEmbedded community layers. Keeping it small
+   makes it easy to test and maintain.
+
+-  The Yocto Project team runs manual and automated tests using a small,
+   fixed set of reference hardware as well as emulated targets.
+
+-  The Yocto Project uses an autobuilder, which provides continuous
+   build and integration tests.
+
+**Q:** How do I get support for my board added to the Yocto Project?
+
+**A:** Support for an additional board is added by creating a Board
+Support Package (BSP) layer for it. For more information on how to
+create a BSP layer, see the
+":ref:`dev-manual/dev-manual-common-tasks:understanding and creating layers`"
+section in the Yocto Project Development Tasks Manual and the
+:doc:`../bsp-guide/bsp-guide`.
+
+Usually, if the board is not completely exotic, adding support in the
+Yocto Project is fairly straightforward.
+
+**Q:** Are there any products built using the OpenEmbedded build system?
+
+**A:** The software running on the `Vernier
+LabQuest <http://vernier.com/labquest/>`__ is built using the
+OpenEmbedded build system. See the `Vernier
+LabQuest <http://www.vernier.com/products/interfaces/labq/>`__ website
+for more information. There are a number of pre-production devices using
+the OpenEmbedded build system and the Yocto Project team announces them
+as soon as they are released.
+
+**Q:** What does the OpenEmbedded build system produce as output?
+
+**A:** Because you can use the same set of recipes to create output of
+various formats, the output of an OpenEmbedded build depends on how you
+start it. Usually, the output is a flashable image ready for the target
+device.
+
+**Q:** How do I add my package to the Yocto Project?
+
+**A:** To add a package, you need to create a BitBake recipe. For
+information on how to create a BitBake recipe, see the
+":ref:`dev-manual/dev-manual-common-tasks:writing a new recipe`"
+section in the Yocto Project Development Tasks Manual.
+
+**Q:** Do I have to reflash my entire board with a new Yocto Project
+image when recompiling a package?
+
+**A:** The OpenEmbedded build system can build packages in various
+formats such as IPK for OPKG, Debian package (``.deb``), or RPM. You can
+then upgrade the packages using the package tools on the device, much
+like on a desktop distribution such as Ubuntu or Fedora. However,
+package management on the target is entirely optional.
+
+**Q:** I see the error
+'``chmod: XXXXX new permissions are r-xrwxrwx, not r-xr-xr-x``'. What is
+wrong?
+
+**A:** You are probably running the build on an NTFS filesystem. Use
+``ext2``, ``ext3``, or ``ext4`` instead.
+
+**Q:** I see lots of 404 responses for files when the OpenEmbedded build
+system is trying to download sources. Is something wrong?
+
+**A:** Nothing is wrong. The OpenEmbedded build system checks any
+configured source mirrors before downloading from the upstream sources.
+The build system does this searching for both source archives and
+pre-checked out versions of SCM-managed software. These checks help in
+large installations because it can reduce load on the SCM servers
+themselves. The address above is one of the default mirrors configured
+into the build system. Consequently, if an upstream source disappears,
+the team can place sources there so builds continue to work.
+
+**Q:** I have machine-specific data in a package for one machine only
+but the package is being marked as machine-specific in all cases, how do
+I prevent this?
+
+**A:** Set ``SRC_URI_OVERRIDES_PACKAGE_ARCH`` = "0" in the ``.bb`` file
+but make sure the package is manually marked as machine-specific for the
+case that needs it. The code that handles
+``SRC_URI_OVERRIDES_PACKAGE_ARCH`` is in the
+``meta/classes/base.bbclass`` file.
+
+**Q:** I'm behind a firewall and need to use a proxy server. How do I do
+that?
+
+**A:** Most source fetching by the OpenEmbedded build system is done by
+``wget`` and you therefore need to specify the proxy settings in a
+``.wgetrc`` file, which can be in your home directory if you are a
+single user or can be in ``/usr/local/etc/wgetrc`` as a global user
+file.
+
+Following is the applicable code for setting various proxy types in the
+``.wgetrc`` file. By default, these settings are disabled with comments.
+To use them, remove the comments: ::
+
+   # You can set the default proxies for Wget to use for http, https, and ftp.
+   # They will override the value in the environment.
+   #https_proxy = http://proxy.yoyodyne.com:18023/
+   #http_proxy = http://proxy.yoyodyne.com:18023/
+   #ftp_proxy = http://proxy.yoyodyne.com:18023/
+
+   # If you do not want to use proxy at all, set this to off.
+   #use_proxy = on
+
+The Yocto Project also includes a
+``meta-poky/conf/site.conf.sample`` file that shows how to configure CVS
+and Git proxy servers if needed. For more information on setting up
+various proxy types and configuring proxy servers, see the
+":yocto_wiki:`Working Behind a Network Proxy </wiki/Working_Behind_a_Network_Proxy>`"
+Wiki page.
+
+**Q:** What's the difference between target and target\ ``-native``?
+
+**A:** The ``*-native`` targets are designed to run on the system being
+used for the build. These are usually tools that are needed to assist
+the build in some way such as ``quilt-native``, which is used to apply
+patches. The non-native version is the one that runs on the target
+device.
+
+**Q:** I'm seeing random build failures. Help?!
+
+**A:** If the same build is failing in totally different and random
+ways, the most likely explanation is:
+
+-  The hardware you are running the build on has some problem.
+
+-  You are running the build under virtualization, in which case the
+   virtualization probably has bugs.
+
+The OpenEmbedded build system processes a massive amount of data that
+causes lots of network, disk and CPU activity and is sensitive to even
+single-bit failures in any of these areas. True random failures have
+always been traced back to hardware or virtualization issues.
+
+**Q:** When I try to build a native recipe, the build fails with
+``iconv.h`` problems.
+
+**A:** If you get an error message that indicates GNU ``libiconv`` is
+not in use but ``iconv.h`` has been included from ``libiconv``, you need
+to check to see if you have a previously installed version of the header
+file in ``/usr/local/include``.
+::
+
+   #error GNU libiconv not in use but included iconv.h is from libiconv
+
+If you find a previously installed
+file, you should either uninstall it or temporarily rename it and try
+the build again.
+
+This issue is just a single manifestation of "system leakage" issues
+caused when the OpenEmbedded build system finds and uses previously
+installed files during a native build. This type of issue might not be
+limited to ``iconv.h``. Be sure that leakage cannot occur from
+``/usr/local/include`` and ``/opt`` locations.
+
+**Q:** What do we need to ship for license compliance?
+
+**A:** This is a difficult question and you need to consult your lawyer
+for the answer for your specific case. It is worth bearing in mind that
+for GPL compliance, there needs to be enough information shipped to
+allow someone else to rebuild and produce the same end result you are
+shipping. This means sharing the source code, any patches applied to it,
+and also any configuration information about how that package was
+configured and built.
+
+You can find more information on licensing in the
+":ref:`overview-manual/overview-manual-development-environment:licensing`"
+section in the Yocto
+Project Overview and Concepts Manual and also in the
+":ref:`dev-manual/dev-manual-common-tasks:maintaining open source license compliance during your product's lifecycle`"
+section in the Yocto Project Development Tasks Manual.
+
+**Q:** How do I disable the cursor on my touchscreen device?
+
+**A:** You need to create a form factor file as described in the
+":ref:`bsp-filelayout-misc-recipes`" section in
+the Yocto Project Board Support Packages (BSP) Developer's Guide. Set
+the ``HAVE_TOUCHSCREEN`` variable equal to one as follows:
+::
+
+   HAVE_TOUCHSCREEN=1
+
+**Q:** How do I make sure connected network interfaces are brought up by
+default?
+
+**A:** The default interfaces file provided by the netbase recipe does
+not automatically bring up network interfaces. Therefore, you will need
+to add a BSP-specific netbase that includes an interfaces file. See the
+":ref:`bsp-filelayout-misc-recipes`" section in
+the Yocto Project Board Support Packages (BSP) Developer's Guide for
+information on creating these types of miscellaneous recipe files.
+
+For example, add the following files to your layer: ::
+
+   meta-MACHINE/recipes-bsp/netbase/netbase/MACHINE/interfaces
+   meta-MACHINE/recipes-bsp/netbase/netbase_5.0.bbappend
+
+**Q:** How do I create images with more free space?
+
+**A:** By default, the OpenEmbedded build system creates images that are
+1.3 times the size of the populated root filesystem. To affect the image
+size, you need to set various configurations:
+
+-  *Image Size:* The OpenEmbedded build system uses the
+   :term:`IMAGE_ROOTFS_SIZE` variable to define
+   the size of the image in Kbytes. The build system determines the size
+   by taking into account the initial root filesystem size before any
+   modifications such as requested size for the image and any requested
+   additional free disk space to be added to the image.
+
+-  *Overhead:* Use the
+   :term:`IMAGE_OVERHEAD_FACTOR` variable
+   to define the multiplier that the build system applies to the initial
+   image size, which is 1.3 by default.
+
+-  *Additional Free Space:* Use the
+   :term:`IMAGE_ROOTFS_EXTRA_SPACE`
+   variable to add additional free space to the image. The build system
+   adds this space to the image after it determines its
+   ``IMAGE_ROOTFS_SIZE``.
+
+**Q:** Why don't you support directories with spaces in the pathnames?
+
+**A:** The Yocto Project team has tried to do this before but too many
+of the tools the OpenEmbedded build system depends on, such as
+``autoconf``, break when they find spaces in pathnames. Until that
+situation changes, the team will not support spaces in pathnames.
+
+**Q:** How do I use an external toolchain?
+
+**A:** The toolchain configuration is very flexible and customizable. It
+is primarily controlled with the ``TCMODE`` variable. This variable
+controls which ``tcmode-*.inc`` file to include from the
+``meta/conf/distro/include`` directory within the :term:`Source Directory`.
+
+The default value of ``TCMODE`` is "default", which tells the
+OpenEmbedded build system to use its internally built toolchain (i.e.
+``tcmode-default.inc``). However, other patterns are accepted. In
+particular, "external-\*" refers to external toolchains. One example is
+the Sourcery G++ Toolchain. The support for this toolchain resides in
+the separate ``meta-sourcery`` layer at
+http://github.com/MentorEmbedded/meta-sourcery/.
+
+In addition to the toolchain configuration, you also need a
+corresponding toolchain recipe file. This recipe file needs to package
+up any pre-built objects in the toolchain such as ``libgcc``,
+``libstdcc++``, any locales, and ``libc``.
+
+**Q:** How does the OpenEmbedded build system obtain source code and
+will it work behind my firewall or proxy server?
+
+**A:** The way the build system obtains source code is highly
+configurable. You can setup the build system to get source code in most
+environments if HTTP transport is available.
+
+When the build system searches for source code, it first tries the local
+download directory. If that location fails, Poky tries
+:term:`PREMIRRORS`, the upstream source, and then
+:term:`MIRRORS` in that order.
+
+Assuming your distribution is "poky", the OpenEmbedded build system uses
+the Yocto Project source ``PREMIRRORS`` by default for SCM-based
+sources, upstreams for normal tarballs, and then falls back to a number
+of other mirrors including the Yocto Project source mirror if those
+fail.
+
+As an example, you could add a specific server for the build system to
+attempt before any others by adding something like the following to the
+``local.conf`` configuration file: ::
+
+   PREMIRRORS_prepend = "\
+       git://.*/.* http://www.yoctoproject.org/sources/ \n \
+       ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
+       http://.*/.* http://www.yoctoproject.org/sources/ \n \
+       https://.*/.* http://www.yoctoproject.org/sources/ \n"
+
+These changes cause the build system to intercept Git, FTP, HTTP, and
+HTTPS requests and direct them to the ``http://`` sources mirror. You
+can use ``file://`` URLs to point to local directories or network shares
+as well.
+
+Aside from the previous technique, these options also exist:
+::
+
+   BB_NO_NETWORK = "1"
+
+This statement tells BitBake to issue an error
+instead of trying to access the Internet. This technique is useful if
+you want to ensure code builds only from local sources.
+
+Here is another technique:
+::
+
+   BB_FETCH_PREMIRRORONLY = "1"
+
+This statement
+limits the build system to pulling source from the ``PREMIRRORS`` only.
+Again, this technique is useful for reproducing builds.
+
+Here is another technique:
+::
+
+   BB_GENERATE_MIRROR_TARBALLS = "1"
+
+This
+statement tells the build system to generate mirror tarballs. This
+technique is useful if you want to create a mirror server. If not,
+however, the technique can simply waste time during the build.
+
+Finally, consider an example where you are behind an HTTP-only firewall.
+You could make the following changes to the ``local.conf`` configuration
+file as long as the ``PREMIRRORS`` server is current: ::
+
+   PREMIRRORS_prepend = "\
+       ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
+       http://.*/.* http://www.yoctoproject.org/sources/ \n \
+       https://.*/.* http://www.yoctoproject.org/sources/ \n"
+   BB_FETCH_PREMIRRORONLY = "1"
+
+These changes would cause the build system to successfully fetch source
+over HTTP and any network accesses to anything other than the
+``PREMIRRORS`` would fail.
+
+The build system also honors the standard shell environment variables
+``http_proxy``, ``ftp_proxy``, ``https_proxy``, and ``all_proxy`` to
+redirect requests through proxy servers.
+
+.. note::
+
+   You can find more information on the
+   ":yocto_wiki:`Working Behind a Network Proxy </wiki/Working_Behind_a_Network_Proxy>`"
+   Wiki page.
+
+**Q:** Can I get rid of build output so I can start over?
+
+**A:** Yes - you can easily do this. When you use BitBake to build an
+image, all the build output goes into the directory created when you run
+the build environment setup script (i.e.
+````` <#structure-core-script>`__). By default, this :term:`Build Directory`
+is named ``build`` but can be named
+anything you want.
+
+Within the Build Directory, is the ``tmp`` directory. To remove all the
+build output yet preserve any source code or downloaded files from
+previous builds, simply remove the ``tmp`` directory.
+
+**Q:** Why do ``${bindir}`` and ``${libdir}`` have strange values for
+``-native`` recipes?
+
+**A:** Executables and libraries might need to be used from a directory
+other than the directory into which they were initially installed.
+Complicating this situation is the fact that sometimes these executables
+and libraries are compiled with the expectation of being run from that
+initial installation target directory. If this is the case, moving them
+causes problems.
+
+This scenario is a fundamental problem for package maintainers of
+mainstream Linux distributions as well as for the OpenEmbedded build
+system. As such, a well-established solution exists. Makefiles,
+Autotools configuration scripts, and other build systems are expected to
+respect environment variables such as ``bindir``, ``libdir``, and
+``sysconfdir`` that indicate where executables, libraries, and data
+reside when a program is actually run. They are also expected to respect
+a ``DESTDIR`` environment variable, which is prepended to all the other
+variables when the build system actually installs the files. It is
+understood that the program does not actually run from within
+``DESTDIR``.
+
+When the OpenEmbedded build system uses a recipe to build a
+target-architecture program (i.e. one that is intended for inclusion on
+the image being built), that program eventually runs from the root file
+system of that image. Thus, the build system provides a value of
+"/usr/bin" for ``bindir``, a value of "/usr/lib" for ``libdir``, and so
+forth.
+
+Meanwhile, ``DESTDIR`` is a path within the :term:`Build Directory`.
+However, when the recipe builds a
+native program (i.e. one that is intended to run on the build machine),
+that program is never installed directly to the build machine's root
+file system. Consequently, the build system uses paths within the Build
+Directory for ``DESTDIR``, ``bindir`` and related variables. To better
+understand this, consider the following two paths where the first is
+relatively normal and the second is not: ::
+
+   /home/maxtothemax/poky-bootchart2/build/tmp/work/i586-poky-linux/zlib/
+      1.2.8-r0/sysroot-destdir/usr/bin
+
+   /home/maxtothemax/poky-bootchart2/build/tmp/work/x86_64-linux/
+      zlib-native/1.2.8-r0/sysroot-destdir/home/maxtothemax/poky-bootchart2/
+      build/tmp/sysroots/x86_64-linux/usr/bin
+
+.. note::
+
+   Due to these lengthy examples, the paths are artificially broken
+   across lines for readability.
+
+Even if the paths look unusual,
+they both are correct - the first for a target and the second for a
+native recipe. These paths are a consequence of the ``DESTDIR``
+mechanism and while they appear strange, they are correct and in
+practice very effective.
+
+**Q:** The files provided by my ``*-native`` recipe do not appear to be
+available to other recipes. Files are missing from the native sysroot,
+my recipe is installing to the wrong place, or I am getting permissions
+errors during the do_install task in my recipe! What is wrong?
+
+**A:** This situation results when a build system does not recognize the
+environment variables supplied to it by :term:`BitBake`. The
+incident that prompted this FAQ entry involved a Makefile that used an
+environment variable named ``BINDIR`` instead of the more standard
+variable ``bindir``. The makefile's hardcoded default value of
+"/usr/bin" worked most of the time, but not for the recipe's ``-native``
+variant. For another example, permissions errors might be caused by a
+Makefile that ignores ``DESTDIR`` or uses a different name for that
+environment variable. Check the the build system to see if these kinds
+of issues exist.
diff --git a/documentation/ref-manual/faq.xml b/documentation/ref-manual/faq.xml
index d94cb32a86..2f8fcf3242 100644
--- a/documentation/ref-manual/faq.xml
+++ b/documentation/ref-manual/faq.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='faq'>
 <title>FAQ</title>
@@ -322,7 +323,7 @@
     <qandaentry>
         <question>
             <para>
-                What’s the difference between <replaceable>target</replaceable> and <replaceable>target</replaceable><filename>-native</filename>?
+                What's the difference between <replaceable>target</replaceable> and <replaceable>target</replaceable><filename>-native</filename>?
             </para>
         </question>
         <answer>
diff --git a/documentation/ref-manual/history.rst b/documentation/ref-manual/history.rst
new file mode 100644
index 0000000000..e962d92978
--- /dev/null
+++ b/documentation/ref-manual/history.rst
@@ -0,0 +1,74 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+***********************
+Manual Revision History
+***********************
+
+.. list-table::
+   :widths: 10 15 40
+   :header-rows: 1
+
+   * - Revision
+     - Date
+     - Note
+   * - 0.9
+     - November 2010
+     - The initial document released with the Yocto Project 0.9 Release
+   * - 1.0
+     - April 2011
+     - Released with the Yocto Project 1.0 Release.
+   * - 1.1
+     - October 2011
+     - Released with the Yocto Project 1.1 Release.
+   * - 1.2
+     - April 2012
+     - Released with the Yocto Project 1.2 Release.
+   * - 1.3
+     - October 2012
+     - Released with the Yocto Project 1.3 Release.
+   * - 1.4
+     - April 2013
+     - Released with the Yocto Project 1.4 Release.
+   * - 1.5
+     - October 2013
+     - Released with the Yocto Project 1.5 Release.
+   * - 1.6
+     - April 2014
+     - Released with the Yocto Project 1.6 Release.
+   * - 1.7
+     - October 2014
+     - Released with the Yocto Project 1.7 Release.
+   * - 1.8
+     - April 2015
+     - Released with the Yocto Project 1.8 Release.
+   * - 2.0
+     - October 2015
+     - Released with the Yocto Project 2.0 Release.
+   * - 2.1
+     - April 2016
+     - Released with the Yocto Project 2.1 Release.
+   * - 2.2
+     - October 2016
+     - Released with the Yocto Project 2.2 Release.
+   * - 2.3
+     - May 2017
+     - Released with the Yocto Project 2.3 Release.
+   * - 2.4
+     - October 2017
+     - Released with the Yocto Project 2.4 Release.
+   * - 2.5
+     - May 2018
+     - Released with the Yocto Project 2.5 Release.
+   * - 2.6
+     - November 2018
+     - Released with the Yocto Project 2.6 Release.
+   * - 2.7
+     - May 2019
+     - Released with the Yocto Project 2.7 Release.
+   * - 3.0
+     - October 2019
+     - Released with the Yocto Project 3.0 Release.
+   * - 3.1
+     - April 2020
+     - Released with the Yocto Project 3.1 Release.
+
diff --git a/documentation/ref-manual/migration-1.3.rst b/documentation/ref-manual/migration-1.3.rst
new file mode 100644
index 0000000000..ebbc238873
--- /dev/null
+++ b/documentation/ref-manual/migration-1.3.rst
@@ -0,0 +1,195 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+Moving to the Yocto Project 1.3 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 1.3 Release from the prior release.
+
+.. _1.3-local-configuration:
+
+Local Configuration
+-------------------
+
+Differences include changes for
+:term:`SSTATE_MIRRORS` and ``bblayers.conf``.
+
+.. _migration-1.3-sstate-mirrors:
+
+SSTATE_MIRRORS
+~~~~~~~~~~~~~~
+
+The shared state cache (sstate-cache), as pointed to by
+:term:`SSTATE_DIR`, by default now has two-character
+subdirectories to prevent issues arising from too many files in the same
+directory. Also, native sstate-cache packages, which are built to run on
+the host system, will go into a subdirectory named using the distro ID
+string. If you copy the newly structured sstate-cache to a mirror
+location (either local or remote) and then point to it in
+:term:`SSTATE_MIRRORS`, you need to append "PATH"
+to the end of the mirror URL so that the path used by BitBake before the
+mirror substitution is appended to the path used to access the mirror.
+Here is an example: ::
+
+   SSTATE_MIRRORS = "file://.* http://someserver.tld/share/sstate/PATH"
+
+.. _migration-1.3-bblayers-conf:
+
+bblayers.conf
+~~~~~~~~~~~~~
+
+The ``meta-yocto`` layer consists of two parts that correspond to the
+Poky reference distribution and the reference hardware Board Support
+Packages (BSPs), respectively: ``meta-yocto`` and ``meta-yocto-bsp``.
+When running BitBake for the first time after upgrading, your
+``conf/bblayers.conf`` file will be updated to handle this change and
+you will be asked to re-run or restart for the changes to take effect.
+
+.. _1.3-recipes:
+
+Recipes
+-------
+
+Differences include changes for the following:
+
+.. _migration-1.3-python-function-whitespace:
+
+Python Function Whitespace
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+All Python functions must now use four spaces for indentation.
+Previously, an inconsistent mix of spaces and tabs existed, which made
+extending these functions using ``_append`` or ``_prepend`` complicated
+given that Python treats whitespace as syntactically significant. If you
+are defining or extending any Python functions (e.g.
+``populate_packages``, ``do_unpack``, ``do_patch`` and so forth) in
+custom recipes or classes, you need to ensure you are using consistent
+four-space indentation.
+
+.. _migration-1.3-proto=-in-src-uri:
+
+proto= in SRC_URI
+~~~~~~~~~~~~~~~~~
+
+Any use of ``proto=`` in :term:`SRC_URI` needs to be
+changed to ``protocol=``. In particular, this applies to the following
+URIs:
+
+-  ``svn://``
+
+-  ``bzr://``
+
+-  ``hg://``
+
+-  ``osc://``
+
+Other URIs were already using ``protocol=``. This change improves
+consistency.
+
+.. _migration-1.3-nativesdk:
+
+nativesdk
+~~~~~~~~~
+
+The suffix ``nativesdk`` is now implemented as a prefix, which
+simplifies a lot of the packaging code for ``nativesdk`` recipes. All
+custom ``nativesdk`` recipes, which are relocatable packages that are
+native to :term:`SDK_ARCH`, and any references need to
+be updated to use ``nativesdk-*`` instead of ``*-nativesdk``.
+
+.. _migration-1.3-task-recipes:
+
+Task Recipes
+~~~~~~~~~~~~
+
+"Task" recipes are now known as "Package groups" and have been renamed
+from ``task-*.bb`` to ``packagegroup-*.bb``. Existing references to the
+previous ``task-*`` names should work in most cases as there is an
+automatic upgrade path for most packages. However, you should update
+references in your own recipes and configurations as they could be
+removed in future releases. You should also rename any custom ``task-*``
+recipes to ``packagegroup-*``, and change them to inherit
+``packagegroup`` instead of ``task``, as well as taking the opportunity
+to remove anything now handled by ``packagegroup.bbclass``, such as
+providing ``-dev`` and ``-dbg`` packages, setting
+:term:`LIC_FILES_CHKSUM`, and so forth. See the
+":ref:`packagegroup.bbclass <ref-classes-packagegroup>`" section for
+further details.
+
+.. _migration-1.3-image-features:
+
+IMAGE_FEATURES
+~~~~~~~~~~~~~~
+
+Image recipes that previously included "apps-console-core" in
+:term:`IMAGE_FEATURES` should now include "splash"
+instead to enable the boot-up splash screen. Retaining
+"apps-console-core" will still include the splash screen but generates a
+warning. The "apps-x11-core" and "apps-x11-games" ``IMAGE_FEATURES``
+features have been removed.
+
+.. _migration-1.3-removed-recipes:
+
+Removed Recipes
+~~~~~~~~~~~~~~~
+
+The following recipes have been removed. For most of them, it is
+unlikely that you would have any references to them in your own
+:term:`Metadata`. However, you should check your metadata
+against this list to be sure:
+
+-  ``libx11-trim``: Replaced by ``libx11``, which has a negligible
+   size difference with modern Xorg.
+
+-  ``xserver-xorg-lite``: Use ``xserver-xorg``, which has a negligible
+   size difference when DRI and GLX modules are not installed.
+
+-  ``xserver-kdrive``: Effectively unmaintained for many years.
+
+-  ``mesa-xlib``: No longer serves any purpose.
+
+-  ``galago``: Replaced by telepathy.
+
+-  ``gail``: Functionality was integrated into GTK+ 2.13.
+
+-  ``eggdbus``: No longer needed.
+
+-  ``gcc-*-intermediate``: The build has been restructured to avoid
+   the need for this step.
+
+-  ``libgsmd``: Unmaintained for many years. Functionality now
+   provided by ``ofono`` instead.
+
+-  *contacts, dates, tasks, eds-tools*: Largely unmaintained PIM
+   application suite. It has been moved to ``meta-gnome`` in
+   ``meta-openembedded``.
+
+In addition to the previously listed changes, the ``meta-demoapps``
+directory has also been removed because the recipes in it were not being
+maintained and many had become obsolete or broken. Additionally, these
+recipes were not parsed in the default configuration. Many of these
+recipes are already provided in an updated and maintained form within
+the OpenEmbedded community layers such as ``meta-oe`` and
+``meta-gnome``. For the remainder, you can now find them in the
+``meta-extras`` repository, which is in the
+:yocto_git:`Source Repositories <>` at
+http://git.yoctoproject.org/cgit/cgit.cgi/meta-extras/.
+
+.. _1.3-linux-kernel-naming:
+
+Linux Kernel Naming
+-------------------
+
+The naming scheme for kernel output binaries has been changed to now
+include :term:`PE` as part of the filename:
+::
+
+   KERNEL_IMAGE_BASE_NAME ?= "${KERNEL_IMAGETYPE}-${PE}-${PV}-${PR}-${MACHINE}-${DATETIME}"
+
+Because the ``PE`` variable is not set by default, these binary files
+could result with names that include two dash characters. Here is an
+example: ::
+
+   bzImage--3.10.9+git0+cd502a8814_7144bcc4b8-r0-qemux86-64-20130830085431.bin
+
+
diff --git a/documentation/ref-manual/migration-1.4.rst b/documentation/ref-manual/migration-1.4.rst
new file mode 100644
index 0000000000..a658bdff68
--- /dev/null
+++ b/documentation/ref-manual/migration-1.4.rst
@@ -0,0 +1,237 @@
+Moving to the Yocto Project 1.4 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 1.4 Release from the prior release.
+
+.. _migration-1.4-bitbake:
+
+BitBake
+-------
+
+Differences include the following:
+
+-  *Comment Continuation:* If a comment ends with a line continuation
+   (\) character, then the next line must also be a comment. Any
+   instance where this is not the case, now triggers a warning. You must
+   either remove the continuation character, or be sure the next line is
+   a comment.
+
+-  *Package Name Overrides:* The runtime package specific variables
+   :term:`RDEPENDS`,
+   :term:`RRECOMMENDS`,
+   :term:`RSUGGESTS`,
+   :term:`RPROVIDES`,
+   :term:`RCONFLICTS`,
+   :term:`RREPLACES`, :term:`FILES`,
+   :term:`ALLOW_EMPTY`, and the pre, post, install,
+   and uninstall script functions ``pkg_preinst``, ``pkg_postinst``,
+   ``pkg_prerm``, and ``pkg_postrm`` should always have a package name
+   override. For example, use ``RDEPENDS_${PN}`` for the main package
+   instead of ``RDEPENDS``. BitBake uses more strict checks when it
+   parses recipes.
+
+.. _migration-1.4-build-behavior:
+
+Build Behavior
+--------------
+
+Differences include the following:
+
+-  *Shared State Code:* The shared state code has been optimized to
+   avoid running unnecessary tasks. For example, the following no longer
+   populates the target sysroot since that is not necessary:
+   ::
+
+      $ bitbake -c rootfs some-image
+
+   Instead, the system just needs to extract the
+   output package contents, re-create the packages, and construct the
+   root filesystem. This change is unlikely to cause any problems unless
+   you have missing declared dependencies.
+
+-  *Scanning Directory Names:* When scanning for files in
+   :term:`SRC_URI`, the build system now uses
+   :term:`FILESOVERRIDES` instead of
+   :term:`OVERRIDES` for the directory names. In
+   general, the values previously in ``OVERRIDES`` are now in
+   ``FILESOVERRIDES`` as well. However, if you relied upon an additional
+   value you previously added to ``OVERRIDES``, you might now need to
+   add it to ``FILESOVERRIDES`` unless you are already adding it through
+   the :term:`MACHINEOVERRIDES` or
+   :term:`DISTROOVERRIDES` variables, as
+   appropriate. For more related changes, see the
+   "`Variables <#migration-1.4-variables>`__" section.
+
+.. _migration-1.4-proxies-and-fetching-source:
+
+Proxies and Fetching Source
+---------------------------
+
+A new ``oe-git-proxy`` script has been added to replace previous methods
+of handling proxies and fetching source from Git. See the
+``meta-yocto/conf/site.conf.sample`` file for information on how to use
+this script.
+
+.. _migration-1.4-custom-interfaces-file-netbase-change:
+
+Custom Interfaces File (netbase change)
+---------------------------------------
+
+If you have created your own custom ``etc/network/interfaces`` file by
+creating an append file for the ``netbase`` recipe, you now need to
+create an append file for the ``init-ifupdown`` recipe instead, which
+you can find in the :term:`Source Directory` at
+``meta/recipes-core/init-ifupdown``. For information on how to use
+append files, see the
+":ref:`dev-manual/dev-manual-common-tasks:using .bbappend files in your layer`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _migration-1.4-remote-debugging:
+
+Remote Debugging
+----------------
+
+Support for remote debugging with the Eclipse IDE is now separated into
+an image feature (``eclipse-debug``) that corresponds to the
+``packagegroup-core-eclipse-debug`` package group. Previously, the
+debugging feature was included through the ``tools-debug`` image
+feature, which corresponds to the ``packagegroup-core-tools-debug``
+package group.
+
+.. _migration-1.4-variables:
+
+Variables
+---------
+
+The following variables have changed:
+
+-  ``SANITY_TESTED_DISTROS``: This variable now uses a distribution
+   ID, which is composed of the host distributor ID followed by the
+   release. Previously,
+   :term:`SANITY_TESTED_DISTROS` was
+   composed of the description field. For example, "Ubuntu 12.10"
+   becomes "Ubuntu-12.10". You do not need to worry about this change if
+   you are not specifically setting this variable, or if you are
+   specifically setting it to "".
+
+-  ``SRC_URI``: The ``${``\ :term:`PN`\ ``}``,
+   ``${``\ :term:`PF`\ ``}``,
+   ``${``\ :term:`P`\ ``}``, and ``FILE_DIRNAME`` directories
+   have been dropped from the default value of the
+   :term:`FILESPATH` variable, which is used as the
+   search path for finding files referred to in
+   :term:`SRC_URI`. If you have a recipe that relied upon
+   these directories, which would be unusual, then you will need to add
+   the appropriate paths within the recipe or, alternatively, rearrange
+   the files. The most common locations are still covered by ``${BP}``,
+   ``${BPN}``, and "files", which all remain in the default value of
+   :term:`FILESPATH`.
+
+.. _migration-target-package-management-with-rpm:
+
+Target Package Management with RPM
+----------------------------------
+
+If runtime package management is enabled and the RPM backend is
+selected, Smart is now installed for package download, dependency
+resolution, and upgrades instead of Zypper. For more information on how
+to use Smart, run the following command on the target:
+::
+
+   smart --help
+
+.. _migration-1.4-recipes-moved:
+
+Recipes Moved
+-------------
+
+The following recipes were moved from their previous locations because
+they are no longer used by anything in the OpenEmbedded-Core:
+
+-  ``clutter-box2d``: Now resides in the ``meta-oe`` layer.
+
+-  ``evolution-data-server``: Now resides in the ``meta-gnome`` layer.
+
+-  ``gthumb``: Now resides in the ``meta-gnome`` layer.
+
+-  ``gtkhtml2``: Now resides in the ``meta-oe`` layer.
+
+-  ``gupnp``: Now resides in the ``meta-multimedia`` layer.
+
+-  ``gypsy``: Now resides in the ``meta-oe`` layer.
+
+-  ``libcanberra``: Now resides in the ``meta-gnome`` layer.
+
+-  ``libgdata``: Now resides in the ``meta-gnome`` layer.
+
+-  ``libmusicbrainz``: Now resides in the ``meta-multimedia`` layer.
+
+-  ``metacity``: Now resides in the ``meta-gnome`` layer.
+
+-  ``polkit``: Now resides in the ``meta-oe`` layer.
+
+-  ``zeroconf``: Now resides in the ``meta-networking`` layer.
+
+.. _migration-1.4-removals-and-renames:
+
+Removals and Renames
+--------------------
+
+The following list shows what has been removed or renamed:
+
+-  ``evieext``: Removed because it has been removed from ``xserver``
+   since 2008.
+
+-  *Gtk+ DirectFB:* Removed support because upstream Gtk+ no longer
+   supports it as of version 2.18.
+
+-  ``libxfontcache / xfontcacheproto``: Removed because they were
+   removed from the Xorg server in 2008.
+
+-  ``libxp / libxprintapputil / libxprintutil / printproto``: Removed
+   because the XPrint server was removed from Xorg in 2008.
+
+-  ``libxtrap / xtrapproto``: Removed because their functionality was
+   broken upstream.
+
+-  *linux-yocto 3.0 kernel:* Removed with linux-yocto 3.8 kernel being
+   added. The linux-yocto 3.2 and linux-yocto 3.4 kernels remain as part
+   of the release.
+
+-  ``lsbsetup``: Removed with functionality now provided by
+   ``lsbtest``.
+
+-  ``matchbox-stroke``: Removed because it was never more than a
+   proof-of-concept.
+
+-  ``matchbox-wm-2 / matchbox-theme-sato-2``: Removed because they are
+   not maintained. However, ``matchbox-wm`` and ``matchbox-theme-sato``
+   are still provided.
+
+-  ``mesa-dri``: Renamed to ``mesa``.
+
+-  ``mesa-xlib``: Removed because it was no longer useful.
+
+-  ``mutter``: Removed because nothing ever uses it and the recipe is
+   very old.
+
+-  ``orinoco-conf``: Removed because it has become obsolete.
+
+-  ``update-modules``: Removed because it is no longer used. The
+   kernel module ``postinstall`` and ``postrm`` scripts can now do the
+   same task without the use of this script.
+
+-  ``web``: Removed because it is not maintained. Superseded by
+   ``web-webkit``.
+
+-  ``xf86bigfontproto``: Removed because upstream it has been disabled
+   by default since 2007. Nothing uses ``xf86bigfontproto``.
+
+-  ``xf86rushproto``: Removed because its dependency in ``xserver``
+   was spurious and it was removed in 2005.
+
+-  ``zypper / libzypp / sat-solver``: Removed and been functionally
+   replaced with Smart (``python-smartpm``) when RPM packaging is used
+   and package management is enabled on the target.
+
diff --git a/documentation/ref-manual/migration-1.5.rst b/documentation/ref-manual/migration-1.5.rst
new file mode 100644
index 0000000000..fa6ff92f10
--- /dev/null
+++ b/documentation/ref-manual/migration-1.5.rst
@@ -0,0 +1,355 @@
+Moving to the Yocto Project 1.5 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 1.5 Release from the prior release.
+
+.. _migration-1.5-host-dependency-changes:
+
+Host Dependency Changes
+-----------------------
+
+The OpenEmbedded build system now has some additional requirements on
+the host system:
+
+-  Python 2.7.3+
+
+-  Tar 1.24+
+
+-  Git 1.7.8+
+
+-  Patched version of Make if you are using 3.82. Most distributions
+   that provide Make 3.82 use the patched version.
+
+If the Linux distribution you are using on your build host does not
+provide packages for these, you can install and use the Buildtools
+tarball, which provides an SDK-like environment containing them.
+
+For more information on this requirement, see the "`Required Git, tar,
+Python and gcc Versions <#required-git-tar-python-and-gcc-versions>`__"
+section.
+
+.. _migration-1.5-atom-pc-bsp:
+
+``atom-pc`` Board Support Package (BSP)
+---------------------------------------
+
+The ``atom-pc`` hardware reference BSP has been replaced by a
+``genericx86`` BSP. This BSP is not necessarily guaranteed to work on
+all x86 hardware, but it will run on a wider range of systems than the
+``atom-pc`` did.
+
+.. note::
+
+   Additionally, a
+   genericx86-64
+   BSP has been added for 64-bit Atom systems.
+
+.. _migration-1.5-bitbake:
+
+BitBake
+-------
+
+The following changes have been made that relate to BitBake:
+
+-  BitBake now supports a ``_remove`` operator. The addition of this
+   operator means you will have to rename any items in recipe space
+   (functions, variables) whose names currently contain ``_remove_`` or
+   end with ``_remove`` to avoid unexpected behavior.
+
+-  BitBake's global method pool has been removed. This method is not
+   particularly useful and led to clashes between recipes containing
+   functions that had the same name.
+
+-  The "none" server backend has been removed. The "process" server
+   backend has been serving well as the default for a long time now.
+
+-  The ``bitbake-runtask`` script has been removed.
+
+-  ``${``\ :term:`P`\ ``}`` and
+   ``${``\ :term:`PF`\ ``}`` are no longer added to
+   :term:`PROVIDES` by default in ``bitbake.conf``.
+   These version-specific ``PROVIDES`` items were seldom used.
+   Attempting to use them could result in two versions being built
+   simultaneously rather than just one version due to the way BitBake
+   resolves dependencies.
+
+.. _migration-1.5-qa-warnings:
+
+QA Warnings
+-----------
+
+The following changes have been made to the package QA checks:
+
+-  If you have customized :term:`ERROR_QA` or
+   :term:`WARN_QA` values in your configuration, check
+   that they contain all of the issues that you wish to be reported.
+   Previous Yocto Project versions contained a bug that meant that any
+   item not mentioned in ``ERROR_QA`` or ``WARN_QA`` would be treated as
+   a warning. Consequently, several important items were not already in
+   the default value of ``WARN_QA``. All of the possible QA checks are
+   now documented in the ":ref:`insane.bbclass <ref-classes-insane>`"
+   section.
+
+-  An additional QA check has been added to check if
+   ``/usr/share/info/dir`` is being installed. Your recipe should delete
+   this file within :ref:`ref-tasks-install` if "make
+   install" is installing it.
+
+-  If you are using the buildhistory class, the check for the package
+   version going backwards is now controlled using a standard QA check.
+   Thus, if you have customized your ``ERROR_QA`` or ``WARN_QA`` values
+   and still wish to have this check performed, you should add
+   "version-going-backwards" to your value for one or the other
+   variables depending on how you wish it to be handled. See the
+   documented QA checks in the
+   ":ref:`insane.bbclass <ref-classes-insane>`" section.
+
+.. _migration-1.5-directory-layout-changes:
+
+Directory Layout Changes
+------------------------
+
+The following directory changes exist:
+
+-  Output SDK installer files are now named to include the image name
+   and tuning architecture through the :term:`SDK_NAME`
+   variable.
+
+-  Images and related files are now installed into a directory that is
+   specific to the machine, instead of a parent directory containing
+   output files for multiple machines. The
+   :term:`DEPLOY_DIR_IMAGE` variable continues
+   to point to the directory containing images for the current
+   :term:`MACHINE` and should be used anywhere there is a
+   need to refer to this directory. The ``runqemu`` script now uses this
+   variable to find images and kernel binaries and will use BitBake to
+   determine the directory. Alternatively, you can set the
+   ``DEPLOY_DIR_IMAGE`` variable in the external environment.
+
+-  When buildhistory is enabled, its output is now written under the
+   :term:`Build Directory` rather than
+   :term:`TMPDIR`. Doing so makes it easier to delete
+   ``TMPDIR`` and preserve the build history. Additionally, data for
+   produced SDKs is now split by :term:`IMAGE_NAME`.
+
+-  The ``pkgdata`` directory produced as part of the packaging process
+   has been collapsed into a single machine-specific directory. This
+   directory is located under ``sysroots`` and uses a machine-specific
+   name (i.e. ``tmp/sysroots/machine/pkgdata``).
+
+.. _migration-1.5-shortened-git-srcrev-values:
+
+Shortened Git ``SRCREV`` Values
+-------------------------------
+
+BitBake will now shorten revisions from Git repositories from the normal
+40 characters down to 10 characters within :term:`SRCPV`
+for improved usability in path and file names. This change should be
+safe within contexts where these revisions are used because the chances
+of spatially close collisions is very low. Distant collisions are not a
+major issue in the way the values are used.
+
+.. _migration-1.5-image-features:
+
+``IMAGE_FEATURES``
+------------------
+
+The following changes have been made that relate to
+:term:`IMAGE_FEATURES`:
+
+-  The value of ``IMAGE_FEATURES`` is now validated to ensure invalid
+   feature items are not added. Some users mistakenly add package names
+   to this variable instead of using
+   :term:`IMAGE_INSTALL` in order to have the
+   package added to the image, which does not work. This change is
+   intended to catch those kinds of situations. Valid ``IMAGE_FEATURES``
+   are drawn from ``PACKAGE_GROUP`` definitions,
+   :term:`COMPLEMENTARY_GLOB` and a new
+   "validitems" varflag on ``IMAGE_FEATURES``. The "validitems" varflag
+   change allows additional features to be added if they are not
+   provided using the previous two mechanisms.
+
+-  The previously deprecated "apps-console-core" ``IMAGE_FEATURES`` item
+   is no longer supported. Add "splash" to ``IMAGE_FEATURES`` if you
+   wish to have the splash screen enabled, since this is all that
+   apps-console-core was doing.
+
+.. _migration-1.5-run:
+
+``/run``
+--------
+
+The ``/run`` directory from the Filesystem Hierarchy Standard 3.0 has
+been introduced. You can find some of the implications for this change
+`here <http://cgit.openembedded.org/openembedded-core/commit/?id=0e326280a15b0f2c4ef2ef4ec441f63f55b75873>`__.
+The change also means that recipes that install files to ``/var/run``
+must be changed. You can find a guide on how to make these changes
+`here <https://www.mail-archive.com/openembedded-devel@lists.openembedded.org/msg31649.html>`__.
+
+.. _migration-1.5-removal-of-package-manager-database-within-image-recipes:
+
+Removal of Package Manager Database Within Image Recipes
+--------------------------------------------------------
+
+The image ``core-image-minimal`` no longer adds
+``remove_packaging_data_files`` to
+:term:`ROOTFS_POSTPROCESS_COMMAND`.
+This addition is now handled automatically when "package-management" is
+not in :term:`IMAGE_FEATURES`. If you have custom
+image recipes that make this addition, you should remove the lines, as
+they are not needed and might interfere with correct operation of
+postinstall scripts.
+
+.. _migration-1.5-images-now-rebuild-only-on-changes-instead-of-every-time:
+
+Images Now Rebuild Only on Changes Instead of Every Time
+--------------------------------------------------------
+
+The :ref:`ref-tasks-rootfs` and other related image
+construction tasks are no longer marked as "nostamp". Consequently, they
+will only be re-executed when their inputs have changed. Previous
+versions of the OpenEmbedded build system always rebuilt the image when
+requested rather when necessary.
+
+.. _migration-1.5-task-recipes:
+
+Task Recipes
+------------
+
+The previously deprecated ``task.bbclass`` has now been dropped. For
+recipes that previously inherited from this class, you should rename
+them from ``task-*`` to ``packagegroup-*`` and inherit packagegroup
+instead.
+
+For more information, see the
+":ref:`packagegroup.bbclass <ref-classes-packagegroup>`" section.
+
+.. _migration-1.5-busybox:
+
+BusyBox
+-------
+
+By default, we now split BusyBox into two binaries: one that is suid
+root for those components that need it, and another for the rest of the
+components. Splitting BusyBox allows for optimization that eliminates
+the ``tinylogin`` recipe as recommended by upstream. You can disable
+this split by setting
+:term:`BUSYBOX_SPLIT_SUID` to "0".
+
+.. _migration-1.5-automated-image-testing:
+
+Automated Image Testing
+-----------------------
+
+A new automated image testing framework has been added through the
+:ref:`testimage.bbclass <ref-classes-testimage*>` class. This
+framework replaces the older ``imagetest-qemu`` framework.
+
+You can learn more about performing automated image tests in the
+":ref:`dev-manual/dev-manual-common-tasks:performing automated runtime testing`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _migration-1.5-build-history:
+
+Build History
+-------------
+
+Following are changes to Build History:
+
+-  Installed package sizes: ``installed-package-sizes.txt`` for an image
+   now records the size of the files installed by each package instead
+   of the size of each compressed package archive file.
+
+-  The dependency graphs (``depends*.dot``) now use the actual package
+   names instead of replacing dashes, dots and plus signs with
+   underscores.
+
+-  The ``buildhistory-diff`` and ``buildhistory-collect-srcrevs``
+   utilities have improved command-line handling. Use the ``--help``
+   option for each utility for more information on the new syntax.
+
+For more information on Build History, see the
+":ref:`dev-manual/dev-manual-common-tasks:maintaining build output quality`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _migration-1.5-udev:
+
+``udev``
+--------
+
+Following are changes to ``udev``:
+
+-  ``udev`` no longer brings in ``udev-extraconf`` automatically through
+   :term:`RRECOMMENDS`, since this was originally
+   intended to be optional. If you need the extra rules, then add
+   ``udev-extraconf`` to your image.
+
+-  ``udev`` no longer brings in ``pciutils-ids`` or ``usbutils-ids``
+   through ``RRECOMMENDS``. These are not needed by ``udev`` itself and
+   removing them saves around 350KB.
+
+.. _migration-1.5-removed-renamed-recipes:
+
+Removed and Renamed Recipes
+---------------------------
+
+-  The ``linux-yocto`` 3.2 kernel has been removed.
+
+-  ``libtool-nativesdk`` has been renamed to ``nativesdk-libtool``.
+
+-  ``tinylogin`` has been removed. It has been replaced by a suid
+   portion of Busybox. See the "`BusyBox <#migration-1.5-busybox>`__"
+   section for more information.
+
+-  ``external-python-tarball`` has been renamed to
+   ``buildtools-tarball``.
+
+-  ``web-webkit`` has been removed. It has been functionally replaced by
+   ``midori``.
+
+-  ``imake`` has been removed. It is no longer needed by any other
+   recipe.
+
+-  ``transfig-native`` has been removed. It is no longer needed by any
+   other recipe.
+
+-  ``anjuta-remote-run`` has been removed. Anjuta IDE integration has
+   not been officially supported for several releases.
+
+.. _migration-1.5-other-changes:
+
+Other Changes
+-------------
+
+Following is a list of short entries describing other changes:
+
+-  ``run-postinsts``: Make this generic.
+
+-  ``base-files``: Remove the unnecessary ``media/``\ xxx directories.
+
+-  ``alsa-state``: Provide an empty ``asound.conf`` by default.
+
+-  ``classes/image``: Ensure
+   :term:`BAD_RECOMMENDATIONS` supports
+   pre-renamed package names.
+
+-  ``classes/rootfs_rpm``: Implement ``BAD_RECOMMENDATIONS`` for RPM.
+
+-  ``systemd``: Remove ``systemd_unitdir`` if ``systemd`` is not in
+   :term:`DISTRO_FEATURES`.
+
+-  ``systemd``: Remove ``init.d`` dir if ``systemd`` unit file is
+   present and ``sysvinit`` is not a distro feature.
+
+-  ``libpam``: Deny all services for the ``OTHER`` entries.
+
+-  ``image.bbclass``: Move ``runtime_mapping_rename`` to avoid conflict
+   with ``multilib``. See
+   `YOCTO #4993 <https://bugzilla.yoctoproject.org/show_bug.cgi?id=4993>`_
+   in Bugzilla for more information.
+
+-  ``linux-dtb``: Use kernel build system to generate the ``dtb`` files.
+
+-  ``kern-tools``: Switch from guilt to new ``kgit-s2q`` tool.
+
diff --git a/documentation/ref-manual/migration-1.6.rst b/documentation/ref-manual/migration-1.6.rst
new file mode 100644
index 0000000000..b55be46e55
--- /dev/null
+++ b/documentation/ref-manual/migration-1.6.rst
@@ -0,0 +1,417 @@
+Moving to the Yocto Project 1.6 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 1.6 Release from the prior release.
+
+.. _migration-1.6-archiver-class:
+
+``archiver`` Class
+------------------
+
+The :ref:`archiver <ref-classes-archiver>` class has been rewritten
+and its configuration has been simplified. For more details on the
+source archiver, see the
+":ref:`dev-manual/dev-manual-common-tasks:maintaining open source license compliance during your product's lifecycle`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _migration-1.6-packaging-changes:
+
+Packaging Changes
+-----------------
+
+The following packaging changes have been made:
+
+-  The ``binutils`` recipe no longer produces a ``binutils-symlinks``
+   package. ``update-alternatives`` is now used to handle the preferred
+   ``binutils`` variant on the target instead.
+
+-  The tc (traffic control) utilities have been split out of the main
+   ``iproute2`` package and put into the ``iproute2-tc`` package.
+
+-  The ``gtk-engines`` schemas have been moved to a dedicated
+   ``gtk-engines-schemas`` package.
+
+-  The ``armv7a`` with thumb package architecture suffix has changed.
+   The suffix for these packages with the thumb optimization enabled is
+   "t2" as it should be. Use of this suffix was not the case in the 1.5
+   release. Architecture names will change within package feeds as a
+   result.
+
+.. _migration-1.6-bitbake:
+
+BitBake
+-------
+
+The following changes have been made to :term:`BitBake`.
+
+.. _migration-1.6-matching-branch-requirement-for-git-fetching:
+
+Matching Branch Requirement for Git Fetching
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When fetching source from a Git repository using
+:term:`SRC_URI`, BitBake will now validate the
+:term:`SRCREV` value against the branch. You can specify
+the branch using the following form: SRC_URI =
+"git://server.name/repository;branch=branchname" If you do not specify a
+branch, BitBake looks in the default "master" branch.
+
+Alternatively, if you need to bypass this check (e.g. if you are
+fetching a revision corresponding to a tag that is not on any branch),
+you can add ";nobranch=1" to the end of the URL within ``SRC_URI``.
+
+.. _migration-1.6-bitbake-deps:
+
+Python Definition substitutions
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+BitBake had some previously deprecated Python definitions within its
+``bb`` module removed. You should use their sub-module counterparts
+instead:
+
+-  ``bb.MalformedUrl``: Use ``bb.fetch.MalformedUrl``.
+
+-  ``bb.encodeurl``: Use ``bb.fetch.encodeurl``.
+
+-  ``bb.decodeurl``: Use ``bb.fetch.decodeurl``
+
+-  ``bb.mkdirhier``: Use ``bb.utils.mkdirhier``.
+
+-  ``bb.movefile``: Use ``bb.utils.movefile``.
+
+-  ``bb.copyfile``: Use ``bb.utils.copyfile``.
+
+-  ``bb.which``: Use ``bb.utils.which``.
+
+-  ``bb.vercmp_string``: Use ``bb.utils.vercmp_string``.
+
+-  ``bb.vercmp``: Use ``bb.utils.vercmp``.
+
+.. _migration-1.6-bitbake-fetcher:
+
+SVK Fetcher
+~~~~~~~~~~~
+
+The SVK fetcher has been removed from BitBake.
+
+.. _migration-1.6-bitbake-console-output:
+
+Console Output Error Redirection
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The BitBake console UI will now output errors to ``stderr`` instead of
+``stdout``. Consequently, if you are piping or redirecting the output of
+``bitbake`` to somewhere else, and you wish to retain the errors, you
+will need to add ``2>&1`` (or something similar) to the end of your
+``bitbake`` command line.
+
+.. _migration-1.6-task-taskname-overrides:
+
+``task-``\ taskname Overrides
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``task-``\ taskname overrides have been adjusted so that tasks whose
+names contain underscores have the underscores replaced by hyphens for
+the override so that they now function properly. For example, the task
+override for :ref:`ref-tasks-populate_sdk` is
+``task-populate-sdk``.
+
+.. _migration-1.6-variable-changes:
+
+Changes to Variables
+--------------------
+
+The following variables have changed. For information on the
+OpenEmbedded build system variables, see the "`Variables
+Glossary <#ref-variables-glos>`__" Chapter.
+
+.. _migration-1.6-variable-changes-TMPDIR:
+
+``TMPDIR``
+~~~~~~~~~~
+
+:term:`TMPDIR` can no longer be on an NFS mount. NFS does
+not offer full POSIX locking and inode consistency and can cause
+unexpected issues if used to store ``TMPDIR``.
+
+The check for this occurs on startup. If ``TMPDIR`` is detected on an
+NFS mount, an error occurs.
+
+.. _migration-1.6-variable-changes-PRINC:
+
+``PRINC``
+~~~~~~~~~
+
+The ``PRINC`` variable has been deprecated and triggers a warning if
+detected during a build. For :term:`PR` increments on changes,
+use the PR service instead. You can find out more about this service in
+the ":ref:`dev-manual/dev-manual-common-tasks:working with a pr service`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _migration-1.6-variable-changes-IMAGE_TYPES:
+
+``IMAGE_TYPES``
+~~~~~~~~~~~~~~~
+
+The "sum.jffs2" option for :term:`IMAGE_TYPES` has
+been replaced by the "jffs2.sum" option, which fits the processing
+order.
+
+.. _migration-1.6-variable-changes-COPY_LIC_MANIFEST:
+
+``COPY_LIC_MANIFEST``
+~~~~~~~~~~~~~~~~~~~~~
+
+The :term:`COPY_LIC_MANIFEST` variable must now
+be set to "1" rather than any value in order to enable it.
+
+.. _migration-1.6-variable-changes-COPY_LIC_DIRS:
+
+``COPY_LIC_DIRS``
+~~~~~~~~~~~~~~~~~
+
+The :term:`COPY_LIC_DIRS` variable must now be set
+to "1" rather than any value in order to enable it.
+
+.. _migration-1.6-variable-changes-PACKAGE_GROUP:
+
+``PACKAGE_GROUP``
+~~~~~~~~~~~~~~~~~
+
+The ``PACKAGE_GROUP`` variable has been renamed to
+:term:`FEATURE_PACKAGES` to more accurately
+reflect its purpose. You can still use ``PACKAGE_GROUP`` but the
+OpenEmbedded build system produces a warning message when it encounters
+the variable.
+
+.. _migration-1.6-variable-changes-variable-entry-behavior:
+
+Preprocess and Post Process Command Variable Behavior
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The following variables now expect a semicolon separated list of
+functions to call and not arbitrary shell commands:
+
+  - :term:`ROOTFS_PREPROCESS_COMMAND`
+  - :term:`ROOTFS_POSTPROCESS_COMMAND`
+  - :term:`SDK_POSTPROCESS_COMMAND`
+  - :term:`POPULATE_SDK_POST_TARGET_COMMAND`
+  - :term:`POPULATE_SDK_POST_HOST_COMMAND`
+  - :term:`IMAGE_POSTPROCESS_COMMAND`
+  - :term:`IMAGE_PREPROCESS_COMMAND`
+  - :term:`ROOTFS_POSTUNINSTALL_COMMAND`
+  - :term:`ROOTFS_POSTINSTALL_COMMAND`
+
+For
+migration purposes, you can simply wrap shell commands in a shell
+function and then call the function. Here is an example: ::
+
+   my_postprocess_function() {
+      echo "hello" > ${IMAGE_ROOTFS}/hello.txt
+   }
+   ROOTFS_POSTPROCESS_COMMAND += "my_postprocess_function; "
+
+.. _migration-1.6-package-test-ptest:
+
+Package Test (ptest)
+--------------------
+
+Package Tests (ptest) are built but not installed by default. For
+information on using Package Tests, see the
+":ref:`dev-manual/dev-manual-common-tasks:testing packages with ptest`"
+section in the Yocto Project Development Tasks Manual. For information on the
+``ptest`` class, see the ":ref:`ptest.bbclass <ref-classes-ptest>`"
+section.
+
+.. _migration-1.6-build-changes:
+
+Build Changes
+-------------
+
+Separate build and source directories have been enabled by default for
+selected recipes where it is known to work (a whitelist) and for all
+recipes that inherit the :ref:`cmake <ref-classes-cmake>` class. In
+future releases the :ref:`autotools <ref-classes-autotools>` class
+will enable a separate build directory by default as well. Recipes
+building Autotools-based software that fails to build with a separate
+build directory should be changed to inherit from the
+:ref:`autotools-brokensep <ref-classes-autotools>` class instead of
+the ``autotools`` or ``autotools_stage``\ classes.
+
+.. _migration-1.6-building-qemu-native:
+
+``qemu-native``
+---------------
+
+``qemu-native`` now builds without SDL-based graphical output support by
+default. The following additional lines are needed in your
+``local.conf`` to enable it:
+::
+
+   PACKAGECONFIG_pn-qemu-native = "sdl"
+   ASSUME_PROVIDED += "libsdl-native"
+
+.. note::
+
+   The default
+   local.conf
+   contains these statements. Consequently, if you are building a
+   headless system and using a default
+   local.conf
+   file, you will need comment these two lines out.
+
+.. _migration-1.6-core-image-basic:
+
+``core-image-basic``
+--------------------
+
+``core-image-basic`` has been renamed to ``core-image-full-cmdline``.
+
+In addition to ``core-image-basic`` being renamed,
+``packagegroup-core-basic`` has been renamed to
+``packagegroup-core-full-cmdline`` to match.
+
+.. _migration-1.6-licensing:
+
+Licensing
+---------
+
+The top-level ``LICENSE`` file has been changed to better describe the
+license of the various components of :term:`OpenEmbedded-Core (OE-Core)`. However,
+the licensing itself remains unchanged.
+
+Normally, this change would not cause any side-effects. However, some
+recipes point to this file within
+:term:`LIC_FILES_CHKSUM` (as
+``${COREBASE}/LICENSE``) and thus the accompanying checksum must be
+changed from 3f40d7994397109285ec7b81fdeb3b58 to
+4d92cd373abda3937c2bc47fbc49d690. A better alternative is to have
+``LIC_FILES_CHKSUM`` point to a file describing the license that is
+distributed with the source that the recipe is building, if possible,
+rather than pointing to ``${COREBASE}/LICENSE``.
+
+.. _migration-1.6-cflags-options:
+
+``CFLAGS`` Options
+------------------
+
+The "-fpermissive" option has been removed from the default
+:term:`CFLAGS` value. You need to take action on
+individual recipes that fail when building with this option. You need to
+either patch the recipes to fix the issues reported by the compiler, or
+you need to add "-fpermissive" to ``CFLAGS`` in the recipes.
+
+.. _migration-1.6-custom-images:
+
+Custom Image Output Types
+-------------------------
+
+Custom image output types, as selected using
+:term:`IMAGE_FSTYPES`, must declare their
+dependencies on other image types (if any) using a new
+:term:`IMAGE_TYPEDEP` variable.
+
+.. _migration-1.6-do-package-write-task:
+
+Tasks
+-----
+
+The ``do_package_write`` task has been removed. The task is no longer
+needed.
+
+.. _migration-1.6-update-alternatives-provider:
+
+``update-alternative`` Provider
+-------------------------------
+
+The default ``update-alternatives`` provider has been changed from
+``opkg`` to ``opkg-utils``. This change resolves some troublesome
+circular dependencies. The runtime package has also been renamed from
+``update-alternatives-cworth`` to ``update-alternatives-opkg``.
+
+.. _migration-1.6-virtclass-overrides:
+
+``virtclass`` Overrides
+-----------------------
+
+The ``virtclass`` overrides are now deprecated. Use the equivalent class
+overrides instead (e.g. ``virtclass-native`` becomes ``class-native``.)
+
+.. _migration-1.6-removed-renamed-recipes:
+
+Removed and Renamed Recipes
+---------------------------
+
+The following recipes have been removed:
+
+-  ``packagegroup-toolset-native`` - This recipe is largely unused.
+
+-  ``linux-yocto-3.8`` - Support for the Linux yocto 3.8 kernel has been
+   dropped. Support for the 3.10 and 3.14 kernels have been added with
+   the ``linux-yocto-3.10`` and ``linux-yocto-3.14`` recipes.
+
+-  ``ocf-linux`` - This recipe has been functionally replaced using
+   ``cryptodev-linux``.
+
+-  ``genext2fs`` - ``genext2fs`` is no longer used by the build system
+   and is unmaintained upstream.
+
+-  ``js`` - This provided an ancient version of Mozilla's javascript
+   engine that is no longer needed.
+
+-  ``zaurusd`` - The recipe has been moved to the ``meta-handheld``
+   layer.
+
+-  ``eglibc 2.17`` - Replaced by the ``eglibc 2.19`` recipe.
+
+-  ``gcc 4.7.2`` - Replaced by the now stable ``gcc 4.8.2``.
+
+-  ``external-sourcery-toolchain`` - this recipe is now maintained in
+   the ``meta-sourcery`` layer.
+
+-  ``linux-libc-headers-yocto 3.4+git`` - Now using version 3.10 of the
+   ``linux-libc-headers`` by default.
+
+-  ``meta-toolchain-gmae`` - This recipe is obsolete.
+
+-  ``packagegroup-core-sdk-gmae`` - This recipe is obsolete.
+
+-  ``packagegroup-core-standalone-gmae-sdk-target`` - This recipe is
+   obsolete.
+
+.. _migration-1.6-removed-classes:
+
+Removed Classes
+---------------
+
+The following classes have become obsolete and have been removed:
+
+-  ``module_strip``
+
+-  ``pkg_metainfo``
+
+-  ``pkg_distribute``
+
+-  ``image-empty``
+
+.. _migration-1.6-reference-bsps:
+
+Reference Board Support Packages (BSPs)
+---------------------------------------
+
+The following reference BSPs changes occurred:
+
+-  The BeagleBoard (``beagleboard``) ARM reference hardware has been
+   replaced by the BeagleBone (``beaglebone``) hardware.
+
+-  The RouterStation Pro (``routerstationpro``) MIPS reference hardware
+   has been replaced by the EdgeRouter Lite (``edgerouter``) hardware.
+
+The previous reference BSPs for the ``beagleboard`` and
+``routerstationpro`` machines are still available in a new
+``meta-yocto-bsp-old`` layer in the
+:yocto_git:`Source Repositories <>` at
+http://git.yoctoproject.org/cgit/cgit.cgi/meta-yocto-bsp-old/.
+
+
diff --git a/documentation/ref-manual/migration-1.7.rst b/documentation/ref-manual/migration-1.7.rst
new file mode 100644
index 0000000000..82fd37d3a9
--- /dev/null
+++ b/documentation/ref-manual/migration-1.7.rst
@@ -0,0 +1,225 @@
+Moving to the Yocto Project 1.7 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 1.7 Release from the prior release.
+
+.. _migration-1.7-changes-to-setting-qemu-packageconfig-options:
+
+Changes to Setting QEMU ``PACKAGECONFIG`` Options in ``local.conf``
+-------------------------------------------------------------------
+
+The QEMU recipe now uses a number of
+:term:`PACKAGECONFIG` options to enable various
+optional features. The method used to set defaults for these options
+means that existing ``local.conf`` files will need to be be modified to
+append to ``PACKAGECONFIG`` for ``qemu-native`` and ``nativesdk-qemu``
+instead of setting it. In other words, to enable graphical output for
+QEMU, you should now have these lines in ``local.conf``:
+::
+
+   PACKAGECONFIG_append_pn-qemu-native = " sdl"
+   PACKAGECONFIG_append_pn-nativesdk-qemu = " sdl"
+
+.. _migration-1.7-minimum-git-version:
+
+Minimum Git version
+-------------------
+
+The minimum :ref:`overview-manual/overview-manual-development-environment:git`
+version required on the
+build host is now 1.7.8 because the ``--list`` option is now required by
+BitBake's Git fetcher. As always, if your host distribution does not
+provide a version of Git that meets this requirement, you can use the
+``buildtools-tarball`` that does. See the "`Required Git, tar, Python
+and gcc Versions <#required-git-tar-python-and-gcc-versions>`__" section
+for more information.
+
+.. _migration-1.7-autotools-class-changes:
+
+Autotools Class Changes
+-----------------------
+
+The following :ref:`autotools <ref-classes-autotools>` class changes
+occurred:
+
+-  *A separate build directory is now used by default:* The
+   ``autotools`` class has been changed to use a directory for building
+   (:term:`B`), which is separate from the source directory
+   (:term:`S`). This is commonly referred to as ``B != S``, or
+   an out-of-tree build.
+
+   If the software being built is already capable of building in a
+   directory separate from the source, you do not need to do anything.
+   However, if the software is not capable of being built in this
+   manner, you will need to either patch the software so that it can
+   build separately, or you will need to change the recipe to inherit
+   the :ref:`autotools-brokensep <ref-classes-autotools>` class
+   instead of the ``autotools`` or ``autotools_stage`` classes.
+
+-  The ``--foreign`` option is no longer passed to ``automake`` when
+   running ``autoconf``: This option tells ``automake`` that a
+   particular software package does not follow the GNU standards and
+   therefore should not be expected to distribute certain files such as
+   ``ChangeLog``, ``AUTHORS``, and so forth. Because the majority of
+   upstream software packages already tell ``automake`` to enable
+   foreign mode themselves, the option is mostly superfluous. However,
+   some recipes will need patches for this change. You can easily make
+   the change by patching ``configure.ac`` so that it passes "foreign"
+   to ``AM_INIT_AUTOMAKE()``. See `this
+   commit <http://cgit.openembedded.org/openembedded-core/commit/?id=01943188f85ce6411717fb5bf702d609f55813f2>`__
+   for an example showing how to make the patch.
+
+.. _migration-1.7-binary-configuration-scripts-disabled:
+
+Binary Configuration Scripts Disabled
+-------------------------------------
+
+Some of the core recipes that package binary configuration scripts now
+disable the scripts due to the scripts previously requiring error-prone
+path substitution. Software that links against these libraries using
+these scripts should use the much more robust ``pkg-config`` instead.
+The list of recipes changed in this version (and their configuration
+scripts) is as follows:
+::
+
+   directfb (directfb-config)
+   freetype (freetype-config)
+   gpgme (gpgme-config)
+   libassuan (libassuan-config)
+   libcroco (croco-6.0-config)
+   libgcrypt (libgcrypt-config)
+   libgpg-error (gpg-error-config)
+   libksba (ksba-config)
+   libpcap (pcap-config)
+   libpcre (pcre-config)
+   libpng (libpng-config, libpng16-config)
+   libsdl (sdl-config)
+   libusb-compat (libusb-config)
+   libxml2 (xml2-config)
+   libxslt (xslt-config)
+   ncurses (ncurses-config)
+   neon (neon-config)
+   npth (npth-config)
+   pth (pth-config)
+   taglib (taglib-config)
+
+Additionally, support for ``pkg-config`` has been added to some recipes in the
+previous list in the rare cases where the upstream software package does
+not already provide it.
+
+.. _migration-1.7-glibc-replaces-eglibc:
+
+``eglibc 2.19`` Replaced with ``glibc 2.20``
+--------------------------------------------
+
+Because ``eglibc`` and ``glibc`` were already fairly close, this
+replacement should not require any significant changes to other software
+that links to ``eglibc``. However, there were a number of minor changes
+in ``glibc 2.20`` upstream that could require patching some software
+(e.g. the removal of the ``_BSD_SOURCE`` feature test macro).
+
+``glibc 2.20`` requires version 2.6.32 or greater of the Linux kernel.
+Thus, older kernels will no longer be usable in conjunction with it.
+
+For full details on the changes in ``glibc 2.20``, see the upstream
+release notes
+`here <https://sourceware.org/ml/libc-alpha/2014-09/msg00088.html>`__.
+
+.. _migration-1.7-kernel-module-autoloading:
+
+Kernel Module Autoloading
+-------------------------
+
+The :term:`module_autoload_* <module_autoload>` variable is now
+deprecated and a new
+:term:`KERNEL_MODULE_AUTOLOAD` variable
+should be used instead. Also, :term:`module_conf_* <module_conf>`
+must now be used in conjunction with a new
+:term:`KERNEL_MODULE_PROBECONF` variable.
+The new variables no longer require you to specify the module name as
+part of the variable name. This change not only simplifies usage but
+also allows the values of these variables to be appropriately
+incorporated into task signatures and thus trigger the appropriate tasks
+to re-execute when changed. You should replace any references to
+``module_autoload_*`` with ``KERNEL_MODULE_AUTOLOAD``, and add any
+modules for which ``module_conf_*`` is specified to
+``KERNEL_MODULE_PROBECONF``.
+
+.. _migration-1.7-qa-check-changes:
+
+QA Check Changes
+----------------
+
+The following changes have occurred to the QA check process:
+
+-  Additional QA checks ``file-rdeps`` and ``build-deps`` have been
+   added in order to verify that file dependencies are satisfied (e.g.
+   package contains a script requiring ``/bin/bash``) and build-time
+   dependencies are declared, respectively. For more information, please
+   see the "`QA Error and Warning Messages <#ref-qa-checks>`__" chapter.
+
+-  Package QA checks are now performed during a new
+   :ref:`ref-tasks-package_qa` task rather than being
+   part of the :ref:`ref-tasks-package` task. This allows
+   more parallel execution. This change is unlikely to be an issue
+   except for highly customized recipes that disable packaging tasks
+   themselves by marking them as ``noexec``. For those packages, you
+   will need to disable the ``do_package_qa`` task as well.
+
+-  Files being overwritten during the
+   :ref:`ref-tasks-populate_sysroot` task now
+   trigger an error instead of a warning. Recipes should not be
+   overwriting files written to the sysroot by other recipes. If you
+   have these types of recipes, you need to alter them so that they do
+   not overwrite these files.
+
+   You might now receive this error after changes in configuration or
+   metadata resulting in orphaned files being left in the sysroot. If
+   you do receive this error, the way to resolve the issue is to delete
+   your :term:`TMPDIR` or to move it out of the way and
+   then re-start the build. Anything that has been fully built up to
+   that point and does not need rebuilding will be restored from the
+   shared state cache and the rest of the build will be able to proceed
+   as normal.
+
+.. _migration-1.7-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been removed:
+
+-  ``x-load``: This recipe has been superseded by U-boot SPL for all
+   Cortex-based TI SoCs. For legacy boards, the ``meta-ti`` layer, which
+   contains a maintained recipe, should be used instead.
+
+-  ``ubootchart``: This recipe is obsolete. A ``bootchart2`` recipe has
+   been added to functionally replace it.
+
+-  ``linux-yocto 3.4``: Support for the linux-yocto 3.4 kernel has been
+   dropped. Support for the 3.10 and 3.14 kernels remains, while support
+   for version 3.17 has been added.
+
+-  ``eglibc`` has been removed in favor of ``glibc``. See the
+   "```eglibc 2.19`` Replaced with
+   ``glibc 2.20`` <#migration-1.7-glibc-replaces-eglibc>`__" section for
+   more information.
+
+.. _migration-1.7-miscellaneous-changes:
+
+Miscellaneous Changes
+---------------------
+
+The following miscellaneous change occurred:
+
+-  The build history feature now writes ``build-id.txt`` instead of
+   ``build-id``. Additionally, ``build-id.txt`` now contains the full
+   build header as printed by BitBake upon starting the build. You
+   should manually remove old "build-id" files from your existing build
+   history repositories to avoid confusion. For information on the build
+   history feature, see the
+   ":ref:`dev-manual/dev-manual-common-tasks:maintaining build output quality`"
+   section in the Yocto Project Development Tasks Manual.
+
+
diff --git a/documentation/ref-manual/migration-1.8.rst b/documentation/ref-manual/migration-1.8.rst
new file mode 100644
index 0000000000..d601e6b63b
--- /dev/null
+++ b/documentation/ref-manual/migration-1.8.rst
@@ -0,0 +1,183 @@
+Moving to the Yocto Project 1.8 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 1.8 Release from the prior release.
+
+.. _migration-1.8-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been removed:
+
+-  ``owl-video``: Functionality replaced by ``gst-player``.
+
+-  ``gaku``: Functionality replaced by ``gst-player``.
+
+-  ``gnome-desktop``: This recipe is now available in ``meta-gnome`` and
+   is no longer needed.
+
+-  ``gsettings-desktop-schemas``: This recipe is now available in
+   ``meta-gnome`` and is no longer needed.
+
+-  ``python-argparse``: The ``argparse`` module is already provided in
+   the default Python distribution in a package named
+   ``python-argparse``. Consequently, the separate ``python-argparse``
+   recipe is no longer needed.
+
+-  ``telepathy-python, libtelepathy, telepathy-glib, telepathy-idle, telepathy-mission-control``:
+   All these recipes have moved to ``meta-oe`` and are consequently no
+   longer needed by any recipes in OpenEmbedded-Core.
+
+-  ``linux-yocto_3.10`` and ``linux-yocto_3.17``: Support for the
+   linux-yocto 3.10 and 3.17 kernels has been dropped. Support for the
+   3.14 kernel remains, while support for 3.19 kernel has been added.
+
+-  ``poky-feed-config-opkg``: This recipe has become obsolete and is no
+   longer needed. Use ``distro-feed-config`` from ``meta-oe`` instead.
+
+-  ``libav 0.8.x``: ``libav 9.x`` is now used.
+
+-  ``sed-native``: No longer needed. A working version of ``sed`` is
+   expected to be provided by the host distribution.
+
+.. _migration-1.8-bluez:
+
+BlueZ 4.x / 5.x Selection
+-------------------------
+
+Proper built-in support for selecting BlueZ 5.x in preference to the
+default of 4.x now exists. To use BlueZ 5.x, simply add "bluez5" to your
+:term:`DISTRO_FEATURES` value. If you had
+previously added append files (``*.bbappend``) to make this selection,
+you can now remove them.
+
+Additionally, a ``bluetooth`` class has been added to make selection of
+the appropriate bluetooth support within a recipe a little easier. If
+you wish to make use of this class in a recipe, add something such as
+the following: ::
+
+   inherit bluetooth
+   PACKAGECONFIG ??= "${@bb.utils.contains('DISTRO_FEATURES', 'bluetooth', '${BLUEZ}', '', d)}"
+   PACKAGECONFIG[bluez4] = "--enable-bluetooth,--disable-bluetooth,bluez4"
+   PACKAGECONFIG[bluez5] = "--enable-bluez5,--disable-bluez5,bluez5"
+
+.. _migration-1.8-kernel-build-changes:
+
+Kernel Build Changes
+--------------------
+
+The kernel build process was changed to place the source in a common
+shared work area and to place build artifacts separately in the source
+code tree. In theory, migration paths have been provided for most common
+usages in kernel recipes but this might not work in all cases. In
+particular, users need to ensure that ``${S}`` (source files) and
+``${B}`` (build artifacts) are used correctly in functions such as
+:ref:`ref-tasks-configure` and
+:ref:`ref-tasks-install`. For kernel recipes that do not
+inherit from ``kernel-yocto`` or include ``linux-yocto.inc``, you might
+wish to refer to the ``linux.inc`` file in the ``meta-oe`` layer for the
+kinds of changes you need to make. For reference, here is the
+`commit <http://cgit.openembedded.org/meta-openembedded/commit/meta-oe/recipes-kernel/linux/linux.inc?id=fc7132ede27ac67669448d3d2845ce7d46c6a1ee>`__
+where the ``linux.inc`` file in ``meta-oe`` was updated.
+
+Recipes that rely on the kernel source code and do not inherit the
+module classes might need to add explicit dependencies on the
+``do_shared_workdir`` kernel task, for example: ::
+
+   do_configure[depends] += "virtual/kernel:do_shared_workdir"
+
+.. _migration-1.8-ssl:
+
+SSL 3.0 is Now Disabled in OpenSSL
+----------------------------------
+
+SSL 3.0 is now disabled when building OpenSSL. Disabling SSL 3.0 avoids
+any lingering instances of the POODLE vulnerability. If you feel you
+must re-enable SSL 3.0, then you can add an append file (``*.bbappend``)
+for the ``openssl`` recipe to remove "-no-ssl3" from
+:term:`EXTRA_OECONF`.
+
+.. _migration-1.8-default-sysroot-poisoning:
+
+Default Sysroot Poisoning
+-------------------------
+
+``gcc's`` default sysroot and include directories are now "poisoned". In
+other words, the sysroot and include directories are being redirected to
+a non-existent location in order to catch when host directories are
+being used due to the correct options not being passed. This poisoning
+applies both to the cross-compiler used within the build and to the
+cross-compiler produced in the SDK.
+
+If this change causes something in the build to fail, it almost
+certainly means the various compiler flags and commands are not being
+passed correctly to the underlying piece of software. In such cases, you
+need to take corrective steps.
+
+.. _migration-1.8-rebuild-improvements:
+
+Rebuild Improvements
+--------------------
+
+Changes have been made to the :ref:`base <ref-classes-base>`,
+:ref:`autotools <ref-classes-autotools>`, and
+:ref:`cmake <ref-classes-cmake>` classes to clean out generated files
+when the :ref:`ref-tasks-configure` task needs to be
+re-executed.
+
+One of the improvements is to attempt to run "make clean" during the
+``do_configure`` task if a ``Makefile`` exists. Some software packages
+do not provide a working clean target within their make files. If you
+have such recipes, you need to set
+:term:`CLEANBROKEN` to "1" within the recipe, for example: ::
+
+   CLEANBROKEN = "1"
+
+.. _migration-1.8-qa-check-and-validation-changes:
+
+QA Check and Validation Changes
+-------------------------------
+
+The following QA Check and Validation Changes have occurred:
+
+-  Usage of ``PRINC`` previously triggered a warning. It now triggers an
+   error. You should remove any remaining usage of ``PRINC`` in any
+   recipe or append file.
+
+-  An additional QA check has been added to detect usage of ``${D}`` in
+   :term:`FILES` values where :term:`D` values
+   should not be used at all. The same check ensures that ``$D`` is used
+   in ``pkg_preinst/pkg_postinst/pkg_prerm/pkg_postrm`` functions
+   instead of ``${D}``.
+
+-  :term:`S` now needs to be set to a valid value within a
+   recipe. If ``S`` is not set in the recipe, the directory is not
+   automatically created. If ``S`` does not point to a directory that
+   exists at the time the :ref:`ref-tasks-unpack` task
+   finishes, a warning will be shown.
+
+-  :term:`LICENSE` is now validated for correct
+   formatting of multiple licenses. If the format is invalid (e.g.
+   multiple licenses are specified with no operators to specify how the
+   multiple licenses interact), then a warning will be shown.
+
+.. _migration-1.8-miscellaneous-changes:
+
+Miscellaneous Changes
+---------------------
+
+The following miscellaneous changes have occurred:
+
+-  The ``send-error-report`` script now expects a "-s" option to be
+   specified before the server address. This assumes a server address is
+   being specified.
+
+-  The ``oe-pkgdata-util`` script now expects a "-p" option to be
+   specified before the ``pkgdata`` directory, which is now optional. If
+   the ``pkgdata`` directory is not specified, the script will run
+   BitBake to query :term:`PKGDATA_DIR` from the
+   build environment.
+
+
diff --git a/documentation/ref-manual/migration-2.0.rst b/documentation/ref-manual/migration-2.0.rst
new file mode 100644
index 0000000000..570486ba00
--- /dev/null
+++ b/documentation/ref-manual/migration-2.0.rst
@@ -0,0 +1,281 @@
+Moving to the Yocto Project 2.0 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 2.0 Release from the prior release.
+
+.. _migration-2.0-gcc-5:
+
+GCC 5
+-----
+
+The default compiler is now GCC 5.2. This change has required fixes for
+compilation errors in a number of other recipes.
+
+One important example is a fix for when the Linux kernel freezes at boot
+time on ARM when built with GCC 5. If you are using your own kernel
+recipe or source tree and building for ARM, you will likely need to
+apply this
+`patch <https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit?id=a077224fd35b2f7fbc93f14cf67074fc792fbac2>`__.
+The standard ``linux-yocto`` kernel source tree already has a workaround
+for the same issue.
+
+For further details, see https://gcc.gnu.org/gcc-5/changes.html
+and the porting guide at
+https://gcc.gnu.org/gcc-5/porting_to.html.
+
+Alternatively, you can switch back to GCC 4.9 or 4.8 by setting
+``GCCVERSION`` in your configuration, as follows:
+::
+
+   GCCVERSION = "4.9%"
+
+.. _migration-2.0-Gstreamer-0.10-removed:
+
+Gstreamer 0.10 Removed
+----------------------
+
+Gstreamer 0.10 has been removed in favor of Gstreamer 1.x. As part of
+the change, recipes for Gstreamer 0.10 and related software are now
+located in ``meta-multimedia``. This change results in Qt4 having Phonon
+and Gstreamer support in QtWebkit disabled by default.
+
+.. _migration-2.0-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been moved or removed:
+
+-  ``bluez4``: The recipe is obsolete and has been moved due to
+   ``bluez5`` becoming fully integrated. The ``bluez4`` recipe now
+   resides in ``meta-oe``.
+
+-  ``gamin``: The recipe is obsolete and has been removed.
+
+-  ``gnome-icon-theme``: The recipe's functionally has been replaced by
+   ``adwaita-icon-theme``.
+
+-  Gstreamer 0.10 Recipes: Recipes for Gstreamer 0.10 have been removed
+   in favor of the recipes for Gstreamer 1.x.
+
+-  ``insserv``: The recipe is obsolete and has been removed.
+
+-  ``libunique``: The recipe is no longer used and has been moved to
+   ``meta-oe``.
+
+-  ``midori``: The recipe's functionally has been replaced by
+   ``epiphany``.
+
+-  ``python-gst``: The recipe is obsolete and has been removed since it
+   only contains bindings for Gstreamer 0.10.
+
+-  ``qt-mobility``: The recipe is obsolete and has been removed since it
+   requires ``Gstreamer 0.10``, which has been replaced.
+
+-  ``subversion``: All 1.6.x versions of this recipe have been removed.
+
+-  ``webkit-gtk``: The older 1.8.3 version of this recipe has been
+   removed in favor of ``webkitgtk``.
+
+.. _migration-2.0-bitbake-datastore-improvements:
+
+BitBake datastore improvements
+------------------------------
+
+The method by which BitBake's datastore handles overrides has changed.
+Overrides are now applied dynamically and ``bb.data.update_data()`` is
+now a no-op. Thus, ``bb.data.update_data()`` is no longer required in
+order to apply the correct overrides. In practice, this change is
+unlikely to require any changes to Metadata. However, these minor
+changes in behavior exist:
+
+-  All potential overrides are now visible in the variable history as
+   seen when you run the following:
+   ::
+
+      $ bitbake -e
+
+-  ``d.delVar('``\ VARNAME\ ``')`` and
+   ``d.setVar('``\ VARNAME\ ``', None)`` result in the variable and all
+   of its overrides being cleared out. Before the change, only the
+   non-overridden values were cleared.
+
+.. _migration-2.0-shell-message-function-changes:
+
+Shell Message Function Changes
+------------------------------
+
+The shell versions of the BitBake message functions (i.e. ``bbdebug``,
+``bbnote``, ``bbwarn``, ``bbplain``, ``bberror``, and ``bbfatal``) are
+now connected through to their BitBake equivalents ``bb.debug()``,
+``bb.note()``, ``bb.warn()``, ``bb.plain()``, ``bb.error()``, and
+``bb.fatal()``, respectively. Thus, those message functions that you
+would expect to be printed by the BitBake UI are now actually printed.
+In practice, this change means two things:
+
+-  If you now see messages on the console that you did not previously
+   see as a result of this change, you might need to clean up the calls
+   to ``bbwarn``, ``bberror``, and so forth. Or, you might want to
+   simply remove the calls.
+
+-  The ``bbfatal`` message function now suppresses the full error log in
+   the UI, which means any calls to ``bbfatal`` where you still wish to
+   see the full error log should be replaced by ``die`` or
+   ``bbfatal_log``.
+
+.. _migration-2.0-extra-development-debug-package-cleanup:
+
+Extra Development/Debug Package Cleanup
+---------------------------------------
+
+The following recipes have had extra ``dev/dbg`` packages removed:
+
+-  ``acl``
+
+-  ``apmd``
+
+-  ``aspell``
+
+-  ``attr``
+
+-  ``augeas``
+
+-  ``bzip2``
+
+-  ``cogl``
+
+-  ``curl``
+
+-  ``elfutils``
+
+-  ``gcc-target``
+
+-  ``libgcc``
+
+-  ``libtool``
+
+-  ``libxmu``
+
+-  ``opkg``
+
+-  ``pciutils``
+
+-  ``rpm``
+
+-  ``sysfsutils``
+
+-  ``tiff``
+
+-  ``xz``
+
+All of the above recipes now conform to the standard packaging scheme
+where a single ``-dev``, ``-dbg``, and ``-staticdev`` package exists per
+recipe.
+
+.. _migration-2.0-recipe-maintenance-tracking-data-moved-to-oe-core:
+
+Recipe Maintenance Tracking Data Moved to OE-Core
+-------------------------------------------------
+
+Maintenance tracking data for recipes that was previously part of
+``meta-yocto`` has been moved to :term:`OpenEmbedded-Core (OE-Core)`. The change
+includes ``package_regex.inc`` and ``distro_alias.inc``, which are
+typically enabled when using the ``distrodata`` class. Additionally, the
+contents of ``upstream_tracking.inc`` has now been split out to the
+relevant recipes.
+
+.. _migration-2.0-automatic-stale-sysroot-file-cleanup:
+
+Automatic Stale Sysroot File Cleanup
+------------------------------------
+
+Stale files from recipes that no longer exist in the current
+configuration are now automatically removed from sysroot as well as
+removed from any other place managed by shared state. This automatic
+cleanup means that the build system now properly handles situations such
+as renaming the build system side of recipes, removal of layers from
+``bblayers.conf``, and :term:`DISTRO_FEATURES`
+changes.
+
+Additionally, work directories for old versions of recipes are now
+pruned. If you wish to disable pruning old work directories, you can set
+the following variable in your configuration:
+::
+
+   SSTATE_PRUNE_OBSOLETEWORKDIR = "0"
+
+.. _migration-2.0-linux-yocto-kernel-metadata-repository-now-split-from-source:
+
+``linux-yocto`` Kernel Metadata Repository Now Split from Source
+----------------------------------------------------------------
+
+The ``linux-yocto`` tree has up to now been a combined set of kernel
+changes and configuration (meta) data carried in a single tree. While
+this format is effective at keeping kernel configuration and source
+modifications synchronized, it is not always obvious to developers how
+to manipulate the Metadata as compared to the source.
+
+Metadata processing has now been removed from the
+:ref:`kernel-yocto <ref-classes-kernel-yocto>` class and the external
+Metadata repository ``yocto-kernel-cache``, which has always been used
+to seed the ``linux-yocto`` "meta" branch. This separate ``linux-yocto``
+cache repository is now the primary location for this data. Due to this
+change, ``linux-yocto`` is no longer able to process combined trees.
+Thus, if you need to have your own combined kernel repository, you must
+do the split there as well and update your recipes accordingly. See the
+``meta/recipes-kernel/linux/linux-yocto_4.1.bb`` recipe for an example.
+
+.. _migration-2.0-additional-qa-checks:
+
+Additional QA checks
+--------------------
+
+The following QA checks have been added:
+
+-  Added a "host-user-contaminated" check for ownership issues for
+   packaged files outside of ``/home``. The check looks for files that
+   are incorrectly owned by the user that ran BitBake instead of owned
+   by a valid user in the target system.
+
+-  Added an "invalid-chars" check for invalid (non-UTF8) characters in
+   recipe metadata variable values (i.e.
+   :term:`DESCRIPTION`,
+   :term:`SUMMARY`, :term:`LICENSE`, and
+   :term:`SECTION`). Some package managers do not support
+   these characters.
+
+-  Added an "invalid-packageconfig" check for any options specified in
+   :term:`PACKAGECONFIG` that do not match any
+   ``PACKAGECONFIG`` option defined for the recipe.
+
+.. _migration-2.0-miscellaneous:
+
+Miscellaneous Changes
+---------------------
+
+These additional changes exist:
+
+-  ``gtk-update-icon-cache`` has been renamed to ``gtk-icon-utils``.
+
+-  The ``tools-profile`` :term:`IMAGE_FEATURES`
+   item as well as its corresponding packagegroup and
+   ``packagegroup-core-tools-profile`` no longer bring in ``oprofile``.
+   Bringing in ``oprofile`` was originally added to aid compilation on
+   resource-constrained targets. However, this aid has not been widely
+   used and is not likely to be used going forward due to the more
+   powerful target platforms and the existence of better
+   cross-compilation tools.
+
+-  The :term:`IMAGE_FSTYPES` variable's default
+   value now specifies ``ext4`` instead of ``ext3``.
+
+-  All support for the ``PRINC`` variable has been removed.
+
+-  The ``packagegroup-core-full-cmdline`` packagegroup no longer brings
+   in ``lighttpd`` due to the fact that bringing in ``lighttpd`` is not
+   really in line with the packagegroup's purpose, which is to add full
+   versions of command-line tools that by default are provided by
+   ``busybox``.
+
+
diff --git a/documentation/ref-manual/migration-2.1.rst b/documentation/ref-manual/migration-2.1.rst
new file mode 100644
index 0000000000..a1fd3ea81d
--- /dev/null
+++ b/documentation/ref-manual/migration-2.1.rst
@@ -0,0 +1,434 @@
+Moving to the Yocto Project 2.1 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 2.1 Release from the prior release.
+
+.. _migration-2.1-variable-expansion-in-python-functions:
+
+Variable Expansion in Python Functions
+--------------------------------------
+
+Variable expressions, such as ``${``\ VARNAME\ ``}`` no longer expand
+automatically within Python functions. Suppressing expansion was done to
+allow Python functions to construct shell scripts or other code for
+situations in which you do not want such expressions expanded. For any
+existing code that relies on these expansions, you need to change the
+expansions to expand the value of individual variables through
+``d.getVar()``. To alternatively expand more complex expressions, use
+``d.expand()``.
+
+.. _migration-2.1-overrides-must-now-be-lower-case:
+
+Overrides Must Now be Lower-Case
+--------------------------------
+
+The convention for overrides has always been for them to be lower-case
+characters. This practice is now a requirement as BitBake's datastore
+now assumes lower-case characters in order to give a slight performance
+boost during parsing. In practical terms, this requirement means that
+anything that ends up in :term:`OVERRIDES` must now
+appear in lower-case characters (e.g. values for ``MACHINE``,
+``TARGET_ARCH``, ``DISTRO``, and also recipe names if
+``_pn-``\ recipename overrides are to be effective).
+
+.. _migration-2.1-expand-parameter-to-getvar-and-getvarflag-now-mandatory:
+
+Expand Parameter to ``getVar()`` and ``getVarFlag()`` is Now Mandatory
+----------------------------------------------------------------------
+
+The expand parameter to ``getVar()`` and ``getVarFlag()`` previously
+defaulted to False if not specified. Now, however, no default exists so
+one must be specified. You must change any ``getVar()`` calls that do
+not specify the final expand parameter to calls that do specify the
+parameter. You can run the following ``sed`` command at the base of a
+layer to make this change:
+::
+
+   sed -e 's:\(\.getVar([^,()]*\)):\1, False):g' -i `grep -ril getVar *`
+   sed -e 's:\(\.getVarFlag([^,()]*,[^,()]*\)):\1, False):g' -i `grep -ril getVarFlag *`
+
+.. note::
+
+   The reason for this change is that it prepares the way for changing
+   the default to True in a future Yocto Project release. This future
+   change is a much more sensible default than False. However, the
+   change needs to be made gradually as a sudden change of the default
+   would potentially cause side-effects that would be difficult to
+   detect.
+
+.. _migration-2.1-makefile-environment-changes:
+
+Makefile Environment Changes
+----------------------------
+
+:term:`EXTRA_OEMAKE` now defaults to "" instead of
+"-e MAKEFLAGS=". Setting ``EXTRA_OEMAKE`` to "-e MAKEFLAGS=" by default
+was a historical accident that has required many classes (e.g.
+``autotools``, ``module``) and recipes to override this default in order
+to work with sensible build systems. When upgrading to the release, you
+must edit any recipe that relies upon this old default by either setting
+``EXTRA_OEMAKE`` back to "-e MAKEFLAGS=" or by explicitly setting any
+required variable value overrides using ``EXTRA_OEMAKE``, which is
+typically only needed when a Makefile sets a default value for a
+variable that is inappropriate for cross-compilation using the "="
+operator rather than the "?=" operator.
+
+.. _migration-2.1-libexecdir-reverted-to-prefix-libexec:
+
+``libexecdir`` Reverted to ``${prefix}/libexec``
+------------------------------------------------
+
+The use of ``${libdir}/${BPN}`` as ``libexecdir`` is different as
+compared to all other mainstream distributions, which either uses
+``${prefix}/libexec`` or ``${libdir}``. The use is also contrary to the
+GNU Coding Standards (i.e.
+https://www.gnu.org/prep/standards/html_node/Directory-Variables.html)
+that suggest ``${prefix}/libexec`` and also notes that any
+package-specific nesting should be done by the package itself. Finally,
+having ``libexecdir`` change between recipes makes it very difficult for
+different recipes to invoke binaries that have been installed into
+``libexecdir``. The Filesystem Hierarchy Standard (i.e.
+http://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s07.html) now
+recognizes the use of ``${prefix}/libexec/``, giving distributions the
+choice between ``${prefix}/lib`` or ``${prefix}/libexec`` without
+breaking FHS.
+
+.. _migration-2.1-ac-cv-sizeof-off-t-no-longer-cached-in-site-files:
+
+``ac_cv_sizeof_off_t`` is No Longer Cached in Site Files
+--------------------------------------------------------
+
+For recipes inheriting the :ref:`autotools <ref-classes-autotools>`
+class, ``ac_cv_sizeof_off_t`` is no longer cached in the site files for
+``autoconf``. The reason for this change is because the
+``ac_cv_sizeof_off_t`` value is not necessarily static per architecture
+as was previously assumed. Rather, the value changes based on whether
+large file support is enabled. For most software that uses ``autoconf``,
+this change should not be a problem. However, if you have a recipe that
+bypasses the standard :ref:`ref-tasks-configure` task
+from the ``autotools`` class and the software the recipe is building
+uses a very old version of ``autoconf``, the recipe might be incapable
+of determining the correct size of ``off_t`` during ``do_configure``.
+
+The best course of action is to patch the software as necessary to allow
+the default implementation from the ``autotools`` class to work such
+that ``autoreconf`` succeeds and produces a working configure script,
+and to remove the overridden ``do_configure`` task such that the default
+implementation does get used.
+
+.. _migration-2.1-image-generation-split-out-from-filesystem-generation:
+
+Image Generation is Now Split Out from Filesystem Generation
+------------------------------------------------------------
+
+Previously, for image recipes the :ref:`ref-tasks-rootfs`
+task assembled the filesystem and then from that filesystem generated
+images. With this Yocto Project release, image generation is split into
+separate ```do_image_*`` <#ref-tasks-image>`__ tasks for clarity both in
+operation and in the code.
+
+For most cases, this change does not present any problems. However, if
+you have made customizations that directly modify the ``do_rootfs`` task
+or that mention ``do_rootfs``, you might need to update those changes.
+In particular, if you had added any tasks after ``do_rootfs``, you
+should make edits so that those tasks are after the
+```do_image_complete`` <#ref-tasks-image-complete>`__ task rather than
+after ``do_rootfs`` so that the your added tasks run at the correct
+time.
+
+A minor part of this restructuring is that the post-processing
+definitions and functions have been moved from the
+:ref:`image <ref-classes-image>` class to the
+:ref:`rootfs-postcommands <ref-classes-rootfs*>` class. Functionally,
+however, they remain unchanged.
+
+.. _migration-2.1-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been removed in the 2.1 release:
+
+-  ``gcc`` version 4.8: Versions 4.9 and 5.3 remain.
+
+-  ``qt4``: All support for Qt 4.x has been moved out to a separate
+   ``meta-qt4`` layer because Qt 4 is no longer supported upstream.
+
+-  ``x11vnc``: Moved to the ``meta-oe`` layer.
+
+-  ``linux-yocto-3.14``: No longer supported.
+
+-  ``linux-yocto-3.19``: No longer supported.
+
+-  ``libjpeg``: Replaced by the ``libjpeg-turbo`` recipe.
+
+-  ``pth``: Became obsolete.
+
+-  ``liboil``: Recipe is no longer needed and has been moved to the
+   ``meta-multimedia`` layer.
+
+-  ``gtk-theme-torturer``: Recipe is no longer needed and has been moved
+   to the ``meta-gnome`` layer.
+
+-  ``gnome-mime-data``: Recipe is no longer needed and has been moved to
+   the ``meta-gnome`` layer.
+
+-  ``udev``: Replaced by the ``eudev`` recipe for compatibility when
+   using ``sysvinit`` with newer kernels.
+
+-  ``python-pygtk``: Recipe became obsolete.
+
+-  ``adt-installer``: Recipe became obsolete. See the "`ADT
+   Removed <#migration-2.1-adt-removed>`__" section for more
+   information.
+
+.. _migration-2.1-class-changes:
+
+Class Changes
+-------------
+
+The following classes have changed:
+
+-  ``autotools_stage``: Removed because the
+   :ref:`autotools <ref-classes-autotools>` class now provides its
+   functionality. Recipes that inherited from ``autotools_stage`` should
+   now inherit from ``autotools`` instead.
+
+-  ``boot-directdisk``: Merged into the ``image-vm`` class. The
+   ``boot-directdisk`` class was rarely directly used. Consequently,
+   this change should not cause any issues.
+
+-  ``bootimg``: Merged into the
+   :ref:`image-live <ref-classes-image-live>` class. The ``bootimg``
+   class was rarely directly used. Consequently, this change should not
+   cause any issues.
+
+-  ``packageinfo``: Removed due to its limited use by the Hob UI, which
+   has itself been removed.
+
+.. _migration-2.1-build-system-ui-changes:
+
+Build System User Interface Changes
+-----------------------------------
+
+The following changes have been made to the build system user interface:
+
+-  *Hob GTK+-based UI*: Removed because it is unmaintained and based on
+   the outdated GTK+ 2 library. The Toaster web-based UI is much more
+   capable and is actively maintained. See the
+   ":ref:`toaster-manual/toaster-manual-setup-and-use:using the toaster web interface`"
+   section in the Toaster User Manual for more information on this
+   interface.
+
+-  *"puccho" BitBake UI*: Removed because is unmaintained and no longer
+   useful.
+
+.. _migration-2.1-adt-removed:
+
+ADT Removed
+-----------
+
+The Application Development Toolkit (ADT) has been removed because its
+functionality almost completely overlapped with the :ref:`standard
+SDK <sdk-manual/sdk-using:using the standard sdk>` and the
+:ref:`extensible SDK <sdk-manual/sdk-extensible:using the extensible sdk>`. For
+information on these SDKs and how to build and use them, see the
+:doc:`../sdk-manual/sdk-manual` manual.
+
+.. note::
+
+   The Yocto Project Eclipse IDE Plug-in is still supported and is not
+   affected by this change.
+
+.. _migration-2.1-poky-reference-distribution-changes:
+
+Poky Reference Distribution Changes
+-----------------------------------
+
+The following changes have been made for the Poky distribution:
+
+-  The ``meta-yocto`` layer has been renamed to ``meta-poky`` to better
+   match its purpose, which is to provide the Poky reference
+   distribution. The ``meta-yocto-bsp`` layer retains its original name
+   since it provides reference machines for the Yocto Project and it is
+   otherwise unrelated to Poky. References to ``meta-yocto`` in your
+   ``conf/bblayers.conf`` should automatically be updated, so you should
+   not need to change anything unless you are relying on this naming
+   elsewhere.
+
+-  The :ref:`uninative <ref-classes-uninative>` class is now enabled
+   by default in Poky. This class attempts to isolate the build system
+   from the host distribution's C library and makes re-use of native
+   shared state artifacts across different host distributions practical.
+   With this class enabled, a tarball containing a pre-built C library
+   is downloaded at the start of the build.
+
+   The ``uninative`` class is enabled through the
+   ``meta/conf/distro/include/yocto-uninative.inc`` file, which for
+   those not using the Poky distribution, can include to easily enable
+   the same functionality.
+
+   Alternatively, if you wish to build your own ``uninative`` tarball,
+   you can do so by building the ``uninative-tarball`` recipe, making it
+   available to your build machines (e.g. over HTTP/HTTPS) and setting a
+   similar configuration as the one set by ``yocto-uninative.inc``.
+
+-  Static library generation, for most cases, is now disabled by default
+   in the Poky distribution. Disabling this generation saves some build
+   time as well as the size used for build output artifacts.
+
+   Disabling this library generation is accomplished through a
+   ``meta/conf/distro/include/no-static-libs.inc``, which for those not
+   using the Poky distribution can easily include to enable the same
+   functionality.
+
+   Any recipe that needs to opt-out of having the "--disable-static"
+   option specified on the configure command line either because it is
+   not a supported option for the configure script or because static
+   libraries are needed should set the following variable:
+   DISABLE_STATIC = ""
+
+-  The separate ``poky-tiny`` distribution now uses the musl C library
+   instead of a heavily pared down ``glibc``. Using musl results in a
+   smaller distribution and facilitates much greater maintainability
+   because musl is designed to have a small footprint.
+
+   If you have used ``poky-tiny`` and have customized the ``glibc``
+   configuration you will need to redo those customizations with musl
+   when upgrading to the new release.
+
+.. _migration-2.1-packaging-changes:
+
+Packaging Changes
+-----------------
+
+The following changes have been made to packaging:
+
+-  The ``runuser`` and ``mountpoint`` binaries, which were previously in
+   the main ``util-linux`` package, have been split out into the
+   ``util-linux-runuser`` and ``util-linux-mountpoint`` packages,
+   respectively.
+
+-  The ``python-elementtree`` package has been merged into the
+   ``python-xml`` package.
+
+.. _migration-2.1-tuning-file-changes:
+
+Tuning File Changes
+-------------------
+
+The following changes have been made to the tuning files:
+
+-  The "no-thumb-interwork" tuning feature has been dropped from the ARM
+   tune include files. Because interworking is required for ARM EABI,
+   attempting to disable it through a tuning feature no longer makes
+   sense.
+
+   .. note::
+
+      Support for ARM OABI was deprecated in gcc 4.7.
+
+-  The ``tune-cortexm*.inc`` and ``tune-cortexr4.inc`` files have been
+   removed because they are poorly tested. Until the OpenEmbedded build
+   system officially gains support for CPUs without an MMU, these tuning
+   files would probably be better maintained in a separate layer if
+   needed.
+
+.. _migration-2.1-supporting-gobject-introspection:
+
+Supporting GObject Introspection
+--------------------------------
+
+This release supports generation of GLib Introspective Repository (GIR)
+files through GObject introspection, which is the standard mechanism for
+accessing GObject-based software from runtime environments. You can
+enable, disable, and test the generation of this data. See the
+":ref:`dev-manual/dev-manual-common-tasks:enabling gobject introspection support`"
+section in the Yocto Project Development Tasks Manual for more
+information.
+
+.. _migration-2.1-miscellaneous-changes:
+
+Miscellaneous Changes
+---------------------
+
+These additional changes exist:
+
+-  The minimum Git version has been increased to 1.8.3.1. If your host
+   distribution does not provide a sufficiently recent version, you can
+   install the buildtools, which will provide it. See the "`Required
+   Git, tar, Python and gcc
+   Versions <#required-git-tar-python-and-gcc-versions>`__" section for
+   more information on the buildtools tarball.
+
+-  The buggy and incomplete support for the RPM version 4 package
+   manager has been removed. The well-tested and maintained support for
+   RPM version 5 remains.
+
+-  Previously, the following list of packages were removed if
+   package-management was not in
+   :term:`IMAGE_FEATURES`, regardless of any
+   dependencies:
+   ::
+
+      update-rc.d
+      base-passwd
+      shadow
+      update-alternatives
+
+   run-postinsts With the Yocto Project 2.1 release, these packages are
+   only removed if "read-only-rootfs" is in ``IMAGE_FEATURES``, since
+   they might still be needed for a read-write image even in the absence
+   of a package manager (e.g. if users need to be added, modified, or
+   removed at runtime).
+
+-  The
+   :ref:`devtool modify <sdk-manual/sdk-extensible:use \`\`devtool modify\`\` to modify the source of an existing component>`
+   command now defaults to extracting the source since that is most
+   commonly expected. The "-x" or "--extract" options are now no-ops. If
+   you wish to provide your own existing source tree, you will now need
+   to specify either the "-n" or "--no-extract" options when running
+   ``devtool modify``.
+
+-  If the formfactor for a machine is either not supplied or does not
+   specify whether a keyboard is attached, then the default is to assume
+   a keyboard is attached rather than assume no keyboard. This change
+   primarily affects the Sato UI.
+
+-  The ``.debug`` directory packaging is now automatic. If your recipe
+   builds software that installs binaries into directories other than
+   the standard ones, you no longer need to take care of setting
+   ``FILES_${PN}-dbg`` to pick up the resulting ``.debug`` directories
+   as these directories are automatically found and added.
+
+-  Inaccurate disk and CPU percentage data has been dropped from
+   ``buildstats`` output. This data has been replaced with
+   ``getrusage()`` data and corrected IO statistics. You will probably
+   need to update any custom code that reads the ``buildstats`` data.
+
+-  The ``meta/conf/distro/include/package_regex.inc`` is now deprecated.
+   The contents of this file have been moved to individual recipes.
+
+   .. note::
+
+      Because this file will likely be removed in a future Yocto Project
+      release, it is suggested that you remove any references to the
+      file that might be in your configuration.
+
+-  The ``v86d/uvesafb`` has been removed from the ``genericx86`` and
+   ``genericx86-64`` reference machines, which are provided by the
+   ``meta-yocto-bsp`` layer. Most modern x86 boards do not rely on this
+   file and it only adds kernel error messages during startup. If you do
+   still need to support ``uvesafb``, you can simply add ``v86d`` to
+   your image.
+
+-  Build sysroot paths are now removed from debug symbol files. Removing
+   these paths means that remote GDB using an unstripped build system
+   sysroot will no longer work (although this was never documented to
+   work). The supported method to accomplish something similar is to set
+   ``IMAGE_GEN_DEBUGFS`` to "1", which will generate a companion debug
+   image containing unstripped binaries and associated debug sources
+   alongside the image.
+
+
diff --git a/documentation/ref-manual/migration-2.2.rst b/documentation/ref-manual/migration-2.2.rst
new file mode 100644
index 0000000000..59d0eeeb9d
--- /dev/null
+++ b/documentation/ref-manual/migration-2.2.rst
@@ -0,0 +1,451 @@
+Moving to the Yocto Project 2.2 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 2.2 Release from the prior release.
+
+.. _migration-2.2-minimum-kernel-version:
+
+Minimum Kernel Version
+----------------------
+
+The minimum kernel version for the target system and for SDK is now
+3.2.0, due to the upgrade to ``glibc 2.24``. Specifically, for
+AArch64-based targets the version is 3.14. For Nios II-based targets,
+the minimum kernel version is 3.19.
+
+.. note::
+
+   For x86 and x86_64, you can reset
+   OLDEST_KERNEL
+   to anything down to 2.6.32 if desired.
+
+.. _migration-2.2-staging-directories-in-sysroot-simplified:
+
+Staging Directories in Sysroot Has Been Simplified
+--------------------------------------------------
+
+The way directories are staged in sysroot has been simplified and
+introduces the new :term:`SYSROOT_DIRS`,
+:term:`SYSROOT_DIRS_NATIVE`, and
+:term:`SYSROOT_DIRS_BLACKLIST`. See the
+`v2 patch series on the OE-Core Mailing
+List <http://lists.openembedded.org/pipermail/openembedded-core/2016-May/121365.html>`__
+for additional information.
+
+.. _migration-2.2-removal-of-old-images-from-tmp-deploy-now-enabled:
+
+Removal of Old Images and Other Files in ``tmp/deploy`` Now Enabled
+-------------------------------------------------------------------
+
+Removal of old images and other files in ``tmp/deploy/`` is now enabled
+by default due to a new staging method used for those files. As a result
+of this change, the ``RM_OLD_IMAGE`` variable is now redundant.
+
+.. _migration-2.2-python-changes:
+
+Python Changes
+--------------
+
+The following changes for Python occurred:
+
+.. _migration-2.2-bitbake-now-requires-python-3.4:
+
+BitBake Now Requires Python 3.4+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+BitBake requires Python 3.4 or greater.
+
+.. _migration-2.2-utf-8-locale-required-on-build-host:
+
+UTF-8 Locale Required on Build Host
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+A UTF-8 locale is required on the build host due to Python 3. Since
+C.UTF-8 is not a standard, the default is en_US.UTF-8.
+
+.. _migration-2.2-metadata-now-must-use-python-3-syntax:
+
+Metadata Must Now Use Python 3 Syntax
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The metadata is now required to use Python 3 syntax. For help preparing
+metadata, see any of the many Python 3 porting guides available.
+Alternatively, you can reference the conversion commits for Bitbake and
+you can use :term:`OpenEmbedded-Core (OE-Core)` as a guide for changes. Following are
+particular areas of interest:
+
+  - subprocess command-line pipes needing locale decoding
+
+  - the syntax for octal values changed
+
+  - the ``iter*()`` functions changed name \* iterators now return views, not lists
+
+  - changed names for Python modules
+
+.. _migration-2.2-target-python-recipes-switched-to-python-3:
+
+Target Python Recipes Switched to Python 3
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Most target Python recipes have now been switched to Python 3.
+Unfortunately, systems using RPM as a package manager and providing
+online package-manager support through SMART still require Python 2.
+
+.. note::
+
+   Python 2 and recipes that use it can still be built for the target as
+   with previous versions.
+
+.. _migration-2.2-buildtools-tarball-includes-python-3:
+
+``buildtools-tarball`` Includes Python 3
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``buildtools-tarball`` now includes Python 3.
+
+.. _migration-2.2-uclibc-replaced-by-musl:
+
+uClibc Replaced by musl
+-----------------------
+
+uClibc has been removed in favor of musl. Musl has matured, is better
+maintained, and is compatible with a wider range of applications as
+compared to uClibc.
+
+.. _migration-2.2-B-no-longer-default-working-directory-for-tasks:
+
+``${B}`` No Longer Default Working Directory for Tasks
+------------------------------------------------------
+
+``${``\ :term:`B`\ ``}`` is no longer the default working
+directory for tasks. Consequently, any custom tasks you define now need
+to either have the
+``[``\ :ref:`dirs <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:variable flags>`\ ``]`` flag
+set, or the task needs to change into the appropriate working directory
+manually (e.g using ``cd`` for a shell task).
+
+.. note::
+
+   The preferred method is to use the
+   [dirs]
+   flag.
+
+.. _migration-2.2-runqemu-ported-to-python:
+
+``runqemu`` Ported to Python
+----------------------------
+
+``runqemu`` has been ported to Python and has changed behavior in some
+cases. Previous usage patterns continue to be supported.
+
+The new ``runqemu`` is a Python script. Machine knowledge is no longer
+hardcoded into ``runqemu``. You can choose to use the ``qemuboot``
+configuration file to define the BSP's own arguments and to make it
+bootable with ``runqemu``. If you use a configuration file, use the
+following form:
+::
+
+   image-name-machine.qemuboot.conf
+
+The configuration file
+enables fine-grained tuning of options passed to QEMU without the
+``runqemu`` script hard-coding any knowledge about different machines.
+Using a configuration file is particularly convenient when trying to use
+QEMU with machines other than the ``qemu*`` machines in
+:term:`OpenEmbedded-Core (OE-Core)`. The ``qemuboot.conf`` file is generated by the
+``qemuboot`` class when the root filesystem is being build (i.e. build
+rootfs). QEMU boot arguments can be set in BSP's configuration file and
+the ``qemuboot`` class will save them to ``qemuboot.conf``.
+
+If you want to use ``runqemu`` without a configuration file, use the
+following command form:
+::
+
+   $ runqemu machine rootfs kernel [options]
+
+Supported machines are as follows:
+
+  - qemuarm
+  - qemuarm64
+  - qemux86
+  - qemux86-64
+  - qemuppc
+  - qemumips
+  - qemumips64
+  - qemumipsel
+  - qemumips64el
+
+Consider the
+following example, which uses the ``qemux86-64`` machine, provides a
+root filesystem, provides an image, and uses the ``nographic`` option: ::
+
+   $ runqemu qemux86-64 tmp/deploy/images/qemux86-64/core-image-minimal-qemux86-64.ext4 tmp/deploy/images/qemux86-64/bzImage nographic
+
+Following is a list of variables that can be set in configuration files
+such as ``bsp.conf`` to enable the BSP to be booted by ``runqemu``:
+
+.. note::
+
+   "QB" means "QEMU Boot".
+
+::
+
+   QB_SYSTEM_NAME: QEMU name (e.g. "qemu-system-i386")
+   QB_OPT_APPEND: Options to append to QEMU (e.g. "-show-cursor")
+   QB_DEFAULT_KERNEL: Default kernel to boot (e.g. "bzImage")
+   QB_DEFAULT_FSTYPE: Default FSTYPE to boot (e.g. "ext4")
+   QB_MEM: Memory (e.g. "-m 512")
+   QB_MACHINE: QEMU machine (e.g. "-machine virt")
+   QB_CPU: QEMU cpu (e.g. "-cpu qemu32")
+   QB_CPU_KVM: Similar to QB_CPU except used for kvm support (e.g. "-cpu kvm64")
+   QB_KERNEL_CMDLINE_APPEND: Options to append to the kernel's -append
+                             option (e.g. "console=ttyS0 console=tty")
+   QB_DTB: QEMU dtb name
+   QB_AUDIO_DRV: QEMU audio driver (e.g. "alsa", set it when support audio)
+   QB_AUDIO_OPT: QEMU audio option (e.g. "-soundhw ac97,es1370"), which is used
+                 when QB_AUDIO_DRV is set.
+   QB_KERNEL_ROOT: Kernel's root (e.g. /dev/vda)
+   QB_TAP_OPT: Network option for 'tap' mode (e.g.
+               "-netdev tap,id=net0,ifname=@TAP@,script=no,downscript=no -device virtio-net-device,netdev=net0").
+                runqemu will replace "@TAP@" with the one that is used, such as tap0, tap1 ...
+   QB_SLIRP_OPT: Network option for SLIRP mode (e.g. "-netdev user,id=net0 -device virtio-net-device,netdev=net0")
+   QB_ROOTFS_OPT: Used as rootfs (e.g.
+                  "-drive id=disk0,file=@ROOTFS@,if=none,format=raw -device virtio-blk-device,drive=disk0").
+                  runqemu will replace "@ROOTFS@" with the one which is used, such as
+                  core-image-minimal-qemuarm64.ext4.
+   QB_SERIAL_OPT: Serial port (e.g. "-serial mon:stdio")
+   QB_TCPSERIAL_OPT: tcp serial port option (e.g.
+                     " -device virtio-serial-device -chardev socket,id=virtcon,port=@PORT@,host=127.0.0.1 -device      virtconsole,chardev=virtcon"
+                     runqemu will replace "@PORT@" with the port number which is used.
+
+To use ``runqemu``, set :term:`IMAGE_CLASSES` as
+follows and run ``runqemu``:
+
+.. note::
+
+   For command-line syntax, use
+   runqemu help
+   .
+
+::
+
+   IMAGE_CLASSES += "qemuboot"
+
+.. _migration-2.2-default-linker-hash-style-changed:
+
+Default Linker Hash Style Changed
+---------------------------------
+
+The default linker hash style for ``gcc-cross`` is now "sysv" in order
+to catch recipes that are building software without using the
+OpenEmbedded :term:`LDFLAGS`. This change could result in
+seeing some "No GNU_HASH in the elf binary" QA issues when building such
+recipes. You need to fix these recipes so that they use the expected
+``LDFLAGS``. Depending on how the software is built, the build system
+used by the software (e.g. a Makefile) might need to be patched.
+However, sometimes making this fix is as simple as adding the following
+to the recipe:
+::
+
+   TARGET_CC_ARCH += "${LDFLAGS}"
+
+.. _migration-2.2-kernel-image-base-name-no-longer-uses-kernel-imagetype:
+
+``KERNEL_IMAGE_BASE_NAME`` no Longer Uses ``KERNEL_IMAGETYPE``
+--------------------------------------------------------------
+
+The ``KERNEL_IMAGE_BASE_NAME`` variable no longer uses the
+:term:`KERNEL_IMAGETYPE` variable to create the
+image's base name. Because the OpenEmbedded build system can now build
+multiple kernel image types, this part of the kernel image base name as
+been removed leaving only the following:
+::
+
+   KERNEL_IMAGE_BASE_NAME ?= "${PKGE}-${PKGV}-${PKGR}-${MACHINE}-${DATETIME}"
+
+If you have recipes or
+classes that use ``KERNEL_IMAGE_BASE_NAME`` directly, you might need to
+update the references to ensure they continue to work.
+
+.. _migration-2.2-bitbake-changes:
+
+BitBake Changes
+---------------
+
+The following changes took place for BitBake:
+
+-  The "goggle" UI and standalone image-writer tool have been removed as
+   they both require GTK+ 2.0 and were not being maintained.
+
+-  The Perforce fetcher now supports :term:`SRCREV` for
+   specifying the source revision to use, be it
+   ``${``\ :term:`AUTOREV`\ ``}``, changelist number,
+   p4date, or label, in preference to separate
+   :term:`SRC_URI` parameters to specify these. This
+   change is more in-line with how the other fetchers work for source
+   control systems. Recipes that fetch from Perforce will need to be
+   updated to use ``SRCREV`` in place of specifying the source revision
+   within ``SRC_URI``.
+
+-  Some of BitBake's internal code structures for accessing the recipe
+   cache needed to be changed to support the new multi-configuration
+   functionality. These changes will affect external tools that use
+   BitBake's tinfoil module. For information on these changes, see the
+   changes made to the scripts supplied with OpenEmbedded-Core:
+   `1 <http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=189371f8393971d00bca0fceffd67cc07784f6ee>`__
+   and
+   `2 <http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=4a5aa7ea4d07c2c90a1654b174873abb018acc67>`__.
+
+-  The task management code has been rewritten to avoid using ID
+   indirection in order to improve performance. This change is unlikely
+   to cause any problems for most users. However, the setscene
+   verification function as pointed to by
+   ``BB_SETSCENE_VERIFY_FUNCTION`` needed to change signature.
+   Consequently, a new variable named ``BB_SETSCENE_VERIFY_FUNCTION2``
+   has been added allowing multiple versions of BitBake to work with
+   suitably written metadata, which includes OpenEmbedded-Core and Poky.
+   Anyone with custom BitBake task scheduler code might also need to
+   update the code to handle the new structure.
+
+.. _migration-2.2-swabber-has-been-removed:
+
+Swabber has Been Removed
+------------------------
+
+Swabber, a tool that was intended to detect host contamination in the
+build process, has been removed, as it has been unmaintained and unused
+for some time and was never particularly effective. The OpenEmbedded
+build system has since incorporated a number of mechanisms including
+enhanced QA checks that mean that there is less of a need for such a
+tool.
+
+.. _migration-2.2-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been removed:
+
+-  ``augeas``: No longer needed and has been moved to ``meta-oe``.
+
+-  ``directfb``: Unmaintained and has been moved to ``meta-oe``.
+
+-  ``gcc``: Removed 4.9 version. Versions 5.4 and 6.2 are still present.
+
+-  ``gnome-doc-utils``: No longer needed.
+
+-  ``gtk-doc-stub``: Replaced by ``gtk-doc``.
+
+-  ``gtk-engines``: No longer needed and has been moved to
+   ``meta-gnome``.
+
+-  ``gtk-sato-engine``: Became obsolete.
+
+-  ``libglade``: No longer needed and has been moved to ``meta-oe``.
+
+-  ``libmad``: Unmaintained and functionally replaced by ``libmpg123``.
+   ``libmad`` has been moved to ``meta-oe``.
+
+-  ``libowl``: Became obsolete.
+
+-  ``libxsettings-client``: No longer needed.
+
+-  ``oh-puzzles``: Functionally replaced by ``puzzles``.
+
+-  ``oprofileui``: Became obsolete. OProfile has been largely supplanted
+   by perf.
+
+-  ``packagegroup-core-directfb.bb``: Removed.
+
+-  ``core-image-directfb.bb``: Removed.
+
+-  ``pointercal``: No longer needed and has been moved to ``meta-oe``.
+
+-  ``python-imaging``: No longer needed and moved to ``meta-python``
+
+-  ``python-pyrex``: No longer needed and moved to ``meta-python``.
+
+-  ``sato-icon-theme``: Became obsolete.
+
+-  ``swabber-native``: Swabber has been removed. See the `entry on
+   Swabber <#migration-2.2-swabber-has-been-removed>`__.
+
+-  ``tslib``: No longer needed and has been moved to ``meta-oe``.
+
+-  ``uclibc``: Removed in favor of musl.
+
+-  ``xtscal``: No longer needed and moved to ``meta-oe``
+
+.. _migration-2.2-removed-classes:
+
+Removed Classes
+---------------
+
+The following classes have been removed:
+
+-  ``distutils-native-base``: No longer needed.
+
+-  ``distutils3-native-base``: No longer needed.
+
+-  ``sdl``: Only set :term:`DEPENDS` and
+   :term:`SECTION`, which are better set within the
+   recipe instead.
+
+-  ``sip``: Mostly unused.
+
+-  ``swabber``: See the `entry on
+   Swabber <#migration-2.2-swabber-has-been-removed>`__.
+
+.. _migration-2.2-minor-packaging-changes:
+
+Minor Packaging Changes
+-----------------------
+
+The following minor packaging changes have occurred:
+
+-  ``grub``: Split ``grub-editenv`` into its own package.
+
+-  ``systemd``: Split container and vm related units into a new package,
+   systemd-container.
+
+-  ``util-linux``: Moved ``prlimit`` to a separate
+   ``util-linux-prlimit`` package.
+
+.. _migration-2.2-miscellaneous-changes:
+
+Miscellaneous Changes
+---------------------
+
+The following miscellaneous changes have occurred:
+
+-  ``package_regex.inc``: Removed because the definitions
+   ``package_regex.inc`` previously contained have been moved to their
+   respective recipes.
+
+-  Both ``devtool add`` and ``recipetool create`` now use a fixed
+   :term:`SRCREV` by default when fetching from a Git
+   repository. You can override this in either case to use
+   ``${``\ :term:`AUTOREV`\ ``}`` instead by using the
+   ``-a`` or ``DASHDASHautorev`` command-line option
+
+-  ``distcc``: GTK+ UI is now disabled by default.
+
+-  ``packagegroup-core-tools-testapps``: Removed Piglit.
+
+-  ``image.bbclass``: Renamed COMPRESS(ION) to CONVERSION. This change
+   means that ``COMPRESSIONTYPES``, ``COMPRESS_DEPENDS`` and
+   ``COMPRESS_CMD`` are deprecated in favor of ``CONVERSIONTYPES``,
+   ``CONVERSION_DEPENDS`` and ``CONVERSION_CMD``. The ``COMPRESS*``
+   variable names will still work in the 2.2 release but metadata that
+   does not need to be backwards-compatible should be changed to use the
+   new names as the ``COMPRESS*`` ones will be removed in a future
+   release.
+
+-  ``gtk-doc``: A full version of ``gtk-doc`` is now made available.
+   However, some old software might not be capable of using the current
+   version of ``gtk-doc`` to build documentation. You need to change
+   recipes that build such software so that they explicitly disable
+   building documentation with ``gtk-doc``.
+
+
diff --git a/documentation/ref-manual/migration-2.3.rst b/documentation/ref-manual/migration-2.3.rst
new file mode 100644
index 0000000000..7f34f0cd75
--- /dev/null
+++ b/documentation/ref-manual/migration-2.3.rst
@@ -0,0 +1,530 @@
+Moving to the Yocto Project 2.3 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 2.3 Release from the prior release.
+
+.. _migration-2.3-recipe-specific-sysroots:
+
+Recipe-specific Sysroots
+------------------------
+
+The OpenEmbedded build system now uses one sysroot per recipe to resolve
+long-standing issues with configuration script auto-detection of
+undeclared dependencies. Consequently, you might find that some of your
+previously written custom recipes are missing declared dependencies,
+particularly those dependencies that are incidentally built earlier in a
+typical build process and thus are already likely to be present in the
+shared sysroot in previous releases.
+
+Consider the following:
+
+-  *Declare Build-Time Dependencies:* Because of this new feature, you
+   must explicitly declare all build-time dependencies for your recipe.
+   If you do not declare these dependencies, they are not populated into
+   the sysroot for the recipe.
+
+-  *Specify Pre-Installation and Post-Installation Native Tool
+   Dependencies:* You must specifically specify any special native tool
+   dependencies of ``pkg_preinst`` and ``pkg_postinst`` scripts by using
+   the :term:`PACKAGE_WRITE_DEPS` variable.
+   Specifying these dependencies ensures that these tools are available
+   if these scripts need to be run on the build host during the
+   :ref:`ref-tasks-rootfs` task.
+
+   As an example, see the ``dbus`` recipe. You will see that this recipe
+   has a ``pkg_postinst`` that calls ``systemctl`` if "systemd" is in
+   :term:`DISTRO_FEATURES`. In the example,
+   ``systemd-systemctl-native`` is added to ``PACKAGE_WRITE_DEPS``,
+   which is also conditional on "systemd" being in ``DISTRO_FEATURES``.
+
+-  Examine Recipes that Use ``SSTATEPOSTINSTFUNCS``: You need to
+   examine any recipe that uses ``SSTATEPOSTINSTFUNCS`` and determine
+   steps to take.
+
+   Functions added to ``SSTATEPOSTINSTFUNCS`` are still called as they
+   were in previous Yocto Project releases. However, since a separate
+   sysroot is now being populated for every recipe and if existing
+   functions being called through ``SSTATEPOSTINSTFUNCS`` are doing
+   relocation, then you will need to change these to use a
+   post-installation script that is installed by a function added to
+   :term:`SYSROOT_PREPROCESS_FUNCS`.
+
+   For an example, see the ``pixbufcache`` class in ``meta/classes/`` in
+   the :ref:`overview-manual/overview-manual-development-environment:yocto project source repositories`.
+
+   .. note::
+
+      The
+      SSTATEPOSTINSTFUNCS
+      variable itself is now deprecated in favor of the
+      do_populate_sysroot[postfuncs]
+      task. Consequently, if you do still have any function or functions
+      that need to be called after the sysroot component is created for
+      a recipe, then you would be well advised to take steps to use a
+      post installation script as described previously. Taking these
+      steps prepares your code for when
+      SSTATEPOSTINSTFUNCS
+      is removed in a future Yocto Project release.
+
+-  *Specify the Sysroot when Using Certain External Scripts:* Because
+   the shared sysroot is now gone, the scripts
+   ``oe-find-native-sysroot`` and ``oe-run-native`` have been changed
+   such that you need to specify which recipe's
+   :term:`STAGING_DIR_NATIVE` is used.
+
+.. note::
+
+   You can find more information on how recipe-specific sysroots work in
+   the "
+   staging.bbclass
+   " section.
+
+.. _migration-2.3-path-variable:
+
+``PATH`` Variable
+-----------------
+
+Within the environment used to run build tasks, the environment variable
+``PATH`` is now sanitized such that the normal native binary paths
+(``/bin``, ``/sbin``, ``/usr/bin`` and so forth) are removed and a
+directory containing symbolic links linking only to the binaries from
+the host mentioned in the :term:`HOSTTOOLS` and
+:term:`HOSTTOOLS_NONFATAL` variables is added
+to ``PATH``.
+
+Consequently, any native binaries provided by the host that you need to
+call needs to be in one of these two variables at the configuration
+level.
+
+Alternatively, you can add a native recipe (i.e. ``-native``) that
+provides the binary to the recipe's :term:`DEPENDS`
+value.
+
+.. note::
+
+   PATH
+   is not sanitized in the same way within
+   devshell
+   . If it were, you would have difficulty running host tools for
+   development and debugging within the shell.
+
+.. _migration-2.3-scripts:
+
+Changes to Scripts
+------------------
+
+The following changes to scripts took place:
+
+-  ``oe-find-native-sysroot``: The usage for the
+   ``oe-find-native-sysroot`` script has changed to the following:
+   ::
+
+      $ . oe-find-native-sysroot recipe
+
+   You must now supply a recipe for recipe
+   as part of the command. Prior to the Yocto Project &DISTRO; release, it
+   was not necessary to provide the script with the command.
+
+-  ``oe-run-native``: The usage for the ``oe-run-native`` script has
+   changed to the following:
+   ::
+
+      $ oe-run-native native_recipe tool
+
+   You must
+   supply the name of the native recipe and the tool you want to run as
+   part of the command. Prior to the Yocto Project DISTRO release, it
+   was not necessary to provide the native recipe with the command.
+
+-  ``cleanup-workdir``: The ``cleanup-workdir`` script has been
+   removed because the script was found to be deleting files it should
+   not have, which lead to broken build trees. Rather than trying to
+   delete portions of :term:`TMPDIR` and getting it wrong,
+   it is recommended that you delete ``TMPDIR`` and have it restored
+   from shared state (sstate) on subsequent builds.
+
+-  ``wipe-sysroot``: The ``wipe-sysroot`` script has been removed as
+   it is no longer needed with recipe-specific sysroots.
+
+.. _migration-2.3-functions:
+
+Changes to Functions
+--------------------
+
+The previously deprecated ``bb.data.getVar()``, ``bb.data.setVar()``,
+and related functions have been removed in favor of ``d.getVar()``,
+``d.setVar()``, and so forth.
+
+You need to fix any references to these old functions.
+
+.. _migration-2.3-bitbake-changes:
+
+BitBake Changes
+---------------
+
+The following changes took place for BitBake:
+
+-  *BitBake's Graphical Dependency Explorer UI Replaced:* BitBake's
+   graphical dependency explorer UI ``depexp`` was replaced by
+   ``taskexp`` ("Task Explorer"), which provides a graphical way of
+   exploring the ``task-depends.dot`` file. The data presented by Task
+   Explorer is much more accurate than the data that was presented by
+   ``depexp``. Being able to visualize the data is an often requested
+   feature as standard ``*.dot`` file viewers cannot usual cope with the
+   size of the ``task-depends.dot`` file.
+
+-  *BitBake "-g" Output Changes:* The ``package-depends.dot`` and
+   ``pn-depends.dot`` files as previously generated using the
+   ``bitbake -g`` command have been removed. A ``recipe-depends.dot``
+   file is now generated as a collapsed version of ``task-depends.dot``
+   instead.
+
+   The reason for this change is because ``package-depends.dot`` and
+   ``pn-depends.dot`` largely date back to a time before task-based
+   execution and do not take into account task-level dependencies
+   between recipes, which could be misleading.
+
+-  *Mirror Variable Splitting Changes:* Mirror variables including
+   :term:`MIRRORS`, :term:`PREMIRRORS`,
+   and :term:`SSTATE_MIRRORS` can now separate
+   values entirely with spaces. Consequently, you no longer need "\\n".
+   BitBake looks for pairs of values, which simplifies usage. There
+   should be no change required to existing mirror variable values
+   themselves.
+
+-  *The Subversion (SVN) Fetcher Uses an "ssh" Parameter and Not an
+   "rsh" Parameter:* The SVN fetcher now takes an "ssh" parameter
+   instead of an "rsh" parameter. This new optional parameter is used
+   when the "protocol" parameter is set to "svn+ssh". You can only use
+   the new parameter to specify the ``ssh`` program used by SVN. The SVN
+   fetcher passes the new parameter through the ``SVN_SSH`` environment
+   variable during the :ref:`ref-tasks-fetch` task.
+
+   See the ":ref:`bitbake:svn-fetcher`"
+   section in the BitBake
+   User Manual for additional information.
+
+-  ``BB_SETSCENE_VERIFY_FUNCTION`` and ``BB_SETSCENE_VERIFY_FUNCTION2``
+   Removed: Because the mechanism they were part of is no longer
+   necessary with recipe-specific sysroots, the
+   ``BB_SETSCENE_VERIFY_FUNCTION`` and ``BB_SETSCENE_VERIFY_FUNCTION2``
+   variables have been removed.
+
+.. _migration-2.3-absolute-symlinks:
+
+Absolute Symbolic Links
+-----------------------
+
+Absolute symbolic links (symlinks) within staged files are no longer
+permitted and now trigger an error. Any explicit creation of symlinks
+can use the ``lnr`` script, which is a replacement for ``ln -r``.
+
+If the build scripts in the software that the recipe is building are
+creating a number of absolute symlinks that need to be corrected, you
+can inherit ``relative_symlinks`` within the recipe to turn those
+absolute symlinks into relative symlinks.
+
+.. _migration-2.3-gplv2-and-gplv3-moves:
+
+GPLv2 Versions of GPLv3 Recipes Moved
+-------------------------------------
+
+Older GPLv2 versions of GPLv3 recipes have moved to a separate
+``meta-gplv2`` layer.
+
+If you use :term:`INCOMPATIBLE_LICENSE` to
+exclude GPLv3 or set :term:`PREFERRED_VERSION`
+to substitute a GPLv2 version of a GPLv3 recipe, then you must add the
+``meta-gplv2`` layer to your configuration.
+
+.. note::
+
+   You can find
+   meta-gplv2
+   layer in the OpenEmbedded layer index at
+   .
+
+These relocated GPLv2 recipes do not receive the same level of
+maintenance as other core recipes. The recipes do not get security fixes
+and upstream no longer maintains them. In fact, the upstream community
+is actively hostile towards people that use the old versions of the
+recipes. Moving these recipes into a separate layer both makes the
+different needs of the recipes clearer and clearly identifies the number
+of these recipes.
+
+.. note::
+
+   The long-term solution might be to move to BSD-licensed replacements
+   of the GPLv3 components for those that need to exclude GPLv3-licensed
+   components from the target system. This solution will be investigated
+   for future Yocto Project releases.
+
+.. _migration-2.3-package-management-changes:
+
+Package Management Changes
+--------------------------
+
+The following package management changes took place:
+
+-  Smart package manager is replaced by DNF package manager. Smart has
+   become unmaintained upstream, is not ported to Python 3.x.
+   Consequently, Smart needed to be replaced. DNF is the only feasible
+   candidate.
+
+   The change in functionality is that the on-target runtime package
+   management from remote package feeds is now done with a different
+   tool that has a different set of command-line options. If you have
+   scripts that call the tool directly, or use its API, they need to be
+   fixed.
+
+   For more information, see the `DNF
+   Documentation <http://dnf.readthedocs.io/en/latest/>`__.
+
+-  Rpm 5.x is replaced with Rpm 4.x. This is done for two major reasons:
+
+   -  DNF is API-incompatible with Rpm 5.x and porting it and
+      maintaining the port is non-trivial.
+
+   -  Rpm 5.x itself has limited maintenance upstream, and the Yocto
+      Project is one of the very few remaining users.
+
+-  Berkeley DB 6.x is removed and Berkeley DB 5.x becomes the default:
+
+   -  Version 6.x of Berkeley DB has largely been rejected by the open
+      source community due to its AGPLv3 license. As a result, most
+      mainstream open source projects that require DB are still
+      developed and tested with DB 5.x.
+
+   -  In OE-core, the only thing that was requiring DB 6.x was Rpm 5.x.
+      Thus, no reason exists to continue carrying DB 6.x in OE-core.
+
+-  ``createrepo`` is replaced with ``createrepo_c``.
+
+   ``createrepo_c`` is the current incarnation of the tool that
+   generates remote repository metadata. It is written in C as compared
+   to ``createrepo``, which is written in Python. ``createrepo_c`` is
+   faster and is maintained.
+
+-  Architecture-independent RPM packages are "noarch" instead of "all".
+
+   This change was made because too many places in DNF/RPM4 stack
+   already make that assumption. Only the filenames and the architecture
+   tag has changed. Nothing else has changed in OE-core system,
+   particularly in the :ref:`allarch.bbclass <ref-classes-allarch>`
+   class.
+
+-  Signing of remote package feeds using ``PACKAGE_FEED_SIGN`` is not
+   currently supported. This issue will be fully addressed in a future
+   Yocto Project release. See `defect
+   11209 <https://bugzilla.yoctoproject.org/show_bug.cgi?id=11209>`__
+   for more information on a solution to package feed signing with RPM
+   in the Yocto Project 2.3 release.
+
+-  OPKG now uses the libsolv backend for resolving package dependencies
+   by default. This is vastly superior to OPKG's internal ad-hoc solver
+   that was previously used. This change does have a small impact on
+   disk (around 500 KB) and memory footprint.
+
+   .. note::
+
+      For further details on this change, see the
+      commit message
+      .
+
+.. _migration-2.3-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been removed:
+
+-  ``linux-yocto 4.8``: Version 4.8 has been removed. Versions 4.1
+   (LTSI), 4.4 (LTS), 4.9 (LTS/LTSI) and 4.10 are now present.
+
+-  ``python-smartpm``: Functionally replaced by ``dnf``.
+
+-  ``createrepo``: Replaced by the ``createrepo-c`` recipe.
+
+-  ``rpmresolve``: No longer needed with the move to RPM 4 as RPM
+   itself is used instead.
+
+-  ``gstreamer``: Removed the GStreamer Git version recipes as they
+   have been stale. ``1.10.``\ x recipes are still present.
+
+-  ``alsa-conf-base``: Merged into ``alsa-conf`` since ``libasound``
+   depended on both. Essentially, no way existed to install only one of
+   these.
+
+-  ``tremor``: Moved to ``meta-multimedia``. Fixed-integer Vorbis
+   decoding is not needed by current hardware. Thus, GStreamer's ivorbis
+   plugin has been disabled by default eliminating the need for the
+   ``tremor`` recipe in :term:`OpenEmbedded-Core (OE-Core)`.
+
+-  ``gummiboot``: Replaced by ``systemd-boot``.
+
+.. _migration-2.3-wic-changes:
+
+Wic Changes
+-----------
+
+The following changes have been made to Wic:
+
+.. note::
+
+   For more information on Wic, see the "
+   Creating Partitioned Images Using Wic
+   " section in the Yocto Project Development Tasks Manual.
+
+-  *Default Output Directory Changed:* Wic's default output directory is
+   now the current directory by default instead of the unusual
+   ``/var/tmp/wic``.
+
+   The "-o" and "--outdir" options remain unchanged and are used to
+   specify your preferred output directory if you do not want to use the
+   default directory.
+
+-  *fsimage Plug-in Removed:* The Wic fsimage plugin has been removed as
+   it duplicates functionality of the rawcopy plugin.
+
+.. _migration-2.3-qa-changes:
+
+QA Changes
+----------
+
+The following QA checks have changed:
+
+-  ``unsafe-references-in-binaries``: The
+   ``unsafe-references-in-binaries`` QA check, which was disabled by
+   default, has now been removed. This check was intended to detect
+   binaries in ``/bin`` that link to libraries in ``/usr/lib`` and have
+   the case where the user has ``/usr`` on a separate filesystem to
+   ``/``.
+
+   The removed QA check was buggy. Additionally, ``/usr`` residing on a
+   separate partition from ``/`` is now a rare configuration.
+   Consequently, ``unsafe-references-in-binaries`` was removed.
+
+-  ``file-rdeps``: The ``file-rdeps`` QA check is now an error by
+   default instead of a warning. Because it is an error instead of a
+   warning, you need to address missing runtime dependencies.
+
+   For additional information, see the
+   :ref:`insane <ref-classes-insane>` class and the "`Errors and
+   Warnings <#qa-errors-and-warnings>`__" section.
+
+.. _migration-2.3-miscellaneous-changes:
+
+Miscellaneous Changes
+---------------------
+
+The following miscellaneous changes have occurred:
+
+-  In this release, a number of recipes have been changed to ignore the
+   ``largefile`` :term:`DISTRO_FEATURES` item,
+   enabling large file support unconditionally. This feature has always
+   been enabled by default. Disabling the feature has not been widely
+   tested.
+
+   .. note::
+
+      Future releases of the Yocto Project will remove entirely the
+      ability to disable the
+      largefile
+      feature, which would make it unconditionally enabled everywhere.
+
+-  If the :term:`DISTRO_VERSION` value contains
+   the value of the :term:`DATE` variable, which is the
+   default between Poky releases, the ``DATE`` value is explicitly
+   excluded from ``/etc/issue`` and ``/etc/issue.net``, which is
+   displayed at the login prompt, in order to avoid conflicts with
+   Multilib enabled. Regardless, the ``DATE`` value is inaccurate if the
+   ``base-files`` recipe is restored from shared state (sstate) rather
+   than rebuilt.
+
+   If you need the build date recorded in ``/etc/issue*`` or anywhere
+   else in your image, a better method is to define a post-processing
+   function to do it and have the function called from
+   :term:`ROOTFS_POSTPROCESS_COMMAND`.
+   Doing so ensures the value is always up-to-date with the created
+   image.
+
+-  Dropbear's ``init`` script now disables DSA host keys by default.
+   This change is in line with the systemd service file, which supports
+   RSA keys only, and with recent versions of OpenSSH, which deprecates
+   DSA host keys.
+
+-  The :ref:`buildhistory <ref-classes-buildhistory>` class now
+   correctly uses tabs as separators between all columns in
+   ``installed-package-sizes.txt`` in order to aid import into other
+   tools.
+
+-  The ``USE_LDCONFIG`` variable has been replaced with the "ldconfig"
+   ``DISTRO_FEATURES`` feature. Distributions that previously set:
+   ::
+
+      USE_LDCONFIG = "0"
+
+   should now instead use the following:
+
+   ::
+
+      DISTRO_FEATURES_BACKFILL_CONSIDERED_append = " ldconfig"
+
+-  The default value of
+   :term:`COPYLEFT_LICENSE_INCLUDE` now
+   includes all versions of AGPL licenses in addition to GPL and LGPL.
+
+   .. note::
+
+      The default list is not intended to be guaranteed as a complete
+      safe list. You should seek legal advice based on what you are
+      distributing if you are unsure.
+
+-  Kernel module packages are now suffixed with the kernel version in
+   order to allow module packages from multiple kernel versions to
+   co-exist on a target system. If you wish to return to the previous
+   naming scheme that does not include the version suffix, use the
+   following:
+   ::
+
+      KERNEL_MODULE_PACKAGE_SUFFIX to ""
+
+-  Removal of ``libtool`` ``*.la`` files is now enabled by default. The
+   ``*.la`` files are not actually needed on Linux and relocating them
+   is an unnecessary burden.
+
+   If you need to preserve these ``.la`` files (e.g. in a custom
+   distribution), you must change
+   :term:`INHERIT_DISTRO` such that
+   "remove-libtool" is not included in the value.
+
+-  Extensible SDKs built for GCC 5+ now refuse to install on a
+   distribution where the host GCC version is 4.8 or 4.9. This change
+   resulted from the fact that the installation is known to fail due to
+   the way the ``uninative`` shared state (sstate) package is built. See
+   the :ref:`uninative <ref-classes-uninative>` class for additional
+   information.
+
+-  All native and nativesdk recipes now use a separate
+   ``DISTRO_FEATURES`` value instead of sharing the value used by
+   recipes for the target, in order to avoid unnecessary rebuilds.
+
+   The ``DISTRO_FEATURES`` for ``native`` recipes is
+   :term:`DISTRO_FEATURES_NATIVE` added to
+   an intersection of ``DISTRO_FEATURES`` and
+   :term:`DISTRO_FEATURES_FILTER_NATIVE`.
+
+   For nativesdk recipes, the corresponding variables are
+   :term:`DISTRO_FEATURES_NATIVESDK`
+   and
+   :term:`DISTRO_FEATURES_FILTER_NATIVESDK`.
+
+-  The ``FILESDIR`` variable, which was previously deprecated and rarely
+   used, has now been removed. You should change any recipes that set
+   ``FILESDIR`` to set :term:`FILESPATH` instead.
+
+-  The ``MULTIMACH_HOST_SYS`` variable has been removed as it is no
+   longer needed with recipe-specific sysroots.
+
+
diff --git a/documentation/ref-manual/migration-2.4.rst b/documentation/ref-manual/migration-2.4.rst
new file mode 100644
index 0000000000..260b3204b6
--- /dev/null
+++ b/documentation/ref-manual/migration-2.4.rst
@@ -0,0 +1,327 @@
+Moving to the Yocto Project 2.4 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 2.4 Release from the prior release.
+
+.. _migration-2.4-memory-resident-mode:
+
+Memory Resident Mode
+--------------------
+
+A persistent mode is now available in BitBake's default operation,
+replacing its previous "memory resident mode" (i.e.
+``oe-init-build-env-memres``). Now you only need to set
+:term:`BB_SERVER_TIMEOUT` to a timeout (in
+seconds) and BitBake's server stays resident for that amount of time
+between invocations. The ``oe-init-build-env-memres`` script has been
+removed since a separate environment setup script is no longer needed.
+
+.. _migration-2.4-packaging-changes:
+
+Packaging Changes
+-----------------
+
+This section provides information about packaging changes that have
+occurred:
+
+-  ``python3`` Changes:
+
+   -  The main "python3" package now brings in all of the standard
+      Python 3 distribution rather than a subset. This behavior matches
+      what is expected based on traditional Linux distributions. If you
+      wish to install a subset of Python 3, specify ``python-core`` plus
+      one or more of the individual packages that are still produced.
+
+   -  ``python3``: The ``bz2.py``, ``lzma.py``, and
+      ``_compression.py`` scripts have been moved from the
+      ``python3-misc`` package to the ``python3-compression`` package.
+
+-  ``binutils``: The ``libbfd`` library is now packaged in a separate
+   "libbfd" package. This packaging saves space when certain tools (e.g.
+   ``perf``) are installed. In such cases, the tools only need
+   ``libbfd`` rather than all the packages in ``binutils``.
+
+-  ``util-linux`` Changes:
+
+   -  The ``su`` program is now packaged in a separate "util-linux-su"
+      package, which is only built when "pam" is listed in the
+      :term:`DISTRO_FEATURES` variable.
+      ``util-linux`` should not be installed unless it is needed because
+      ``su`` is normally provided through the shadow file format. The
+      main ``util-linux`` package has runtime dependencies (i.e.
+      :term:`RDEPENDS`) on the ``util-linux-su`` package
+      when "pam" is in ``DISTRO_FEATURES``.
+
+   -  The ``switch_root`` program is now packaged in a separate
+      "util-linux-switch-root" package for small initramfs images that
+      do not need the whole ``util-linux`` package or the busybox
+      binary, which are both much larger than ``switch_root``. The main
+      ``util-linux`` package has a recommended runtime dependency (i.e.
+      :term:`RRECOMMENDS`) on the
+      ``util-linux-switch-root`` package.
+
+   -  The ``ionice`` program is now packaged in a separate
+      "util-linux-ionice" package. The main ``util-linux`` package has a
+      recommended runtime dependency (i.e. ``RRECOMMENDS``) on the
+      ``util-linux-ionice`` package.
+
+-  ``initscripts``: The ``sushell`` program is now packaged in a
+   separate "initscripts-sushell" package. This packaging change allows
+   systems to pull ``sushell`` in when ``selinux`` is enabled. The
+   change also eliminates needing to pull in the entire ``initscripts``
+   package. The main ``initscripts`` package has a runtime dependency
+   (i.e. ``RDEPENDS``) on the ``sushell`` package when "selinux" is in
+   ``DISTRO_FEATURES``.
+
+-  ``glib-2.0``: The ``glib-2.0`` package now has a recommended
+   runtime dependency (i.e. ``RRECOMMENDS``) on the ``shared-mime-info``
+   package, since large portions of GIO are not useful without the MIME
+   database. You can remove the dependency by using the
+   :term:`BAD_RECOMMENDATIONS` variable if
+   ``shared-mime-info`` is too large and is not required.
+
+-  *Go Standard Runtime:* The Go standard runtime has been split out
+   from the main ``go`` recipe into a separate ``go-runtime`` recipe.
+
+.. _migration-2.4-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been removed:
+
+-  ``acpitests``: This recipe is not maintained.
+
+-  ``autogen-native``: No longer required by Grub, oe-core, or
+   meta-oe.
+
+-  ``bdwgc``: Nothing in OpenEmbedded-Core requires this recipe. It
+   has moved to meta-oe.
+
+-  ``byacc``: This recipe was only needed by rpm 5.x and has moved to
+   meta-oe.
+
+-  ``gcc (5.4)``: The 5.4 series dropped the recipe in favor of 6.3 /
+   7.2.
+
+-  ``gnome-common``: Deprecated upstream and no longer needed.
+
+-  ``go-bootstrap-native``: Go 1.9 does its own bootstrapping so this
+   recipe has been removed.
+
+-  ``guile``: This recipe was only needed by ``autogen-native`` and
+   ``remake``. The recipe is no longer needed by either of these
+   programs.
+
+-  ``libclass-isa-perl``: This recipe was previously needed for LSB 4,
+   no longer needed.
+
+-  ``libdumpvalue-perl``: This recipe was previously needed for LSB 4,
+   no longer needed.
+
+-  ``libenv-perl``: This recipe was previously needed for LSB 4, no
+   longer needed.
+
+-  ``libfile-checktree-perl``: This recipe was previously needed for
+   LSB 4, no longer needed.
+
+-  ``libi18n-collate-perl``: This recipe was previously needed for LSB
+   4, no longer needed.
+
+-  ``libiconv``: This recipe was only needed for ``uclibc``, which was
+   removed in the previous release. ``glibc`` and ``musl`` have their
+   own implementations. ``meta-mingw`` still needs ``libiconv``, so it
+   has been moved to ``meta-mingw``.
+
+-  ``libpng12``: This recipe was previously needed for LSB. The
+   current ``libpng`` is 1.6.x.
+
+-  ``libpod-plainer-perl``: This recipe was previously needed for LSB
+   4, no longer needed.
+
+-  ``linux-yocto (4.1)``: This recipe was removed in favor of 4.4,
+   4.9, 4.10 and 4.12.
+
+-  ``mailx``: This recipe was previously only needed for LSB
+   compatibility, and upstream is defunct.
+
+-  ``mesa (git version only)``: The git version recipe was stale with
+   respect to the release version.
+
+-  ``ofono (git version only)``: The git version recipe was stale with
+   respect to the release version.
+
+-  ``portmap``: This recipe is obsolete and is superseded by
+   ``rpcbind``.
+
+-  ``python3-pygpgme``: This recipe is old and unmaintained. It was
+   previously required by ``dnf``, which has switched to official
+   ``gpgme`` Python bindings.
+
+-  ``python-async``: This recipe has been removed in favor of the
+   Python 3 version.
+
+-  ``python-gitdb``: This recipe has been removed in favor of the
+   Python 3 version.
+
+-  ``python-git``: This recipe was removed in favor of the Python 3
+   version.
+
+-  ``python-mako``: This recipe was removed in favor of the Python 3
+   version.
+
+-  ``python-pexpect``: This recipe was removed in favor of the Python
+   3 version.
+
+-  ``python-ptyprocess``: This recipe was removed in favor of Python
+   the 3 version.
+
+-  ``python-pycurl``: Nothing is using this recipe in
+   OpenEmbedded-Core (i.e. ``meta-oe``).
+
+-  ``python-six``: This recipe was removed in favor of the Python 3
+   version.
+
+-  ``python-smmap``: This recipe was removed in favor of the Python 3
+   version.
+
+-  ``remake``: Using ``remake`` as the provider of ``virtual/make`` is
+   broken. Consequently, this recipe is not needed in OpenEmbedded-Core.
+
+.. _migration-2.4-kernel-device-tree-move:
+
+Kernel Device Tree Move
+-----------------------
+
+Kernel Device Tree support is now easier to enable in a kernel recipe.
+The Device Tree code has moved to a
+:ref:`kernel-devicetree <ref-classes-kernel-devicetree>` class.
+Functionality is automatically enabled for any recipe that inherits the
+:ref:`kernel <ref-classes-kernel>` class and sets the
+:term:`KERNEL_DEVICETREE` variable. The
+previous mechanism for doing this,
+``meta/recipes-kernel/linux/linux-dtb.inc``, is still available to avoid
+breakage, but triggers a deprecation warning. Future releases of the
+Yocto Project will remove ``meta/recipes-kernel/linux/linux-dtb.inc``.
+It is advisable to remove any ``require`` statements that request
+``meta/recipes-kernel/linux/linux-dtb.inc`` from any custom kernel
+recipes you might have. This will avoid breakage in post 2.4 releases.
+
+.. _migration-2.4-package-qa-changes:
+
+Package QA Changes
+------------------
+
+The following package QA changes took place:
+
+-  The "unsafe-references-in-scripts" QA check has been removed.
+
+-  If you refer to ``${COREBASE}/LICENSE`` within
+   :term:`LIC_FILES_CHKSUM` you receive a
+   warning because this file is a description of the license for
+   OE-Core. Use ``${COMMON_LICENSE_DIR}/MIT`` if your recipe is
+   MIT-licensed and you cannot use the preferred method of referring to
+   a file within the source tree.
+
+.. _migration-2.4-readme-changes:
+
+``README`` File Changes
+-----------------------
+
+The following are changes to ``README`` files:
+
+-  The main Poky ``README`` file has been moved to the ``meta-poky``
+   layer and has been renamed ``README.poky``. A symlink has been
+   created so that references to the old location work.
+
+-  The ``README.hardware`` file has been moved to ``meta-yocto-bsp``. A
+   symlink has been created so that references to the old location work.
+
+-  A ``README.qemu`` file has been created with coverage of the
+   ``qemu*`` machines.
+
+.. _migration-2.4-miscellaneous-changes:
+
+Miscellaneous Changes
+---------------------
+
+The following are additional changes:
+
+-  The ``ROOTFS_PKGMANAGE_BOOTSTRAP`` variable and any references to it
+   have been removed. You should remove this variable from any custom
+   recipes.
+
+-  The ``meta-yocto`` directory has been removed.
+
+   .. note::
+
+      In the Yocto Project 2.1 release
+      meta-yocto
+      was renamed to
+      meta-poky
+      and the
+      meta-yocto
+      subdirectory remained to avoid breaking existing configurations.
+
+-  The ``maintainers.inc`` file, which tracks maintainers by listing a
+   primary person responsible for each recipe in OE-Core, has been moved
+   from ``meta-poky`` to OE-Core (i.e. from
+   ``meta-poky/conf/distro/include`` to ``meta/conf/distro/include``).
+
+-  The :ref:`buildhistory <ref-classes-buildhistory>` class now makes
+   a single commit per build rather than one commit per subdirectory in
+   the repository. This behavior assumes the commits are enabled with
+   :term:`BUILDHISTORY_COMMIT` = "1", which
+   is typical. Previously, the ``buildhistory`` class made one commit
+   per subdirectory in the repository in order to make it easier to see
+   the changes for a particular subdirectory. To view a particular
+   change, specify that subdirectory as the last parameter on the
+   ``git show`` or ``git diff`` commands.
+
+-  The ``x86-base.inc`` file, which is included by all x86-based machine
+   configurations, now sets :term:`IMAGE_FSTYPES`
+   using ``?=`` to "live" rather than appending with ``+=``. This change
+   makes the default easier to override.
+
+-  BitBake fires multiple "BuildStarted" events when multiconfig is
+   enabled (one per configuration). For more information, see the
+   ":ref:`Events <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:events>`" section in the BitBake User
+   Manual.
+
+-  By default, the ``security_flags.inc`` file sets a
+   :term:`GCCPIE` variable with an option to enable
+   Position Independent Executables (PIE) within ``gcc``. Enabling PIE
+   in the GNU C Compiler (GCC), makes Return Oriented Programming (ROP)
+   attacks much more difficult to execute.
+
+-  OE-Core now provides a ``bitbake-layers`` plugin that implements a
+   "create-layer" subcommand. The implementation of this subcommand has
+   resulted in the ``yocto-layer`` script being deprecated and will
+   likely be removed in the next Yocto Project release.
+
+-  The ``vmdk``, ``vdi``, and ``qcow2`` image file types are now used in
+   conjunction with the "wic" image type through ``CONVERSION_CMD``.
+   Consequently, the equivalent image types are now ``wic.vmdk``,
+   ``wic.vdi``, and ``wic.qcow2``, respectively.
+
+-  ``do_image_<type>[depends]`` has replaced ``IMAGE_DEPENDS_<type>``.
+   If you have your own classes that implement custom image types, then
+   you need to update them.
+
+-  OpenSSL 1.1 has been introduced. However, the default is still 1.0.x
+   through the :term:`PREFERRED_VERSION`
+   variable. This preference is set is due to the remaining
+   compatibility issues with other software. The
+   :term:`PROVIDES` variable in the openssl 1.0 recipe
+   now includes "openssl10" as a marker that can be used in
+   :term:`DEPENDS` within recipes that build software
+   that still depend on OpenSSL 1.0.
+
+-  To ensure consistent behavior, BitBake's "-r" and "-R" options (i.e.
+   prefile and postfile), which are used to read or post-read additional
+   configuration files from the command line, now only affect the
+   current BitBake command. Before these BitBake changes, these options
+   would "stick" for future executions.
+
+
diff --git a/documentation/ref-manual/migration-2.5.rst b/documentation/ref-manual/migration-2.5.rst
new file mode 100644
index 0000000000..a2adc17757
--- /dev/null
+++ b/documentation/ref-manual/migration-2.5.rst
@@ -0,0 +1,310 @@
+Moving to the Yocto Project 2.5 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 2.5 Release from the prior release.
+
+.. _migration-2.5-packaging-changes:
+
+Packaging Changes
+-----------------
+
+This section provides information about packaging changes that have
+occurred:
+
+-  ``bind-libs``: The libraries packaged by the bind recipe are in a
+   separate ``bind-libs`` package.
+
+-  ``libfm-gtk``: The ``libfm`` GTK+ bindings are split into a
+   separate ``libfm-gtk`` package.
+
+-  ``flex-libfl``: The flex recipe splits out libfl into a separate
+   ``flex-libfl`` package to avoid too many dependencies being pulled in
+   where only the library is needed.
+
+-  ``grub-efi``: The ``grub-efi`` configuration is split into a
+   separate ``grub-bootconf`` recipe. However, the dependency
+   relationship from ``grub-efi`` is through a virtual/grub-bootconf
+   provider making it possible to have your own recipe provide the
+   dependency. Alternatively, you can use a BitBake append file to bring
+   the configuration back into the ``grub-efi`` recipe.
+
+-  *armv7a Legacy Package Feed Support:* Legacy support is removed for
+   transitioning from ``armv7a`` to ``armv7a-vfp-neon`` in package
+   feeds, which was previously enabled by setting
+   ``PKGARCHCOMPAT_ARMV7A``. This transition occurred in 2011 and active
+   package feeds should by now be updated to the new naming.
+
+.. _migration-2.5-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been removed:
+
+-  ``gcc``: The version 6.4 recipes are replaced by 7.x.
+
+-  ``gst-player``: Renamed to ``gst-examples`` as per upstream.
+
+-  ``hostap-utils``: This software package is obsolete.
+
+-  ``latencytop``: This recipe is no longer maintained upstream. The
+   last release was in 2009.
+
+-  ``libpfm4``: The only file that requires this recipe is
+   ``oprofile``, which has been removed.
+
+-  ``linux-yocto``: The version 4.4, 4.9, and 4.10 recipes have been
+   removed. Versions 4.12, 4.14, and 4.15 remain.
+
+-  ``man``: This recipe has been replaced by modern ``man-db``
+
+-  ``mkelfimage``: This tool has been removed in the upstream coreboot
+   project, and is no longer needed with the removal of the ELF image
+   type.
+
+-  ``nativesdk-postinst-intercept``: This recipe is not maintained.
+
+-  ``neon``: This software package is no longer maintained upstream
+   and is no longer needed by anything in OpenEmbedded-Core.
+
+-  ``oprofile``: The functionality of this recipe is replaced by
+   ``perf`` and keeping compatibility on an ongoing basis with ``musl``
+   is difficult.
+
+-  ``pax``: This software package is obsolete.
+
+-  ``stat``: This software package is not maintained upstream.
+   ``coreutils`` provides a modern stat binary.
+
+-  ``zisofs-tools-native``: This recipe is no longer needed because
+   the compressed ISO image feature has been removed.
+
+.. _migration-2.5-scripts-and-tools-changes:
+
+Scripts and Tools Changes
+-------------------------
+
+The following are changes to scripts and tools:
+
+-  ``yocto-bsp``, ``yocto-kernel``, and ``yocto-layer``: The
+   ``yocto-bsp``, ``yocto-kernel``, and ``yocto-layer`` scripts
+   previously shipped with poky but not in OpenEmbedded-Core have been
+   removed. These scripts are not maintained and are outdated. In many
+   cases, they are also limited in scope. The
+   ``bitbake-layers create-layer`` command is a direct replacement for
+   ``yocto-layer``. See the documentation to create a BSP or kernel
+   recipe in the ":ref:`bsp-guide/bsp:bsp kernel recipe example`" section.
+
+-  ``devtool finish``: ``devtool finish`` now exits with an error if
+   there are uncommitted changes or a rebase/am in progress in the
+   recipe's source repository. If this error occurs, there might be
+   uncommitted changes that will not be included in updates to the
+   patches applied by the recipe. A -f/--force option is provided for
+   situations that the uncommitted changes are inconsequential and you
+   want to proceed regardless.
+
+-  ``scripts/oe-setup-rpmrepo`` script: The functionality of
+   ``scripts/oe-setup-rpmrepo`` is replaced by
+   ``bitbake package-index``.
+
+-  ``scripts/test-dependencies.sh`` script: The script is largely made
+   obsolete by the recipe-specific sysroots functionality introduced in
+   the previous release.
+
+.. _migration-2.5-bitbake-changes:
+
+BitBake Changes
+---------------
+
+The following are BitBake changes:
+
+-  The ``--runall`` option has changed. There are two different
+   behaviors people might want:
+
+   -  *Behavior A:* For a given target (or set of targets) look through
+      the task graph and run task X only if it is present and will be
+      built.
+
+   -  *Behavior B:* For a given target (or set of targets) look through
+      the task graph and run task X if any recipe in the taskgraph has
+      such a target, even if it is not in the original task graph.
+
+   The ``--runall`` option now performs "Behavior B". Previously
+   ``--runall`` behaved like "Behavior A". A ``--runonly`` option has
+   been added to retain the ability to perform "Behavior A".
+
+-  Several explicit "run this task for all recipes in the dependency
+   tree" tasks have been removed (e.g. ``fetchall``, ``checkuriall``,
+   and the ``*all`` tasks provided by the ``distrodata`` and
+   ``archiver`` classes). There is a BitBake option to complete this for
+   any arbitrary task. For example:
+   ::
+
+      bitbake <target> -c fetchall
+
+   should now be replaced with:
+   ::
+
+      bitbake <target> --runall=fetch
+
+.. _migration-2.5-python-and-python3-changes:
+
+Python and Python 3 Changes
+---------------------------
+
+The following are auto-packaging changes to Python and Python 3:
+
+The script-managed ``python-*-manifest.inc`` files that were previously
+used to generate Python and Python 3 packages have been replaced with a
+JSON-based file that is easier to read and maintain. A new task is
+available for maintainers of the Python recipes to update the JSON file
+when upgrading to new Python versions. You can now edit the file
+directly instead of having to edit a script and run it to update the
+file.
+
+One particular change to note is that the Python recipes no longer have
+build-time provides for their packages. This assumes ``python-foo`` is
+one of the packages provided by the Python recipe. You can no longer run
+``bitbake python-foo`` or have a
+:term:`DEPENDS` on ``python-foo``,
+but doing either of the following causes the package to work as
+expected: ::
+
+   IMAGE_INSTALL_append = " python-foo"
+
+or ::
+
+   RDEPENDS_${PN} = "python-foo"
+
+The earlier build-time provides behavior was a quirk of the
+way the Python manifest file was created. For more information on this
+change please see `this
+commit <http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=8d94b9db221d1def42f091b991903faa2d1651ce>`__.
+
+.. _migration-2.5-miscellaneous-changes:
+
+Miscellaneous Changes
+---------------------
+
+The following are additional changes:
+
+-  The ``kernel`` class supports building packages for multiple kernels.
+   If your kernel recipe or ``.bbappend`` file mentions packaging at
+   all, you should replace references to the kernel in package names
+   with ``${KERNEL_PACKAGE_NAME}``. For example, if you disable
+   automatic installation of the kernel image using
+   ``RDEPENDS_kernel-base = ""`` you can avoid warnings using
+   ``RDEPENDS_${KERNEL_PACKAGE_NAME}-base = ""`` instead.
+
+-  The ``buildhistory`` class commits changes to the repository by
+   default so you no longer need to set ``BUILDHISTORY_COMMIT = "1"``.
+   If you want to disable commits you need to set
+   ``BUILDHISTORY_COMMIT = "0"`` in your configuration.
+
+-  The ``beaglebone`` reference machine has been renamed to
+   ``beaglebone-yocto``. The ``beaglebone-yocto`` BSP is a reference
+   implementation using only mainline components available in
+   OpenEmbedded-Core and ``meta-yocto-bsp``, whereas Texas Instruments
+   maintains a full-featured BSP in the ``meta-ti`` layer. This rename
+   avoids the previous name clash that existed between the two BSPs.
+
+-  The ``update-alternatives`` class no longer works with SysV ``init``
+   scripts because this usage has been problematic. Also, the
+   ``sysklogd`` recipe no longer uses ``update-alternatives`` because it
+   is incompatible with other implementations.
+
+-  By default, the :ref:`cmake <ref-classes-cmake>` class uses
+   ``ninja`` instead of ``make`` for building. This improves build
+   performance. If a recipe is broken with ``ninja``, then the recipe
+   can set ``OECMAKE_GENERATOR = "Unix Makefiles"`` to change back to
+   ``make``.
+
+-  The previously deprecated ``base_*`` functions have been removed in
+   favor of their replacements in ``meta/lib/oe`` and
+   ``bitbake/lib/bb``. These are typically used from recipes and
+   classes. Any references to the old functions must be updated. The
+   following table shows the removed functions and their replacements:
+
+   +------------------------------+----------------------------------------------------------+
+   | *Removed*                    | *Replacement*                                            |
+   +==============================+==========================================================+
+   | base_path_join()             | oe.path.join()                                           |
+   +------------------------------+----------------------------------------------------------+
+   | base_path_relative()         | oe.path.relative()                                       |
+   +------------------------------+----------------------------------------------------------+
+   | base_path_out()              | oe.path.format_display()                                 |
+   +------------------------------+----------------------------------------------------------+
+   | base_read_file()             | oe.utils.read_file()                                     |
+   +------------------------------+----------------------------------------------------------+
+   | base_ifelse()                | oe.utils.ifelse()                                        |
+   +------------------------------+----------------------------------------------------------+
+   | base_conditional()           | oe.utils.conditional()                                   |
+   +------------------------------+----------------------------------------------------------+
+   | base_less_or_equal()         | oe.utils.less_or_equal()                                 |
+   +------------------------------+----------------------------------------------------------+
+   | base_version_less_or_equal() | oe.utils.version_less_or_equal()                         |
+   +------------------------------+----------------------------------------------------------+
+   | base_contains()              | bb.utils.contains()                                      |
+   +------------------------------+----------------------------------------------------------+
+   | base_both_contain()          | oe.utils.both_contain()                                  |
+   +------------------------------+----------------------------------------------------------+
+   | base_prune_suffix()          | oe.utils.prune_suffix()                                  |
+   +------------------------------+----------------------------------------------------------+
+   | oe_filter()                  | oe.utils.str_filter()                                    |
+   +------------------------------+----------------------------------------------------------+
+   | oe_filter_out()              | oe.utils.str_filter_out() (or use the \_remove operator) |
+   +------------------------------+----------------------------------------------------------+
+
+-  Using ``exit 1`` to explicitly defer a postinstall script until first
+   boot is now deprecated since it is not an obvious mechanism and can
+   mask actual errors. If you want to explicitly defer a postinstall to
+   first boot on the target rather than at ``rootfs`` creation time, use
+   ``pkg_postinst_ontarget()`` or call
+   ``postinst_intercept delay_to_first_boot`` from ``pkg_postinst()``.
+   Any failure of a ``pkg_postinst()`` script (including ``exit 1``)
+   will trigger a warning during ``do_rootfs``.
+
+   For more information, see the
+   ":ref:`dev-manual/dev-manual-common-tasks:post-installation scripts`"
+   section in the Yocto Project Development Tasks Manual.
+
+-  The ``elf`` image type has been removed. This image type was removed
+   because the ``mkelfimage`` tool that was required to create it is no
+   longer provided by coreboot upstream and required updating every time
+   ``binutils`` updated.
+
+-  Support for .iso image compression (previously enabled through
+   ``COMPRESSISO = "1"``) has been removed. The userspace tools
+   (``zisofs-tools``) are unmaintained and ``squashfs`` provides better
+   performance and compression. In order to build a live image with
+   squashfs+lz4 compression enabled you should now set
+   ``LIVE_ROOTFS_TYPE = "squashfs-lz4"`` and ensure that ``live`` is in
+   ``IMAGE_FSTYPES``.
+
+-  Recipes with an unconditional dependency on ``libpam`` are only
+   buildable with ``pam`` in ``DISTRO_FEATURES``. If the dependency is
+   truly optional then it is recommended that the dependency be
+   conditional upon ``pam`` being in ``DISTRO_FEATURES``.
+
+-  For EFI-based machines, the bootloader (``grub-efi`` by default) is
+   installed into the image at /boot. Wic can be used to split the
+   bootloader into separate boot and rootfs partitions if necessary.
+
+-  Patches whose context does not match exactly (i.e. where patch
+   reports "fuzz" when applying) will generate a warning. For an example
+   of this see `this
+   commit <http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=cc97bc08125b63821ce3f616771830f77c456f57>`__.
+
+-  Layers are expected to set ``LAYERSERIES_COMPAT_layername`` to match
+   the version(s) of OpenEmbedded-Core they are compatible with. This is
+   specified as codenames using spaces to separate multiple values (e.g.
+   "rocko sumo"). If a layer does not set
+   ``LAYERSERIES_COMPAT_layername``, a warning will is shown. If a layer
+   sets a value that does not include the current version ("sumo" for
+   the 2.5 release), then an error will be produced.
+
+-  The ``TZ`` environment variable is set to "UTC" within the build
+   environment in order to fix reproducibility problems in some recipes.
+
+
diff --git a/documentation/ref-manual/migration-2.6.rst b/documentation/ref-manual/migration-2.6.rst
new file mode 100644
index 0000000000..f16aaaa975
--- /dev/null
+++ b/documentation/ref-manual/migration-2.6.rst
@@ -0,0 +1,476 @@
+Moving to the Yocto Project 2.6 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 2.6 Release from the prior release.
+
+.. _migration-2.6-gcc-changes:
+
+GCC 8.2 is Now Used by Default
+------------------------------
+
+The GNU Compiler Collection version 8.2 is now used by default for
+compilation. For more information on what has changed in the GCC 8.x
+release, see https://gcc.gnu.org/gcc-8/changes.html.
+
+If you still need to compile with version 7.x, GCC 7.3 is also provided.
+You can select this version by setting the and can be selected by
+setting the :term:`GCCVERSION` variable to "7.%" in
+your configuration.
+
+.. _migration-2.6-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been removed:
+
+- *beecrypt*: No longer needed since moving to RPM 4.
+- *bigreqsproto*: Replaced by ``xorgproto``.
+- *calibrateproto*: Removed in favor of ``xinput``.
+- *compositeproto*: Replaced by ``xorgproto``.
+- *damageproto*: Replaced by ``xorgproto``.
+- *dmxproto*: Replaced by ``xorgproto``.
+- *dri2proto*: Replaced by ``xorgproto``.
+- *dri3proto*: Replaced by ``xorgproto``.
+- *eee-acpi-scripts*: Became obsolete.
+- *fixesproto*: Replaced by ``xorgproto``.
+- *fontsproto*: Replaced by ``xorgproto``.
+- *fstests*: Became obsolete.
+- *gccmakedep*: No longer used.
+- *glproto*: Replaced by ``xorgproto``.
+- *gnome-desktop3*: No longer needed. This recipe has moved to ``meta-oe``.
+- *icon-naming-utils*: No longer used since the Sato theme was removed in 2016.
+- *inputproto*: Replaced by ``xorgproto``.
+- *kbproto*: Replaced by ``xorgproto``.
+- *libusb-compat*: Became obsolete.
+- *libuser*: Became obsolete.
+- *libnfsidmap*: No longer an external requirement since ``nfs-utils`` 2.2.1. ``libnfsidmap`` is now integrated.
+- *libxcalibrate*: No longer needed with ``xinput``
+- *mktemp*: Became obsolete. The ``mktemp`` command is provided by both ``busybox`` and ``coreutils``.
+- *ossp-uuid*: Is not being maintained and has mostly been replaced by ``uuid.h`` in ``util-linux``.
+- *pax-utils*: No longer needed. Previous QA tests that did use this recipe are now done at build time.
+- *pcmciautils*: Became obsolete.
+- *pixz*: No longer needed. ``xz`` now supports multi-threaded compression.
+- *presentproto*: Replaced by ``xorgproto``.
+- *randrproto*: Replaced by ``xorgproto``.
+- *recordproto*: Replaced by ``xorgproto``.
+- *renderproto*: Replaced by ``xorgproto``.
+- *resourceproto*: Replaced by ``xorgproto``.
+- *scrnsaverproto*: Replaced by ``xorgproto``.
+- *trace-cmd*: Became obsolete. ``perf`` replaced this recipe's functionally.
+- *videoproto*: Replaced by ``xorgproto``.
+- *wireless-tools*: Became obsolete. Superseded by ``iw``.
+- *xcmiscproto*: Replaced by ``xorgproto``.
+- *xextproto*: Replaced by ``xorgproto``.
+- *xf86dgaproto*: Replaced by ``xorgproto``.
+- *xf86driproto*: Replaced by ``xorgproto``.
+- *xf86miscproto*: Replaced by ``xorgproto``.
+- *xf86-video-omapfb*: Became obsolete. Use kernel modesetting driver instead.
+- *xf86-video-omap*: Became obsolete. Use kernel modesetting driver instead.
+- *xf86vidmodeproto*: Replaced by ``xorgproto``.
+- *xineramaproto*: Replaced by ``xorgproto``.
+- *xproto*: Replaced by ``xorgproto``.
+- *yasm*: No longer needed since previous usages are now satisfied by ``nasm``.
+
+.. _migration-2.6-packaging-changes:
+
+Packaging Changes
+-----------------
+
+The following packaging changes have been made:
+
+-  *cmake*: ``cmake.m4`` and ``toolchain`` files have been moved to
+   the main package.
+
+-  *iptables*: The ``iptables`` modules have been split into
+   separate packages.
+
+-  *alsa-lib*: ``libasound`` is now in the main ``alsa-lib`` package
+   instead of ``libasound``.
+
+-  *glibc*: ``libnss-db`` is now in its own package along with a
+   ``/var/db/makedbs.sh`` script to update databases.
+
+-  *python and python3*: The main package has been removed from
+   the recipe. You must install specific packages or ``python-modules``
+   / ``python3-modules`` for everything.
+
+-  *systemtap*: Moved ``systemtap-exporter`` into its own package.
+
+.. _migration-2.6-xorg-protocol-dependencies:
+
+XOrg Protocol dependencies
+--------------------------
+
+The ``*proto`` upstream repositories have been combined into one
+"xorgproto" repository. Thus, the corresponding recipes have also been
+combined into a single ``xorgproto`` recipe. Any recipes that depend
+upon the older ``*proto`` recipes need to be changed to depend on the
+newer ``xorgproto`` recipe instead.
+
+For names of recipes removed because of this repository change, see the
+`Removed Recipes <#migration-2.6-removed-recipes>`__ section.
+
+.. _migration-2.6-distutils-distutils3-fetching-dependencies:
+
+``distutils`` and ``distutils3`` Now Prevent Fetching Dependencies During the ``do_configure`` Task
+---------------------------------------------------------------------------------------------------
+
+Previously, it was possible for Python recipes that inherited the
+:ref:`distutils <ref-classes-distutils>` and
+:ref:`distutils3 <ref-classes-distutils3>` classes to fetch code
+during the :ref:`ref-tasks-configure` task to satisfy
+dependencies mentioned in ``setup.py`` if those dependencies were not
+provided in the sysroot (i.e. recipes providing the dependencies were
+missing from :term:`DEPENDS`).
+
+.. note::
+
+   This change affects classes beyond just the two mentioned (i.e.
+   distutils
+   and
+   distutils3
+   ). Any recipe that inherits
+   distutils\*
+   classes are affected. For example, the
+   setuptools
+   and
+   setuptools3
+   recipes are affected since they inherit the
+   distutils\*
+   classes.
+
+Fetching these types of dependencies that are not provided in the
+sysroot negatively affects the ability to reproduce builds. This type of
+fetching is now explicitly disabled. Consequently, any missing
+dependencies in Python recipes that use these classes now result in an
+error during the ``do_configure`` task.
+
+.. _migration-2.6-linux-yocto-configuration-audit-issues-now-correctly-reported:
+
+``linux-yocto`` Configuration Audit Issues Now Correctly Reported
+-----------------------------------------------------------------
+
+Due to a bug, the kernel configuration audit functionality was not
+writing out any resulting warnings during the build. This issue is now
+corrected. You might notice these warnings now if you have a custom
+kernel configuration with a ``linux-yocto`` style kernel recipe.
+
+.. _migration-2.6-image-kernel-artifact-naming-changes:
+
+Image/Kernel Artifact Naming Changes
+------------------------------------
+
+The following changes have been made:
+
+-  Name variables (e.g. :term:`IMAGE_NAME`) use a new
+   ``IMAGE_VERSION_SUFFIX`` variable instead of
+   :term:`DATETIME`. Using ``IMAGE_VERSION_SUFFIX``
+   allows easier and more direct changes.
+
+   The ``IMAGE_VERSION_SUFFIX`` variable is set in the ``bitbake.conf``
+   configuration file as follows:
+   ::
+
+      IMAGE_VERSION_SUFFIX = "-${DATETIME}"
+
+-  Several variables have changed names for consistency:
+   ::
+
+      Old Variable                  Name New Variable Name
+      ========================================================
+      KERNEL_IMAGE_BASE_NAME        :term:`KERNEL_IMAGE_NAME`
+      KERNEL_IMAGE_SYMLINK_NAME     :term:`KERNEL_IMAGE_LINK_NAME`
+      MODULE_TARBALL_BASE_NAME      :term:`MODULE_TARBALL_NAME`
+      MODULE_TARBALL_SYMLINK_NAME   :term:`MODULE_TARBALL_LINK_NAME`
+      INITRAMFS_BASE_NAME           :term:`INITRAMFS_NAME`
+
+-  The ``MODULE_IMAGE_BASE_NAME`` variable has been removed. The module
+   tarball name is now controlled directly with the
+   :term:`MODULE_TARBALL_NAME` variable.
+
+-  The :term:`KERNEL_DTB_NAME` and
+   :term:`KERNEL_DTB_LINK_NAME` variables
+   have been introduced to control kernel Device Tree Binary (DTB)
+   artifact names instead of mangling ``KERNEL_IMAGE_*`` variables.
+
+-  The :term:`KERNEL_FIT_NAME` and
+   :term:`KERNEL_FIT_LINK_NAME` variables
+   have been introduced to specify the name of flattened image tree
+   (FIT) kernel images similar to other deployed artifacts.
+
+-  The :term:`MODULE_TARBALL_NAME` and
+   :term:`MODULE_TARBALL_LINK_NAME`
+   variable values no longer include the "module-" prefix or ".tgz"
+   suffix. These parts are now hardcoded so that the values are
+   consistent with other artifact naming variables.
+
+-  Added the :term:`INITRAMFS_LINK_NAME`
+   variable so that the symlink can be controlled similarly to other
+   artifact types.
+
+-  :term:`INITRAMFS_NAME` now uses
+   "${PKGE}-${PKGV}-${PKGR}-${MACHINE}${IMAGE_VERSION_SUFFIX}" instead
+   of "${PV}-${PR}-${MACHINE}-${DATETIME}", which makes it consistent
+   with other variables.
+
+.. _migration-2.6-serial-console-deprecated:
+
+``SERIAL_CONSOLE`` Deprecated
+-----------------------------
+
+The :term:`SERIAL_CONSOLE` variable has been
+functionally replaced by the
+:term:`SERIAL_CONSOLES` variable for some time.
+With the Yocto Project 2.6 release, ``SERIAL_CONSOLE`` has been
+officially deprecated.
+
+``SERIAL_CONSOLE`` will continue to work as before for the 2.6 release.
+However, for the sake of future compatibility, it is recommended that
+you replace all instances of ``SERIAL_CONSOLE`` with
+``SERIAL_CONSOLES``.
+
+.. note::
+
+   The only difference in usage is that
+   SERIAL_CONSOLES
+   expects entries to be separated using semicolons as compared to
+   SERIAL_CONSOLE
+   , which expects spaces.
+
+.. _migration-2.6-poky-sets-unknown-configure-option-to-qa-error:
+
+Configure Script Reports Unknown Options as Errors
+--------------------------------------------------
+
+If the configure script reports an unknown option, this now triggers a
+QA error instead of a warning. Any recipes that previously got away with
+specifying such unknown options now need to be fixed.
+
+.. _migration-2.6-override-changes:
+
+Override Changes
+----------------
+
+The following changes have occurred:
+
+-  The ``virtclass-native`` and ``virtclass-nativesdk`` Overrides Have
+   Been Removed: The ``virtclass-native`` and ``virtclass-nativesdk``
+   overrides have been deprecated since 2012 in favor of
+   ``class-native`` and ``class-nativesdk``, respectively. Both
+   ``virtclass-native`` and ``virtclass-nativesdk`` are now dropped.
+
+   .. note::
+
+      The
+      virtclass-multilib-
+      overrides for multilib are still valid.
+
+-  The ``forcevariable`` Override Now Has a Higher Priority Than
+   ``libc`` Overrides: The ``forcevariable`` override is documented to
+   be the highest priority override. However, due to a long-standing
+   quirk of how :term:`OVERRIDES` is set, the ``libc``
+   overrides (e.g. ``libc-glibc``, ``libc-musl``, and so forth)
+   erroneously had a higher priority. This issue is now corrected.
+
+   It is likely this change will not cause any problems. However, it is
+   possible with some unusual configurations that you might see a change
+   in behavior if you were relying on the previous behavior. Be sure to
+   check how you use ``forcevariable`` and ``libc-*`` overrides in your
+   custom layers and configuration files to ensure they make sense.
+
+-  The ``build-${BUILD_OS}`` Override Has Been Removed: The
+   ``build-${BUILD_OS}``, which is typically ``build-linux``, override
+   has been removed because building on a host operating system other
+   than a recent version of Linux is neither supported nor recommended.
+   Dropping the override avoids giving the impression that other host
+   operating systems might be supported.
+
+-  The "_remove" operator now preserves whitespace. Consequently, when
+   specifying list items to remove, be aware that leading and trailing
+   whitespace resulting from the removal is retained.
+
+   See the ":ref:`bitbake:removing-override-style-syntax`"
+   section in the BitBake User Manual for a detailed example.
+
+.. _migration-2.6-systemd-configuration-now-split-out-to-system-conf:
+
+``systemd`` Configuration is Now Split Into ``systemd-conf``
+------------------------------------------------------------
+
+The configuration for the ``systemd`` recipe has been moved into a
+``system-conf`` recipe. Moving this configuration to a separate recipe
+avoids the ``systemd`` recipe from becoming machine-specific for cases
+where machine-specific configurations need to be applied (e.g. for
+``qemu*`` machines).
+
+Currently, the new recipe packages the following files:
+::
+
+   ${sysconfdir}/machine-id
+   ${sysconfdir}/systemd/coredump.conf
+   ${sysconfdir}/systemd/journald.conf
+   ${sysconfdir}/systemd/logind.conf
+   ${sysconfdir}/systemd/system.conf
+   ${sysconfdir}/systemd/user.conf
+
+If you previously used bbappend files to append the ``systemd`` recipe to
+change any of the listed files, you must do so for the ``systemd-conf``
+recipe instead.
+
+.. _migration-2.6-automatic-testing-changes:
+
+Automatic Testing Changes
+-------------------------
+
+This section provides information about automatic testing changes:
+
+-  ``TEST_IMAGE`` Variable Removed: Prior to this release, you set the
+   ``TEST_IMAGE`` variable to "1" to enable automatic testing for
+   successfully built images. The ``TEST_IMAGE`` variable no longer
+   exists and has been replaced by the
+   :term:`TESTIMAGE_AUTO` variable.
+
+-  Inheriting the ``testimage`` and ``testsdk`` Classes: Best
+   practices now dictate that you use the
+   :term:`IMAGE_CLASSES` variable rather than the
+   :term:`INHERIT` variable when you inherit the
+   :ref:`testimage <ref-classes-testimage*>` and
+   :ref:`testsdk <ref-classes-testsdk>` classes used for automatic
+   testing.
+
+.. _migration-2.6-openssl-changes:
+
+OpenSSL Changes
+---------------
+
+`OpenSSL <https://www.openssl.org/>`__ has been upgraded from 1.0 to
+1.1. By default, this upgrade could cause problems for recipes that have
+both versions in their dependency chains. The problem is that both
+versions cannot be installed together at build time.
+
+.. note::
+
+   It is possible to have both versions of the library at runtime.
+
+.. _migration-2.6-bitbake-changes:
+
+BitBake Changes
+---------------
+
+The server logfile ``bitbake-cookerdaemon.log`` is now always placed in
+the :term:`Build Directory` instead of the current
+directory.
+
+.. _migration-2.6-security-changes:
+
+Security Changes
+----------------
+
+The Poky distribution now uses security compiler flags by default.
+Inclusion of these flags could cause new failures due to stricter
+checking for various potential security issues in code.
+
+.. _migration-2.6-post-installation-changes:
+
+Post Installation Changes
+-------------------------
+
+You must explicitly mark post installs to defer to the target. If you
+want to explicitly defer a postinstall to first boot on the target
+rather than at rootfs creation time, use ``pkg_postinst_ontarget()`` or
+call ``postinst_intercept delay_to_first_boot`` from ``pkg_postinst()``.
+Any failure of a ``pkg_postinst()`` script (including exit 1) triggers
+an error during the :ref:`ref-tasks-rootfs` task.
+
+For more information on post-installation behavior, see the
+":ref:`dev-manual/dev-manual-common-tasks:post-installation scripts`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _migration-2.6-python-3-profile-guided-optimizations:
+
+Python 3 Profile-Guided Optimization
+------------------------------------
+
+The ``python3`` recipe now enables profile-guided optimization. Using
+this optimization requires a little extra build time in exchange for
+improved performance on the target at runtime. Additionally, the
+optimization is only enabled if the current
+:term:`MACHINE` has support for user-mode emulation in
+QEMU (i.e. "qemu-usermode" is in
+:term:`MACHINE_FEATURES`, which it is by
+default).
+
+If you wish to disable Python profile-guided optimization regardless of
+the value of ``MACHINE_FEATURES``, then ensure that
+:term:`PACKAGECONFIG` for the ``python3`` recipe
+does not contain "pgo". You could accomplish the latter using the
+following at the configuration level:
+::
+
+   PACKAGECONFIG_remove_pn-python3 = "pgo"
+
+Alternatively, you can set ``PACKAGECONFIG`` using an append file
+for the ``python3`` recipe.
+
+.. _migration-2.6-miscellaneous-changes:
+
+Miscellaneous Changes
+---------------------
+
+The following miscellaneous changes occurred:
+
+-  Default to using the Thumb-2 instruction set for armv7a and above. If
+   you have any custom recipes that build software that needs to be
+   built with the ARM instruction set, change the recipe to set the
+   instruction set as follows:
+   ::
+
+      ARM_INSTRUCTION_SET = "arm"
+
+-  ``run-postinsts`` no longer uses ``/etc/*-postinsts`` for
+   ``dpkg/opkg`` in favor of built-in postinst support. RPM behavior
+   remains unchanged.
+
+-  The ``NOISO`` and ``NOHDD`` variables are no longer used. You now
+   control building ``*.iso`` and ``*.hddimg`` image types directly by
+   using the :term:`IMAGE_FSTYPES` variable.
+
+-  The ``scripts/contrib/mkefidisk.sh`` has been removed in favor of
+   Wic.
+
+-  ``kernel-modules`` has been removed from
+   :term:`RRECOMMENDS` for ``qemumips`` and
+   ``qemumips64`` machines. Removal also impacts the ``x86-base.inc``
+   file.
+
+   .. note::
+
+      genericx86
+      and
+      genericx86-64
+      retain
+      kernel-modules
+      as part of the
+      RRECOMMENDS
+      variable setting.
+
+-  The ``LGPLv2_WHITELIST_GPL-3.0`` variable has been removed. If you
+   are setting this variable in your configuration, set or append it to
+   the ``WHITELIST_GPL-3.0`` variable instead.
+
+-  ``${ASNEEDED}`` is now included in the
+   :term:`TARGET_LDFLAGS` variable directly. The
+   remaining definitions from ``meta/conf/distro/include/as-needed.inc``
+   have been moved to corresponding recipes.
+
+-  Support for DSA host keys has been dropped from the OpenSSH recipes.
+   If you are still using DSA keys, you must switch over to a more
+   secure algorithm as recommended by OpenSSH upstream.
+
+-  The ``dhcp`` recipe now uses the ``dhcpd6.conf`` configuration file
+   in ``dhcpd6.service`` for IPv6 DHCP rather than re-using
+   ``dhcpd.conf``, which is now reserved for IPv4.
+
+
diff --git a/documentation/ref-manual/migration-2.7.rst b/documentation/ref-manual/migration-2.7.rst
new file mode 100644
index 0000000000..7e628fc3ec
--- /dev/null
+++ b/documentation/ref-manual/migration-2.7.rst
@@ -0,0 +1,180 @@
+Moving to the Yocto Project 2.7 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 2.7 Release from the prior release.
+
+.. _migration-2.7-bitbake-changes:
+
+BitBake Changes
+---------------
+
+The following changes have been made to BitBake:
+
+-  BitBake now checks anonymous Python functions and pure Python
+   functions (e.g. ``def funcname:``) in the metadata for tab
+   indentation. If found, BitBake produces a warning.
+
+-  Bitbake now checks
+   :term:`BBFILE_COLLECTIONS` for duplicate
+   entries and triggers an error if any are found.
+
+.. _migration-2.7-eclipse-support-dropped:
+
+Eclipse Support Removed
+-----------------------
+
+Support for the Eclipse IDE has been removed. Support continues for
+those releases prior to 2.7 that did include support. The 2.7 release
+does not include the Eclipse Yocto plugin.
+
+.. _migration-2.7-qemu-native-splits-system-and-user-mode-parts:
+
+``qemu-native`` Splits the System and User-Mode Parts
+-----------------------------------------------------
+
+The system and user-mode parts of ``qemu-native`` are now split.
+``qemu-native`` provides the user-mode components and
+``qemu-system-native`` provides the system components. If you have
+recipes that depend on QEMU's system emulation functionality at build
+time, they should now depend upon ``qemu-system-native`` instead of
+``qemu-native``.
+
+.. _migration-2.7-upstream-tracking.inc-removed:
+
+The ``upstream-tracking.inc`` File Has Been Removed
+---------------------------------------------------
+
+The previously deprecated ``upstream-tracking.inc`` file is now removed.
+Any ``UPSTREAM_TRACKING*`` variables are now set in the corresponding
+recipes instead.
+
+Remove any references you have to the ``upstream-tracking.inc`` file in
+your configuration.
+
+.. _migration-2.7-distro-features-libc-removed:
+
+The ``DISTRO_FEATURES_LIBC`` Variable Has Been Removed
+------------------------------------------------------
+
+The ``DISTRO_FEATURES_LIBC`` variable is no longer used. The ability to
+configure glibc using kconfig has been removed for quite some time
+making the ``libc-*`` features set no longer effective.
+
+Remove any references you have to ``DISTRO_FEATURES_LIBC`` in your own
+layers.
+
+.. _migration-2.7-license-values:
+
+License Value Corrections
+-------------------------
+
+The following corrections have been made to the
+:term:`LICENSE` values set by recipes:
+
+- *socat*: Corrected ``LICENSE`` to be "GPLv2" rather than "GPLv2+".
+- *libgfortran*: Set license to "GPL-3.0-with-GCC-exception".
+- *elfutils*: Removed "Elfutils-Exception" and set to "GPLv2" for shared libraries
+
+.. _migration-2.7-packaging-changes:
+
+Packaging Changes
+-----------------
+
+This section provides information about packaging changes.
+
+-  ``bind``: The ``nsupdate`` binary has been moved to the
+   ``bind-utils`` package.
+
+-  Debug split: The default debug split has been changed to create
+   separate source packages (i.e. package_name\ ``-dbg`` and
+   package_name\ ``-src``). If you are currently using ``dbg-pkgs`` in
+   :term:`IMAGE_FEATURES` to bring in debug
+   symbols and you still need the sources, you must now also add
+   ``src-pkgs`` to ``IMAGE_FEATURES``. Source packages remain in the
+   target portion of the SDK by default, unless you have set your own
+   value for :term:`SDKIMAGE_FEATURES` that
+   does not include ``src-pkgs``.
+
+-  Mount all using ``util-linux``: ``/etc/default/mountall`` has moved
+   into the -mount sub-package.
+
+-  Splitting binaries using ``util-linux``: ``util-linux`` now splits
+   each binary into its own package for fine-grained control. The main
+   ``util-linux`` package pulls in the individual binary packages using
+   the :term:`RRECOMMENDS` and
+   :term:`RDEPENDS` variables. As a result, existing
+   images should not see any changes assuming
+   :term:`NO_RECOMMENDATIONS` is not set.
+
+-  ``netbase/base-files``: ``/etc/hosts`` has moved from ``netbase`` to
+   ``base-files``.
+
+-  ``tzdata``: The main package has been converted to an empty meta
+   package that pulls in all ``tzdata`` packages by default.
+
+-  ``lrzsz``: This package has been removed from
+   ``packagegroup-self-hosted`` and
+   ``packagegroup-core-tools-testapps``. The X/Y/ZModem support is less
+   likely to be needed on modern systems. If you are relying on these
+   packagegroups to include the ``lrzsz`` package in your image, you now
+   need to explicitly add the package.
+
+.. _migration-2.7-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been removed:
+
+- *gcc*: Drop version 7.3 recipes. Version 8.3 now remains.
+- *linux-yocto*: Drop versions 4.14 and 4.18 recipes. Versions 4.19 and 5.0 remain.
+- *go*: Drop version 1.9 recipes. Versions 1.11 and 1.12 remain.
+- *xvideo-tests*: Became obsolete.
+- *libart-lgpl*: Became obsolete.
+- *gtk-icon-utils-native*: These tools are now provided by gtk+3-native
+- *gcc-cross-initial*: No longer needed. gcc-cross/gcc-crosssdk is now used instead.
+- *gcc-crosssdk-initial*: No longer needed. gcc-cross/gcc-crosssdk is now used instead.
+- *glibc-initial*: Removed because the benefits of having it for site_config are currently outweighed by the cost of building the recipe.
+
+.. _migration-2.7-removed-classes:
+
+Removed Classes
+---------------
+
+The following classes have been removed:
+
+- *distutils-tools*: This class was never used.
+- *bugzilla.bbclass*: Became obsolete.
+- *distrodata*: This functionally has been replaced by a more modern tinfoil-based implementation.
+
+.. _migration-2.7-miscellaneous-changes:
+
+Miscellaneous Changes
+---------------------
+
+The following miscellaneous changes occurred:
+
+-  The ``distro`` subdirectory of the Poky repository has been removed
+   from the top-level ``scripts`` directory.
+
+-  Perl now builds for the target using
+   `perl-cross <http://arsv.github.io/perl-cross/>`_ for better
+   maintainability and improved build performance. This change should
+   not present any problems unless you have heavily customized your Perl
+   recipe.
+
+-  ``arm-tunes``: Removed the "-march" option if mcpu is already added.
+
+-  ``update-alternatives``: Convert file renames to
+   :term:`PACKAGE_PREPROCESS_FUNCS`
+
+-  ``base/pixbufcache``: Obsolete ``sstatecompletions`` code has been
+   removed.
+
+-  :ref:`native <ref-classes-native>` class:
+   :term:`RDEPENDS` handling has been enabled.
+
+-  ``inetutils``: This recipe has rsh disabled.
+
+
diff --git a/documentation/ref-manual/migration-3.0.rst b/documentation/ref-manual/migration-3.0.rst
new file mode 100644
index 0000000000..e1305dfccf
--- /dev/null
+++ b/documentation/ref-manual/migration-3.0.rst
@@ -0,0 +1,321 @@
+Moving to the Yocto Project 3.0 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 3.0 Release from the prior release.
+
+.. _migration-3.0-init-system-selection:
+
+Init System Selection
+---------------------
+
+Changing the init system manager previously required setting a number of
+different variables. You can now change the manager by setting the
+``INIT_MANAGER`` variable and the corresponding include files (i.e.
+``conf/distro/include/init-manager-*.conf``). Include files are provided
+for four values: "none", "sysvinit", "systemd", and "mdev-busybox". The
+default value, "none", for ``INIT_MANAGER`` should allow your current
+settings to continue working. However, it is advisable to explicitly set
+``INIT_MANAGER``.
+
+.. _migration-3.0-lsb-support-removed:
+
+LSB Support Removed
+-------------------
+
+Linux Standard Base (LSB) as a standard is not current, and is not well
+suited for embedded applications. Support can be continued in a separate
+layer if needed. However, presently LSB support has been removed from
+the core.
+
+As a result of this change, the ``poky-lsb`` derivative distribution
+configuration that was also used for testing alternative configurations
+has been replaced with a ``poky-altcfg`` distribution that has LSB parts
+removed.
+
+.. _migration-3.0-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been removed.
+
+-  ``core-image-lsb-dev``: Part of removed LSB support.
+
+-  ``core-image-lsb``: Part of removed LSB support.
+
+-  ``core-image-lsb-sdk``: Part of removed LSB support.
+
+-  ``cve-check-tool``: Functionally replaced by the ``cve-update-db``
+   recipe and ``cve-check`` class.
+
+-  ``eglinfo``: No longer maintained. ``eglinfo`` from ``mesa-demos`` is
+   an adequate and maintained alternative.
+
+-  ``gcc-8.3``: Version 8.3 removed. Replaced by 9.2.
+
+-  ``gnome-themes-standard``: Only needed by gtk+ 2.x, which has been
+   removed.
+
+-  ``gtk+``: GTK+ 2 is obsolete and has been replaced by gtk+3.
+
+-  ``irda-utils``: Has become obsolete. IrDA support has been removed
+   from the Linux kernel in version 4.17 and later.
+
+-  ``libnewt-python``: ``libnewt`` Python support merged into main
+   ``libnewt`` recipe.
+
+-  ``libsdl``: Replaced by newer ``libsdl2``.
+
+-  ``libx11-diet``: Became obsolete.
+
+-  ``libxx86dga``: Removed obsolete client library.
+
+-  ``libxx86misc``: Removed. Library is redundant.
+
+-  ``linux-yocto``: Version 5.0 removed, which is now redundant (5.2 /
+   4.19 present).
+
+-  ``lsbinitscripts``: Part of removed LSB support.
+
+-  ``lsb``: Part of removed LSB support.
+
+-  ``lsbtest``: Part of removed LSB support.
+
+-  ``openssl10``: Replaced by newer ``openssl`` version 1.1.
+
+-  ``packagegroup-core-lsb``: Part of removed LSB support.
+
+-  ``python-nose``: Removed the Python 2.x version of the recipe.
+
+-  ``python-numpy``: Removed the Python 2.x version of the recipe.
+
+-  ``python-scons``: Removed the Python 2.x version of the recipe.
+
+-  ``source-highlight``: No longer needed.
+
+-  ``stress``: Replaced by ``stress-ng``.
+
+-  ``vulkan``: Split into ``vulkan-loader``, ``vulkan-headers``, and
+   ``vulkan-tools``.
+
+-  ``weston-conf``: Functionality moved to ``weston-init``.
+
+.. _migration-3.0-packaging-changes:
+
+Packaging Changes
+-----------------
+
+The following packaging changes have occurred.
+
+-  The `Epiphany <https://en.wikipedia.org/wiki/GNOME_Web>`__ browser
+   has been dropped from ``packagegroup-self-hosted`` as it has not been
+   needed inside ``build-appliance-image`` for quite some time and was
+   causing resource problems.
+
+-  ``libcap-ng`` Python support has been moved to a separate
+   ``libcap-ng-python`` recipe to streamline the build process when the
+   Python bindings are not needed.
+
+-  ``libdrm`` now packages the file ``amdgpu.ids`` into a separate
+   ``libdrm-amdgpu`` package.
+
+-  ``python3``: The ``runpy`` module is now in the ``python3-core``
+   package as it is required to support the common "python3 -m" command
+   usage.
+
+-  ``distcc`` now provides separate ``distcc-client`` and
+   ``distcc-server`` packages as typically one or the other are needed,
+   rather than both.
+
+-  ``python*-setuptools`` recipes now separately package the
+   ``pkg_resources`` module in a ``python-pkg-resources`` /
+   ``python3-pkg-resources`` package as the module is useful independent
+   of the rest of the setuptools package. The main ``python-setuptools``
+   / ``python3-setuptools`` package depends on this new package so you
+   should only need to update dependencies unless you want to take
+   advantage of the increased granularity.
+
+.. _migration-3.0-cve-checking:
+
+CVE Checking
+------------
+
+``cve-check-tool`` has been functionally replaced by a new
+``cve-update-db`` recipe and functionality built into the ``cve-check``
+class. The result uses NVD JSON data feeds rather than the deprecated
+XML feeds that ``cve-check-tool`` was using, supports CVSSv3 scoring,
+and makes other improvements.
+
+Additionally, the ``CVE_CHECK_CVE_WHITELIST`` variable has been replaced
+by ``CVE_CHECK_WHITELIST``.
+
+.. _migration-3.0-bitbake-changes:
+
+Bitbake Changes
+---------------
+
+The following BitBake changes have occurred.
+
+-  ``addtask`` statements now properly validate dependent tasks.
+   Previously, an invalid task was silently ignored. With this change,
+   the invalid task generates a warning.
+
+-  Other invalid ``addtask`` and ``deltask`` usages now trigger these
+   warnings: "multiple target tasks arguments with addtask / deltask",
+   and "multiple before/after clauses".
+
+-  The "multiconfig" prefix is now shortened to "mc". "multiconfig" will
+   continue to work, however it may be removed in a future release.
+
+-  The ``bitbake -g`` command no longer generates a
+   ``recipe-depends.dot`` file as the contents (i.e. a reprocessed
+   version of ``task-depends.dot``) were confusing.
+
+-  The ``bb.build.FuncFailed`` exception, previously raised by
+   ``bb.build.exec_func()`` when certain other exceptions have occurred,
+   has been removed. The real underlying exceptions will be raised
+   instead. If you have calls to ``bb.build.exec_func()`` in custom
+   classes or ``tinfoil-using`` scripts, any references to
+   ``bb.build.FuncFailed`` should be cleaned up.
+
+-  Additionally, the ``bb.build.exec_func()`` no longer accepts the
+   "pythonexception" parameter. The function now always raises
+   exceptions. Remove this argument in any calls to
+   ``bb.build.exec_func()`` in custom classes or scripts.
+
+-  The
+   :term:`bitbake:BB_SETSCENE_VERIFY_FUNCTION2`
+   is no longer used. In the unlikely event that you have any references
+   to it, they should be removed.
+
+-  The ``RunQueueExecuteScenequeue`` and ``RunQueueExecuteTasks`` events
+   have been removed since setscene tasks are now executed as part of
+   the normal runqueue. Any event handling code in custom classes or
+   scripts that handles these two events need to be updated.
+
+-  The arguments passed to functions used with
+   :term:`bitbake:BB_HASHCHECK_FUNCTION`
+   have changed. If you are using your own custom hash check function,
+   see
+   http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=40a5e193c4ba45c928fccd899415ea56b5417725
+   for details.
+
+-  Task specifications in ``BB_TASKDEPDATA`` and class implementations
+   used in signature generator classes now use "<fn>:<task>" everywhere
+   rather than the "." delimiter that was being used in some places.
+   This change makes it consistent with all areas in the code. Custom
+   signature generator classes and code that reads ``BB_TASKDEPDATA``
+   need to be updated to use ':' as a separator rather than '.'.
+
+.. _migration-3.0-sanity-checks:
+
+Sanity Checks
+-------------
+
+The following sanity check changes occurred.
+
+-  :term:`SRC_URI` is now checked for usage of two
+   problematic items:
+
+   -  "${PN}" prefix/suffix use - Warnings always appear if ${PN} is
+      used. You must fix the issue regardless of whether multiconfig or
+      anything else that would cause prefixing/suffixing to happen.
+
+   -  Github archive tarballs - these are not guaranteed to be stable.
+      Consequently, it is likely that the tarballs will be refreshed and
+      thus the SRC_URI checksums will fail to apply. It is recommended
+      that you fetch either an official release tarball or a specific
+      revision from the actual Git repository instead.
+
+   Either one of these items now trigger a warning by default. If you
+   wish to disable this check, remove ``src-uri-bad`` from
+   :term:`WARN_QA`.
+
+-  The ``file-rdeps`` runtime dependency check no longer expands
+   :term:`RDEPENDS` recursively as there is no mechanism
+   to ensure they can be fully computed, and thus races sometimes result
+   in errors either showing up or not. Thus, you might now see errors
+   for missing runtime dependencies that were previously satisfied
+   recursively. Here is an example: package A contains a shell script
+   starting with ``#!/bin/bash`` but has no dependency on bash. However,
+   package A depends on package B, which does depend on bash. You need
+   to add the missing dependency or dependencies to resolve the warning.
+
+-  Setting ``DEPENDS_${PN}`` anywhere (i.e. typically in a recipe) now
+   triggers an error. The error is triggered because
+   :term:`DEPENDS` is not a package-specific variable
+   unlike RDEPENDS. You should set ``DEPENDS`` instead.
+
+-  systemd currently does not work well with the musl C library because
+   only upstream officially supports linking the library with glibc.
+   Thus, a warning is shown when building systemd in conjunction with
+   musl.
+
+.. _migration-3.0-miscellaneous-changes:
+
+Miscellaneous Changes
+---------------------
+
+The following miscellaneous changes have occurred.
+
+-  The ``gnome`` class has been removed because it now does very little.
+   You should update recipes that previously inherited this class to do
+   the following: inherit gnomebase gtk-icon-cache gconf mime
+
+-  The ``meta/recipes-kernel/linux/linux-dtb.inc`` file has been
+   removed. This file was previously deprecated in favor of setting
+   :term:`KERNEL_DEVICETREE` in any kernel
+   recipe and only produced a warning. Remove any ``include`` or
+   ``require`` statements pointing to this file.
+
+-  :term:`TARGET_CFLAGS`,
+   :term:`TARGET_CPPFLAGS`,
+   :term:`TARGET_CXXFLAGS`, and
+   :term:`TARGET_LDFLAGS` are no longer exported
+   to the external environment. This change did not require any changes
+   to core recipes, which is a good indicator that no changes will be
+   required. However, if for some reason the software being built by one
+   of your recipes is expecting these variables to be set, then building
+   the recipe will fail. In such cases, you must either export the
+   variable or variables in the recipe or change the scripts so that
+   exporting is not necessary.
+
+-  You must change the host distro identifier used in
+   :term:`NATIVELSBSTRING` to use all lowercase
+   characters even if it does not contain a version number. This change
+   is necessary only if you are not using ``uninative`` and
+   :term:`SANITY_TESTED_DISTROS`.
+
+-  In the ``base-files`` recipe, writing the hostname into
+   ``/etc/hosts`` and ``/etc/hostname`` is now done within the main
+   :ref:`ref-tasks-install` function rather than in the
+   ``do_install_basefilesissue`` function. The reason for the change is
+   because ``do_install_basefilesissue`` is more easily overridden
+   without having to duplicate the hostname functionality. If you have
+   done the latter (e.g. in a ``base-files`` bbappend), then you should
+   remove it from your customized ``do_install_basefilesissue``
+   function.
+
+-  The ``wic --expand`` command now uses commas to separate "key:value"
+   pairs rather than hyphens.
+
+   .. note::
+
+      The wic command-line help is not updated.
+
+   You must update any scripts or commands where you use
+   ``wic --expand`` with multiple "key:value" pairs.
+
+-  UEFI image variable settings have been moved from various places to a
+   central ``conf/image-uefi.conf``. This change should not influence
+   any existing configuration as the ``meta/conf/image-uefi.conf`` in
+   the core metadata sets defaults that can be overridden in the same
+   manner as before.
+
+-  ``conf/distro/include/world-broken.inc`` has been removed. For cases
+   where certain recipes need to be disabled when using the musl C
+   library, these recipes now have ``COMPATIBLE_HOST_libc-musl`` set
+   with a comment that explains why.
+
+
diff --git a/documentation/ref-manual/migration-3.1.rst b/documentation/ref-manual/migration-3.1.rst
new file mode 100644
index 0000000000..92c8c77613
--- /dev/null
+++ b/documentation/ref-manual/migration-3.1.rst
@@ -0,0 +1,276 @@
+Moving to the Yocto Project 3.1 Release
+=======================================
+
+This section provides migration information for moving to the Yocto
+Project 3.1 Release from the prior release.
+
+.. _migration-3.1-minimum-system-requirements:
+
+Minimum system requirements
+---------------------------
+
+The following versions / requirements of build host components have been
+updated:
+
+-  gcc 5.0
+
+-  python 3.5
+
+-  tar 1.28
+
+-  ``rpcgen`` is now required on the host (part of the ``libc-dev-bin``
+   package on Ubuntu, Debian and related distributions, and the
+   ``glibc`` package on RPM-based distributions).
+
+Additionally, the ``makeinfo`` and ``pod2man`` tools are *no longer*
+required on the host.
+
+.. _migration-3.1-mpc8315e-rdb-removed:
+
+mpc8315e-rdb machine removed
+----------------------------
+
+The MPC8315E-RDB machine is old/obsolete and unobtainable, thus given
+the maintenance burden the ``mpc8315e-rdb`` machine configuration that
+supported it has been removed in this release. The removal does leave a
+gap in official PowerPC reference hardware support; this may change in
+future if a suitable machine with accompanying support resources is
+found.
+
+.. _migration-3.1-python-2-removed:
+
+Python 2 removed
+----------------
+
+Due to the expiration of upstream support in January 2020, support for
+Python 2 has now been removed; it is recommended that you use Python 3
+instead. If absolutely needed there is a meta-python2 community layer
+containing Python 2, related classes and various Python 2-based modules,
+however it should not be considered as supported.
+
+.. _migration-3.1-reproducible-builds:
+
+Reproducible builds now enabled by default
+------------------------------------------
+
+In order to avoid unnecessary differences in output files (aiding binary
+reproducibility), the Poky distribution configuration
+(``DISTRO = "poky"``) now inherits the ``reproducible_build`` class by
+default.
+
+.. _migration-3.1-ptest-feature-impact:
+
+Impact of ptest feature is now more significant
+-----------------------------------------------
+
+The Poky distribution configuration (``DISTRO = "poky"``) enables ptests
+by default to enable runtime testing of various components. In this
+release, a dependency needed to be added that has resulted in a
+significant increase in the number of components that will be built just
+when building a simple image such as core-image-minimal. If you do not
+need runtime tests enabled for core components, then it is recommended
+that you remove "ptest" from
+:term:`DISTRO_FEATURES` to save a significant
+amount of build time e.g. by adding the following in your configuration:
+::
+
+   DISTRO_FEATURES_remove = "ptest"
+
+.. _migration-3.1-removed-recipes:
+
+Removed recipes
+---------------
+
+The following recipes have been removed:
+
+-  ``chkconfig``: obsolete
+
+-  ``console-tools``: obsolete
+
+-  ``enchant``: replaced by ``enchant2``
+
+-  ``foomatic-filters``: obsolete
+
+-  ``libidn``: no longer needed, moved to meta-oe
+
+-  ``libmodulemd``: replaced by ``libmodulemd-v1``
+
+-  ``linux-yocto``: drop 4.19, 5.2 version recipes (5.4 now provided)
+
+-  ``nspr``: no longer needed, moved to meta-oe
+
+-  ``nss``: no longer needed, moved to meta-oe
+
+-  ``python``: Python 2 removed (Python 3 preferred)
+
+-  ``python-setuptools``: Python 2 version removed (python3-setuptools
+   preferred)
+
+-  ``sysprof``: no longer needed, moved to meta-oe
+
+-  ``texi2html``: obsolete
+
+-  ``u-boot-fw-utils``: functionally replaced by ``libubootenv``
+
+.. _migration-3.1-features-check:
+
+features_check class replaces distro_features_check
+---------------------------------------------------
+
+The ``distro_features_check`` class has had its functionality expanded,
+now supporting ``ANY_OF_MACHINE_FEATURES``,
+``REQUIRED_MACHINE_FEATURES``, ``CONFLICT_MACHINE_FEATURES``,
+``ANY_OF_COMBINED_FEATURES``, ``REQUIRED_COMBINED_FEATURES``,
+``CONFLICT_COMBINED_FEATURES``. As a result the class has now been
+renamed to ``features_check``; the ``distro_features_check`` class still
+exists but generates a warning and redirects to the new class. In
+preparation for a future removal of the old class it is recommended that
+you update recipes currently inheriting ``distro_features_check`` to
+inherit ``features_check`` instead.
+
+.. _migration-3.1-removed-classes:
+
+Removed classes
+---------------
+
+The following classes have been removed:
+
+-  ``distutils-base``: moved to meta-python2
+
+-  ``distutils``: moved to meta-python2
+
+-  ``libc-common``: merged into the glibc recipe as nothing else used
+   it.
+
+-  ``python-dir``: moved to meta-python2
+
+-  ``pythonnative``: moved to meta-python2
+
+-  ``setuptools``: moved to meta-python2
+
+-  ``tinderclient``: dropped as it was obsolete.
+
+.. _migration-3.1-src-uri-checksums:
+
+SRC_URI checksum behaviour
+--------------------------
+
+Previously, recipes by tradition included both SHA256 and MD5 checksums
+for remotely fetched files in :term:`SRC_URI`, even
+though only one is actually mandated. However, the MD5 checksum does not
+add much given its inherent weakness; thus when a checksum fails only
+the SHA256 sum will now be printed. The md5sum will still be verified if
+it is specified.
+
+.. _migration-3.1-npm:
+
+npm fetcher changes
+-------------------
+
+The npm fetcher has been completely reworked in this release. The npm
+fetcher now only fetches the package source itself and no longer the
+dependencies; there is now also an npmsw fetcher which explicitly
+fetches the shrinkwrap file and the dependencies. This removes the
+slightly awkward ``NPM_LOCKDOWN`` and ``NPM_SHRINKWRAP`` variables which
+pointed to local files; the lockdown file is no longer needed at all.
+Additionally, the package name in ``npm://`` entries in
+:term:`SRC_URI` is now specified using a ``package``
+parameter instead of the earlier ``name`` which overlapped with the
+generic ``name`` parameter. All recipes using the npm fetcher will need
+to be changed as a result.
+
+An example of the new scheme: ::
+
+   SRC_URI = "npm://registry.npmjs.org;package=array-flatten;version=1.1.1 \\
+              npmsw://${THISDIR}/npm-shrinkwrap.json"
+
+Another example where the sources are fetched from git rather than an npm repository: ::
+
+   SRC_URI = "git://github.com/foo/bar.git;protocol=https \
+              npmsw://${THISDIR}/npm-shrinkwrap.json"
+
+devtool and recipetool have also been updated to match with the npm
+fetcher changes. Other than producing working and more complete recipes
+for npm sources, there is also a minor change to the command line for
+devtool: the ``--fetch-dev`` option has been renamed to ``--npm-dev`` as
+it is npm-specific.
+
+.. _migration-3.1-packaging-changes:
+
+Packaging changes
+-----------------
+
+-  ``intltool`` has been removed from ``packagegroup-core-sdk`` as it is
+   rarely needed to build modern software - gettext can do most of the
+   things it used to be needed for. ``intltool`` has also been removed
+   from ``packagegroup-core-self-hosted`` as it is not needed to for
+   standard builds.
+
+-  git: ``git-am``, ``git-difftool``, ``git-submodule``, and
+   ``git-request-pull`` are no longer perl-based, so are now installed
+   with the main ``git`` package instead of within ``git-perltools``.
+
+-  The ``ldconfig`` binary built as part of glibc has now been moved to
+   its own ``ldconfig`` package (note no ``glibc-`` prefix). This
+   package is in the :term:`RRECOMMENDS` of the main
+   ``glibc`` package if ``ldconfig`` is present in
+   :term:`DISTRO_FEATURES`.
+
+-  ``libevent`` now splits each shared library into its own package (as
+   Debian does). Since these are shared libraries and will be pulled in
+   through the normal shared library dependency handling, there should
+   be no impact to existing configurations other than less unnecessary
+   libraries being installed in some cases.
+
+-  linux-firmware now has a new package for ``bcm4366c`` and includes
+   available NVRAM config files into the ``bcm43340``, ``bcm43362``,
+   ``bcm43430`` and ``bcm4356-pcie`` packages.
+
+-  ``harfbuzz`` now splits the new ``libharfbuzz-subset.so`` library
+   into its own package to reduce the main package size in cases where
+   ``libharfbuzz-subset.so`` is not needed.
+
+.. _migration-3.1-package-qa-warnings:
+
+Additional warnings
+-------------------
+
+Warnings will now be shown at ``do_package_qa`` time in the following
+circumstances:
+
+-  A recipe installs ``.desktop`` files containing ``MimeType`` keys but
+   does not inherit the new ``mime-xdg`` class
+
+-  A recipe installs ``.xml`` files into ``${datadir}/mime/packages``
+   but does not inherit the ``mime`` class
+
+.. _migration-3.1-x86-live-wic:
+
+``wic`` image type now used instead of ``live`` by default for x86
+------------------------------------------------------------------
+
+``conf/machine/include/x86-base.inc`` (inherited by most x86 machine
+configurations) now specifies ``wic`` instead of ``live`` by default in
+:term:`IMAGE_FSTYPES`. The ``live`` image type will
+likely be removed in a future release so it is recommended that you use
+``wic`` instead.
+
+.. _migration-3.1-misc:
+
+Miscellaneous changes
+---------------------
+
+-  The undocumented ``SRC_DISTRIBUTE_LICENSES`` variable has now been
+   removed in favour of a new ``AVAILABLE_LICENSES`` variable which is
+   dynamically set based upon license files found in
+   ``${COMMON_LICENSE_DIR}`` and ``${LICENSE_PATH}``.
+
+-  The tune definition for big-endian microblaze machines is now
+   ``microblaze`` instead of ``microblazeeb``.
+
+-  ``newlib`` no longer has built-in syscalls. ``libgloss`` should then
+   provide the syscalls, ``crt0.o`` and other functions that are no
+   longer part of ``newlib`` itself. If you are using
+   ``TCLIBC = "newlib"`` this now means that you must link applications
+   with both ``newlib`` and ``libgloss``, whereas before ``newlib``
+   would run in many configurations by itself.
diff --git a/documentation/ref-manual/migration-general.rst b/documentation/ref-manual/migration-general.rst
new file mode 100644
index 0000000000..182482ec43
--- /dev/null
+++ b/documentation/ref-manual/migration-general.rst
@@ -0,0 +1,54 @@
+General Migration Considerations
+================================
+
+Some considerations are not tied to a specific Yocto Project release.
+This section presents information you should consider when migrating to
+any new Yocto Project release.
+
+-  *Dealing with Customized Recipes*:
+
+   Issues could arise if you take
+   older recipes that contain customizations and simply copy them
+   forward expecting them to work after you migrate to new Yocto Project
+   metadata. For example, suppose you have a recipe in your layer that
+   is a customized version of a core recipe copied from the earlier
+   release, rather than through the use of an append file. When you
+   migrate to a newer version of Yocto Project, the metadata (e.g.
+   perhaps an include file used by the recipe) could have changed in a
+   way that would break the build. Say, for example, a function is
+   removed from an include file and the customized recipe tries to call
+   that function.
+
+   You could "forward-port" all your customizations in your recipe so
+   that everything works for the new release. However, this is not the
+   optimal solution as you would have to repeat this process with each
+   new release if changes occur that give rise to problems.
+
+   The better solution (where practical) is to use append files
+   (``*.bbappend``) to capture any customizations you want to make to a
+   recipe. Doing so, isolates your changes from the main recipe making
+   them much more manageable. However, sometimes it is not practical to
+   use an append file. A good example of this is when introducing a
+   newer or older version of a recipe in another layer.
+
+-  *Updating Append Files*:
+
+   Since append files generally only contain
+   your customizations, they often do not need to be adjusted for new
+   releases. However, if the ``.bbappend`` file is specific to a
+   particular version of the recipe (i.e. its name does not use the %
+   wildcard) and the version of the recipe to which it is appending has
+   changed, then you will at a minimum need to rename the append file to
+   match the name of the recipe file. A mismatch between an append file
+   and its corresponding recipe file (``.bb``) will trigger an error
+   during parsing.
+
+   Depending on the type of customization the append file applies, other
+   incompatibilities might occur when you upgrade. For example, if your
+   append file applies a patch and the recipe to which it is appending
+   is updated to a newer version, the patch might no longer apply. If
+   this is the case and assuming the patch is still needed, you must
+   modify the patch file so that it does apply.
+
+
+
diff --git a/documentation/ref-manual/migration.rst b/documentation/ref-manual/migration.rst
new file mode 100644
index 0000000000..6c6119daec
--- /dev/null
+++ b/documentation/ref-manual/migration.rst
@@ -0,0 +1,30 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+******************************************
+Migrating to a Newer Yocto Project Release
+******************************************
+
+This chapter provides information you can use to migrate work to a newer
+Yocto Project release. You can find the same information in the release
+notes for a given release.
+
+.. toctree::
+
+   migration-general
+   migration-1.3
+   migration-1.4
+   migration-1.5
+   migration-1.6
+   migration-1.7
+   migration-1.8
+   migration-2.0
+   migration-2.1
+   migration-2.2
+   migration-2.3
+   migration-2.4
+   migration-2.5
+   migration-2.6
+   migration-2.7
+   migration-3.0
+   migration-3.1
+
diff --git a/documentation/ref-manual/migration.xml b/documentation/ref-manual/migration.xml
index affc8b90a7..d3d5b16bdd 100644
--- a/documentation/ref-manual/migration.xml
+++ b/documentation/ref-manual/migration.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='migration'>
 <title>Migrating to a Newer Yocto Project Release</title>
diff --git a/documentation/ref-manual/ref-classes.rst b/documentation/ref-manual/ref-classes.rst
new file mode 100644
index 0000000000..60ce8efd21
--- /dev/null
+++ b/documentation/ref-manual/ref-classes.rst
@@ -0,0 +1,2963 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+*******
+Classes
+*******
+
+Class files are used to abstract common functionality and share it
+amongst multiple recipe (``.bb``) files. To use a class file, you simply
+make sure the recipe inherits the class. In most cases, when a recipe
+inherits a class it is enough to enable its features. There are cases,
+however, where in the recipe you might need to set variables or override
+some default behavior.
+
+Any :term:`Metadata` usually found in a recipe can also be
+placed in a class file. Class files are identified by the extension
+``.bbclass`` and are usually placed in a ``classes/`` directory beneath
+the ``meta*/`` directory found in the :term:`Source Directory`.
+Class files can also be pointed to by
+:term:`BUILDDIR` (e.g. ``build/``) in the same way as
+``.conf`` files in the ``conf`` directory. Class files are searched for
+in :term:`BBPATH` using the same method by which ``.conf``
+files are searched.
+
+This chapter discusses only the most useful and important classes. Other
+classes do exist within the ``meta/classes`` directory in the Source
+Directory. You can reference the ``.bbclass`` files directly for more
+information.
+
+.. _ref-classes-allarch:
+
+``allarch.bbclass``
+===================
+
+The ``allarch`` class is inherited by recipes that do not produce
+architecture-specific output. The class disables functionality that is
+normally needed for recipes that produce executable binaries (such as
+building the cross-compiler and a C library as pre-requisites, and
+splitting out of debug symbols during packaging).
+
+.. note::
+
+   Unlike some distro recipes (e.g. Debian), OpenEmbedded recipes that
+   produce packages that depend on tunings through use of the
+   :term:`RDEPENDS` and
+   :term:`TUNE_PKGARCH` variables, should never be
+   configured for all architectures using ``allarch``. This is the case
+   even if the recipes do not produce architecture-specific output.
+
+   Configuring such recipes for all architectures causes the
+   ```do_package_write_*`` tasks to
+   have different signatures for the machines with different tunings.
+   Additionally, unnecessary rebuilds occur every time an image for a
+   different ``MACHINE`` is built even when the recipe never changes.
+
+By default, all recipes inherit the :ref:`base <ref-classes-base>` and
+:ref:`package <ref-classes-package>` classes, which enable
+functionality needed for recipes that produce executable output. If your
+recipe, for example, only produces packages that contain configuration
+files, media files, or scripts (e.g. Python and Perl), then it should
+inherit the ``allarch`` class.
+
+.. _ref-classes-archiver:
+
+``archiver.bbclass``
+====================
+
+The ``archiver`` class supports releasing source code and other
+materials with the binaries.
+
+For more details on the source archiver, see the
+":ref:`dev-manual/dev-manual-common-tasks:maintaining open source license compliance during your product's lifecycle`"
+section in the Yocto Project Development Tasks Manual. You can also see
+the :term:`ARCHIVER_MODE` variable for information
+about the variable flags (varflags) that help control archive creation.
+
+.. _ref-classes-autotools:
+
+``autotools*.bbclass``
+======================
+
+The ``autotools*`` classes support Autotooled packages.
+
+The ``autoconf``, ``automake``, and ``libtool`` packages bring
+standardization. This class defines a set of tasks (e.g. ``configure``,
+``compile`` and so forth) that work for all Autotooled packages. It
+should usually be enough to define a few standard variables and then
+simply ``inherit autotools``. These classes can also work with software
+that emulates Autotools. For more information, see the
+":ref:`new-recipe-autotooled-package`" section
+in the Yocto Project Development Tasks Manual.
+
+By default, the ``autotools*`` classes use out-of-tree builds (i.e.
+``autotools.bbclass`` building with ``B != S``).
+
+If the software being built by a recipe does not support using
+out-of-tree builds, you should have the recipe inherit the
+``autotools-brokensep`` class. The ``autotools-brokensep`` class behaves
+the same as the ``autotools`` class but builds with :term:`B`
+== :term:`S`. This method is useful when out-of-tree build
+support is either not present or is broken.
+
+.. note::
+
+   It is recommended that out-of-tree support be fixed and used if at
+   all possible.
+
+It's useful to have some idea of how the tasks defined by the
+``autotools*`` classes work and what they do behind the scenes.
+
+-  :ref:`ref-tasks-configure` - Regenerates the
+   configure script (using ``autoreconf``) and then launches it with a
+   standard set of arguments used during cross-compilation. You can pass
+   additional parameters to ``configure`` through the ``EXTRA_OECONF``
+   or :term:`PACKAGECONFIG_CONFARGS`
+   variables.
+
+-  :ref:`ref-tasks-compile` - Runs ``make`` with
+   arguments that specify the compiler and linker. You can pass
+   additional arguments through the ``EXTRA_OEMAKE`` variable.
+
+-  :ref:`ref-tasks-install` - Runs ``make install`` and
+   passes in ``${``\ :term:`D`\ ``}`` as ``DESTDIR``.
+
+.. _ref-classes-base:
+
+``base.bbclass``
+================
+
+The ``base`` class is special in that every ``.bb`` file implicitly
+inherits the class. This class contains definitions for standard basic
+tasks such as fetching, unpacking, configuring (empty by default),
+compiling (runs any ``Makefile`` present), installing (empty by default)
+and packaging (empty by default). These classes are often overridden or
+extended by other classes such as the
+:ref:`autotools <ref-classes-autotools>` class or the
+:ref:`package <ref-classes-package>` class.
+
+The class also contains some commonly used functions such as
+``oe_runmake``, which runs ``make`` with the arguments specified in
+:term:`EXTRA_OEMAKE` variable as well as the
+arguments passed directly to ``oe_runmake``.
+
+.. _ref-classes-bash-completion:
+
+``bash-completion.bbclass``
+===========================
+
+Sets up packaging and dependencies appropriate for recipes that build
+software that includes bash-completion data.
+
+.. _ref-classes-bin-package:
+
+``bin_package.bbclass``
+=======================
+
+The ``bin_package`` class is a helper class for recipes that extract the
+contents of a binary package (e.g. an RPM) and install those contents
+rather than building the binary from source. The binary package is
+extracted and new packages in the configured output package format are
+created. Extraction and installation of proprietary binaries is a good
+example use for this class.
+
+.. note::
+
+   For RPMs and other packages that do not contain a subdirectory, you
+   should specify an appropriate fetcher parameter to point to the
+   subdirectory. For example, if BitBake is using the Git fetcher (
+   git://
+   ), the "subpath" parameter limits the checkout to a specific subpath
+   of the tree. Here is an example where
+   ${BP}
+   is used so that the files are extracted into the subdirectory
+   expected by the default value of
+   S
+   :
+   ::
+
+           SRC_URI = "git://example.com/downloads/somepackage.rpm;subpath=${BP}"
+
+
+   See the "
+   Fetchers
+   " section in the BitBake User Manual for more information on
+   supported BitBake Fetchers.
+
+.. _ref-classes-binconfig:
+
+``binconfig.bbclass``
+=====================
+
+The ``binconfig`` class helps to correct paths in shell scripts.
+
+Before ``pkg-config`` had become widespread, libraries shipped shell
+scripts to give information about the libraries and include paths needed
+to build software (usually named ``LIBNAME-config``). This class assists
+any recipe using such scripts.
+
+During staging, the OpenEmbedded build system installs such scripts into
+the ``sysroots/`` directory. Inheriting this class results in all paths
+in these scripts being changed to point into the ``sysroots/`` directory
+so that all builds that use the script use the correct directories for
+the cross compiling layout. See the
+:term:`BINCONFIG_GLOB` variable for more
+information.
+
+.. _ref-classes-binconfig-disabled:
+
+``binconfig-disabled.bbclass``
+==============================
+
+An alternative version of the :ref:`binconfig <ref-classes-binconfig>`
+class, which disables binary configuration scripts by making them return
+an error in favor of using ``pkg-config`` to query the information. The
+scripts to be disabled should be specified using the
+:term:`BINCONFIG` variable within the recipe inheriting
+the class.
+
+.. _ref-classes-blacklist:
+
+``blacklist.bbclass``
+=====================
+
+The ``blacklist`` class prevents the OpenEmbedded build system from
+building specific recipes (blacklists them). To use this class, inherit
+the class globally and set :term:`PNBLACKLIST` for
+each recipe you wish to blacklist. Specify the :term:`PN`
+value as a variable flag (varflag) and provide a reason, which is
+reported, if the package is requested to be built as the value. For
+example, if you want to blacklist a recipe called "exoticware", you add
+the following to your ``local.conf`` or distribution configuration:
+::
+
+   INHERIT += "blacklist"
+   PNBLACKLIST[exoticware] = "Not supported by our organization."
+
+.. _ref-classes-buildhistory:
+
+``buildhistory.bbclass``
+========================
+
+The ``buildhistory`` class records a history of build output metadata,
+which can be used to detect possible regressions as well as used for
+analysis of the build output. For more information on using Build
+History, see the
+":ref:`dev-manual/dev-manual-common-tasks:maintaining build output quality`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _ref-classes-buildstats:
+
+``buildstats.bbclass``
+======================
+
+The ``buildstats`` class records performance statistics about each task
+executed during the build (e.g. elapsed time, CPU usage, and I/O usage).
+
+When you use this class, the output goes into the
+:term:`BUILDSTATS_BASE` directory, which defaults
+to ``${TMPDIR}/buildstats/``. You can analyze the elapsed time using
+``scripts/pybootchartgui/pybootchartgui.py``, which produces a cascading
+chart of the entire build process and can be useful for highlighting
+bottlenecks.
+
+Collecting build statistics is enabled by default through the
+:term:`USER_CLASSES` variable from your
+``local.conf`` file. Consequently, you do not have to do anything to
+enable the class. However, if you want to disable the class, simply
+remove "buildstats" from the ``USER_CLASSES`` list.
+
+.. _ref-classes-buildstats-summary:
+
+``buildstats-summary.bbclass``
+==============================
+
+When inherited globally, prints statistics at the end of the build on
+sstate re-use. In order to function, this class requires the
+:ref:`buildstats <ref-classes-buildstats>` class be enabled.
+
+.. _ref-classes-ccache:
+
+``ccache.bbclass``
+==================
+
+The ``ccache`` class enables the C/C++ Compiler Cache for the build.
+This class is used to give a minor performance boost during the build.
+However, using the class can lead to unexpected side-effects. Thus, it
+is recommended that you do not use this class. See
+http://ccache.samba.org/ for information on the C/C++ Compiler
+Cache.
+
+.. _ref-classes-chrpath:
+
+``chrpath.bbclass``
+===================
+
+The ``chrpath`` class is a wrapper around the "chrpath" utility, which
+is used during the build process for ``nativesdk``, ``cross``, and
+``cross-canadian`` recipes to change ``RPATH`` records within binaries
+in order to make them relocatable.
+
+.. _ref-classes-clutter:
+
+``clutter.bbclass``
+===================
+
+The ``clutter`` class consolidates the major and minor version naming
+and other common items used by Clutter and related recipes.
+
+.. note::
+
+   Unlike some other classes related to specific libraries, recipes
+   building other software that uses Clutter do not need to inherit this
+   class unless they use the same recipe versioning scheme that the
+   Clutter and related recipes do.
+
+.. _ref-classes-cmake:
+
+``cmake.bbclass``
+=================
+
+The ``cmake`` class allows for recipes that need to build software using
+the `CMake <https://cmake.org/overview/>`__ build system. You can use
+the :term:`EXTRA_OECMAKE` variable to specify
+additional configuration options to be passed using the ``cmake``
+command line.
+
+On the occasion that you would be installing custom CMake toolchain
+files supplied by the application being built, you should install them
+to the preferred CMake Module directory: ``${D}${datadir}/cmake/``
+Modules during
+:ref:`ref-tasks-install`.
+
+.. _ref-classes-cml1:
+
+``cml1.bbclass``
+================
+
+The ``cml1`` class provides basic support for the Linux kernel style
+build configuration system.
+
+.. _ref-classes-compress_doc:
+
+``compress_doc.bbclass``
+========================
+
+Enables compression for man pages and info pages. This class is intended
+to be inherited globally. The default compression mechanism is gz (gzip)
+but you can select an alternative mechanism by setting the
+:term:`DOC_COMPRESS` variable.
+
+.. _ref-classes-copyleft_compliance:
+
+``copyleft_compliance.bbclass``
+===============================
+
+The ``copyleft_compliance`` class preserves source code for the purposes
+of license compliance. This class is an alternative to the ``archiver``
+class and is still used by some users even though it has been deprecated
+in favor of the :ref:`archiver <ref-classes-archiver>` class.
+
+.. _ref-classes-copyleft_filter:
+
+``copyleft_filter.bbclass``
+===========================
+
+A class used by the :ref:`archiver <ref-classes-archiver>` and
+:ref:`copyleft_compliance <ref-classes-copyleft_compliance>` classes
+for filtering licenses. The ``copyleft_filter`` class is an internal
+class and is not intended to be used directly.
+
+.. _ref-classes-core-image:
+
+``core-image.bbclass``
+======================
+
+The ``core-image`` class provides common definitions for the
+``core-image-*`` image recipes, such as support for additional
+:term:`IMAGE_FEATURES`.
+
+.. _ref-classes-cpan:
+
+``cpan*.bbclass``
+=================
+
+The ``cpan*`` classes support Perl modules.
+
+Recipes for Perl modules are simple. These recipes usually only need to
+point to the source's archive and then inherit the proper class file.
+Building is split into two methods depending on which method the module
+authors used.
+
+-  Modules that use old ``Makefile.PL``-based build system require
+   ``cpan.bbclass`` in their recipes.
+
+-  Modules that use ``Build.PL``-based build system require using
+   ``cpan_build.bbclass`` in their recipes.
+
+Both build methods inherit the ``cpan-base`` class for basic Perl
+support.
+
+.. _ref-classes-cross:
+
+``cross.bbclass``
+=================
+
+The ``cross`` class provides support for the recipes that build the
+cross-compilation tools.
+
+.. _ref-classes-cross-canadian:
+
+``cross-canadian.bbclass``
+==========================
+
+The ``cross-canadian`` class provides support for the recipes that build
+the Canadian Cross-compilation tools for SDKs. See the
+":ref:`overview-manual/overview-manual-concepts:cross-development toolchain generation`"
+section in the Yocto Project Overview and Concepts Manual for more
+discussion on these cross-compilation tools.
+
+.. _ref-classes-crosssdk:
+
+``crosssdk.bbclass``
+====================
+
+The ``crosssdk`` class provides support for the recipes that build the
+cross-compilation tools used for building SDKs. See the
+":ref:`overview-manual/overview-manual-concepts:cross-development toolchain generation`"
+section in the Yocto Project Overview and Concepts Manual for more
+discussion on these cross-compilation tools.
+
+.. _ref-classes-debian:
+
+``debian.bbclass``
+==================
+
+The ``debian`` class renames output packages so that they follow the
+Debian naming policy (i.e. ``glibc`` becomes ``libc6`` and
+``glibc-devel`` becomes ``libc6-dev``.) Renaming includes the library
+name and version as part of the package name.
+
+If a recipe creates packages for multiple libraries (shared object files
+of ``.so`` type), use the :term:`LEAD_SONAME`
+variable in the recipe to specify the library on which to apply the
+naming scheme.
+
+.. _ref-classes-deploy:
+
+``deploy.bbclass``
+==================
+
+The ``deploy`` class handles deploying files to the
+:term:`DEPLOY_DIR_IMAGE` directory. The main
+function of this class is to allow the deploy step to be accelerated by
+shared state. Recipes that inherit this class should define their own
+:ref:`ref-tasks-deploy` function to copy the files to be
+deployed to :term:`DEPLOYDIR`, and use ``addtask`` to
+add the task at the appropriate place, which is usually after
+:ref:`ref-tasks-compile` or
+:ref:`ref-tasks-install`. The class then takes care of
+staging the files from ``DEPLOYDIR`` to ``DEPLOY_DIR_IMAGE``.
+
+.. _ref-classes-devshell:
+
+``devshell.bbclass``
+====================
+
+The ``devshell`` class adds the ``do_devshell`` task. Distribution
+policy dictates whether to include this class. See the ":ref:`platdev-appdev-devshell`"
+section in the Yocto Project Development Tasks Manual for more
+information about using ``devshell``.
+
+.. _ref-classes-devupstream:
+
+``devupstream.bbclass``
+=======================
+
+The ``devupstream`` class uses
+:term:`BBCLASSEXTEND` to add a variant of the
+recipe that fetches from an alternative URI (e.g. Git) instead of a
+tarball. Following is an example:
+::
+
+   BBCLASSEXTEND = "devupstream:target"
+   SRC_URI_class-devupstream = "git://git.example.com/example"
+   SRCREV_class-devupstream = "abcd1234"
+
+Adding the above statements to your recipe creates a variant that has
+:term:`DEFAULT_PREFERENCE` set to "-1".
+Consequently, you need to select the variant of the recipe to use it.
+Any development-specific adjustments can be done by using the
+``class-devupstream`` override. Here is an example:
+::
+
+   DEPENDS_append_class-devupstream = " gperf-native"
+   do_configure_prepend_class-devupstream() {
+       touch ${S}/README
+   }
+
+The class
+currently only supports creating a development variant of the target
+recipe, not ``native`` or ``nativesdk`` variants.
+
+The ``BBCLASSEXTEND`` syntax (i.e. ``devupstream:target``) provides
+support for ``native`` and ``nativesdk`` variants. Consequently, this
+functionality can be added in a future release.
+
+Support for other version control systems such as Subversion is limited
+due to BitBake's automatic fetch dependencies (e.g.
+``subversion-native``).
+
+.. _ref-classes-distro_features_check:
+
+``distro_features_check.bbclass``
+=================================
+
+The ``distro_features_check`` class allows individual recipes to check
+for required and conflicting
+:term:`DISTRO_FEATURES`.
+
+This class provides support for the
+:term:`REQUIRED_DISTRO_FEATURES` and
+:term:`CONFLICT_DISTRO_FEATURES`
+variables. If any conditions specified in the recipe using the above
+variables are not met, the recipe will be skipped.
+
+.. _ref-classes-distutils:
+
+``distutils*.bbclass``
+======================
+
+The ``distutils*`` classes support recipes for Python version 2.x
+extensions, which are simple. These recipes usually only need to point
+to the source's archive and then inherit the proper class. Building is
+split into two methods depending on which method the module authors
+used.
+
+-  Extensions that use an Autotools-based build system require Autotools
+   and the classes based on ``distutils`` in their recipes.
+
+-  Extensions that use build systems based on ``distutils`` require the
+   ``distutils`` class in their recipes.
+
+-  Extensions that use build systems based on ``setuptools`` require the
+   :ref:`setuptools <ref-classes-setuptools>` class in their recipes.
+
+The ``distutils-common-base`` class is required by some of the
+``distutils*`` classes to provide common Python2 support.
+
+.. _ref-classes-distutils3:
+
+``distutils3*.bbclass``
+=======================
+
+The ``distutils3*`` classes support recipes for Python version 3.x
+extensions, which are simple. These recipes usually only need to point
+to the source's archive and then inherit the proper class. Building is
+split into three methods depending on which method the module authors
+used.
+
+-  Extensions that use an Autotools-based build system require Autotools
+   and ``distutils``-based classes in their recipes.
+
+-  Extensions that use ``distutils``-based build systems require the
+   ``distutils`` class in their recipes.
+
+-  Extensions that use build systems based on ``setuptools3`` require
+   the :ref:`setuptools3 <ref-classes-setuptools>` class in their
+   recipes.
+
+The ``distutils3*`` classes either inherit their corresponding
+``distutils*`` class or replicate them using a Python3 version instead
+(e.g. ``distutils3-base`` inherits ``distutils-common-base``, which is
+the same as ``distutils-base`` but inherits ``python3native`` instead of
+``pythonnative``).
+
+.. _ref-classes-externalsrc:
+
+``externalsrc.bbclass``
+=======================
+
+The ``externalsrc`` class supports building software from source code
+that is external to the OpenEmbedded build system. Building software
+from an external source tree means that the build system's normal fetch,
+unpack, and patch process is not used.
+
+By default, the OpenEmbedded build system uses the :term:`S`
+and :term:`B` variables to locate unpacked recipe source code
+and to build it, respectively. When your recipe inherits the
+``externalsrc`` class, you use the
+:term:`EXTERNALSRC` and
+:term:`EXTERNALSRC_BUILD` variables to
+ultimately define ``S`` and ``B``.
+
+By default, this class expects the source code to support recipe builds
+that use the :term:`B` variable to point to the directory in
+which the OpenEmbedded build system places the generated objects built
+from the recipes. By default, the ``B`` directory is set to the
+following, which is separate from the source directory (``S``):
+::
+
+   ${WORKDIR}/${BPN}/{PV}/
+
+See these variables for more information:
+:term:`WORKDIR`, :term:`BPN`, and
+:term:`PV`,
+
+For more information on the ``externalsrc`` class, see the comments in
+``meta/classes/externalsrc.bbclass`` in the :term:`Source Directory`.
+For information on how to use the
+``externalsrc`` class, see the
+":ref:`dev-manual/dev-manual-common-tasks:building software from an external source`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _ref-classes-extrausers:
+
+``extrausers.bbclass``
+======================
+
+The ``extrausers`` class allows additional user and group configuration
+to be applied at the image level. Inheriting this class either globally
+or from an image recipe allows additional user and group operations to
+be performed using the
+:term:`EXTRA_USERS_PARAMS` variable.
+
+.. note::
+
+   The user and group operations added using the
+   extrausers
+   class are not tied to a specific recipe outside of the recipe for the
+   image. Thus, the operations can be performed across the image as a
+   whole. Use the
+   useradd
+   class to add user and group configuration to a specific recipe.
+
+Here is an example that uses this class in an image recipe:
+::
+
+   inherit extrausers
+   EXTRA_USERS_PARAMS = "\
+       useradd -p '' tester; \
+       groupadd developers; \
+       userdel nobody; \
+       groupdel -g video; \
+       groupmod -g 1020 developers; \
+       usermod -s /bin/sh tester; \
+       "
+
+Here is an example that adds two users named "tester-jim" and "tester-sue" and assigns
+passwords:
+::
+
+   inherit extrausers
+   EXTRA_USERS_PARAMS = "\
+       useradd -P tester01 tester-jim; \
+       useradd -P tester01 tester-sue; \
+       "
+
+Finally, here is an example that sets the root password to "1876*18":
+::
+
+   inherit extrausers
+   EXTRA_USERS_PARAMS = "\
+       usermod -P 1876*18 root; \
+       "
+
+.. _ref-classes-fontcache:
+
+``fontcache.bbclass``
+=====================
+
+The ``fontcache`` class generates the proper post-install and
+post-remove (postinst and postrm) scriptlets for font packages. These
+scriptlets call ``fc-cache`` (part of ``Fontconfig``) to add the fonts
+to the font information cache. Since the cache files are
+architecture-specific, ``fc-cache`` runs using QEMU if the postinst
+scriptlets need to be run on the build host during image creation.
+
+If the fonts being installed are in packages other than the main
+package, set :term:`FONT_PACKAGES` to specify the
+packages containing the fonts.
+
+.. _ref-classes-fs-uuid:
+
+``fs-uuid.bbclass``
+===================
+
+The ``fs-uuid`` class extracts UUID from
+``${``\ :term:`ROOTFS`\ ``}``, which must have been built
+by the time that this function gets called. The ``fs-uuid`` class only
+works on ``ext`` file systems and depends on ``tune2fs``.
+
+.. _ref-classes-gconf:
+
+``gconf.bbclass``
+=================
+
+The ``gconf`` class provides common functionality for recipes that need
+to install GConf schemas. The schemas will be put into a separate
+package (``${``\ :term:`PN`\ ``}-gconf``) that is created
+automatically when this class is inherited. This package uses the
+appropriate post-install and post-remove (postinst/postrm) scriptlets to
+register and unregister the schemas in the target image.
+
+.. _ref-classes-gettext:
+
+``gettext.bbclass``
+===================
+
+The ``gettext`` class provides support for building software that uses
+the GNU ``gettext`` internationalization and localization system. All
+recipes building software that use ``gettext`` should inherit this
+class.
+
+.. _ref-classes-gnomebase:
+
+``gnomebase.bbclass``
+=====================
+
+The ``gnomebase`` class is the base class for recipes that build
+software from the GNOME stack. This class sets
+:term:`SRC_URI` to download the source from the GNOME
+mirrors as well as extending :term:`FILES` with the typical
+GNOME installation paths.
+
+.. _ref-classes-gobject-introspection:
+
+``gobject-introspection.bbclass``
+=================================
+
+Provides support for recipes building software that supports GObject
+introspection. This functionality is only enabled if the
+"gobject-introspection-data" feature is in
+:term:`DISTRO_FEATURES` as well as
+"qemu-usermode" being in
+:term:`MACHINE_FEATURES`.
+
+.. note::
+
+   This functionality is backfilled by default and, if not applicable,
+   should be disabled through
+   DISTRO_FEATURES_BACKFILL_CONSIDERED
+   or
+   MACHINE_FEATURES_BACKFILL_CONSIDERED
+   , respectively.
+
+.. _ref-classes-grub-efi:
+
+``grub-efi.bbclass``
+====================
+
+The ``grub-efi`` class provides ``grub-efi``-specific functions for
+building bootable images.
+
+This class supports several variables:
+
+-  :term:`INITRD`: Indicates list of filesystem images to
+   concatenate and use as an initial RAM disk (initrd) (optional).
+
+-  :term:`ROOTFS`: Indicates a filesystem image to include
+   as the root filesystem (optional).
+
+-  :term:`GRUB_GFXSERIAL`: Set this to "1" to have
+   graphics and serial in the boot menu.
+
+-  :term:`LABELS`: A list of targets for the automatic
+   configuration.
+
+-  :term:`APPEND`: An override list of append strings for
+   each ``LABEL``.
+
+-  :term:`GRUB_OPTS`: Additional options to add to the
+   configuration (optional). Options are delimited using semi-colon
+   characters (``;``).
+
+-  :term:`GRUB_TIMEOUT`: Timeout before executing
+   the default ``LABEL`` (optional).
+
+.. _ref-classes-gsettings:
+
+``gsettings.bbclass``
+=====================
+
+The ``gsettings`` class provides common functionality for recipes that
+need to install GSettings (glib) schemas. The schemas are assumed to be
+part of the main package. Appropriate post-install and post-remove
+(postinst/postrm) scriptlets are added to register and unregister the
+schemas in the target image.
+
+.. _ref-classes-gtk-doc:
+
+``gtk-doc.bbclass``
+===================
+
+The ``gtk-doc`` class is a helper class to pull in the appropriate
+``gtk-doc`` dependencies and disable ``gtk-doc``.
+
+.. _ref-classes-gtk-icon-cache:
+
+``gtk-icon-cache.bbclass``
+==========================
+
+The ``gtk-icon-cache`` class generates the proper post-install and
+post-remove (postinst/postrm) scriptlets for packages that use GTK+ and
+install icons. These scriptlets call ``gtk-update-icon-cache`` to add
+the fonts to GTK+'s icon cache. Since the cache files are
+architecture-specific, ``gtk-update-icon-cache`` is run using QEMU if
+the postinst scriptlets need to be run on the build host during image
+creation.
+
+.. _ref-classes-gtk-immodules-cache:
+
+``gtk-immodules-cache.bbclass``
+===============================
+
+The ``gtk-immodules-cache`` class generates the proper post-install and
+post-remove (postinst/postrm) scriptlets for packages that install GTK+
+input method modules for virtual keyboards. These scriptlets call
+``gtk-update-icon-cache`` to add the input method modules to the cache.
+Since the cache files are architecture-specific,
+``gtk-update-icon-cache`` is run using QEMU if the postinst scriptlets
+need to be run on the build host during image creation.
+
+If the input method modules being installed are in packages other than
+the main package, set
+:term:`GTKIMMODULES_PACKAGES` to specify
+the packages containing the modules.
+
+.. _ref-classes-gzipnative:
+
+``gzipnative.bbclass``
+======================
+
+The ``gzipnative`` class enables the use of different native versions of
+``gzip`` and ``pigz`` rather than the versions of these tools from the
+build host.
+
+.. _ref-classes-icecc:
+
+``icecc.bbclass``
+=================
+
+The ``icecc`` class supports
+`Icecream <https://github.com/icecc/icecream>`__, which facilitates
+taking compile jobs and distributing them among remote machines.
+
+The class stages directories with symlinks from ``gcc`` and ``g++`` to
+``icecc``, for both native and cross compilers. Depending on each
+configure or compile, the OpenEmbedded build system adds the directories
+at the head of the ``PATH`` list and then sets the ``ICECC_CXX`` and
+``ICEC_CC`` variables, which are the paths to the ``g++`` and ``gcc``
+compilers, respectively.
+
+For the cross compiler, the class creates a ``tar.gz`` file that
+contains the Yocto Project toolchain and sets ``ICECC_VERSION``, which
+is the version of the cross-compiler used in the cross-development
+toolchain, accordingly.
+
+The class handles all three different compile stages (i.e native
+,cross-kernel and target) and creates the necessary environment
+``tar.gz`` file to be used by the remote machines. The class also
+supports SDK generation.
+
+If :term:`ICECC_PATH` is not set in your
+``local.conf`` file, then the class tries to locate the ``icecc`` binary
+using ``which``. If :term:`ICECC_ENV_EXEC` is set
+in your ``local.conf`` file, the variable should point to the
+``icecc-create-env`` script provided by the user. If you do not point to
+a user-provided script, the build system uses the default script
+provided by the recipe ``icecc-create-env-native.bb``.
+
+.. note::
+
+   This script is a modified version and not the one that comes with
+   icecc.
+
+If you do not want the Icecream distributed compile support to apply to
+specific recipes or classes, you can effectively "blacklist" them by
+listing the recipes and classes using the
+:term:`ICECC_USER_PACKAGE_BL` and
+:term:`ICECC_USER_CLASS_BL`, variables,
+respectively, in your ``local.conf`` file. Doing so causes the
+OpenEmbedded build system to handle these compilations locally.
+
+Additionally, you can list recipes using the
+:term:`ICECC_USER_PACKAGE_WL` variable in
+your ``local.conf`` file to force ``icecc`` to be enabled for recipes
+using an empty :term:`PARALLEL_MAKE` variable.
+
+Inheriting the ``icecc`` class changes all sstate signatures.
+Consequently, if a development team has a dedicated build system that
+populates :term:`SSTATE_MIRRORS` and they want to
+reuse sstate from ``SSTATE_MIRRORS``, then all developers and the build
+system need to either inherit the ``icecc`` class or nobody should.
+
+At the distribution level, you can inherit the ``icecc`` class to be
+sure that all builders start with the same sstate signatures. After
+inheriting the class, you can then disable the feature by setting the
+:term:`ICECC_DISABLED` variable to "1" as follows:
+::
+
+   INHERIT_DISTRO_append = " icecc"
+   ICECC_DISABLED ??= "1"
+
+This practice
+makes sure everyone is using the same signatures but also requires
+individuals that do want to use Icecream to enable the feature
+individually as follows in your ``local.conf`` file:
+::
+
+   ICECC_DISABLED = ""
+
+.. _ref-classes-image:
+
+``image.bbclass``
+=================
+
+The ``image`` class helps support creating images in different formats.
+First, the root filesystem is created from packages using one of the
+``rootfs*.bbclass`` files (depending on the package format used) and
+then one or more image files are created.
+
+-  The ``IMAGE_FSTYPES`` variable controls the types of images to
+   generate.
+
+-  The ``IMAGE_INSTALL`` variable controls the list of packages to
+   install into the image.
+
+For information on customizing images, see the
+":ref:`usingpoky-extend-customimage`" section
+in the Yocto Project Development Tasks Manual. For information on how
+images are created, see the
+":ref:`images-dev-environment`" section in the
+Yocto Project Overview and Concpets Manual.
+
+.. _ref-classes-image-buildinfo:
+
+``image-buildinfo.bbclass``
+===========================
+
+The ``image-buildinfo`` class writes information to the target
+filesystem on ``/etc/build``.
+
+.. _ref-classes-image_types:
+
+``image_types.bbclass``
+=======================
+
+The ``image_types`` class defines all of the standard image output types
+that you can enable through the
+:term:`IMAGE_FSTYPES` variable. You can use this
+class as a reference on how to add support for custom image output
+types.
+
+By default, the :ref:`image <ref-classes-image>` class automatically
+enables the ``image_types`` class. The ``image`` class uses the
+``IMGCLASSES`` variable as follows:
+::
+
+   IMGCLASSES = "rootfs_${IMAGE_PKGTYPE} image_types ${IMAGE_CLASSES}"
+   IMGCLASSES += "${@['populate_sdk_base', 'populate_sdk_ext']['linux' in d.getVar("SDK_OS")]}"
+   IMGCLASSES += "${@bb.utils.contains_any('IMAGE_FSTYPES', 'live iso hddimg', 'image-live', '', d)}"
+   IMGCLASSES += "${@bb.utils.contains('IMAGE_FSTYPES', 'container', 'image-container', '', d)}"
+   IMGCLASSES += "image_types_wic"
+   IMGCLASSES += "rootfs-postcommands"
+   IMGCLASSES += "image-postinst-intercepts"
+   inherit ${IMGCLASSES}
+
+The ``image_types`` class also handles conversion and compression of images.
+
+.. note::
+
+   To build a VMware VMDK image, you need to add "wic.vmdk" to
+   IMAGE_FSTYPES
+   . This would also be similar for Virtual Box Virtual Disk Image
+   ("vdi") and QEMU Copy On Write Version 2 ("qcow2") images.
+
+.. _ref-classes-image-live:
+
+``image-live.bbclass``
+======================
+
+This class controls building "live" (i.e. HDDIMG and ISO) images. Live
+images contain syslinux for legacy booting, as well as the bootloader
+specified by :term:`EFI_PROVIDER` if
+:term:`MACHINE_FEATURES` contains "efi".
+
+Normally, you do not use this class directly. Instead, you add "live" to
+:term:`IMAGE_FSTYPES`.
+
+.. _ref-classes-image-mklibs:
+
+``image-mklibs.bbclass``
+========================
+
+The ``image-mklibs`` class enables the use of the ``mklibs`` utility
+during the :ref:`ref-tasks-rootfs` task, which optimizes
+the size of libraries contained in the image.
+
+By default, the class is enabled in the ``local.conf.template`` using
+the :term:`USER_CLASSES` variable as follows:
+::
+
+   USER_CLASSES ?= "buildstats image-mklibs image-prelink"
+
+.. _ref-classes-image-prelink:
+
+``image-prelink.bbclass``
+=========================
+
+The ``image-prelink`` class enables the use of the ``prelink`` utility
+during the :ref:`ref-tasks-rootfs` task, which optimizes
+the dynamic linking of shared libraries to reduce executable startup
+time.
+
+By default, the class is enabled in the ``local.conf.template`` using
+the :term:`USER_CLASSES` variable as follows:
+::
+
+   USER_CLASSES ?= "buildstats image-mklibs image-prelink"
+
+.. _ref-classes-insane:
+
+``insane.bbclass``
+==================
+
+The ``insane`` class adds a step to the package generation process so
+that output quality assurance checks are generated by the OpenEmbedded
+build system. A range of checks are performed that check the build's
+output for common problems that show up during runtime. Distribution
+policy usually dictates whether to include this class.
+
+You can configure the sanity checks so that specific test failures
+either raise a warning or an error message. Typically, failures for new
+tests generate a warning. Subsequent failures for the same test would
+then generate an error message once the metadata is in a known and good
+condition. See the "`QA Error and Warning Messages <#ref-qa-checks>`__"
+Chapter for a list of all the warning and error messages you might
+encounter using a default configuration.
+
+Use the :term:`WARN_QA` and
+:term:`ERROR_QA` variables to control the behavior of
+these checks at the global level (i.e. in your custom distro
+configuration). However, to skip one or more checks in recipes, you
+should use :term:`INSANE_SKIP`. For example, to skip
+the check for symbolic link ``.so`` files in the main package of a
+recipe, add the following to the recipe. You need to realize that the
+package name override, in this example ``${PN}``, must be used:
+::
+
+   INSANE_SKIP_${PN} += "dev-so"
+
+Please keep in mind that the QA checks
+exist in order to detect real or potential problems in the packaged
+output. So exercise caution when disabling these checks.
+
+The following list shows the tests you can list with the ``WARN_QA`` and
+``ERROR_QA`` variables:
+
+-  ``already-stripped:`` Checks that produced binaries have not
+   already been stripped prior to the build system extracting debug
+   symbols. It is common for upstream software projects to default to
+   stripping debug symbols for output binaries. In order for debugging
+   to work on the target using ``-dbg`` packages, this stripping must be
+   disabled.
+
+-  ``arch:`` Checks the Executable and Linkable Format (ELF) type, bit
+   size, and endianness of any binaries to ensure they match the target
+   architecture. This test fails if any binaries do not match the type
+   since there would be an incompatibility. The test could indicate that
+   the wrong compiler or compiler options have been used. Sometimes
+   software, like bootloaders, might need to bypass this check.
+
+-  ``buildpaths:`` Checks for paths to locations on the build host
+   inside the output files. Currently, this test triggers too many false
+   positives and thus is not normally enabled.
+
+-  ``build-deps:`` Determines if a build-time dependency that is
+   specified through :term:`DEPENDS`, explicit
+   :term:`RDEPENDS`, or task-level dependencies exists
+   to match any runtime dependency. This determination is particularly
+   useful to discover where runtime dependencies are detected and added
+   during packaging. If no explicit dependency has been specified within
+   the metadata, at the packaging stage it is too late to ensure that
+   the dependency is built, and thus you can end up with an error when
+   the package is installed into the image during the
+   :ref:`ref-tasks-rootfs` task because the auto-detected
+   dependency was not satisfied. An example of this would be where the
+   :ref:`update-rc.d <ref-classes-update-rc.d>` class automatically
+   adds a dependency on the ``initscripts-functions`` package to
+   packages that install an initscript that refers to
+   ``/etc/init.d/functions``. The recipe should really have an explicit
+   ``RDEPENDS`` for the package in question on ``initscripts-functions``
+   so that the OpenEmbedded build system is able to ensure that the
+   ``initscripts`` recipe is actually built and thus the
+   ``initscripts-functions`` package is made available.
+
+-  ``compile-host-path:`` Checks the
+   :ref:`ref-tasks-compile` log for indications that
+   paths to locations on the build host were used. Using such paths
+   might result in host contamination of the build output.
+
+-  ``debug-deps:`` Checks that all packages except ``-dbg`` packages
+   do not depend on ``-dbg`` packages, which would cause a packaging
+   bug.
+
+-  ``debug-files:`` Checks for ``.debug`` directories in anything but
+   the ``-dbg`` package. The debug files should all be in the ``-dbg``
+   package. Thus, anything packaged elsewhere is incorrect packaging.
+
+-  ``dep-cmp:`` Checks for invalid version comparison statements in
+   runtime dependency relationships between packages (i.e. in
+   :term:`RDEPENDS`,
+   :term:`RRECOMMENDS`,
+   :term:`RSUGGESTS`,
+   :term:`RPROVIDES`,
+   :term:`RREPLACES`, and
+   :term:`RCONFLICTS` variable values). Any invalid
+   comparisons might trigger failures or undesirable behavior when
+   passed to the package manager.
+
+-  ``desktop:`` Runs the ``desktop-file-validate`` program against any
+   ``.desktop`` files to validate their contents against the
+   specification for ``.desktop`` files.
+
+-  ``dev-deps:`` Checks that all packages except ``-dev`` or
+   ``-staticdev`` packages do not depend on ``-dev`` packages, which
+   would be a packaging bug.
+
+-  ``dev-so:`` Checks that the ``.so`` symbolic links are in the
+   ``-dev`` package and not in any of the other packages. In general,
+   these symlinks are only useful for development purposes. Thus, the
+   ``-dev`` package is the correct location for them. Some very rare
+   cases do exist for dynamically loaded modules where these symlinks
+   are needed instead in the main package.
+
+-  ``file-rdeps:`` Checks that file-level dependencies identified by
+   the OpenEmbedded build system at packaging time are satisfied. For
+   example, a shell script might start with the line ``#!/bin/bash``.
+   This line would translate to a file dependency on ``/bin/bash``. Of
+   the three package managers that the OpenEmbedded build system
+   supports, only RPM directly handles file-level dependencies,
+   resolving them automatically to packages providing the files.
+   However, the lack of that functionality in the other two package
+   managers does not mean the dependencies do not still need resolving.
+   This QA check attempts to ensure that explicitly declared
+   :term:`RDEPENDS` exist to handle any file-level
+   dependency detected in packaged files.
+
+-  ``files-invalid:`` Checks for :term:`FILES` variable
+   values that contain "//", which is invalid.
+
+-  ``host-user-contaminated:`` Checks that no package produced by the
+   recipe contains any files outside of ``/home`` with a user or group
+   ID that matches the user running BitBake. A match usually indicates
+   that the files are being installed with an incorrect UID/GID, since
+   target IDs are independent from host IDs. For additional information,
+   see the section describing the
+   :ref:`ref-tasks-install` task.
+
+-  ``incompatible-license:`` Report when packages are excluded from
+   being created due to being marked with a license that is in
+   :term:`INCOMPATIBLE_LICENSE`.
+
+-  ``install-host-path:`` Checks the
+   :ref:`ref-tasks-install` log for indications that
+   paths to locations on the build host were used. Using such paths
+   might result in host contamination of the build output.
+
+-  ``installed-vs-shipped:`` Reports when files have been installed
+   within ``do_install`` but have not been included in any package by
+   way of the :term:`FILES` variable. Files that do not
+   appear in any package cannot be present in an image later on in the
+   build process. Ideally, all installed files should be packaged or not
+   installed at all. These files can be deleted at the end of
+   ``do_install`` if the files are not needed in any package.
+
+-  ``invalid-chars:`` Checks that the recipe metadata variables
+   :term:`DESCRIPTION`,
+   :term:`SUMMARY`, :term:`LICENSE`, and
+   :term:`SECTION` do not contain non-UTF-8 characters.
+   Some package managers do not support such characters.
+
+-  ``invalid-packageconfig:`` Checks that no undefined features are
+   being added to :term:`PACKAGECONFIG`. For
+   example, any name "foo" for which the following form does not exist:
+   ::
+
+      PACKAGECONFIG[foo] = "..."
+
+-  ``la:`` Checks ``.la`` files for any ``TMPDIR`` paths. Any ``.la``
+   file containing these paths is incorrect since ``libtool`` adds the
+   correct sysroot prefix when using the files automatically itself.
+
+-  ``ldflags:`` Ensures that the binaries were linked with the
+   :term:`LDFLAGS` options provided by the build system.
+   If this test fails, check that the ``LDFLAGS`` variable is being
+   passed to the linker command.
+
+-  ``libdir:`` Checks for libraries being installed into incorrect
+   (possibly hardcoded) installation paths. For example, this test will
+   catch recipes that install ``/lib/bar.so`` when ``${base_libdir}`` is
+   "lib32". Another example is when recipes install
+   ``/usr/lib64/foo.so`` when ``${libdir}`` is "/usr/lib".
+
+-  ``libexec:`` Checks if a package contains files in
+   ``/usr/libexec``. This check is not performed if the ``libexecdir``
+   variable has been set explicitly to ``/usr/libexec``.
+
+-  ``packages-list:`` Checks for the same package being listed
+   multiple times through the :term:`PACKAGES` variable
+   value. Installing the package in this manner can cause errors during
+   packaging.
+
+-  ``perm-config:`` Reports lines in ``fs-perms.txt`` that have an
+   invalid format.
+
+-  ``perm-line:`` Reports lines in ``fs-perms.txt`` that have an
+   invalid format.
+
+-  ``perm-link:`` Reports lines in ``fs-perms.txt`` that specify
+   'link' where the specified target already exists.
+
+-  ``perms:`` Currently, this check is unused but reserved.
+
+-  ``pkgconfig:`` Checks ``.pc`` files for any
+   :term:`TMPDIR`/:term:`WORKDIR` paths.
+   Any ``.pc`` file containing these paths is incorrect since
+   ``pkg-config`` itself adds the correct sysroot prefix when the files
+   are accessed.
+
+-  ``pkgname:`` Checks that all packages in
+   :term:`PACKAGES` have names that do not contain
+   invalid characters (i.e. characters other than 0-9, a-z, ., +, and
+   -).
+
+-  ``pkgv-undefined:`` Checks to see if the ``PKGV`` variable is
+   undefined during :ref:`ref-tasks-package`.
+
+-  ``pkgvarcheck:`` Checks through the variables
+   :term:`RDEPENDS`,
+   :term:`RRECOMMENDS`,
+   :term:`RSUGGESTS`,
+   :term:`RCONFLICTS`,
+   :term:`RPROVIDES`,
+   :term:`RREPLACES`, :term:`FILES`,
+   :term:`ALLOW_EMPTY`, ``pkg_preinst``,
+   ``pkg_postinst``, ``pkg_prerm`` and ``pkg_postrm``, and reports if
+   there are variable sets that are not package-specific. Using these
+   variables without a package suffix is bad practice, and might
+   unnecessarily complicate dependencies of other packages within the
+   same recipe or have other unintended consequences.
+
+-  ``pn-overrides:`` Checks that a recipe does not have a name
+   (:term:`PN`) value that appears in
+   :term:`OVERRIDES`. If a recipe is named such that
+   its ``PN`` value matches something already in ``OVERRIDES`` (e.g.
+   ``PN`` happens to be the same as :term:`MACHINE` or
+   :term:`DISTRO`), it can have unexpected consequences.
+   For example, assignments such as ``FILES_${PN} = "xyz"`` effectively
+   turn into ``FILES = "xyz"``.
+
+-  ``rpaths:`` Checks for rpaths in the binaries that contain build
+   system paths such as ``TMPDIR``. If this test fails, bad ``-rpath``
+   options are being passed to the linker commands and your binaries
+   have potential security issues.
+
+-  ``split-strip:`` Reports that splitting or stripping debug symbols
+   from binaries has failed.
+
+-  ``staticdev:`` Checks for static library files (``*.a``) in
+   non-``staticdev`` packages.
+
+-  ``symlink-to-sysroot:`` Checks for symlinks in packages that point
+   into :term:`TMPDIR` on the host. Such symlinks will
+   work on the host, but are clearly invalid when running on the target.
+
+-  ``textrel:`` Checks for ELF binaries that contain relocations in
+   their ``.text`` sections, which can result in a performance impact at
+   runtime. See the explanation for the
+   ```ELF binary`` <#qa-issue-textrel>`__ message for more information
+   regarding runtime performance issues.
+
+-  ``unlisted-pkg-lics:`` Checks that all declared licenses applying
+   for a package are also declared on the recipe level (i.e. any license
+   in ``LICENSE_*`` should appear in :term:`LICENSE`).
+
+-  ``useless-rpaths:`` Checks for dynamic library load paths (rpaths)
+   in the binaries that by default on a standard system are searched by
+   the linker (e.g. ``/lib`` and ``/usr/lib``). While these paths will
+   not cause any breakage, they do waste space and are unnecessary.
+
+-  ``var-undefined:`` Reports when variables fundamental to packaging
+   (i.e. :term:`WORKDIR`,
+   :term:`DEPLOY_DIR`, :term:`D`,
+   :term:`PN`, and :term:`PKGD`) are undefined
+   during :ref:`ref-tasks-package`.
+
+-  ``version-going-backwards:`` If Build History is enabled, reports
+   when a package being written out has a lower version than the
+   previously written package under the same name. If you are placing
+   output packages into a feed and upgrading packages on a target system
+   using that feed, the version of a package going backwards can result
+   in the target system not correctly upgrading to the "new" version of
+   the package.
+
+   .. note::
+
+      If you are not using runtime package management on your target
+      system, then you do not need to worry about this situation.
+
+-  ``xorg-driver-abi:`` Checks that all packages containing Xorg
+   drivers have ABI dependencies. The ``xserver-xorg`` recipe provides
+   driver ABI names. All drivers should depend on the ABI versions that
+   they have been built against. Driver recipes that include
+   ``xorg-driver-input.inc`` or ``xorg-driver-video.inc`` will
+   automatically get these versions. Consequently, you should only need
+   to explicitly add dependencies to binary driver recipes.
+
+.. _ref-classes-insserv:
+
+``insserv.bbclass``
+===================
+
+The ``insserv`` class uses the ``insserv`` utility to update the order
+of symbolic links in ``/etc/rc?.d/`` within an image based on
+dependencies specified by LSB headers in the ``init.d`` scripts
+themselves.
+
+.. _ref-classes-kernel:
+
+``kernel.bbclass``
+==================
+
+The ``kernel`` class handles building Linux kernels. The class contains
+code to build all kernel trees. All needed headers are staged into the
+``STAGING_KERNEL_DIR`` directory to allow out-of-tree module builds
+using the :ref:`module <ref-classes-module>` class.
+
+This means that each built kernel module is packaged separately and
+inter-module dependencies are created by parsing the ``modinfo`` output.
+If all modules are required, then installing the ``kernel-modules``
+package installs all packages with modules and various other kernel
+packages such as ``kernel-vmlinux``.
+
+The ``kernel`` class contains logic that allows you to embed an initial
+RAM filesystem (initramfs) image when you build the kernel image. For
+information on how to build an initramfs, see the
+":ref:`building-an-initramfs-image`" section in
+the Yocto Project Development Tasks Manual.
+
+Various other classes are used by the ``kernel`` and ``module`` classes
+internally including the :ref:`kernel-arch <ref-classes-kernel-arch>`,
+:ref:`module-base <ref-classes-module-base>`, and
+:ref:`linux-kernel-base <ref-classes-linux-kernel-base>` classes.
+
+.. _ref-classes-kernel-arch:
+
+``kernel-arch.bbclass``
+=======================
+
+The ``kernel-arch`` class sets the ``ARCH`` environment variable for
+Linux kernel compilation (including modules).
+
+.. _ref-classes-kernel-devicetree:
+
+``kernel-devicetree.bbclass``
+=============================
+
+The ``kernel-devicetree`` class, which is inherited by the
+:ref:`kernel <ref-classes-kernel>` class, supports device tree
+generation.
+
+.. _ref-classes-kernel-fitimage:
+
+``kernel-fitimage.bbclass``
+===========================
+
+The ``kernel-fitimage`` class provides support to pack a kernel Image,
+device trees and a RAM disk into a single FIT image. In theory, a FIT
+image can support any number of kernels, RAM disks and device-trees.
+However, ``kernel-fitimage`` currently only supports
+limited usescases: just one kernel image, an optional RAM disk, and
+any number of device tree.
+
+To create a FIT image, it is required that :term:`KERNEL_CLASSES`
+is set to "kernel-fitimage" and :term:`KERNEL_IMAGETYPE`
+is set to "fitImage".
+
+The options for the device tree compiler passed to mkimage -D feature
+when creating the FIT image are specified using the
+:term:`UBOOT_MKIMAGE_DTCOPTS` variable.
+
+Only a single kernel can be added to the FIT image created by
+``kernel-fitimage`` and the kernel image in FIT is mandatory. The
+address where the kernel image is to be loaded by U-boot is
+specified by :term:`UBOOT_LOADADDRESS` and the entrypoint by
+:term:`UBOOT_ENTRYPOINT`.
+
+Multiple device trees can be added to the FIT image created by
+``kernel-fitimage`` and the device tree is optional.
+The address where the device tree is to be loaded by U-boot is
+specified by :term:`UBOOT_DTBO_LOADADDRESS` for device tree overlays
+and by `:term:`UBOOT_DTB_LOADADDRESS` for device tree binaries.
+
+Only a single RAM disk can be added to the FIT image created by
+``kernel-fitimage`` and the RAM disk in FIT is optional.
+The address where the RAM disk image is to be loaded by U-boot
+is specified by :term:`UBOOT_RD_LOADADDRESS` and the entrypoint by
+:term:`UBOOT_RD_ENTRYPOINT`. The ramdisk is added to FIT image when
+:term:`INITRAMFS_IMAGE` is specified.
+
+The FIT image generated by ``kernel-fitimage`` class is signed when the
+variables :term:`UBOOT_SIGN_ENABLE`, :term:`UBOOT_MKIMAGE_DTCOPTS`,
+:term:`UBOOT_SIGN_KEYDIR` and :term:`UBOOT_SIGN_KEYNAME` are set
+appropriately. The default values used for :term:`FIT_HASH_ALG` and
+:term:`FIT_SIGN_ALG` in ``kernel-fitimage`` are "sha256" and
+"rsa2048" respectively.
+
+
+.. _ref-classes-kernel-grub:
+
+``kernel-grub.bbclass``
+=======================
+
+The ``kernel-grub`` class updates the boot area and the boot menu with
+the kernel as the priority boot mechanism while installing a RPM to
+update the kernel on a deployed target.
+
+.. _ref-classes-kernel-module-split:
+
+``kernel-module-split.bbclass``
+===============================
+
+The ``kernel-module-split`` class provides common functionality for
+splitting Linux kernel modules into separate packages.
+
+.. _ref-classes-kernel-uboot:
+
+``kernel-uboot.bbclass``
+========================
+
+The ``kernel-uboot`` class provides support for building from
+vmlinux-style kernel sources.
+
+.. _ref-classes-kernel-uimage:
+
+``kernel-uimage.bbclass``
+=========================
+
+The ``kernel-uimage`` class provides support to pack uImage.
+
+.. _ref-classes-kernel-yocto:
+
+``kernel-yocto.bbclass``
+========================
+
+The ``kernel-yocto`` class provides common functionality for building
+from linux-yocto style kernel source repositories.
+
+.. _ref-classes-kernelsrc:
+
+``kernelsrc.bbclass``
+=====================
+
+The ``kernelsrc`` class sets the Linux kernel source and version.
+
+.. _ref-classes-lib_package:
+
+``lib_package.bbclass``
+=======================
+
+The ``lib_package`` class supports recipes that build libraries and
+produce executable binaries, where those binaries should not be
+installed by default along with the library. Instead, the binaries are
+added to a separate ``${``\ :term:`PN`\ ``}-bin`` package to
+make their installation optional.
+
+.. _ref-classes-libc*:
+
+``libc*.bbclass``
+=================
+
+The ``libc*`` classes support recipes that build packages with ``libc``:
+
+-  The ``libc-common`` class provides common support for building with
+   ``libc``.
+
+-  The ``libc-package`` class supports packaging up ``glibc`` and
+   ``eglibc``.
+
+.. _ref-classes-license:
+
+``license.bbclass``
+===================
+
+The ``license`` class provides license manifest creation and license
+exclusion. This class is enabled by default using the default value for
+the :term:`INHERIT_DISTRO` variable.
+
+.. _ref-classes-linux-kernel-base:
+
+``linux-kernel-base.bbclass``
+=============================
+
+The ``linux-kernel-base`` class provides common functionality for
+recipes that build out of the Linux kernel source tree. These builds
+goes beyond the kernel itself. For example, the Perf recipe also
+inherits this class.
+
+.. _ref-classes-linuxloader:
+
+``linuxloader.bbclass``
+=======================
+
+Provides the function ``linuxloader()``, which gives the value of the
+dynamic loader/linker provided on the platform. This value is used by a
+number of other classes.
+
+.. _ref-classes-logging:
+
+``logging.bbclass``
+===================
+
+The ``logging`` class provides the standard shell functions used to log
+messages for various BitBake severity levels (i.e. ``bbplain``,
+``bbnote``, ``bbwarn``, ``bberror``, ``bbfatal``, and ``bbdebug``).
+
+This class is enabled by default since it is inherited by the ``base``
+class.
+
+.. _ref-classes-meta:
+
+``meta.bbclass``
+================
+
+The ``meta`` class is inherited by recipes that do not build any output
+packages themselves, but act as a "meta" target for building other
+recipes.
+
+.. _ref-classes-metadata_scm:
+
+``metadata_scm.bbclass``
+========================
+
+The ``metadata_scm`` class provides functionality for querying the
+branch and revision of a Source Code Manager (SCM) repository.
+
+The :ref:`base <ref-classes-base>` class uses this class to print the
+revisions of each layer before starting every build. The
+``metadata_scm`` class is enabled by default because it is inherited by
+the ``base`` class.
+
+.. _ref-classes-migrate_localcount:
+
+``migrate_localcount.bbclass``
+==============================
+
+The ``migrate_localcount`` class verifies a recipe's localcount data and
+increments it appropriately.
+
+.. _ref-classes-mime:
+
+``mime.bbclass``
+================
+
+The ``mime`` class generates the proper post-install and post-remove
+(postinst/postrm) scriptlets for packages that install MIME type files.
+These scriptlets call ``update-mime-database`` to add the MIME types to
+the shared database.
+
+.. _ref-classes-mirrors:
+
+``mirrors.bbclass``
+===================
+
+The ``mirrors`` class sets up some standard
+:term:`MIRRORS` entries for source code mirrors. These
+mirrors provide a fall-back path in case the upstream source specified
+in :term:`SRC_URI` within recipes is unavailable.
+
+This class is enabled by default since it is inherited by the
+:ref:`base <ref-classes-base>` class.
+
+.. _ref-classes-module:
+
+``module.bbclass``
+==================
+
+The ``module`` class provides support for building out-of-tree Linux
+kernel modules. The class inherits the
+:ref:`module-base <ref-classes-module-base>` and
+:ref:`kernel-module-split <ref-classes-kernel-module-split>` classes,
+and implements the :ref:`ref-tasks-compile` and
+:ref:`ref-tasks-install` tasks. The class provides
+everything needed to build and package a kernel module.
+
+For general information on out-of-tree Linux kernel modules, see the
+":ref:`kernel-dev/kernel-dev-common:incorporating out-of-tree modules`"
+section in the Yocto Project Linux Kernel Development Manual.
+
+.. _ref-classes-module-base:
+
+``module-base.bbclass``
+=======================
+
+The ``module-base`` class provides the base functionality for building
+Linux kernel modules. Typically, a recipe that builds software that
+includes one or more kernel modules and has its own means of building
+the module inherits this class as opposed to inheriting the
+:ref:`module <ref-classes-module>` class.
+
+.. _ref-classes-multilib*:
+
+``multilib*.bbclass``
+=====================
+
+The ``multilib*`` classes provide support for building libraries with
+different target optimizations or target architectures and installing
+them side-by-side in the same image.
+
+For more information on using the Multilib feature, see the
+":ref:`combining-multiple-versions-library-files-into-one-image`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _ref-classes-native:
+
+``native.bbclass``
+==================
+
+The ``native`` class provides common functionality for recipes that
+build tools to run on the `build host <#hardware-build-system-term>`__
+(i.e. tools that use the compiler or other tools from the build host).
+
+You can create a recipe that builds tools that run natively on the host
+a couple different ways:
+
+-  Create a myrecipe\ ``-native.bb`` recipe that inherits the ``native``
+   class. If you use this method, you must order the inherit statement
+   in the recipe after all other inherit statements so that the
+   ``native`` class is inherited last.
+
+   .. note::
+
+      When creating a recipe this way, the recipe name must follow this
+      naming convention:
+      ::
+
+         myrecipe-native.bb
+
+
+      Not using this naming convention can lead to subtle problems
+      caused by existing code that depends on that naming convention.
+
+-  Create or modify a target recipe that contains the following:
+   ::
+
+      BBCLASSEXTEND = "native"
+
+   Inside the
+   recipe, use ``_class-native`` and ``_class-target`` overrides to
+   specify any functionality specific to the respective native or target
+   case.
+
+Although applied differently, the ``native`` class is used with both
+methods. The advantage of the second method is that you do not need to
+have two separate recipes (assuming you need both) for native and
+target. All common parts of the recipe are automatically shared.
+
+.. _ref-classes-nativesdk:
+
+``nativesdk.bbclass``
+=====================
+
+The ``nativesdk`` class provides common functionality for recipes that
+wish to build tools to run as part of an SDK (i.e. tools that run on
+:term:`SDKMACHINE`).
+
+You can create a recipe that builds tools that run on the SDK machine a
+couple different ways:
+
+-  Create a ``nativesdk-``\ myrecipe\ ``.bb`` recipe that inherits the
+   ``nativesdk`` class. If you use this method, you must order the
+   inherit statement in the recipe after all other inherit statements so
+   that the ``nativesdk`` class is inherited last.
+
+-  Create a ``nativesdk`` variant of any recipe by adding the following:
+   ::
+
+       BBCLASSEXTEND = "nativesdk"
+
+   Inside the
+   recipe, use ``_class-nativesdk`` and ``_class-target`` overrides to
+   specify any functionality specific to the respective SDK machine or
+   target case.
+
+.. note::
+
+   When creating a recipe, you must follow this naming convention:
+   ::
+
+           nativesdk-myrecipe.bb
+
+
+   Not doing so can lead to subtle problems because code exists that
+   depends on the naming convention.
+
+Although applied differently, the ``nativesdk`` class is used with both
+methods. The advantage of the second method is that you do not need to
+have two separate recipes (assuming you need both) for the SDK machine
+and the target. All common parts of the recipe are automatically shared.
+
+.. _ref-classes-nopackages:
+
+``nopackages.bbclass``
+======================
+
+Disables packaging tasks for those recipes and classes where packaging
+is not needed.
+
+.. _ref-classes-npm:
+
+``npm.bbclass``
+===============
+
+Provides support for building Node.js software fetched using the `node
+package manager (NPM) <https://en.wikipedia.org/wiki/Npm_(software)>`__.
+
+.. note::
+
+   Currently, recipes inheriting this class must use the
+   npm://
+   fetcher to have dependencies fetched and packaged automatically.
+
+For information on how to create NPM packages, see the
+":ref:`dev-manual/dev-manual-common-tasks:creating node package manager (npm) packages`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _ref-classes-oelint:
+
+``oelint.bbclass``
+==================
+
+The ``oelint`` class is an obsolete lint checking tool that exists in
+``meta/classes`` in the :term:`Source Directory`.
+
+A number of classes exist that could be generally useful in OE-Core but
+are never actually used within OE-Core itself. The ``oelint`` class is
+one such example. However, being aware of this class can reduce the
+proliferation of different versions of similar classes across multiple
+layers.
+
+.. _ref-classes-own-mirrors:
+
+``own-mirrors.bbclass``
+=======================
+
+The ``own-mirrors`` class makes it easier to set up your own
+:term:`PREMIRRORS` from which to first fetch source
+before attempting to fetch it from the upstream specified in
+:term:`SRC_URI` within each recipe.
+
+To use this class, inherit it globally and specify
+:term:`SOURCE_MIRROR_URL`. Here is an example:
+::
+
+   INHERIT += "own-mirrors"
+   SOURCE_MIRROR_URL = "http://example.com/my-source-mirror"
+
+You can specify only a single URL
+in ``SOURCE_MIRROR_URL``.
+
+.. _ref-classes-package:
+
+``package.bbclass``
+===================
+
+The ``package`` class supports generating packages from a build's
+output. The core generic functionality is in ``package.bbclass``. The
+code specific to particular package types resides in these
+package-specific classes:
+:ref:`package_deb <ref-classes-package_deb>`,
+:ref:`package_rpm <ref-classes-package_rpm>`,
+:ref:`package_ipk <ref-classes-package_ipk>`, and
+:ref:`package_tar <ref-classes-package_tar>`.
+
+.. note::
+
+   The
+   package_tar
+   class is broken and not supported. It is recommended that you do not
+   use this class.
+
+You can control the list of resulting package formats by using the
+``PACKAGE_CLASSES`` variable defined in your ``conf/local.conf``
+configuration file, which is located in the :term:`Build Directory`.
+When defining the variable, you can
+specify one or more package types. Since images are generated from
+packages, a packaging class is needed to enable image generation. The
+first class listed in this variable is used for image generation.
+
+If you take the optional step to set up a repository (package feed) on
+the development host that can be used by DNF, you can install packages
+from the feed while you are running the image on the target (i.e.
+runtime installation of packages). For more information, see the
+":ref:`dev-manual/dev-manual-common-tasks:using runtime package management`"
+section in the Yocto Project Development Tasks Manual.
+
+The package-specific class you choose can affect build-time performance
+and has space ramifications. In general, building a package with IPK
+takes about thirty percent less time as compared to using RPM to build
+the same or similar package. This comparison takes into account a
+complete build of the package with all dependencies previously built.
+The reason for this discrepancy is because the RPM package manager
+creates and processes more :term:`Metadata` than the IPK package
+manager. Consequently, you might consider setting ``PACKAGE_CLASSES`` to
+"package_ipk" if you are building smaller systems.
+
+Before making your package manager decision, however, you should
+consider some further things about using RPM:
+
+-  RPM starts to provide more abilities than IPK due to the fact that it
+   processes more Metadata. For example, this information includes
+   individual file types, file checksum generation and evaluation on
+   install, sparse file support, conflict detection and resolution for
+   Multilib systems, ACID style upgrade, and repackaging abilities for
+   rollbacks.
+
+-  For smaller systems, the extra space used for the Berkeley Database
+   and the amount of metadata when using RPM can affect your ability to
+   perform on-device upgrades.
+
+You can find additional information on the effects of the package class
+at these two Yocto Project mailing list links:
+
+-  https://lists.yoctoproject.org/pipermail/poky/2011-May/006362.html
+
+-  https://lists.yoctoproject.org/pipermail/poky/2011-May/006363.html
+
+.. _ref-classes-package_deb:
+
+``package_deb.bbclass``
+=======================
+
+The ``package_deb`` class provides support for creating packages that
+use the Debian (i.e. ``.deb``) file format. The class ensures the
+packages are written out in a ``.deb`` file format to the
+``${``\ :term:`DEPLOY_DIR_DEB`\ ``}`` directory.
+
+This class inherits the :ref:`package <ref-classes-package>` class and
+is enabled through the :term:`PACKAGE_CLASSES`
+variable in the ``local.conf`` file.
+
+.. _ref-classes-package_ipk:
+
+``package_ipk.bbclass``
+=======================
+
+The ``package_ipk`` class provides support for creating packages that
+use the IPK (i.e. ``.ipk``) file format. The class ensures the packages
+are written out in a ``.ipk`` file format to the
+``${``\ :term:`DEPLOY_DIR_IPK`\ ``}`` directory.
+
+This class inherits the :ref:`package <ref-classes-package>` class and
+is enabled through the :term:`PACKAGE_CLASSES`
+variable in the ``local.conf`` file.
+
+.. _ref-classes-package_rpm:
+
+``package_rpm.bbclass``
+=======================
+
+The ``package_rpm`` class provides support for creating packages that
+use the RPM (i.e. ``.rpm``) file format. The class ensures the packages
+are written out in a ``.rpm`` file format to the
+``${``\ :term:`DEPLOY_DIR_RPM`\ ``}`` directory.
+
+This class inherits the :ref:`package <ref-classes-package>` class and
+is enabled through the :term:`PACKAGE_CLASSES`
+variable in the ``local.conf`` file.
+
+.. _ref-classes-package_tar:
+
+``package_tar.bbclass``
+=======================
+
+The ``package_tar`` class provides support for creating tarballs. The
+class ensures the packages are written out in a tarball format to the
+``${``\ :term:`DEPLOY_DIR_TAR`\ ``}`` directory.
+
+This class inherits the :ref:`package <ref-classes-package>` class and
+is enabled through the :term:`PACKAGE_CLASSES`
+variable in the ``local.conf`` file.
+
+.. note::
+
+   You cannot specify the
+   package_tar
+   class first using the
+   PACKAGE_CLASSES
+   variable. You must use
+   .deb
+   ,
+   .ipk
+   , or
+   .rpm
+   file formats for your image or SDK.
+
+.. _ref-classes-packagedata:
+
+``packagedata.bbclass``
+=======================
+
+The ``packagedata`` class provides common functionality for reading
+``pkgdata`` files found in :term:`PKGDATA_DIR`. These
+files contain information about each output package produced by the
+OpenEmbedded build system.
+
+This class is enabled by default because it is inherited by the
+:ref:`package <ref-classes-package>` class.
+
+.. _ref-classes-packagegroup:
+
+``packagegroup.bbclass``
+========================
+
+The ``packagegroup`` class sets default values appropriate for package
+group recipes (e.g. ``PACKAGES``, ``PACKAGE_ARCH``, ``ALLOW_EMPTY``, and
+so forth). It is highly recommended that all package group recipes
+inherit this class.
+
+For information on how to use this class, see the
+":ref:`usingpoky-extend-customimage-customtasks`"
+section in the Yocto Project Development Tasks Manual.
+
+Previously, this class was called the ``task`` class.
+
+.. _ref-classes-patch:
+
+``patch.bbclass``
+=================
+
+The ``patch`` class provides all functionality for applying patches
+during the :ref:`ref-tasks-patch` task.
+
+This class is enabled by default because it is inherited by the
+:ref:`base <ref-classes-base>` class.
+
+.. _ref-classes-perlnative:
+
+``perlnative.bbclass``
+======================
+
+When inherited by a recipe, the ``perlnative`` class supports using the
+native version of Perl built by the build system rather than using the
+version provided by the build host.
+
+.. _ref-classes-pixbufcache:
+
+``pixbufcache.bbclass``
+=======================
+
+The ``pixbufcache`` class generates the proper post-install and
+post-remove (postinst/postrm) scriptlets for packages that install
+pixbuf loaders, which are used with ``gdk-pixbuf``. These scriptlets
+call ``update_pixbuf_cache`` to add the pixbuf loaders to the cache.
+Since the cache files are architecture-specific, ``update_pixbuf_cache``
+is run using QEMU if the postinst scriptlets need to be run on the build
+host during image creation.
+
+If the pixbuf loaders being installed are in packages other than the
+recipe's main package, set
+:term:`PIXBUF_PACKAGES` to specify the packages
+containing the loaders.
+
+.. _ref-classes-pkgconfig:
+
+``pkgconfig.bbclass``
+=====================
+
+The ``pkgconfig`` class provides a standard way to get header and
+library information by using ``pkg-config``. This class aims to smooth
+integration of ``pkg-config`` into libraries that use it.
+
+During staging, BitBake installs ``pkg-config`` data into the
+``sysroots/`` directory. By making use of sysroot functionality within
+``pkg-config``, the ``pkgconfig`` class no longer has to manipulate the
+files.
+
+.. _ref-classes-populate-sdk:
+
+``populate_sdk.bbclass``
+========================
+
+The ``populate_sdk`` class provides support for SDK-only recipes. For
+information on advantages gained when building a cross-development
+toolchain using the :ref:`ref-tasks-populate_sdk`
+task, see the ":ref:`sdk-manual/sdk-appendix-obtain:building an sdk installer`"
+section in the Yocto Project Application Development and the Extensible
+Software Development Kit (eSDK) manual.
+
+.. _ref-classes-populate-sdk-*:
+
+``populate_sdk_*.bbclass``
+==========================
+
+The ``populate_sdk_*`` classes support SDK creation and consist of the
+following classes:
+
+-  ``populate_sdk_base``: The base class supporting SDK creation under
+   all package managers (i.e. DEB, RPM, and opkg).
+
+-  ``populate_sdk_deb``: Supports creation of the SDK given the Debian
+   package manager.
+
+-  ``populate_sdk_rpm``: Supports creation of the SDK given the RPM
+   package manager.
+
+-  ``populate_sdk_ipk``: Supports creation of the SDK given the opkg
+   (IPK format) package manager.
+
+-  ``populate_sdk_ext``: Supports extensible SDK creation under all
+   package managers.
+
+The ``populate_sdk_base`` class inherits the appropriate
+``populate_sdk_*`` (i.e. ``deb``, ``rpm``, and ``ipk``) based on
+:term:`IMAGE_PKGTYPE`.
+
+The base class ensures all source and destination directories are
+established and then populates the SDK. After populating the SDK, the
+``populate_sdk_base`` class constructs two sysroots:
+``${``\ :term:`SDK_ARCH`\ ``}-nativesdk``, which
+contains the cross-compiler and associated tooling, and the target,
+which contains a target root filesystem that is configured for the SDK
+usage. These two images reside in :term:`SDK_OUTPUT`,
+which consists of the following:
+::
+
+   ${SDK_OUTPUT}/${SDK_ARCH}-nativesdk-pkgs
+   ${SDK_OUTPUT}/${SDKTARGETSYSROOT}/target-pkgs
+
+Finally, the base populate SDK class creates the toolchain environment
+setup script, the tarball of the SDK, and the installer.
+
+The respective ``populate_sdk_deb``, ``populate_sdk_rpm``, and
+``populate_sdk_ipk`` classes each support the specific type of SDK.
+These classes are inherited by and used with the ``populate_sdk_base``
+class.
+
+For more information on the cross-development toolchain generation, see
+the ":ref:`overview-manual/overview-manual-concepts:cross-development toolchain generation`"
+section in the Yocto Project Overview and Concepts Manual. For
+information on advantages gained when building a cross-development
+toolchain using the :ref:`ref-tasks-populate_sdk`
+task, see the
+":ref:`sdk-manual/sdk-appendix-obtain:building an sdk installer`"
+section in the Yocto Project Application Development and the Extensible
+Software Development Kit (eSDK) manual.
+
+.. _ref-classes-prexport:
+
+``prexport.bbclass``
+====================
+
+The ``prexport`` class provides functionality for exporting
+:term:`PR` values.
+
+.. note::
+
+   This class is not intended to be used directly. Rather, it is enabled
+   when using "
+   bitbake-prserv-tool export
+   ".
+
+.. _ref-classes-primport:
+
+``primport.bbclass``
+====================
+
+The ``primport`` class provides functionality for importing
+:term:`PR` values.
+
+.. note::
+
+   This class is not intended to be used directly. Rather, it is enabled
+   when using "
+   bitbake-prserv-tool import
+   ".
+
+.. _ref-classes-prserv:
+
+``prserv.bbclass``
+==================
+
+The ``prserv`` class provides functionality for using a :ref:`PR
+service <dev-manual/dev-manual-common-tasks:working with a pr service>` in order to
+automatically manage the incrementing of the :term:`PR`
+variable for each recipe.
+
+This class is enabled by default because it is inherited by the
+:ref:`package <ref-classes-package>` class. However, the OpenEmbedded
+build system will not enable the functionality of this class unless
+:term:`PRSERV_HOST` has been set.
+
+.. _ref-classes-ptest:
+
+``ptest.bbclass``
+=================
+
+The ``ptest`` class provides functionality for packaging and installing
+runtime tests for recipes that build software that provides these tests.
+
+This class is intended to be inherited by individual recipes. However,
+the class' functionality is largely disabled unless "ptest" appears in
+:term:`DISTRO_FEATURES`. See the
+":ref:`dev-manual/dev-manual-common-tasks:testing packages with ptest`"
+section in the Yocto Project Development Tasks Manual for more information
+on ptest.
+
+.. _ref-classes-ptest-gnome:
+
+``ptest-gnome.bbclass``
+=======================
+
+Enables package tests (ptests) specifically for GNOME packages, which
+have tests intended to be executed with ``gnome-desktop-testing``.
+
+For information on setting up and running ptests, see the
+":ref:`dev-manual/dev-manual-common-tasks:testing packages with ptest`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _ref-classes-python-dir:
+
+``python-dir.bbclass``
+======================
+
+The ``python-dir`` class provides the base version, location, and site
+package location for Python.
+
+.. _ref-classes-python3native:
+
+``python3native.bbclass``
+=========================
+
+The ``python3native`` class supports using the native version of Python
+3 built by the build system rather than support of the version provided
+by the build host.
+
+.. _ref-classes-pythonnative:
+
+``pythonnative.bbclass``
+========================
+
+When inherited by a recipe, the ``pythonnative`` class supports using
+the native version of Python built by the build system rather than using
+the version provided by the build host.
+
+.. _ref-classes-qemu:
+
+``qemu.bbclass``
+================
+
+The ``qemu`` class provides functionality for recipes that either need
+QEMU or test for the existence of QEMU. Typically, this class is used to
+run programs for a target system on the build host using QEMU's
+application emulation mode.
+
+.. _ref-classes-recipe_sanity:
+
+``recipe_sanity.bbclass``
+=========================
+
+The ``recipe_sanity`` class checks for the presence of any host system
+recipe prerequisites that might affect the build (e.g. variables that
+are set or software that is present).
+
+.. _ref-classes-relocatable:
+
+``relocatable.bbclass``
+=======================
+
+The ``relocatable`` class enables relocation of binaries when they are
+installed into the sysroot.
+
+This class makes use of the :ref:`chrpath <ref-classes-chrpath>` class
+and is used by both the :ref:`cross <ref-classes-cross>` and
+:ref:`native <ref-classes-native>` classes.
+
+.. _ref-classes-remove-libtool:
+
+``remove-libtool.bbclass``
+==========================
+
+The ``remove-libtool`` class adds a post function to the
+:ref:`ref-tasks-install` task to remove all ``.la`` files
+installed by ``libtool``. Removing these files results in them being
+absent from both the sysroot and target packages.
+
+If a recipe needs the ``.la`` files to be installed, then the recipe can
+override the removal by setting ``REMOVE_LIBTOOL_LA`` to "0" as follows:
+::
+
+   REMOVE_LIBTOOL_LA = "0"
+
+.. note::
+
+   The
+   remove-libtool
+   class is not enabled by default.
+
+.. _ref-classes-report-error:
+
+``report-error.bbclass``
+========================
+
+The ``report-error`` class supports enabling the :ref:`error reporting
+tool <dev-manual/dev-manual-common-tasks:using the error reporting tool>`",
+which allows you to submit build error information to a central database.
+
+The class collects debug information for recipe, recipe version, task,
+machine, distro, build system, target system, host distro, branch,
+commit, and log. From the information, report files using a JSON format
+are created and stored in
+``${``\ :term:`LOG_DIR`\ ``}/error-report``.
+
+.. _ref-classes-rm-work:
+
+``rm_work.bbclass``
+===================
+
+The ``rm_work`` class supports deletion of temporary workspace, which
+can ease your hard drive demands during builds.
+
+The OpenEmbedded build system can use a substantial amount of disk space
+during the build process. A portion of this space is the work files
+under the ``${TMPDIR}/work`` directory for each recipe. Once the build
+system generates the packages for a recipe, the work files for that
+recipe are no longer needed. However, by default, the build system
+preserves these files for inspection and possible debugging purposes. If
+you would rather have these files deleted to save disk space as the
+build progresses, you can enable ``rm_work`` by adding the following to
+your ``local.conf`` file, which is found in the :term:`Build Directory`.
+::
+
+   INHERIT += "rm_work"
+
+If you are
+modifying and building source code out of the work directory for a
+recipe, enabling ``rm_work`` will potentially result in your changes to
+the source being lost. To exclude some recipes from having their work
+directories deleted by ``rm_work``, you can add the names of the recipe
+or recipes you are working on to the ``RM_WORK_EXCLUDE`` variable, which
+can also be set in your ``local.conf`` file. Here is an example:
+::
+
+   RM_WORK_EXCLUDE += "busybox glibc"
+
+.. _ref-classes-rootfs*:
+
+``rootfs*.bbclass``
+===================
+
+The ``rootfs*`` classes support creating the root filesystem for an
+image and consist of the following classes:
+
+-  The ``rootfs-postcommands`` class, which defines filesystem
+   post-processing functions for image recipes.
+
+-  The ``rootfs_deb`` class, which supports creation of root filesystems
+   for images built using ``.deb`` packages.
+
+-  The ``rootfs_rpm`` class, which supports creation of root filesystems
+   for images built using ``.rpm`` packages.
+
+-  The ``rootfs_ipk`` class, which supports creation of root filesystems
+   for images built using ``.ipk`` packages.
+
+-  The ``rootfsdebugfiles`` class, which installs additional files found
+   on the build host directly into the root filesystem.
+
+The root filesystem is created from packages using one of the
+``rootfs*.bbclass`` files as determined by the
+:term:`PACKAGE_CLASSES` variable.
+
+For information on how root filesystem images are created, see the
+:ref:`image-generation-dev-environment`"
+section in the Yocto Project Overview and Concepts Manual.
+
+.. _ref-classes-sanity:
+
+``sanity.bbclass``
+==================
+
+The ``sanity`` class checks to see if prerequisite software is present
+on the host system so that users can be notified of potential problems
+that might affect their build. The class also performs basic user
+configuration checks from the ``local.conf`` configuration file to
+prevent common mistakes that cause build failures. Distribution policy
+usually determines whether to include this class.
+
+.. _ref-classes-scons:
+
+``scons.bbclass``
+=================
+
+The ``scons`` class supports recipes that need to build software that
+uses the SCons build system. You can use the
+:term:`EXTRA_OESCONS` variable to specify
+additional configuration options you want to pass SCons command line.
+
+.. _ref-classes-sdl:
+
+``sdl.bbclass``
+===============
+
+The ``sdl`` class supports recipes that need to build software that uses
+the Simple DirectMedia Layer (SDL) library.
+
+.. _ref-classes-setuptools:
+
+``setuptools.bbclass``
+======================
+
+The ``setuptools`` class supports Python version 2.x extensions that use
+build systems based on ``setuptools``. If your recipe uses these build
+systems, the recipe needs to inherit the ``setuptools`` class.
+
+.. _ref-classes-setuptools3:
+
+``setuptools3.bbclass``
+=======================
+
+The ``setuptools3`` class supports Python version 3.x extensions that
+use build systems based on ``setuptools3``. If your recipe uses these
+build systems, the recipe needs to inherit the ``setuptools3`` class.
+
+.. _ref-classes-sign_rpm:
+
+``sign_rpm.bbclass``
+====================
+
+The ``sign_rpm`` class supports generating signed RPM packages.
+
+.. _ref-classes-sip:
+
+``sip.bbclass``
+===============
+
+The ``sip`` class supports recipes that build or package SIP-based
+Python bindings.
+
+.. _ref-classes-siteconfig:
+
+``siteconfig.bbclass``
+======================
+
+The ``siteconfig`` class provides functionality for handling site
+configuration. The class is used by the
+:ref:`autotools <ref-classes-autotools>` class to accelerate the
+:ref:`ref-tasks-configure` task.
+
+.. _ref-classes-siteinfo:
+
+``siteinfo.bbclass``
+====================
+
+The ``siteinfo`` class provides information about the targets that might
+be needed by other classes or recipes.
+
+As an example, consider Autotools, which can require tests that must
+execute on the target hardware. Since this is not possible in general
+when cross compiling, site information is used to provide cached test
+results so these tests can be skipped over but still make the correct
+values available. The ``meta/site directory`` contains test results
+sorted into different categories such as architecture, endianness, and
+the ``libc`` used. Site information provides a list of files containing
+data relevant to the current build in the ``CONFIG_SITE`` variable that
+Autotools automatically picks up.
+
+The class also provides variables like ``SITEINFO_ENDIANNESS`` and
+``SITEINFO_BITS`` that can be used elsewhere in the metadata.
+
+.. _ref-classes-spdx:
+
+``spdx.bbclass``
+================
+
+The ``spdx`` class integrates real-time license scanning, generation of
+SPDX standard output, and verification of license information during the
+build.
+
+.. note::
+
+   This class is currently at the prototype stage in the 1.6 release.
+
+.. _ref-classes-sstate:
+
+``sstate.bbclass``
+==================
+
+The ``sstate`` class provides support for Shared State (sstate). By
+default, the class is enabled through the
+:term:`INHERIT_DISTRO` variable's default value.
+
+For more information on sstate, see the
+":ref:`overview-manual/overview-manual-concepts:shared state cache`"
+section in the Yocto Project Overview and Concepts Manual.
+
+.. _ref-classes-staging:
+
+``staging.bbclass``
+===================
+
+The ``staging`` class installs files into individual recipe work
+directories for sysroots. The class contains the following key tasks:
+
+-  The :ref:`ref-tasks-populate_sysroot` task,
+   which is responsible for handing the files that end up in the recipe
+   sysroots.
+
+-  The
+   :ref:`ref-tasks-prepare_recipe_sysroot`
+   task (a "partner" task to the ``populate_sysroot`` task), which
+   installs the files into the individual recipe work directories (i.e.
+   :term:`WORKDIR`).
+
+The code in the ``staging`` class is complex and basically works in two
+stages:
+
+-  *Stage One:* The first stage addresses recipes that have files they
+   want to share with other recipes that have dependencies on the
+   originating recipe. Normally these dependencies are installed through
+   the :ref:`ref-tasks-install` task into
+   ``${``\ :term:`D`\ ``}``. The ``do_populate_sysroot`` task
+   copies a subset of these files into ``${SYSROOT_DESTDIR}``. This
+   subset of files is controlled by the
+   :term:`SYSROOT_DIRS`,
+   :term:`SYSROOT_DIRS_NATIVE`, and
+   :term:`SYSROOT_DIRS_BLACKLIST`
+   variables.
+
+   .. note::
+
+      Additionally, a recipe can customize the files further by
+      declaring a processing function in the
+      SYSROOT_PREPROCESS_FUNCS
+      variable.
+
+   A shared state (sstate) object is built from these files and the
+   files are placed into a subdirectory of
+   ```tmp/sysroots-components/`` <#structure-build-tmp-sysroots-components>`__.
+   The files are scanned for hardcoded paths to the original
+   installation location. If the location is found in text files, the
+   hardcoded locations are replaced by tokens and a list of the files
+   needing such replacements is created. These adjustments are referred
+   to as "FIXMEs". The list of files that are scanned for paths is
+   controlled by the :term:`SSTATE_SCAN_FILES`
+   variable.
+
+-  *Stage Two:* The second stage addresses recipes that want to use
+   something from another recipe and declare a dependency on that recipe
+   through the :term:`DEPENDS` variable. The recipe will
+   have a
+   :ref:`ref-tasks-prepare_recipe_sysroot`
+   task and when this task executes, it creates the ``recipe-sysroot``
+   and ``recipe-sysroot-native`` in the recipe work directory (i.e.
+   :term:`WORKDIR`). The OpenEmbedded build system
+   creates hard links to copies of the relevant files from
+   ``sysroots-components`` into the recipe work directory.
+
+   .. note::
+
+      If hard links are not possible, the build system uses actual
+      copies.
+
+   The build system then addresses any "FIXMEs" to paths as defined from
+   the list created in the first stage.
+
+   Finally, any files in ``${bindir}`` within the sysroot that have the
+   prefix "``postinst-``" are executed.
+
+   .. note::
+
+      Although such sysroot post installation scripts are not
+      recommended for general use, the files do allow some issues such
+      as user creation and module indexes to be addressed.
+
+   Because recipes can have other dependencies outside of ``DEPENDS``
+   (e.g. ``do_unpack[depends] += "tar-native:do_populate_sysroot"``),
+   the sysroot creation function ``extend_recipe_sysroot`` is also added
+   as a pre-function for those tasks whose dependencies are not through
+   ``DEPENDS`` but operate similarly.
+
+   When installing dependencies into the sysroot, the code traverses the
+   dependency graph and processes dependencies in exactly the same way
+   as the dependencies would or would not be when installed from sstate.
+   This processing means, for example, a native tool would have its
+   native dependencies added but a target library would not have its
+   dependencies traversed or installed. The same sstate dependency code
+   is used so that builds should be identical regardless of whether
+   sstate was used or not. For a closer look, see the
+   ``setscene_depvalid()`` function in the
+   :ref:`sstate <ref-classes-sstate>` class.
+
+   The build system is careful to maintain manifests of the files it
+   installs so that any given dependency can be installed as needed. The
+   sstate hash of the installed item is also stored so that if it
+   changes, the build system can reinstall it.
+
+.. _ref-classes-syslinux:
+
+``syslinux.bbclass``
+====================
+
+The ``syslinux`` class provides syslinux-specific functions for building
+bootable images.
+
+The class supports the following variables:
+
+-  :term:`INITRD`: Indicates list of filesystem images to
+   concatenate and use as an initial RAM disk (initrd). This variable is
+   optional.
+
+-  :term:`ROOTFS`: Indicates a filesystem image to include
+   as the root filesystem. This variable is optional.
+
+-  :term:`AUTO_SYSLINUXMENU`: Enables creating
+   an automatic menu when set to "1".
+
+-  :term:`LABELS`: Lists targets for automatic
+   configuration.
+
+-  :term:`APPEND`: Lists append string overrides for each
+   label.
+
+-  :term:`SYSLINUX_OPTS`: Lists additional options
+   to add to the syslinux file. Semicolon characters separate multiple
+   options.
+
+-  :term:`SYSLINUX_SPLASH`: Lists a background
+   for the VGA boot menu when you are using the boot menu.
+
+-  :term:`SYSLINUX_DEFAULT_CONSOLE`: Set
+   to "console=ttyX" to change kernel boot default console.
+
+-  :term:`SYSLINUX_SERIAL`: Sets an alternate
+   serial port. Or, turns off serial when the variable is set with an
+   empty string.
+
+-  :term:`SYSLINUX_SERIAL_TTY`: Sets an
+   alternate "console=tty..." kernel boot argument.
+
+.. _ref-classes-systemd:
+
+``systemd.bbclass``
+===================
+
+The ``systemd`` class provides support for recipes that install systemd
+unit files.
+
+The functionality for this class is disabled unless you have "systemd"
+in :term:`DISTRO_FEATURES`.
+
+Under this class, the recipe or Makefile (i.e. whatever the recipe is
+calling during the :ref:`ref-tasks-install` task)
+installs unit files into
+``${``\ :term:`D`\ ``}${systemd_unitdir}/system``. If the unit
+files being installed go into packages other than the main package, you
+need to set :term:`SYSTEMD_PACKAGES` in your
+recipe to identify the packages in which the files will be installed.
+
+You should set :term:`SYSTEMD_SERVICE` to the
+name of the service file. You should also use a package name override to
+indicate the package to which the value applies. If the value applies to
+the recipe's main package, use ``${``\ :term:`PN`\ ``}``. Here
+is an example from the connman recipe:
+::
+
+   SYSTEMD_SERVICE_${PN} = "connman.service"
+
+Services are set up to start on boot automatically
+unless you have set
+:term:`SYSTEMD_AUTO_ENABLE` to "disable".
+
+For more information on ``systemd``, see the
+":ref:`dev-manual/dev-manual-common-tasks:selecting an initialization manager`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _ref-classes-systemd-boot:
+
+``systemd-boot.bbclass``
+========================
+
+The ``systemd-boot`` class provides functions specific to the
+systemd-boot bootloader for building bootable images. This is an
+internal class and is not intended to be used directly.
+
+.. note::
+
+   The
+   systemd-boot
+   class is a result from merging the
+   gummiboot
+   class used in previous Yocto Project releases with the
+   systemd
+   project.
+
+Set the :term:`EFI_PROVIDER` variable to
+"systemd-boot" to use this class. Doing so creates a standalone EFI
+bootloader that is not dependent on systemd.
+
+For information on more variables used and supported in this class, see
+the :term:`SYSTEMD_BOOT_CFG`,
+:term:`SYSTEMD_BOOT_ENTRIES`, and
+:term:`SYSTEMD_BOOT_TIMEOUT` variables.
+
+You can also see the `Systemd-boot
+documentation <http://www.freedesktop.org/wiki/Software/systemd/systemd-boot/>`__
+for more information.
+
+.. _ref-classes-terminal:
+
+``terminal.bbclass``
+====================
+
+The ``terminal`` class provides support for starting a terminal session.
+The :term:`OE_TERMINAL` variable controls which
+terminal emulator is used for the session.
+
+Other classes use the ``terminal`` class anywhere a separate terminal
+session needs to be started. For example, the
+:ref:`patch <ref-classes-patch>` class assuming
+:term:`PATCHRESOLVE` is set to "user", the
+:ref:`cml1 <ref-classes-cml1>` class, and the
+:ref:`devshell <ref-classes-devshell>` class all use the ``terminal``
+class.
+
+.. _ref-classes-testimage*:
+
+``testimage*.bbclass``
+======================
+
+The ``testimage*`` classes support running automated tests against
+images using QEMU and on actual hardware. The classes handle loading the
+tests and starting the image. To use the classes, you need to perform
+steps to set up the environment.
+
+.. note::
+
+   Best practices include using
+   IMAGE_CLASSES
+   rather than
+   INHERIT
+   to inherit the
+   testimage
+   class for automated image testing.
+
+The tests are commands that run on the target system over ``ssh``. Each
+test is written in Python and makes use of the ``unittest`` module.
+
+The ``testimage.bbclass`` runs tests on an image when called using the
+following:
+::
+
+   $ bitbake -c testimage image
+
+The ``testimage-auto`` class
+runs tests on an image after the image is constructed (i.e.
+:term:`TESTIMAGE_AUTO` must be set to "1").
+
+For information on how to enable, run, and create new tests, see the
+":ref:`dev-manual/dev-manual-common-tasks:performing automated runtime testing`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _ref-classes-testsdk:
+
+``testsdk.bbclass``
+===================
+
+This class supports running automated tests against software development
+kits (SDKs). The ``testsdk`` class runs tests on an SDK when called
+using the following:
+::
+
+   $ bitbake -c testsdk image
+
+.. note::
+
+   Best practices include using
+   IMAGE_CLASSES
+   rather than
+   INHERIT
+   to inherit the
+   testsdk
+   class for automated SDK testing.
+
+.. _ref-classes-texinfo:
+
+``texinfo.bbclass``
+===================
+
+This class should be inherited by recipes whose upstream packages invoke
+the ``texinfo`` utilities at build-time. Native and cross recipes are
+made to use the dummy scripts provided by ``texinfo-dummy-native``, for
+improved performance. Target architecture recipes use the genuine
+Texinfo utilities. By default, they use the Texinfo utilities on the
+host system.
+
+.. note::
+
+   If you want to use the Texinfo recipe shipped with the build system,
+   you can remove "texinfo-native" from
+   ASSUME_PROVIDED
+   and makeinfo from
+   SANITY_REQUIRED_UTILITIES
+   .
+
+.. _ref-classes-tinderclient:
+
+``tinderclient.bbclass``
+========================
+
+The ``tinderclient`` class submits build results to an external
+Tinderbox instance.
+
+.. note::
+
+   This class is currently unmaintained.
+
+.. _ref-classes-toaster:
+
+``toaster.bbclass``
+===================
+
+The ``toaster`` class collects information about packages and images and
+sends them as events that the BitBake user interface can receive. The
+class is enabled when the Toaster user interface is running.
+
+This class is not intended to be used directly.
+
+.. _ref-classes-toolchain-scripts:
+
+``toolchain-scripts.bbclass``
+=============================
+
+The ``toolchain-scripts`` class provides the scripts used for setting up
+the environment for installed SDKs.
+
+.. _ref-classes-typecheck:
+
+``typecheck.bbclass``
+=====================
+
+The ``typecheck`` class provides support for validating the values of
+variables set at the configuration level against their defined types.
+The OpenEmbedded build system allows you to define the type of a
+variable using the "type" varflag. Here is an example:
+::
+
+   IMAGE_FEATURES[type] = "list"
+
+.. _ref-classes-uboot-config:
+
+``uboot-config.bbclass``
+========================
+
+The ``uboot-config`` class provides support for U-Boot configuration for
+a machine. Specify the machine in your recipe as follows:
+::
+
+   UBOOT_CONFIG ??= <default>
+   UBOOT_CONFIG[foo] = "config,images"
+
+You can also specify the machine using this method:
+::
+
+   UBOOT_MACHINE = "config"
+
+See the :term:`UBOOT_CONFIG` and :term:`UBOOT_MACHINE` variables for additional
+information.
+
+.. _ref-classes-uninative:
+
+``uninative.bbclass``
+=====================
+
+Attempts to isolate the build system from the host distribution's C
+library in order to make re-use of native shared state artifacts across
+different host distributions practical. With this class enabled, a
+tarball containing a pre-built C library is downloaded at the start of
+the build. In the Poky reference distribution this is enabled by default
+through ``meta/conf/distro/include/yocto-uninative.inc``. Other
+distributions that do not derive from poky can also
+"``require conf/distro/include/yocto-uninative.inc``" to use this.
+Alternatively if you prefer, you can build the uninative-tarball recipe
+yourself, publish the resulting tarball (e.g. via HTTP) and set
+``UNINATIVE_URL`` and ``UNINATIVE_CHECKSUM`` appropriately. For an
+example, see the ``meta/conf/distro/include/yocto-uninative.inc``.
+
+The ``uninative`` class is also used unconditionally by the extensible
+SDK. When building the extensible SDK, ``uninative-tarball`` is built
+and the resulting tarball is included within the SDK.
+
+.. _ref-classes-update-alternatives:
+
+``update-alternatives.bbclass``
+===============================
+
+The ``update-alternatives`` class helps the alternatives system when
+multiple sources provide the same command. This situation occurs when
+several programs that have the same or similar function are installed
+with the same name. For example, the ``ar`` command is available from
+the ``busybox``, ``binutils`` and ``elfutils`` packages. The
+``update-alternatives`` class handles renaming the binaries so that
+multiple packages can be installed without conflicts. The ``ar`` command
+still works regardless of which packages are installed or subsequently
+removed. The class renames the conflicting binary in each package and
+symlinks the highest priority binary during installation or removal of
+packages.
+
+To use this class, you need to define a number of variables:
+
+-  :term:`ALTERNATIVE`
+
+-  :term:`ALTERNATIVE_LINK_NAME`
+
+-  :term:`ALTERNATIVE_TARGET`
+
+-  :term:`ALTERNATIVE_PRIORITY`
+
+These variables list alternative commands needed by a package, provide
+pathnames for links, default links for targets, and so forth. For
+details on how to use this class, see the comments in the
+:yocto_git:`update-alternatives.bbclass </cgit/cgit.cgi/poky/tree/meta/classes/update-alternatives.bbclass>`
+file.
+
+.. note::
+
+   You can use the
+   update-alternatives
+   command directly in your recipes. However, this class simplifies
+   things in most cases.
+
+.. _ref-classes-update-rc.d:
+
+``update-rc.d.bbclass``
+=======================
+
+The ``update-rc.d`` class uses ``update-rc.d`` to safely install an
+initialization script on behalf of the package. The OpenEmbedded build
+system takes care of details such as making sure the script is stopped
+before a package is removed and started when the package is installed.
+
+Three variables control this class: ``INITSCRIPT_PACKAGES``,
+``INITSCRIPT_NAME`` and ``INITSCRIPT_PARAMS``. See the variable links
+for details.
+
+.. _ref-classes-useradd:
+
+``useradd*.bbclass``
+====================
+
+The ``useradd*`` classes support the addition of users or groups for
+usage by the package on the target. For example, if you have packages
+that contain system services that should be run under their own user or
+group, you can use these classes to enable creation of the user or
+group. The ``meta-skeleton/recipes-skeleton/useradd/useradd-example.bb``
+recipe in the :term:`Source Directory` provides a simple
+example that shows how to add three users and groups to two packages.
+See the ``useradd-example.bb`` recipe for more information on how to use
+these classes.
+
+The ``useradd_base`` class provides basic functionality for user or
+groups settings.
+
+The ``useradd*`` classes support the
+:term:`USERADD_PACKAGES`,
+:term:`USERADD_PARAM`,
+:term:`GROUPADD_PARAM`, and
+:term:`GROUPMEMS_PARAM` variables.
+
+The ``useradd-staticids`` class supports the addition of users or groups
+that have static user identification (``uid``) and group identification
+(``gid``) values.
+
+The default behavior of the OpenEmbedded build system for assigning
+``uid`` and ``gid`` values when packages add users and groups during
+package install time is to add them dynamically. This works fine for
+programs that do not care what the values of the resulting users and
+groups become. In these cases, the order of the installation determines
+the final ``uid`` and ``gid`` values. However, if non-deterministic
+``uid`` and ``gid`` values are a problem, you can override the default,
+dynamic application of these values by setting static values. When you
+set static values, the OpenEmbedded build system looks in
+:term:`BBPATH` for ``files/passwd`` and ``files/group``
+files for the values.
+
+To use static ``uid`` and ``gid`` values, you need to set some
+variables. See the :term:`USERADDEXTENSION`,
+:term:`USERADD_UID_TABLES`,
+:term:`USERADD_GID_TABLES`, and
+:term:`USERADD_ERROR_DYNAMIC` variables.
+You can also see the :ref:`useradd <ref-classes-useradd>` class for
+additional information.
+
+.. note::
+
+   You do not use the
+   useradd-staticids
+   class directly. You either enable or disable the class by setting the
+   USERADDEXTENSION
+   variable. If you enable or disable the class in a configured system,
+   TMPDIR
+   might contain incorrect
+   uid
+   and
+   gid
+   values. Deleting the
+   TMPDIR
+   directory will correct this condition.
+
+.. _ref-classes-utility-tasks:
+
+``utility-tasks.bbclass``
+=========================
+
+The ``utility-tasks`` class provides support for various "utility" type
+tasks that are applicable to all recipes, such as
+:ref:`ref-tasks-clean` and
+:ref:`ref-tasks-listtasks`.
+
+This class is enabled by default because it is inherited by the
+:ref:`base <ref-classes-base>` class.
+
+.. _ref-classes-utils:
+
+``utils.bbclass``
+=================
+
+The ``utils`` class provides some useful Python functions that are
+typically used in inline Python expressions (e.g. ``${@...}``). One
+example use is for ``bb.utils.contains()``.
+
+This class is enabled by default because it is inherited by the
+:ref:`base <ref-classes-base>` class.
+
+.. _ref-classes-vala:
+
+``vala.bbclass``
+================
+
+The ``vala`` class supports recipes that need to build software written
+using the Vala programming language.
+
+.. _ref-classes-waf:
+
+``waf.bbclass``
+===============
+
+The ``waf`` class supports recipes that need to build software that uses
+the Waf build system. You can use the
+:term:`EXTRA_OECONF` or
+:term:`PACKAGECONFIG_CONFARGS` variables
+to specify additional configuration options to be passed on the Waf
+command line.
diff --git a/documentation/ref-manual/ref-classes.xml b/documentation/ref-manual/ref-classes.xml
index f9bbddd724..1dcd5fdd03 100644
--- a/documentation/ref-manual/ref-classes.xml
+++ b/documentation/ref-manual/ref-classes.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-classes'>
 <title>Classes</title>
@@ -1742,6 +1743,12 @@ This check was removed for YP 2.3 release
                 </note>
                 </para></listitem>
 -->
+            <listitem><para><emphasis><filename>unlisted-pkg-lics:</filename></emphasis>
+                Checks that all declared licenses applying for a package are also
+                declared on the recipe level (i.e. any license in
+                <filename>LICENSE_*</filename> should appear in
+                <link linkend='var-LICENSE'><filename>LICENSE</filename></link>).
+                </para></listitem>
             <listitem><para><emphasis><filename>useless-rpaths:</filename></emphasis>
                 Checks for dynamic library load paths (rpaths) in the binaries that
                 by default on a standard system are searched by the linker (e.g.
@@ -1873,8 +1880,82 @@ This check was removed for YP 2.3 release
 
     <para>
         The <filename>kernel-fitimage</filename> class provides support to
-        pack zImages.
+        pack a kernel Image, device trees and a RAM disk into a single
+        FIT image. In theory, a FIT image can support any number of kernels,
+        RAM disks and device-trees.
+        However, <filename>kernel-fitimage</filename> currently only supports
+        limited usescases: just one kernel image, an optional RAM disk, and
+        any number of device tree.
+    </para>
+
+    <para>
+        To create a FIT image, it is required that
+        <filename><link linkend='var-KERNEL_CLASSES'>KERNEL_CLASSES</link></filename>
+        is set to "kernel-fitimage" and
+        <filename><link linkend='var-KERNEL_IMAGETYPE'>KERNEL_IMAGETYPE</link></filename>
+        is set to "fitImage".
+    </para>
+
+    <para>
+        The options for the device tree compiler passed to mkimage -D feature
+        when creating the FIT image are specified using the
+        <filename><link linkend='var-UBOOT_MKIMAGE_DTCOPTS'>UBOOT_MKIMAGE_DTCOPTS</link></filename>
+        variable.
+    </para>
+
+    <para>
+        Only a single kernel can be added to the FIT image created by
+        <filename>kernel-fitimage</filename> and the kernel image in FIT is
+        mandatory.
+        The address where the kernel image is to be loaded by U-boot is
+        specified by
+        <filename><link linkend='var-UBOOT_LOADADDRESS'>UBOOT_LOADADDRESS</link></filename>
+        and the entrypoint by
+        <filename><link linkend='var-UBOOT_ENTRYPOINT'>UBOOT_ENTRYPOINT</link></filename>.
+    </para>
+
+    <para>
+        Multiple device trees can be added to the FIT image created by
+        <filename>kernel-fitimage</filename> and the device tree is optional.
+        The address where the device tree is to be loaded by U-boot is
+        specified by
+        <filename><link linkend='var-UBOOT_DTBO_LOADADDRESS'>UBOOT_DTBO_LOADADDRESS</link></filename>
+        for device tree overlays and by
+        <filename><link linkend='var-UBOOT_DTB_LOADADDRESS'>UBOOT_DTB_LOADADDRESS</link></filename>
+        for device tree binaries.
+    </para>
+
+    <para>
+        Only a single RAM disk can be added to the FIT image created by
+        <filename>kernel-fitimage</filename> and the RAM disk in FIT is
+        optional.
+        The address where the RAM disk image is to be loaded by U-boot
+        is specified by
+        <filename><link linkend='var-UBOOT_RD_LOADADDRESS'>UBOOT_RD_LOADADDRESS</link></filename>
+        and the entrypoint by
+        <filename><link linkend='var-UBOOT_RD_ENTRYPOINT'>UBOOT_RD_ENTRYPOINT</link></filename>.
+        The ramdisk is added to FIT image when
+        <filename><link linkend='var-INITRAMFS_IMAGE'>INITRAMFS_IMAGE</link></filename>
+        is specified.
+    </para>
+
+    <para>
+        The FIT image generated by <filename>kernel-fitimage</filename> class
+        is signed when the variables
+        <filename><link linkend='var-UBOOT_SIGN_ENABLE'>UBOOT_SIGN_ENABLE</link></filename>,
+        <filename><link linkend='var-UBOOT_MKIMAGE_DTCOPTS'>UBOOT_MKIMAGE_DTCOPTS</link></filename>,
+        <filename><link linkend='var-UBOOT_SIGN_KEYDIR'>UBOOT_SIGN_KEYDIR</link></filename>
+        and
+        <filename><link linkend='var-UBOOT_SIGN_KEYNAME'>UBOOT_SIGN_KEYNAME</link></filename>
+        are set appropriately.
+        The default values used for
+        <filename><link linkend='var-FIT_HASH_ALG'>FIT_HASH_ALG</link></filename>
+        and
+        <filename><link linkend='var-FIT_SIGN_ALG'>FIT_SIGN_ALG</link></filename>
+        in <filename>kernel-fitimage</filename> are "sha256" and "rsa2048"
+        respectively.
     </para>
+
 </section>
 
 <section id='ref-classes-kernel-grub'>
diff --git a/documentation/ref-manual/ref-devtool-reference.rst b/documentation/ref-manual/ref-devtool-reference.rst
new file mode 100644
index 0000000000..eaca45ae25
--- /dev/null
+++ b/documentation/ref-manual/ref-devtool-reference.rst
@@ -0,0 +1,625 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+***************************
+``devtool`` Quick Reference
+***************************
+
+The ``devtool`` command-line tool provides a number of features that
+help you build, test, and package software. This command is available
+alongside the ``bitbake`` command. Additionally, the ``devtool`` command
+is a key part of the extensible SDK.
+
+This chapter provides a Quick Reference for the ``devtool`` command. For
+more information on how to apply the command when using the extensible
+SDK, see the ":doc:`../sdk-manual/sdk-extensible`" chapter in the Yocto
+Project Application Development and the Extensible Software Development
+Kit (eSDK) manual.
+
+.. _devtool-getting-help:
+
+Getting Help
+============
+
+The ``devtool`` command line is organized similarly to Git in that it
+has a number of sub-commands for each function. You can run
+``devtool --help`` to see all the commands:
+::
+
+   $ devtool -h
+   NOTE: Starting bitbake server...
+   usage: devtool [--basepath BASEPATH] [--bbpath BBPATH] [-d] [-q] [--color COLOR] [-h] <subcommand> ...
+
+   OpenEmbedded development tool
+
+   options:
+     --basepath BASEPATH   Base directory of SDK / build directory
+     --bbpath BBPATH       Explicitly specify the BBPATH, rather than getting it from the metadata
+     -d, --debug           Enable debug output
+     -q, --quiet           Print only errors
+     --color COLOR         Colorize output (where COLOR is auto, always, never)
+     -h, --help            show this help message and exit
+
+   subcommands:
+     Beginning work on a recipe:
+       add                   Add a new recipe
+       modify                Modify the source for an existing recipe
+       upgrade               Upgrade an existing recipe
+     Getting information:
+       status                Show workspace status
+       latest-version        Report the latest version of an existing recipe
+       check-upgrade-status  Report upgradability for multiple (or all) recipes
+       search                Search available recipes
+     Working on a recipe in the workspace:
+       build                 Build a recipe
+       rename                Rename a recipe file in the workspace
+       edit-recipe           Edit a recipe file
+       find-recipe           Find a recipe file
+       configure-help        Get help on configure script options
+       update-recipe         Apply changes from external source tree to recipe
+       reset                 Remove a recipe from your workspace
+       finish                Finish working on a recipe in your workspace
+     Testing changes on target:
+       deploy-target         Deploy recipe output files to live target machine
+       undeploy-target       Undeploy recipe output files in live target machine
+       build-image           Build image including workspace recipe packages
+     Advanced:
+       create-workspace      Set up workspace in an alternative location
+       extract               Extract the source for an existing recipe
+       sync                  Synchronize the source tree for an existing recipe
+       menuconfig            Alter build-time configuration for a recipe
+       import                Import exported tar archive into workspace
+       export                Export workspace into a tar archive
+     other:
+       selftest-reverse      Reverse value (for selftest)
+       pluginfile            Print the filename of this plugin
+       bbdir                 Print the BBPATH directory of this plugin
+       count                 How many times have this plugin been registered.
+       multiloaded           How many times have this plugin been initialized
+   Use devtool <subcommand> --help to get help on a specific command
+
+As directed in the general help output, you can
+get more syntax on a specific command by providing the command name and
+using "--help":
+::
+
+   $ devtool add --help
+   NOTE: Starting bitbake server...
+   usage: devtool add [-h] [--same-dir | --no-same-dir] [--fetch URI] [--npm-dev] [--version VERSION] [--no-git] [--srcrev SRCREV | --autorev] [--srcbranch SRCBRANCH] [--binary] [--also-native] [--src-subdir SUBDIR] [--mirrors]
+                      [--provides PROVIDES]
+                      [recipename] [srctree] [fetchuri]
+
+   Adds a new recipe to the workspace to build a specified source tree. Can optionally fetch a remote URI and unpack it to create the source tree.
+
+   arguments:
+     recipename            Name for new recipe to add (just name - no version, path or extension). If not specified, will attempt to auto-detect it.
+     srctree               Path to external source tree. If not specified, a subdirectory of /media/build1/poky/build/workspace/sources will be used.
+     fetchuri              Fetch the specified URI and extract it to create the source tree
+
+   options:
+     -h, --help            show this help message and exit
+     --same-dir, -s        Build in same directory as source
+     --no-same-dir         Force build in a separate build directory
+     --fetch URI, -f URI   Fetch the specified URI and extract it to create the source tree (deprecated - pass as positional argument instead)
+     --npm-dev             For npm, also fetch devDependencies
+     --version VERSION, -V VERSION
+                           Version to use within recipe (PV)
+     --no-git, -g          If fetching source, do not set up source tree as a git repository
+     --srcrev SRCREV, -S SRCREV
+                           Source revision to fetch if fetching from an SCM such as git (default latest)
+     --autorev, -a         When fetching from a git repository, set SRCREV in the recipe to a floating revision instead of fixed
+     --srcbranch SRCBRANCH, -B SRCBRANCH
+                           Branch in source repository if fetching from an SCM such as git (default master)
+     --binary, -b          Treat the source tree as something that should be installed verbatim (no compilation, same directory structure). Useful with binary packages e.g. RPMs.
+     --also-native         Also add native variant (i.e. support building recipe for the build host as well as the target machine)
+     --src-subdir SUBDIR   Specify subdirectory within source tree to use
+     --mirrors             Enable PREMIRRORS and MIRRORS for source tree fetching (disable by default).
+     --provides PROVIDES, -p PROVIDES
+                           Specify an alias for the item provided by the recipe. E.g. virtual/libgl
+
+.. _devtool-the-workspace-layer-structure:
+
+The Workspace Layer Structure
+=============================
+
+``devtool`` uses a "Workspace" layer in which to accomplish builds. This
+layer is not specific to any single ``devtool`` command but is rather a
+common working area used across the tool.
+
+The following figure shows the workspace structure:
+
+.. image:: figures/build-workspace-directory.png
+   :align: center
+   :scale: 70%
+
+::
+
+   attic - A directory created if devtool believes it must preserve
+           anything when you run "devtool reset".  For example, if you
+           run "devtool add", make changes to the recipe, and then
+           run "devtool reset", devtool takes notice that the file has
+           been changed and moves it into the attic should you still
+           want the recipe.
+
+   README - Provides information on what is in workspace layer and how to
+            manage it.
+
+   .devtool_md5 - A checksum file used by devtool.
+
+   appends - A directory that contains *.bbappend files, which point to
+             external source.
+
+   conf - A configuration directory that contains the layer.conf file.
+
+   recipes - A directory containing recipes.  This directory contains a
+             folder for each directory added whose name matches that of the
+             added recipe.  devtool places the recipe.bb file
+             within that sub-directory.
+
+   sources - A directory containing a working copy of the source files used
+             when building the recipe.  This is the default directory used
+             as the location of the source tree when you do not provide a
+             source tree path.  This directory contains a folder for each
+             set of source files matched to a corresponding recipe.
+
+.. _devtool-adding-a-new-recipe-to-the-workspace:
+
+Adding a New Recipe to the Workspace Layer
+==========================================
+
+Use the ``devtool add`` command to add a new recipe to the workspace
+layer. The recipe you add should not exist - ``devtool`` creates it for
+you. The source files the recipe uses should exist in an external area.
+
+The following example creates and adds a new recipe named ``jackson`` to
+a workspace layer the tool creates. The source code built by the recipes
+resides in ``/home/user/sources/jackson``:
+::
+
+   $ devtool add jackson /home/user/sources/jackson
+
+If you add a recipe and the workspace layer does not exist, the command
+creates the layer and populates it as described in "`The Workspace Layer
+Structure <#devtool-the-workspace-layer-structure>`__" section.
+
+Running ``devtool add`` when the workspace layer exists causes the tool
+to add the recipe, append files, and source files into the existing
+workspace layer. The ``.bbappend`` file is created to point to the
+external source tree.
+
+.. note::
+
+   If your recipe has runtime dependencies defined, you must be sure
+   that these packages exist on the target hardware before attempting to
+   run your application. If dependent packages (e.g. libraries) do not
+   exist on the target, your application, when run, will fail to find
+   those functions. For more information, see the
+   ":ref:`ref-manual/ref-devtool-reference:deploying your software on the target machine`"
+   section.
+
+By default, ``devtool add`` uses the latest revision (i.e. master) when
+unpacking files from a remote URI. In some cases, you might want to
+specify a source revision by branch, tag, or commit hash. You can
+specify these options when using the ``devtool add`` command:
+
+-  To specify a source branch, use the ``--srcbranch`` option:
+   ::
+
+      $ devtool add --srcbranch DISTRO_NAME_NO_CAP jackson /home/user/sources/jackson
+
+   In the previous example, you are checking out the DISTRO_NAME_NO_CAP
+   branch.
+
+-  To specify a specific tag or commit hash, use the ``--srcrev``
+   option:
+   ::
+
+      $ devtool add --srcrev DISTRO_REL_TAG jackson /home/user/sources/jackson
+      $ devtool add --srcrev some_commit_hash /home/user/sources/jackson
+
+   The previous examples check out the
+   DISTRO_REL_TAG tag and the commit associated with the
+   some_commit_hash hash.
+
+.. note::
+
+   If you prefer to use the latest revision every time the recipe is
+   built, use the options --autorev or -a.
+
+.. _devtool-extracting-the-source-for-an-existing-recipe:
+
+Extracting the Source for an Existing Recipe
+============================================
+
+Use the ``devtool extract`` command to extract the source for an
+existing recipe. When you use this command, you must supply the root
+name of the recipe (i.e. no version, paths, or extensions), and you must
+supply the directory to which you want the source extracted.
+
+Additional command options let you control the name of a development
+branch into which you can checkout the source and whether or not to keep
+a temporary directory, which is useful for debugging.
+
+.. _devtool-synchronizing-a-recipes-extracted-source-tree:
+
+Synchronizing a Recipe's Extracted Source Tree
+==============================================
+
+Use the ``devtool sync`` command to synchronize a previously extracted
+source tree for an existing recipe. When you use this command, you must
+supply the root name of the recipe (i.e. no version, paths, or
+extensions), and you must supply the directory to which you want the
+source extracted.
+
+Additional command options let you control the name of a development
+branch into which you can checkout the source and whether or not to keep
+a temporary directory, which is useful for debugging.
+
+.. _devtool-modifying-a-recipe:
+
+Modifying an Existing Recipe
+============================
+
+Use the ``devtool modify`` command to begin modifying the source of an
+existing recipe. This command is very similar to the
+```add`` <#devtool-adding-a-new-recipe-to-the-workspace>`__ command
+except that it does not physically create the recipe in the workspace
+layer because the recipe already exists in an another layer.
+
+The ``devtool modify`` command extracts the source for a recipe, sets it
+up as a Git repository if the source had not already been fetched from
+Git, checks out a branch for development, and applies any patches from
+the recipe as commits on top. You can use the following command to
+checkout the source files:
+::
+
+   $ devtool modify recipe
+
+Using the above command form, ``devtool`` uses the existing recipe's
+:term:`SRC_URI` statement to locate the upstream source,
+extracts the source into the default sources location in the workspace.
+The default development branch used is "devtool".
+
+.. _devtool-edit-an-existing-recipe:
+
+Edit an Existing Recipe
+=======================
+
+Use the ``devtool edit-recipe`` command to run the default editor, which
+is identified using the ``EDITOR`` variable, on the specified recipe.
+
+When you use the ``devtool edit-recipe`` command, you must supply the
+root name of the recipe (i.e. no version, paths, or extensions). Also,
+the recipe file itself must reside in the workspace as a result of the
+``devtool add`` or ``devtool upgrade`` commands. However, you can
+override that requirement by using the "-a" or "--any-recipe" option.
+Using either of these options allows you to edit any recipe regardless
+of its location.
+
+.. _devtool-updating-a-recipe:
+
+Updating a Recipe
+=================
+
+Use the ``devtool update-recipe`` command to update your recipe with
+patches that reflect changes you make to the source files. For example,
+if you know you are going to work on some code, you could first use the
+```devtool modify`` <#devtool-modifying-a-recipe>`__ command to extract
+the code and set up the workspace. After which, you could modify,
+compile, and test the code.
+
+When you are satisfied with the results and you have committed your
+changes to the Git repository, you can then run the
+``devtool update-recipe`` to create the patches and update the recipe:
+::
+
+   $ devtool update-recipe recipe
+
+If you run the ``devtool update-recipe``
+without committing your changes, the command ignores the changes.
+
+Often, you might want to apply customizations made to your software in
+your own layer rather than apply them to the original recipe. If so, you
+can use the ``-a`` or ``--append`` option with the
+``devtool update-recipe`` command. These options allow you to specify
+the layer into which to write an append file:
+::
+
+   $ devtool update-recipe recipe -a base-layer-directory
+
+The ``*.bbappend`` file is created at the
+appropriate path within the specified layer directory, which may or may
+not be in your ``bblayers.conf`` file. If an append file already exists,
+the command updates it appropriately.
+
+.. _devtool-checking-on-the-upgrade-status-of-a-recipe:
+
+Checking on the Upgrade Status of a Recipe
+==========================================
+
+Upstream recipes change over time. Consequently, you might find that you
+need to determine if you can upgrade a recipe to a newer version.
+
+To check on the upgrade status of a recipe, use the
+``devtool check-upgrade-status`` command. The command displays a table
+of your current recipe versions, the latest upstream versions, the email
+address of the recipe's maintainer, and any additional information such
+as commit hash strings and reasons you might not be able to upgrade a
+particular recipe.
+
+.. note::
+
+   -  For the ``oe-core`` layer, recipe maintainers come from the
+      `maintainers.inc <http://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/meta/conf/distro/include/maintainers.inc>`_
+      file.
+
+   -  If the recipe is using the :ref:`bitbake:git-fetcher`
+      rather than a
+      tarball, the commit hash points to the commit that matches the
+      recipe's latest version tag.
+
+As with all ``devtool`` commands, you can get help on the individual
+command:
+::
+
+   $ devtool check-upgrade-status -h
+   NOTE: Starting bitbake server...
+   usage: devtool check-upgrade-status [-h] [--all] [recipe [recipe ...]]
+
+   Prints a table of recipes together with versions currently provided by recipes, and latest upstream versions, when there is a later version available
+
+   arguments:
+     recipe      Name of the recipe to report (omit to report upgrade info for all recipes)
+
+   options:
+     -h, --help  show this help message and exit
+     --all, -a   Show all recipes, not just recipes needing upgrade
+
+Unless you provide a specific recipe name on the command line, the
+command checks all recipes in all configured layers.
+
+Following is a partial example table that reports on all the recipes.
+Notice the reported reason for not upgrading the ``base-passwd`` recipe.
+In this example, while a new version is available upstream, you do not
+want to use it because the dependency on ``cdebconf`` is not easily
+satisfied.
+
+.. note::
+
+   When a reason for not upgrading displays, the reason is usually
+   written into the recipe using the RECIPE_NO_UPDATE_REASON
+   variable. See the base-passwd.bb recipe for an example.
+
+::
+
+   $ devtool check-upgrade-status ...
+   NOTE: acpid 2.0.30 2.0.31 Ross Burton <ross.burton@intel.com>
+   NOTE: u-boot-fw-utils 2018.11 2019.01 Marek Vasut <marek.vasut@gmail.com> d3689267f92c5956e09cc7d1baa4700141662bff
+   NOTE: u-boot-tools 2018.11 2019.01 Marek Vasut <marek.vasut@gmail.com> d3689267f92c5956e09cc7d1baa4700141662bff . . .
+   NOTE: base-passwd 3.5.29 3.5.45 Anuj Mittal <anuj.mittal@intel.com> cannot be updated due to: Version 3.5.38 requires cdebconf for update-passwd utility
+   NOTE: busybox 1.29.2 1.30.0 Andrej Valek <andrej.valek@siemens.com>
+   NOTE: dbus-test 1.12.10 1.12.12 Chen Qi <Qi.Chen@windriver.com>
+
+.. _devtool-upgrading-a-recipe:
+
+Upgrading a Recipe
+==================
+
+As software matures, upstream recipes are upgraded to newer versions. As
+a developer, you need to keep your local recipes up-to-date with the
+upstream version releases. Several methods exist by which you can
+upgrade recipes. You can read about them in the ":ref:`gs-upgrading-recipes`"
+section of the Yocto Project Development Tasks Manual. This section
+overviews the ``devtool upgrade`` command.
+
+Before you upgrade a recipe, you can check on its upgrade status. See
+the ":ref:`devtool-checking-on-the-upgrade-status-of-a-recipe`" section
+for more information.
+
+The ``devtool upgrade`` command upgrades an existing recipe to a more
+recent version of the recipe upstream. The command puts the upgraded
+recipe file along with any associated files into a "workspace" and, if
+necessary, extracts the source tree to a specified location. During the
+upgrade, patches associated with the recipe are rebased or added as
+needed.
+
+When you use the ``devtool upgrade`` command, you must supply the root
+name of the recipe (i.e. no version, paths, or extensions), and you must
+supply the directory to which you want the source extracted. Additional
+command options let you control things such as the version number to
+which you want to upgrade (i.e. the :term:`PV`), the source
+revision to which you want to upgrade (i.e. the
+:term:`SRCREV`), whether or not to apply patches, and so
+forth.
+
+You can read more on the ``devtool upgrade`` workflow in the
+":ref:`sdk-devtool-use-devtool-upgrade-to-create-a-version-of-the-recipe-that-supports-a-newer-version-of-the-software`"
+section in the Yocto Project Application Development and the Extensible
+Software Development Kit (eSDK) manual. You can also see an example of
+how to use ``devtool upgrade`` in the ":ref:`gs-using-devtool-upgrade`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _devtool-resetting-a-recipe:
+
+Resetting a Recipe
+==================
+
+Use the ``devtool reset`` command to remove a recipe and its
+configuration (e.g. the corresponding ``.bbappend`` file) from the
+workspace layer. Realize that this command deletes the recipe and the
+append file. The command does not physically move them for you.
+Consequently, you must be sure to physically relocate your updated
+recipe and the append file outside of the workspace layer before running
+the ``devtool reset`` command.
+
+If the ``devtool reset`` command detects that the recipe or the append
+files have been modified, the command preserves the modified files in a
+separate "attic" subdirectory under the workspace layer.
+
+Here is an example that resets the workspace directory that contains the
+``mtr`` recipe:
+::
+
+   $ devtool reset mtr
+   NOTE: Cleaning sysroot for recipe mtr...
+   NOTE: Leaving source tree /home/scottrif/poky/build/workspace/sources/mtr as-is; if you no longer need it then please delete it manually
+   $
+
+.. _devtool-building-your-recipe:
+
+Building Your Recipe
+====================
+
+Use the ``devtool build`` command to build your recipe. The
+``devtool build`` command is equivalent to the
+``bitbake -c populate_sysroot`` command.
+
+When you use the ``devtool build`` command, you must supply the root
+name of the recipe (i.e. do not provide versions, paths, or extensions).
+You can use either the "-s" or the "--disable-parallel-make" options to
+disable parallel makes during the build. Here is an example:
+::
+
+   $ devtool build recipe
+
+.. _devtool-building-your-image:
+
+Building Your Image
+===================
+
+Use the ``devtool build-image`` command to build an image, extending it
+to include packages from recipes in the workspace. Using this command is
+useful when you want an image that ready for immediate deployment onto a
+device for testing. For proper integration into a final image, you need
+to edit your custom image recipe appropriately.
+
+When you use the ``devtool build-image`` command, you must supply the
+name of the image. This command has no command line options:
+::
+
+   $ devtool build-image image
+
+.. _devtool-deploying-your-software-on-the-target-machine:
+
+Deploying Your Software on the Target Machine
+=============================================
+
+Use the ``devtool deploy-target`` command to deploy the recipe's build
+output to the live target machine:
+::
+
+   $ devtool deploy-target recipe target
+
+The target is the address of the target machine, which must be running
+an SSH server (i.e. ``user@hostname[:destdir]``).
+
+This command deploys all files installed during the
+:ref:`ref-tasks-install` task. Furthermore, you do not
+need to have package management enabled within the target machine. If
+you do, the package manager is bypassed.
+
+.. note::
+
+   The ``deploy-target`` functionality is for development only. You
+   should never use it to update an image that will be used in
+   production.
+
+Some conditions exist that could prevent a deployed application from
+behaving as expected. When both of the following conditions exist, your
+application has the potential to not behave correctly when run on the
+target:
+
+-  You are deploying a new application to the target and the recipe you
+   used to build the application had correctly defined runtime
+   dependencies.
+
+-  The target does not physically have the packages on which the
+   application depends installed.
+
+If both of these conditions exist, your application will not behave as
+expected. The reason for this misbehavior is because the
+``devtool deploy-target`` command does not deploy the packages (e.g.
+libraries) on which your new application depends. The assumption is that
+the packages are already on the target. Consequently, when a runtime
+call is made in the application for a dependent function (e.g. a library
+call), the function cannot be found.
+
+To be sure you have all the dependencies local to the target, you need
+to be sure that the packages are pre-deployed (installed) on the target
+before attempting to run your application.
+
+.. _devtool-removing-your-software-from-the-target-machine:
+
+Removing Your Software from the Target Machine
+==============================================
+
+Use the ``devtool undeploy-target`` command to remove deployed build
+output from the target machine. For the ``devtool undeploy-target``
+command to work, you must have previously used the
+":ref:`devtool deploy-target <ref-manual/ref-devtool-reference:deploying your software on the target machine>`"
+command.
+::
+
+   $ devtool undeploy-target recipe target
+
+The target is the
+address of the target machine, which must be running an SSH server (i.e.
+``user@hostname``).
+
+.. _devtool-creating-the-workspace:
+
+Creating the Workspace Layer in an Alternative Location
+=======================================================
+
+Use the ``devtool create-workspace`` command to create a new workspace
+layer in your :term:`Build Directory`. When you create a
+new workspace layer, it is populated with the ``README`` file and the
+``conf`` directory only.
+
+The following example creates a new workspace layer in your current
+working and by default names the workspace layer "workspace":
+::
+
+   $ devtool create-workspace
+
+You can create a workspace layer anywhere by supplying a pathname with
+the command. The following command creates a new workspace layer named
+"new-workspace":
+::
+
+   $ devtool create-workspace /home/scottrif/new-workspace
+
+.. _devtool-get-the-status-of-the-recipes-in-your-workspace:
+
+Get the Status of the Recipes in Your Workspace
+===============================================
+
+Use the ``devtool status`` command to list the recipes currently in your
+workspace. Information includes the paths to their respective external
+source trees.
+
+The ``devtool status`` command has no command-line options:
+::
+
+   $ devtool status
+
+Following is sample output after using
+:ref:`devtool add <ref-manual/ref-devtool-reference:adding a new recipe to the workspace layer>`
+to create and add the ``mtr_0.86.bb`` recipe to the ``workspace`` directory:
+::
+
+   $ devtool status mtr
+   :/home/scottrif/poky/build/workspace/sources/mtr (/home/scottrif/poky/build/workspace/recipes/mtr/mtr_0.86.bb)
+   $
+
+.. _devtool-search-for-available-target-recipes:
+
+Search for Available Target Recipes
+===================================
+
+Use the ``devtool search`` command to search for available target
+recipes. The command matches the recipe name, package name, description,
+and installed files. The command displays the recipe name as a result of
+a match.
+
+When you use the ``devtool search`` command, you must supply a keyword.
+The command uses the keyword when searching for a match.
diff --git a/documentation/ref-manual/ref-devtool-reference.xml b/documentation/ref-manual/ref-devtool-reference.xml
index 11f7399c5a..6c3ccc3034 100644
--- a/documentation/ref-manual/ref-devtool-reference.xml
+++ b/documentation/ref-manual/ref-devtool-reference.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-devtool-reference'>
     <title><filename>devtool</filename> Quick Reference</title>
diff --git a/documentation/ref-manual/ref-features.rst b/documentation/ref-manual/ref-features.rst
new file mode 100644
index 0000000000..ae5a0e3b24
--- /dev/null
+++ b/documentation/ref-manual/ref-features.rst
@@ -0,0 +1,353 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+********
+Features
+********
+
+This chapter provides a reference of shipped machine and distro features
+you can include as part of your image, a reference on image features you
+can select, and a reference on feature backfilling.
+
+Features provide a mechanism for working out which packages should be
+included in the generated images. Distributions can select which
+features they want to support through the ``DISTRO_FEATURES`` variable,
+which is set or appended to in a distribution's configuration file such
+as ``poky.conf``, ``poky-tiny.conf``, ``poky-lsb.conf`` and so forth.
+Machine features are set in the ``MACHINE_FEATURES`` variable, which is
+set in the machine configuration file and specifies the hardware
+features for a given machine.
+
+These two variables combine to work out which kernel modules, utilities,
+and other packages to include. A given distribution can support a
+selected subset of features so some machine features might not be
+included if the distribution itself does not support them.
+
+One method you can use to determine which recipes are checking to see if
+a particular feature is contained or not is to ``grep`` through the
+:term:`Metadata` for the feature. Here is an example that
+discovers the recipes whose build is potentially changed based on a
+given feature:
+::
+
+   $ cd poky
+   $ git grep 'contains.*MACHINE_FEATURES.*feature'
+
+.. _ref-features-machine:
+
+Machine Features
+================
+
+The items below are features you can use with
+:term:`MACHINE_FEATURES`. Features do not have a
+one-to-one correspondence to packages, and they can go beyond simply
+controlling the installation of a package or packages. Sometimes a
+feature can influence how certain recipes are built. For example, a
+feature might determine whether a particular configure option is
+specified within the :ref:`ref-tasks-configure` task
+for a particular recipe.
+
+This feature list only represents features as shipped with the Yocto
+Project metadata:
+
+-  *acpi:* Hardware has ACPI (x86/x86_64 only)
+
+-  *alsa:* Hardware has ALSA audio drivers
+
+-  *apm:* Hardware uses APM (or APM emulation)
+
+-  *bluetooth:* Hardware has integrated BT
+
+-  *efi:* Support for booting through EFI
+
+-  *ext2:* Hardware HDD or Microdrive
+
+-  *keyboard:* Hardware has a keyboard
+
+-  *pcbios:* Support for booting through BIOS
+
+-  *pci:* Hardware has a PCI bus
+
+-  *pcmcia:* Hardware has PCMCIA or CompactFlash sockets
+
+-  *phone:* Mobile phone (voice) support
+
+-  *qvga:* Machine has a QVGA (320x240) display
+
+-  *rtc:* Machine has a Real-Time Clock
+
+-  *screen:* Hardware has a screen
+
+-  *serial:* Hardware has serial support (usually RS232)
+
+-  *touchscreen:* Hardware has a touchscreen
+
+-  *usbgadget:* Hardware is USB gadget device capable
+
+-  *usbhost:* Hardware is USB Host capable
+
+-  *vfat:* FAT file system support
+
+-  *wifi:* Hardware has integrated WiFi
+
+.. _ref-features-distro:
+
+Distro Features
+===============
+
+The items below are features you can use with
+:term:`DISTRO_FEATURES` to enable features across
+your distribution. Features do not have a one-to-one correspondence to
+packages, and they can go beyond simply controlling the installation of
+a package or packages. In most cases, the presence or absence of a
+feature translates to the appropriate option supplied to the configure
+script during the :ref:`ref-tasks-configure` task for
+the recipes that optionally support the feature.
+
+Some distro features are also machine features. These select features
+make sense to be controlled both at the machine and distribution
+configuration level. See the
+:term:`COMBINED_FEATURES` variable for more
+information.
+
+This list only represents features as shipped with the Yocto Project
+metadata:
+
+-  *alsa:* Include ALSA support (OSS compatibility kernel modules
+   installed if available).
+
+-  *api-documentation:* Enables generation of API documentation during
+   recipe builds. The resulting documentation is added to SDK tarballs
+   when the ``bitbake -c populate_sdk`` command is used. See the
+   ":ref:`sdk-manual/sdk-appendix-customizing-standard:adding api documentation to the standard sdk`"
+   section in the Yocto Project Application Development and the
+   Extensible Software Development Kit (eSDK) manual.
+
+-  *bluetooth:* Include bluetooth support (integrated BT only).
+
+-  *cramfs:* Include CramFS support.
+
+-  *directfb:* Include DirectFB support.
+
+-  *ext2:* Include tools for supporting for devices with internal
+   HDD/Microdrive for storing files (instead of Flash only devices).
+
+-  *ipsec:* Include IPSec support.
+
+-  *ipv6:* Include IPv6 support.
+
+-  *keyboard:* Include keyboard support (e.g. keymaps will be loaded
+   during boot).
+
+-  *ldconfig:* Include support for ldconfig and ``ld.so.conf`` on the
+   target.
+
+-  *nfs:* Include NFS client support (for mounting NFS exports on
+   device).
+
+-  *opengl:* Include the Open Graphics Library, which is a
+   cross-language, multi-platform application programming interface used
+   for rendering two and three-dimensional graphics.
+
+-  *pci:* Include PCI bus support.
+
+-  *pcmcia:* Include PCMCIA/CompactFlash support.
+
+-  *ppp:* Include PPP dialup support.
+
+-  *ptest:* Enables building the package tests where supported by
+   individual recipes. For more information on package tests, see the
+   ":ref:`dev-manual/dev-manual-common-tasks:testing packages with ptest`" section
+   in the Yocto Project Development Tasks Manual.
+
+-  *smbfs:* Include SMB networks client support (for mounting
+   Samba/Microsoft Windows shares on device).
+
+-  *systemd:* Include support for this ``init`` manager, which is a full
+   replacement of for ``init`` with parallel starting of services,
+   reduced shell overhead, and other features. This ``init`` manager is
+   used by many distributions.
+
+-  *usbgadget:* Include USB Gadget Device support (for USB
+   networking/serial/storage).
+
+-  *usbhost:* Include USB Host support (allows to connect external
+   keyboard, mouse, storage, network etc).
+
+-  *usrmerge:* Merges the ``/bin``, ``/sbin``, ``/lib``, and ``/lib64``
+   directories into their respective counterparts in the ``/usr``
+   directory to provide better package and application compatibility.
+
+-  *wayland:* Include the Wayland display server protocol and the
+   library that supports it.
+
+-  *wifi:* Include WiFi support (integrated only).
+
+-  *x11:* Include the X server and libraries.
+
+.. _ref-features-image:
+
+Image Features
+==============
+
+The contents of images generated by the OpenEmbedded build system can be
+controlled by the :term:`IMAGE_FEATURES` and
+:term:`EXTRA_IMAGE_FEATURES` variables that
+you typically configure in your image recipes. Through these variables,
+you can add several different predefined packages such as development
+utilities or packages with debug information needed to investigate
+application problems or profile applications.
+
+The following image features are available for all images:
+
+-  *allow-empty-password:* Allows Dropbear and OpenSSH to accept root
+   logins and logins from accounts having an empty password string.
+
+-  *dbg-pkgs:* Installs debug symbol packages for all packages installed
+   in a given image.
+
+-  *debug-tweaks:* Makes an image suitable for development (e.g. allows
+   root logins without passwords and enables post-installation logging).
+   See the 'allow-empty-password', 'empty-root-password', and
+   'post-install-logging' features in this list for additional
+   information.
+
+-  *dev-pkgs:* Installs development packages (headers and extra library
+   links) for all packages installed in a given image.
+
+-  *doc-pkgs:* Installs documentation packages for all packages
+   installed in a given image.
+
+-  *empty-root-password:* Sets the root password to an empty string,
+   which allows logins with a blank password.
+
+-  *package-management:* Installs package management tools and preserves
+   the package manager database.
+
+-  *post-install-logging:* Enables logging postinstall script runs to
+   the ``/var/log/postinstall.log`` file on first boot of the image on
+   the target system.
+
+   .. note::
+
+      To make the
+      /var/log
+      directory on the target persistent, use the
+      VOLATILE_LOG_DIR
+      variable by setting it to "no".
+
+-  *ptest-pkgs:* Installs ptest packages for all ptest-enabled recipes.
+
+-  *read-only-rootfs:* Creates an image whose root filesystem is
+   read-only. See the
+   ":ref:`dev-manual/dev-manual-common-tasks:creating a read-only root filesystem`"
+   section in the Yocto Project Development Tasks Manual for more
+   information.
+
+-  *splash:* Enables showing a splash screen during boot. By default,
+   this screen is provided by ``psplash``, which does allow
+   customization. If you prefer to use an alternative splash screen
+   package, you can do so by setting the ``SPLASH`` variable to a
+   different package name (or names) within the image recipe or at the
+   distro configuration level.
+
+-  *staticdev-pkgs:* Installs static development packages, which are
+   static libraries (i.e. ``*.a`` files), for all packages installed in
+   a given image.
+
+Some image features are available only when you inherit the
+:ref:`core-image <ref-classes-core-image>` class. The current list of
+these valid features is as follows:
+
+-  *hwcodecs:* Installs hardware acceleration codecs.
+
+-  *nfs-server:* Installs an NFS server.
+
+-  *perf:* Installs profiling tools such as ``perf``, ``systemtap``, and
+   ``LTTng``. For general information on user-space tools, see the
+   :doc:`../sdk-manual/sdk-manual` manual.
+
+-  *ssh-server-dropbear:* Installs the Dropbear minimal SSH server.
+
+-  *ssh-server-openssh:* Installs the OpenSSH SSH server, which is more
+   full-featured than Dropbear. Note that if both the OpenSSH SSH server
+   and the Dropbear minimal SSH server are present in
+   ``IMAGE_FEATURES``, then OpenSSH will take precedence and Dropbear
+   will not be installed.
+
+-  *tools-debug:* Installs debugging tools such as ``strace`` and
+   ``gdb``. For information on GDB, see the
+   ":ref:`platdev-gdb-remotedebug`" section
+   in the Yocto Project Development Tasks Manual. For information on
+   tracing and profiling, see the :doc:`../profile-manual/profile-manual`.
+
+-  *tools-sdk:* Installs a full SDK that runs on the device.
+
+-  *tools-testapps:* Installs device testing tools (e.g. touchscreen
+   debugging).
+
+-  *x11:* Installs the X server.
+
+-  *x11-base:* Installs the X server with a minimal environment.
+
+-  *x11-sato:* Installs the OpenedHand Sato environment.
+
+.. _ref-features-backfill:
+
+Feature Backfilling
+===================
+
+Sometimes it is necessary in the OpenEmbedded build system to extend
+:term:`MACHINE_FEATURES` or
+:term:`DISTRO_FEATURES` to control functionality
+that was previously enabled and not able to be disabled. For these
+cases, we need to add an additional feature item to appear in one of
+these variables, but we do not want to force developers who have
+existing values of the variables in their configuration to add the new
+feature in order to retain the same overall level of functionality.
+Thus, the OpenEmbedded build system has a mechanism to automatically
+"backfill" these added features into existing distro or machine
+configurations. You can see the list of features for which this is done
+by finding the
+:term:`DISTRO_FEATURES_BACKFILL` and
+:term:`MACHINE_FEATURES_BACKFILL`
+variables in the ``meta/conf/bitbake.conf`` file.
+
+Because such features are backfilled by default into all configurations
+as described in the previous paragraph, developers who wish to disable
+the new features need to be able to selectively prevent the backfilling
+from occurring. They can do this by adding the undesired feature or
+features to the
+:term:`DISTRO_FEATURES_BACKFILL_CONSIDERED`
+or
+:term:`MACHINE_FEATURES_BACKFILL_CONSIDERED`
+variables for distro features and machine features respectively.
+
+Here are two examples to help illustrate feature backfilling:
+
+-  *The "pulseaudio" distro feature option*: Previously, PulseAudio
+   support was enabled within the Qt and GStreamer frameworks. Because
+   of this, the feature is backfilled and thus enabled for all distros
+   through the ``DISTRO_FEATURES_BACKFILL`` variable in the
+   ``meta/conf/bitbake.conf`` file. However, your distro needs to
+   disable the feature. You can disable the feature without affecting
+   other existing distro configurations that need PulseAudio support by
+   adding "pulseaudio" to ``DISTRO_FEATURES_BACKFILL_CONSIDERED`` in
+   your distro's ``.conf`` file. Adding the feature to this variable
+   when it also exists in the ``DISTRO_FEATURES_BACKFILL`` variable
+   prevents the build system from adding the feature to your
+   configuration's ``DISTRO_FEATURES``, effectively disabling the
+   feature for that particular distro.
+
+-  *The "rtc" machine feature option*: Previously, real time clock (RTC)
+   support was enabled for all target devices. Because of this, the
+   feature is backfilled and thus enabled for all machines through the
+   ``MACHINE_FEATURES_BACKFILL`` variable in the
+   ``meta/conf/bitbake.conf`` file. However, your target device does not
+   have this capability. You can disable RTC support for your device
+   without affecting other machines that need RTC support by adding the
+   feature to your machine's ``MACHINE_FEATURES_BACKFILL_CONSIDERED``
+   list in the machine's ``.conf`` file. Adding the feature to this
+   variable when it also exists in the ``MACHINE_FEATURES_BACKFILL``
+   variable prevents the build system from adding the feature to your
+   configuration's ``MACHINE_FEATURES``, effectively disabling RTC
+   support for that particular machine.
diff --git a/documentation/ref-manual/ref-features.xml b/documentation/ref-manual/ref-features.xml
index 294b297c20..8cab5ec3a8 100644
--- a/documentation/ref-manual/ref-features.xml
+++ b/documentation/ref-manual/ref-features.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-features'>
     <title>Features</title>
diff --git a/documentation/ref-manual/ref-images.rst b/documentation/ref-manual/ref-images.rst
new file mode 100644
index 0000000000..c88d4d75ca
--- /dev/null
+++ b/documentation/ref-manual/ref-images.rst
@@ -0,0 +1,139 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+******
+Images
+******
+
+The OpenEmbedded build system provides several example images to satisfy
+different needs. When you issue the ``bitbake`` command you provide a
+"top-level" recipe that essentially begins the build for the type of
+image you want.
+
+.. note::
+
+   Building an image without GNU General Public License Version 3
+   (GPLv3), GNU Lesser General Public License Version 3 (LGPLv3), and
+   the GNU Affero General Public License Version 3 (AGPL-3.0) components
+   is only supported for minimal and base images. Furthermore, if you
+   are going to build an image using non-GPLv3 and similarly licensed
+   components, you must make the following changes in the
+   local.conf
+   file before using the BitBake command to build the minimal or base
+   image:
+   ::
+
+           1. Comment out the EXTRA_IMAGE_FEATURES line
+           2. Set INCOMPATIBLE_LICENSE = "GPL-3.0 LGPL-3.0 AGPL-3.0"
+
+
+From within the ``poky`` Git repository, you can use the following
+command to display the list of directories within the :term:`Source Directory`
+that contain image recipe files: ::
+
+   $ ls meta*/recipes*/images/*.bb
+
+Following is a list of supported recipes:
+
+-  ``build-appliance-image``: An example virtual machine that contains
+   all the pieces required to run builds using the build system as well
+   as the build system itself. You can boot and run the image using
+   either the `VMware
+   Player <http://www.vmware.com/products/player/overview.html>`__ or
+   `VMware
+   Workstation <http://www.vmware.com/products/workstation/overview.html>`__.
+   For more information on this image, see the :yocto_home:`Build
+   Appliance </software-item/build-appliance>` page
+   on the Yocto Project website.
+
+-  ``core-image-base``: A console-only image that fully supports the
+   target device hardware.
+
+-  ``core-image-clutter``: An image with support for the Open GL-based
+   toolkit Clutter, which enables development of rich and animated
+   graphical user interfaces.
+
+-  ``core-image-full-cmdline``: A console-only image with more
+   full-featured Linux system functionality installed.
+
+-  ``core-image-lsb``: An image that conforms to the Linux Standard Base
+   (LSB) specification. This image requires a distribution configuration
+   that enables LSB compliance (e.g. ``poky-lsb``). If you build
+   ``core-image-lsb`` without that configuration, the image will not be
+   LSB-compliant.
+
+-  ``core-image-lsb-dev``: A ``core-image-lsb`` image that is suitable
+   for development work using the host. The image includes headers and
+   libraries you can use in a host development environment. This image
+   requires a distribution configuration that enables LSB compliance
+   (e.g. ``poky-lsb``). If you build ``core-image-lsb-dev`` without that
+   configuration, the image will not be LSB-compliant.
+
+-  ``core-image-lsb-sdk``: A ``core-image-lsb`` that includes everything
+   in the cross-toolchain but also includes development headers and
+   libraries to form a complete standalone SDK. This image requires a
+   distribution configuration that enables LSB compliance (e.g.
+   ``poky-lsb``). If you build ``core-image-lsb-sdk`` without that
+   configuration, the image will not be LSB-compliant. This image is
+   suitable for development using the target.
+
+-  ``core-image-minimal``: A small image just capable of allowing a
+   device to boot.
+
+-  ``core-image-minimal-dev``: A ``core-image-minimal`` image suitable
+   for development work using the host. The image includes headers and
+   libraries you can use in a host development environment.
+
+-  ``core-image-minimal-initramfs``: A ``core-image-minimal`` image that
+   has the Minimal RAM-based Initial Root Filesystem (initramfs) as part
+   of the kernel, which allows the system to find the first "init"
+   program more efficiently. See the
+   :term:`PACKAGE_INSTALL` variable for
+   additional information helpful when working with initramfs images.
+
+-  ``core-image-minimal-mtdutils``: A ``core-image-minimal`` image that
+   has support for the Minimal MTD Utilities, which let the user
+   interact with the MTD subsystem in the kernel to perform operations
+   on flash devices.
+
+-  ``core-image-rt``: A ``core-image-minimal`` image plus a real-time
+   test suite and tools appropriate for real-time use.
+
+-  ``core-image-rt-sdk``: A ``core-image-rt`` image that includes
+   everything in the cross-toolchain. The image also includes
+   development headers and libraries to form a complete stand-alone SDK
+   and is suitable for development using the target.
+
+-  ``core-image-sato``: An image with Sato support, a mobile environment
+   and visual style that works well with mobile devices. The image
+   supports X11 with a Sato theme and applications such as a terminal,
+   editor, file manager, media player, and so forth.
+
+-  ``core-image-sato-dev``: A ``core-image-sato`` image suitable for
+   development using the host. The image includes libraries needed to
+   build applications on the device itself, testing and profiling tools,
+   and debug symbols. This image was formerly ``core-image-sdk``.
+
+-  ``core-image-sato-sdk``: A ``core-image-sato`` image that includes
+   everything in the cross-toolchain. The image also includes
+   development headers and libraries to form a complete standalone SDK
+   and is suitable for development using the target.
+
+-  ``core-image-testmaster``: A "master" image designed to be used for
+   automated runtime testing. Provides a "known good" image that is
+   deployed to a separate partition so that you can boot into it and use
+   it to deploy a second image to be tested. You can find more
+   information about runtime testing in the
+   ":ref:`dev-manual/dev-manual-common-tasks:performing automated runtime testing`"
+   section in the Yocto Project Development Tasks Manual.
+
+-  ``core-image-testmaster-initramfs``: A RAM-based Initial Root
+   Filesystem (initramfs) image tailored for use with the
+   ``core-image-testmaster`` image.
+
+-  ``core-image-weston``: A very basic Wayland image with a terminal.
+   This image provides the Wayland protocol libraries and the reference
+   Weston compositor. For more information, see the
+   ":ref:`dev-manual/dev-manual-common-tasks:using wayland and weston`"
+   section in the Yocto Project Development Tasks Manual.
+
+-  ``core-image-x11``: A very basic X11 image with a terminal.
diff --git a/documentation/ref-manual/ref-images.xml b/documentation/ref-manual/ref-images.xml
index 1f96186c6e..6f10a6fd2a 100644
--- a/documentation/ref-manual/ref-images.xml
+++ b/documentation/ref-manual/ref-images.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-images'>
     <title>Images</title>
@@ -8,7 +9,7 @@
     <para>
         The OpenEmbedded build system provides several example
         images to satisfy different needs.
-        When you issue the <filename>bitbake</filename> command you provide a “top-level” recipe
+        When you issue the <filename>bitbake</filename> command you provide a "top-level" recipe
         that essentially begins the build for the type of image you want.
     </para>
 
@@ -99,7 +100,7 @@
             <listitem><para id='images-core-image-minimal-initramfs'><filename>core-image-minimal-initramfs</filename>:
                 A <filename>core-image-minimal</filename> image that has the Minimal RAM-based
                 Initial Root Filesystem (initramfs) as part of the kernel,
-                which allows the system to find the first “init” program more efficiently.
+                which allows the system to find the first "init" program more efficiently.
                 See the
                 <link linkend='var-PACKAGE_INSTALL'><filename>PACKAGE_INSTALL</filename></link>
                 variable for additional information helpful when working with
diff --git a/documentation/ref-manual/ref-kickstart.rst b/documentation/ref-manual/ref-kickstart.rst
new file mode 100644
index 0000000000..45222de05b
--- /dev/null
+++ b/documentation/ref-manual/ref-kickstart.rst
@@ -0,0 +1,212 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+*******************************************
+OpenEmbedded Kickstart (``.wks``) Reference
+*******************************************
+
+.. _openembedded-kickstart-wks-reference:
+
+Introduction
+============
+
+The current Wic implementation supports only the basic kickstart
+partitioning commands: ``partition`` (or ``part`` for short) and
+``bootloader``.
+
+.. note::
+
+   Future updates will implement more commands and options. If you use
+   anything that is not specifically supported, results can be
+   unpredictable.
+
+This chapter provides a reference on the available kickstart commands.
+The information lists the commands, their syntax, and meanings.
+Kickstart commands are based on the Fedora kickstart versions but with
+modifications to reflect Wic capabilities. You can see the original
+documentation for those commands at the following link:
+http://pykickstart.readthedocs.io/en/latest/kickstart-docs.html
+
+Command: part or partition
+==========================
+
+Either of these commands creates a partition on the system and uses the
+following syntax:
+::
+
+   part [mntpoint] 
+   partition [mntpoint]
+
+If you do not
+provide mntpoint, Wic creates a partition but does not mount it.
+
+The ``mntpoint`` is where the partition is mounted and must be in one of
+the following forms:
+
+-  ``/path``: For example, "/", "/usr", or "/home"
+
+-  ``swap``: The created partition is used as swap space
+
+Specifying a mntpoint causes the partition to automatically be mounted.
+Wic achieves this by adding entries to the filesystem table (fstab)
+during image generation. In order for Wic to generate a valid fstab, you
+must also provide one of the ``--ondrive``, ``--ondisk``, or
+``--use-uuid`` partition options as part of the command.
+
+.. note::
+
+   The mount program must understand the PARTUUID syntax you use with
+   --use-uuid
+   and non-root
+   mountpoint
+   , including swap. The busybox versions of these application are
+   currently excluded.
+
+Here is an example that uses "/" as the mountpoint. The command uses
+``--ondisk`` to force the partition onto the ``sdb`` disk: part /
+--source rootfs --ondisk sdb --fstype=ext3 --label platform --align 1024
+
+Here is a list that describes other supported options you can use with
+the ``part`` and ``partition`` commands:
+
+-  ``--size``: The minimum partition size in MBytes. Specify an
+   integer value such as 500. Do not append the number with "MB". You do
+   not need this option if you use ``--source``.
+
+-  ``--fixed-size``: The exact partition size in MBytes. You cannot
+   specify with ``--size``. An error occurs when assembling the disk
+   image if the partition data is larger than ``--fixed-size``.
+
+-  ``--source``: This option is a Wic-specific option that names the
+   source of the data that populates the partition. The most common
+   value for this option is "rootfs", but you can use any value that
+   maps to a valid source plugin. For information on the source plugins,
+   see the ":ref:`dev-manual/dev-manual-common-tasks:using the wic plugin interface`"
+   section in the Yocto Project Development Tasks Manual.
+
+   If you use ``--source rootfs``, Wic creates a partition as large as
+   needed and fills it with the contents of the root filesystem pointed
+   to by the ``-r`` command-line option or the equivalent rootfs derived
+   from the ``-e`` command-line option. The filesystem type used to
+   create the partition is driven by the value of the ``--fstype``
+   option specified for the partition. See the entry on ``--fstype``
+   that follows for more information.
+
+   If you use ``--source plugin-name``, Wic creates a partition as large
+   as needed and fills it with the contents of the partition that is
+   generated by the specified plugin name using the data pointed to by
+   the ``-r`` command-line option or the equivalent rootfs derived from
+   the ``-e`` command-line option. Exactly what those contents are and
+   filesystem type used are dependent on the given plugin
+   implementation.
+
+   If you do not use the ``--source`` option, the ``wic`` command
+   creates an empty partition. Consequently, you must use the ``--size``
+   option to specify the size of the empty partition.
+
+-  ``--ondisk`` or ``--ondrive``: Forces the partition to be created
+   on a particular disk.
+
+-  ``--fstype``: Sets the file system type for the partition. Valid
+   values are:
+
+   -  ``ext4``
+
+   -  ``ext3``
+
+   -  ``ext2``
+
+   -  ``btrfs``
+
+   -  ``squashfs``
+
+   -  ``swap``
+
+-  ``--fsoptions``: Specifies a free-form string of options to be used
+   when mounting the filesystem. This string is copied into the
+   ``/etc/fstab`` file of the installed system and should be enclosed in
+   quotes. If not specified, the default string is "defaults".
+
+-  ``--label label``: Specifies the label to give to the filesystem to
+   be made on the partition. If the given label is already in use by
+   another filesystem, a new label is created for the partition.
+
+-  ``--active``: Marks the partition as active.
+
+-  ``--align (in KBytes)``: This option is a Wic-specific option that
+   says to start partitions on boundaries given x KBytes.
+
+-  ``--no-table``: This option is a Wic-specific option. Using the
+   option reserves space for the partition and causes it to become
+   populated. However, the partition is not added to the partition
+   table.
+
+-  ``--exclude-path``: This option is a Wic-specific option that
+   excludes the given relative path from the resulting image. This
+   option is only effective with the rootfs source plugin.
+
+-  ``--extra-space``: This option is a Wic-specific option that adds
+   extra space after the space filled by the content of the partition.
+   The final size can exceed the size specified by the ``--size``
+   option. The default value is 10 Mbytes.
+
+-  ``--overhead-factor``: This option is a Wic-specific option that
+   multiplies the size of the partition by the option's value. You must
+   supply a value greater than or equal to "1". The default value is
+   "1.3".
+
+-  ``--part-name``: This option is a Wic-specific option that
+   specifies a name for GPT partitions.
+
+-  ``--part-type``: This option is a Wic-specific option that
+   specifies the partition type globally unique identifier (GUID) for
+   GPT partitions. You can find the list of partition type GUIDs at
+   http://en.wikipedia.org/wiki/GUID_Partition_Table#Partition_type_GUIDs.
+
+-  ``--use-uuid``: This option is a Wic-specific option that causes
+   Wic to generate a random GUID for the partition. The generated
+   identifier is used in the bootloader configuration to specify the
+   root partition.
+
+-  ``--uuid``: This option is a Wic-specific option that specifies the
+   partition UUID.
+
+-  ``--fsuuid``: This option is a Wic-specific option that specifies
+   the filesystem UUID. You can generate or modify
+   :term:`WKS_FILE` with this option if a preconfigured
+   filesystem UUID is added to the kernel command line in the bootloader
+   configuration before you run Wic.
+
+-  ``--system-id``: This option is a Wic-specific option that
+   specifies the partition system ID, which is a one byte long,
+   hexadecimal parameter with or without the 0x prefix.
+
+-  ``--mkfs-extraopts``: This option specifies additional options to
+   pass to the ``mkfs`` utility. Some default options for certain
+   filesystems do not take effect. See Wic's help on kickstart (i.e.
+   ``wic help kickstart``).
+
+Command: bootloader
+===================
+
+This command specifies how the bootloader should be configured and
+supports the following options:
+
+.. note::
+
+   Bootloader functionality and boot partitions are implemented by the
+   various
+   --source
+   plugins that implement bootloader functionality. The bootloader
+   command essentially provides a means of modifying bootloader
+   configuration.
+
+-  ``--timeout``: Specifies the number of seconds before the
+   bootloader times out and boots the default option.
+
+-  ``--append``: Specifies kernel parameters. These parameters will be
+   added to the syslinux ``APPEND`` or ``grub`` kernel command line.
+
+-  ``--configfile``: Specifies a user-defined configuration file for
+   the bootloader. You can provide a full pathname for the file or a
+   file that exists in the ``canned-wks`` folder. This option overrides
+   all other bootloader options.
diff --git a/documentation/ref-manual/ref-kickstart.xml b/documentation/ref-manual/ref-kickstart.xml
index 1128bd50d0..45db1c0ff8 100644
--- a/documentation/ref-manual/ref-kickstart.xml
+++ b/documentation/ref-manual/ref-kickstart.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-kickstart'>
 <title>OpenEmbedded Kickstart (<filename>.wks</filename>) Reference</title>
diff --git a/documentation/ref-manual/ref-manual-customization.xsl b/documentation/ref-manual/ref-manual-customization.xsl
index c58dd905b9..3181f618e2 100644
--- a/documentation/ref-manual/ref-manual-customization.xsl
+++ b/documentation/ref-manual/ref-manual-customization.xsl
@@ -1,4 +1,6 @@
 <?xml version='1.0'?>
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
+
 <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns="http://www.w3.org/1999/xhtml" xmlns:fo="http://www.w3.org/1999/XSL/Format" version="1.0">
 
   <xsl:import href="http://downloads.yoctoproject.org/mirror/docbook-mirror/docbook-xsl-1.76.1/xhtml/docbook.xsl" />
diff --git a/documentation/ref-manual/ref-manual.rst b/documentation/ref-manual/ref-manual.rst
new file mode 100644
index 0000000000..a106af21d8
--- /dev/null
+++ b/documentation/ref-manual/ref-manual.rst
@@ -0,0 +1,31 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+==============================
+Yocto Project Reference Manual
+==============================
+
+|
+
+.. toctree::
+   :caption: Table of Contents
+   :numbered:
+
+   ref-system-requirements
+   ref-terms
+   ref-release-process
+   migration
+   ref-structure
+   ref-classes
+   ref-tasks
+   ref-devtool-reference
+   ref-kickstart
+   ref-qa-checks
+   ref-images
+   ref-features
+   ref-variables
+   ref-varlocality
+   faq
+   resources
+   history
+
+.. include:: /boilerplate.rst
diff --git a/documentation/ref-manual/ref-manual.xml b/documentation/ref-manual/ref-manual.xml
index 1b82a41a7d..9a914f19cf 100755
--- a/documentation/ref-manual/ref-manual.xml
+++ b/documentation/ref-manual/ref-manual.xml
@@ -128,28 +128,8 @@
             </revision>
             <revision>
                 <revnumber>3.1</revnumber>
-                <date>April 2020</date>
-                <revremark>Released with the Yocto Project 3.1 Release.</revremark>
-            </revision>
-            <revision>
-                <revnumber>3.1.1</revnumber>
-                <date>June 2020</date>
-                <revremark>Released with the Yocto Project 3.1.1 Release.</revremark>
-            </revision>
-            <revision>
-                <revnumber>3.1.2</revnumber>
-                <date>August 2020</date>
-                <revremark>Released with the Yocto Project 3.1.2 Release.</revremark>
-            </revision>
-            <revision>
-                <revnumber>3.1.3</revnumber>
-                <date>October 2020</date>
-                <revremark>Released with the Yocto Project 3.1.3 Release.</revremark>
-            </revision>
-            <revision>
-                <revnumber>3.1.4</revnumber>
                 <date>&REL_MONTH_YEAR;</date>
-                <revremark>Released with the Yocto Project 3.1.4 Release.</revremark>
+                <revremark>Released with the Yocto Project 3.1 Release.</revremark>
             </revision>
         </revhistory>
 
diff --git a/documentation/ref-manual/ref-qa-checks.rst b/documentation/ref-manual/ref-qa-checks.rst
new file mode 100644
index 0000000000..3e76ac1509
--- /dev/null
+++ b/documentation/ref-manual/ref-qa-checks.rst
@@ -0,0 +1,533 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+*****************************
+QA Error and Warning Messages
+*****************************
+
+.. _qa-introduction:
+
+Introduction
+============
+
+When building a recipe, the OpenEmbedded build system performs various
+QA checks on the output to ensure that common issues are detected and
+reported. Sometimes when you create a new recipe to build new software,
+it will build with no problems. When this is not the case, or when you
+have QA issues building any software, it could take a little time to
+resolve them.
+
+While it is tempting to ignore a QA message or even to disable QA
+checks, it is best to try and resolve any reported QA issues. This
+chapter provides a list of the QA messages and brief explanations of the
+issues you could encounter so that you can properly resolve problems.
+
+The next section provides a list of all QA error and warning messages
+based on a default configuration. Each entry provides the message or
+error form along with an explanation.
+
+.. note::
+
+   -  At the end of each message, the name of the associated QA test (as
+      listed in the ":ref:`insane.bbclass <ref-classes-insane>`"
+      section) appears within square brackets.
+
+   -  As mentioned, this list of error and warning messages is for QA
+      checks only. The list does not cover all possible build errors or
+      warnings you could encounter.
+
+   -  Because some QA checks are disabled by default, this list does not
+      include all possible QA check errors and warnings.
+
+.. _qa-errors-and-warnings:
+
+Errors and Warnings
+===================
+
+-  ``<packagename>: <path> is using libexec please relocate to <libexecdir> [libexec]``
+
+   The specified package contains files in ``/usr/libexec`` when the
+   distro configuration uses a different path for ``<libexecdir>`` By
+   default, ``<libexecdir>`` is ``$prefix/libexec``. However, this
+   default can be changed (e.g. ``${libdir}``).
+
+    
+
+-  ``package <packagename> contains bad RPATH <rpath> in file <file> [rpaths]``
+
+   The specified binary produced by the recipe contains dynamic library
+   load paths (rpaths) that contain build system paths such as
+   :term:`TMPDIR`, which are incorrect for the target and
+   could potentially be a security issue. Check for bad ``-rpath``
+   options being passed to the linker in your
+   :ref:`ref-tasks-compile` log. Depending on the build
+   system used by the software being built, there might be a configure
+   option to disable rpath usage completely within the build of the
+   software.
+
+    
+
+-  ``<packagename>: <file> contains probably-redundant RPATH <rpath> [useless-rpaths]``
+
+   The specified binary produced by the recipe contains dynamic library
+   load paths (rpaths) that on a standard system are searched by default
+   by the linker (e.g. ``/lib`` and ``/usr/lib``). While these paths
+   will not cause any breakage, they do waste space and are unnecessary.
+   Depending on the build system used by the software being built, there
+   might be a configure option to disable rpath usage completely within
+   the build of the software.
+
+    
+
+-  ``<packagename> requires <files>, but no providers in its RDEPENDS [file-rdeps]``
+
+   A file-level dependency has been identified from the specified
+   package on the specified files, but there is no explicit
+   corresponding entry in :term:`RDEPENDS`. If
+   particular files are required at runtime then ``RDEPENDS`` should be
+   declared in the recipe to ensure the packages providing them are
+   built.
+
+    
+
+-  ``<packagename1> rdepends on <packagename2>, but it isn't a build dependency? [build-deps]``
+
+   A runtime dependency exists between the two specified packages, but
+   there is nothing explicit within the recipe to enable the
+   OpenEmbedded build system to ensure that dependency is satisfied.
+   This condition is usually triggered by an
+   :term:`RDEPENDS` value being added at the packaging
+   stage rather than up front, which is usually automatic based on the
+   contents of the package. In most cases, you should change the recipe
+   to add an explicit ``RDEPENDS`` for the dependency.
+
+    
+
+-  ``non -dev/-dbg/nativesdk- package contains symlink .so: <packagename> path '<path>' [dev-so]``
+
+   Symlink ``.so`` files are for development only, and should therefore
+   go into the ``-dev`` package. This situation might occur if you add
+   ``*.so*`` rather than ``*.so.*`` to a non-dev package. Change
+   :term:`FILES` (and possibly
+   :term:`PACKAGES`) such that the specified ``.so``
+   file goes into an appropriate ``-dev`` package.
+
+    
+
+-  ``non -staticdev package contains static .a library: <packagename> path '<path>' [staticdev]``
+
+   Static ``.a`` library files should go into a ``-staticdev`` package.
+   Change :term:`FILES` (and possibly
+   :term:`PACKAGES`) such that the specified ``.a`` file
+   goes into an appropriate ``-staticdev`` package.
+
+    
+
+-  ``<packagename>: found library in wrong location [libdir]``
+
+   The specified file may have been installed into an incorrect
+   (possibly hardcoded) installation path. For example, this test will
+   catch recipes that install ``/lib/bar.so`` when ``${base_libdir}`` is
+   "lib32". Another example is when recipes install
+   ``/usr/lib64/foo.so`` when ``${libdir}`` is "/usr/lib". False
+   positives occasionally exist. For these cases add "libdir" to
+   :term:`INSANE_SKIP` for the package.
+
+    
+
+-  ``non debug package contains .debug directory: <packagename> path <path> [debug-files]``
+
+   The specified package contains a ``.debug`` directory, which should
+   not appear in anything but the ``-dbg`` package. This situation might
+   occur if you add a path which contains a ``.debug`` directory and do
+   not explicitly add the ``.debug`` directory to the ``-dbg`` package.
+   If this is the case, add the ``.debug`` directory explicitly to
+   ``FILES_${PN}-dbg``. See :term:`FILES` for additional
+   information on ``FILES``.
+
+    
+
+-  ``Architecture did not match (<machine_arch> to <file_arch>) on <file> [arch]``
+
+   By default, the OpenEmbedded build system checks the Executable and
+   Linkable Format (ELF) type, bit size, and endianness of any binaries
+   to ensure they match the target architecture. This test fails if any
+   binaries do not match the type since there would be an
+   incompatibility. The test could indicate that the wrong compiler or
+   compiler options have been used. Sometimes software, like
+   bootloaders, might need to bypass this check. If the file you receive
+   the error for is firmware that is not intended to be executed within
+   the target operating system or is intended to run on a separate
+   processor within the device, you can add "arch" to
+   :term:`INSANE_SKIP` for the package. Another
+   option is to check the :ref:`ref-tasks-compile` log
+   and verify that the compiler options being used are correct.
+
+    
+
+-  ``Bit size did not match (<machine_bits> to <file_bits>) <recipe> on <file> [arch]``
+
+   By default, the OpenEmbedded build system checks the Executable and
+   Linkable Format (ELF) type, bit size, and endianness of any binaries
+   to ensure they match the target architecture. This test fails if any
+   binaries do not match the type since there would be an
+   incompatibility. The test could indicate that the wrong compiler or
+   compiler options have been used. Sometimes software, like
+   bootloaders, might need to bypass this check. If the file you receive
+   the error for is firmware that is not intended to be executed within
+   the target operating system or is intended to run on a separate
+   processor within the device, you can add "arch" to
+   :term:`INSANE_SKIP` for the package. Another
+   option is to check the :ref:`ref-tasks-compile` log
+   and verify that the compiler options being used are correct.
+
+    
+
+-  ``Endianness did not match (<machine_endianness> to <file_endianness>) on <file> [arch]``
+
+   By default, the OpenEmbedded build system checks the Executable and
+   Linkable Format (ELF) type, bit size, and endianness of any binaries
+   to ensure they match the target architecture. This test fails if any
+   binaries do not match the type since there would be an
+   incompatibility. The test could indicate that the wrong compiler or
+   compiler options have been used. Sometimes software, like
+   bootloaders, might need to bypass this check. If the file you receive
+   the error for is firmware that is not intended to be executed within
+   the target operating system or is intended to run on a separate
+   processor within the device, you can add "arch" to
+   :term:`INSANE_SKIP` for the package. Another
+   option is to check the :ref:`ref-tasks-compile` log
+   and verify that the compiler options being used are correct.
+
+    
+
+-  ``ELF binary '<file>' has relocations in .text [textrel]``
+
+   The specified ELF binary contains relocations in its ``.text``
+   sections. This situation can result in a performance impact at
+   runtime.
+
+   Typically, the way to solve this performance issue is to add "-fPIC"
+   or "-fpic" to the compiler command-line options. For example, given
+   software that reads :term:`CFLAGS` when you build it,
+   you could add the following to your recipe:
+   ::
+
+      CFLAGS_append = " -fPIC "
+
+   For more information on text relocations at runtime, see
+   http://www.akkadia.org/drepper/textrelocs.html.
+
+    
+
+-  ``No GNU_HASH in the elf binary: '<file>' [ldflags]``
+
+   This indicates that binaries produced when building the recipe have
+   not been linked with the :term:`LDFLAGS` options
+   provided by the build system. Check to be sure that the ``LDFLAGS``
+   variable is being passed to the linker command. A common workaround
+   for this situation is to pass in ``LDFLAGS`` using
+   :term:`TARGET_CC_ARCH` within the recipe as
+   follows:
+   ::
+
+      TARGET_CC_ARCH += "${LDFLAGS}"
+
+    
+
+-  ``Package <packagename> contains Xorg driver (<driver>) but no xorg-abi- dependencies [xorg-driver-abi]``
+
+   The specified package contains an Xorg driver, but does not have a
+   corresponding ABI package dependency. The xserver-xorg recipe
+   provides driver ABI names. All drivers should depend on the ABI
+   versions that they have been built against. Driver recipes that
+   include ``xorg-driver-input.inc`` or ``xorg-driver-video.inc`` will
+   automatically get these versions. Consequently, you should only need
+   to explicitly add dependencies to binary driver recipes.
+
+    
+
+-  ``The /usr/share/info/dir file is not meant to be shipped in a particular package. [infodir]``
+
+   The ``/usr/share/info/dir`` should not be packaged. Add the following
+   line to your :ref:`ref-tasks-install` task or to your
+   ``do_install_append`` within the recipe as follows:
+   ::
+
+      rm ${D}${infodir}/dir
+   
+
+-  ``Symlink <path> in <packagename> points to TMPDIR [symlink-to-sysroot]``
+
+   The specified symlink points into :term:`TMPDIR` on the
+   host. Such symlinks will work on the host. However, they are clearly
+   invalid when running on the target. You should either correct the
+   symlink to use a relative path or remove the symlink.
+
+    
+
+-  ``<file> failed sanity test (workdir) in path <path> [la]``
+
+   The specified ``.la`` file contains :term:`TMPDIR`
+   paths. Any ``.la`` file containing these paths is incorrect since
+   ``libtool`` adds the correct sysroot prefix when using the files
+   automatically itself.
+
+    
+
+-  ``<file> failed sanity test (tmpdir) in path <path> [pkgconfig]``
+
+   The specified ``.pc`` file contains
+   :term:`TMPDIR`\ ``/``\ :term:`WORKDIR`
+   paths. Any ``.pc`` file containing these paths is incorrect since
+   ``pkg-config`` itself adds the correct sysroot prefix when the files
+   are accessed.
+
+    
+
+-  ``<packagename> rdepends on <debug_packagename> [debug-deps]``
+
+   A dependency exists between the specified non-dbg package (i.e. a
+   package whose name does not end in ``-dbg``) and a package that is a
+   ``dbg`` package. The ``dbg`` packages contain debug symbols and are
+   brought in using several different methods:
+
+   -  Using the ``dbg-pkgs``
+      :term:`IMAGE_FEATURES` value.
+
+   -  Using :term:`IMAGE_INSTALL`.
+
+   -  As a dependency of another ``dbg`` package that was brought in
+      using one of the above methods.
+
+   The dependency might have been automatically added because the
+   ``dbg`` package erroneously contains files that it should not contain
+   (e.g. a non-symlink ``.so`` file) or it might have been added
+   manually (e.g. by adding to :term:`RDEPENDS`).
+
+    
+
+-  ``<packagename> rdepends on <dev_packagename> [dev-deps]``
+
+   A dependency exists between the specified non-dev package (a package
+   whose name does not end in ``-dev``) and a package that is a ``dev``
+   package. The ``dev`` packages contain development headers and are
+   usually brought in using several different methods:
+
+   -  Using the ``dev-pkgs``
+      :term:`IMAGE_FEATURES` value.
+
+   -  Using :term:`IMAGE_INSTALL`.
+
+   -  As a dependency of another ``dev`` package that was brought in
+      using one of the above methods.
+
+   The dependency might have been automatically added (because the
+   ``dev`` package erroneously contains files that it should not have
+   (e.g. a non-symlink ``.so`` file) or it might have been added
+   manually (e.g. by adding to :term:`RDEPENDS`).
+
+    
+
+-  ``<var>_<packagename> is invalid: <comparison> (<value>)   only comparisons <, =, >, <=, and >= are allowed [dep-cmp]``
+
+   If you are adding a versioned dependency relationship to one of the
+   dependency variables (:term:`RDEPENDS`,
+   :term:`RRECOMMENDS`,
+   :term:`RSUGGESTS`,
+   :term:`RPROVIDES`,
+   :term:`RREPLACES`, or
+   :term:`RCONFLICTS`), you must only use the named
+   comparison operators. Change the versioned dependency values you are
+   adding to match those listed in the message.
+
+    
+
+-  ``<recipename>: The compile log indicates that host include and/or library paths were used. Please check the log '<logfile>' for more information. [compile-host-path]``
+
+   The log for the :ref:`ref-tasks-compile` task
+   indicates that paths on the host were searched for files, which is
+   not appropriate when cross-compiling. Look for "is unsafe for
+   cross-compilation" or "CROSS COMPILE Badness" in the specified log
+   file.
+
+    
+
+-  ``<recipename>: The install log indicates that host include and/or library paths were used. Please check the log '<logfile>' for more information. [install-host-path]``
+
+   The log for the :ref:`ref-tasks-install` task
+   indicates that paths on the host were searched for files, which is
+   not appropriate when cross-compiling. Look for "is unsafe for
+   cross-compilation" or "CROSS COMPILE Badness" in the specified log
+   file.
+
+    
+
+-  ``This autoconf log indicates errors, it looked at host include and/or library paths while determining system capabilities. Rerun configure task after fixing this. The path was '<path>'``
+
+   The log for the :ref:`ref-tasks-configure` task
+   indicates that paths on the host were searched for files, which is
+   not appropriate when cross-compiling. Look for "is unsafe for
+   cross-compilation" or "CROSS COMPILE Badness" in the specified log
+   file.
+
+    
+
+-  ``<packagename> doesn't match the [a-z0-9.+-]+ regex [pkgname]``
+
+   The convention within the OpenEmbedded build system (sometimes
+   enforced by the package manager itself) is to require that package
+   names are all lower case and to allow a restricted set of characters.
+   If your recipe name does not match this, or you add packages to
+   :term:`PACKAGES` that do not conform to the
+   convention, then you will receive this error. Rename your recipe. Or,
+   if you have added a non-conforming package name to ``PACKAGES``,
+   change the package name appropriately.
+
+    
+
+-  ``<recipe>: configure was passed unrecognized options: <options> [unknown-configure-option]``
+
+   The configure script is reporting that the specified options are
+   unrecognized. This situation could be because the options were
+   previously valid but have been removed from the configure script. Or,
+   there was a mistake when the options were added and there is another
+   option that should be used instead. If you are unsure, consult the
+   upstream build documentation, the ``./configure --help`` output, and
+   the upstream change log or release notes. Once you have worked out
+   what the appropriate change is, you can update
+   :term:`EXTRA_OECONF`,
+   :term:`PACKAGECONFIG_CONFARGS`, or the
+   individual :term:`PACKAGECONFIG` option values
+   accordingly.
+
+    
+
+-  ``Recipe <recipefile> has PN of "<recipename>" which is in OVERRIDES, this can result in unexpected behavior. [pn-overrides]``
+
+   The specified recipe has a name (:term:`PN`) value that
+   appears in :term:`OVERRIDES`. If a recipe is named
+   such that its ``PN`` value matches something already in ``OVERRIDES``
+   (e.g. ``PN`` happens to be the same as :term:`MACHINE`
+   or :term:`DISTRO`), it can have unexpected
+   consequences. For example, assignments such as
+   ``FILES_${PN} = "xyz"`` effectively turn into ``FILES = "xyz"``.
+   Rename your recipe (or if ``PN`` is being set explicitly, change the
+   ``PN`` value) so that the conflict does not occur. See
+   :term:`FILES` for additional information.
+
+    
+
+-  ``<recipefile>: Variable <variable> is set as not being package specific, please fix this. [pkgvarcheck]``
+
+   Certain variables (:term:`RDEPENDS`,
+   :term:`RRECOMMENDS`,
+   :term:`RSUGGESTS`,
+   :term:`RCONFLICTS`,
+   :term:`RPROVIDES`,
+   :term:`RREPLACES`, :term:`FILES`,
+   ``pkg_preinst``, ``pkg_postinst``, ``pkg_prerm``, ``pkg_postrm``, and
+   :term:`ALLOW_EMPTY`) should always be set specific
+   to a package (i.e. they should be set with a package name override
+   such as ``RDEPENDS_${PN} = "value"`` rather than
+   ``RDEPENDS = "value"``). If you receive this error, correct any
+   assignments to these variables within your recipe.
+
+    
+
+-  ``File '<file>' from <recipename> was already stripped, this will prevent future debugging! [already-stripped]``
+
+   Produced binaries have already been stripped prior to the build
+   system extracting debug symbols. It is common for upstream software
+   projects to default to stripping debug symbols for output binaries.
+   In order for debugging to work on the target using ``-dbg`` packages,
+   this stripping must be disabled.
+
+   Depending on the build system used by the software being built,
+   disabling this stripping could be as easy as specifying an additional
+   configure option. If not, disabling stripping might involve patching
+   the build scripts. In the latter case, look for references to "strip"
+   or "STRIP", or the "-s" or "-S" command-line options being specified
+   on the linker command line (possibly through the compiler command
+   line if preceded with "-Wl,").
+
+   .. note::
+
+      Disabling stripping here does not mean that the final packaged
+      binaries will be unstripped. Once the OpenEmbedded build system
+      splits out debug symbols to the
+      -dbg
+      package, it will then strip the symbols from the binaries.
+
+    
+
+-  ``<packagename> is listed in PACKAGES multiple times, this leads to packaging errors. [packages-list]``
+
+   Package names must appear only once in the
+   :term:`PACKAGES` variable. You might receive this
+   error if you are attempting to add a package to ``PACKAGES`` that is
+   already in the variable's value.
+
+    
+
+-  ``FILES variable for package <packagename> contains '//' which is invalid. Attempting to fix this but you should correct the metadata. [files-invalid]``
+
+   The string "//" is invalid in a Unix path. Correct all occurrences
+   where this string appears in a :term:`FILES` variable so
+   that there is only a single "/".
+
+    
+
+-  ``<recipename>: Files/directories were installed but not shipped in any package [installed-vs-shipped]``
+
+   Files have been installed within the
+   :ref:`ref-tasks-install` task but have not been
+   included in any package by way of the :term:`FILES`
+   variable. Files that do not appear in any package cannot be present
+   in an image later on in the build process. You need to do one of the
+   following:
+
+   -  Add the files to ``FILES`` for the package you want them to appear
+      in (e.g. ``FILES_${``\ :term:`PN`\ ``}`` for the main
+      package).
+
+   -  Delete the files at the end of the ``do_install`` task if the
+      files are not needed in any package.
+
+    
+
+-  ``<oldpackage>-<oldpkgversion> was registered as shlib provider for <library>, changing it to <newpackage>-<newpkgversion> because it was built later``
+
+   This message means that both ``<oldpackage>`` and ``<newpackage>``
+   provide the specified shared library. You can expect this message
+   when a recipe has been renamed. However, if that is not the case, the
+   message might indicate that a private version of a library is being
+   erroneously picked up as the provider for a common library. If that
+   is the case, you should add the library's ``.so`` file name to
+   :term:`PRIVATE_LIBS` in the recipe that provides
+   the private version of the library.
+
+-  ``LICENSE_<packagename> includes licenses (<licenses>) that are not listed in LICENSE [unlisted-pkg-lics]``
+
+   The :term:`LICENSE` of the recipe should be a superset
+   of all the licenses of all packages produced by this recipe. In other
+   words, any license in ``LICENSE_*`` should also appear in
+   :term:`LICENSE`.
+
+    
+
+Configuring and Disabling QA Checks
+===================================
+
+You can configure the QA checks globally so that specific check failures
+either raise a warning or an error message, using the
+:term:`WARN_QA` and :term:`ERROR_QA`
+variables, respectively. You can also disable checks within a particular
+recipe using :term:`INSANE_SKIP`. For information on
+how to work with the QA checks, see the
+":ref:`insane.bbclass <ref-classes-insane>`" section.
+
+.. note::
+
+   Please keep in mind that the QA checks exist in order to detect real
+   or potential problems in the packaged output. So exercise caution
+   when disabling these checks.
diff --git a/documentation/ref-manual/ref-qa-checks.xml b/documentation/ref-manual/ref-qa-checks.xml
index 515106ae68..0071e4a55d 100644
--- a/documentation/ref-manual/ref-qa-checks.xml
+++ b/documentation/ref-manual/ref-qa-checks.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-qa-checks'>
 <title>QA Error and Warning Messages</title>
@@ -1170,6 +1171,31 @@ can be found then it should be implemented.  I can't find one at the moment.
             </listitem>
         </itemizedlist>
     </para>
+
+    <para>
+        <itemizedlist>
+            <listitem>
+                <para id='qa-issue-unlisted-pkg-lics'>
+                    <code>
+     LICENSE_&lt;packagename&gt; includes licenses (&lt;licenses&gt;) that are not listed in LICENSE [unlisted-pkg-lics]
+                    </code>
+                </para>
+
+                <para>
+                    The <link linkend='var-LICENSE'><filename>LICENSE</filename></link>
+                    of the recipe should be a superset of all the licenses of
+                    all packages produced by this recipe.
+                    In other words, any license in <filename>LICENSE_*</filename>
+                    should also appear in
+                    <link linkend='var-LICENSE'><filename>LICENSE</filename></link>.
+                </para>
+
+                <para>
+                    &nbsp;
+                </para>
+            </listitem>
+        </itemizedlist>
+    </para>
 </section>
 
 <section id='configuring-and-disabling-qa-checks'>
diff --git a/documentation/ref-manual/ref-release-process.rst b/documentation/ref-manual/ref-release-process.rst
new file mode 100644
index 0000000000..be041e7254
--- /dev/null
+++ b/documentation/ref-manual/ref-release-process.rst
@@ -0,0 +1,193 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+*****************************************************
+Yocto Project Releases and the Stable Release Process
+*****************************************************
+
+The Yocto Project release process is predictable and consists of both
+major and minor (point) releases. This brief chapter provides
+information on how releases are named, their life cycle, and their
+stability.
+
+Major and Minor Release Cadence
+===============================
+
+The Yocto Project delivers major releases (e.g. DISTRO) using a six
+month cadence roughly timed each April and October of the year.
+Following are examples of some major YP releases with their codenames
+also shown. See the "`Major Release
+Codenames <#major-release-codenames>`__" section for information on
+codenames used with major releases.
+
+  - 2.2 (Morty) 
+  - 2.1 (Krogoth)
+  - 2.0 (Jethro) 
+
+While the cadence is never perfect, this timescale facilitates
+regular releases that have strong QA cycles while not overwhelming users
+with too many new releases. The cadence is predictable and avoids many
+major holidays in various geographies.
+
+The Yocto project delivers minor (point) releases on an unscheduled
+basis and are usually driven by the accumulation of enough significant
+fixes or enhancements to the associated major release. Following are
+some example past point releases:
+
+  - 2.1.1
+  - 2.1.2
+  - 2.2.1 
+
+The point release
+indicates a point in the major release branch where a full QA cycle and
+release process validates the content of the new branch.
+
+.. note::
+
+   Realize that there can be patches merged onto the stable release
+   branches as and when they become available.
+
+Major Release Codenames
+=======================
+
+Each major release receives a codename that identifies the release in
+the :ref:`overview-manual/overview-manual-development-environment:yocto project source repositories`.
+The concept is that branches of :term:`Metadata` with the same
+codename are likely to be compatible and thus work together.
+
+.. note::
+
+   Codenames are associated with major releases because a Yocto Project
+   release number (e.g. DISTRO) could conflict with a given layer or
+   company versioning scheme. Codenames are unique, interesting, and
+   easily identifiable.
+
+Releases are given a nominal release version as well but the codename is
+used in repositories for this reason. You can find information on Yocto
+Project releases and codenames at
+https://wiki.yoctoproject.org/wiki/Releases.
+
+Stable Release Process
+======================
+
+Once released, the release enters the stable release process at which
+time a person is assigned as the maintainer for that stable release.
+This maintainer monitors activity for the release by investigating and
+handling nominated patches and backport activity. Only fixes and
+enhancements that have first been applied on the "master" branch (i.e.
+the current, in-development branch) are considered for backporting to a
+stable release.
+
+.. note::
+
+   The current Yocto Project policy regarding backporting is to consider
+   bug fixes and security fixes only. Policy dictates that features are
+   not backported to a stable release. This policy means generic recipe
+   version upgrades are unlikely to be accepted for backporting. The
+   exception to this policy occurs when a strong reason exists such as
+   the fix happens to also be the preferred upstream approach.
+
+Stable release branches have strong maintenance for about a year after
+their initial release. Should significant issues be found for any
+release regardless of its age, fixes could be backported to older
+releases. For issues that are not backported given an older release,
+Community LTS trees and branches exist where community members share
+patches for older releases. However, these types of patches do not go
+through the same release process as do point releases. You can find more
+information about stable branch maintenance at
+https://wiki.yoctoproject.org/wiki/Stable_branch_maintenance.
+
+Testing and Quality Assurance
+=============================
+
+Part of the Yocto Project development and release process is quality
+assurance through the execution of test strategies. Test strategies
+provide the Yocto Project team a way to ensure a release is validated.
+Additionally, because the test strategies are visible to you as a
+developer, you can validate your projects. This section overviews the
+available test infrastructure used in the Yocto Project. For information
+on how to run available tests on your projects, see the
+":ref:`dev-manual/dev-manual-common-tasks:performing automated runtime testing`"
+section in the Yocto Project Development Tasks Manual.
+
+The QA/testing infrastructure is woven into the project to the point
+where core developers take some of it for granted. The infrastructure
+consists of the following pieces:
+
+-  ``bitbake-selftest``: A standalone command that runs unit tests on
+   key pieces of BitBake and its fetchers.
+
+-  :ref:`sanity.bbclass <ref-classes-sanity>`: This automatically
+   included class checks the build environment for missing tools (e.g.
+   ``gcc``) or common misconfigurations such as
+   :term:`MACHINE` set incorrectly.
+
+-  :ref:`insane.bbclass <ref-classes-insane>`: This class checks the
+   generated output from builds for sanity. For example, if building for
+   an ARM target, did the build produce ARM binaries. If, for example,
+   the build produced PPC binaries then there is a problem.
+
+-  :ref:`testimage.bbclass <ref-classes-testimage*>`: This class
+   performs runtime testing of images after they are built. The tests
+   are usually used with :doc:`QEMU <../dev-manual/dev-manual-qemu>`
+   to boot the images and check the combined runtime result boot
+   operation and functions. However, the test can also use the IP
+   address of a machine to test.
+
+-  :ref:`ptest <dev-manual/dev-manual-common-tasks:testing packages with ptest>`:
+   Runs tests against packages produced during the build for a given
+   piece of software. The test allows the packages to be be run within a
+   target image.
+
+-  ``oe-selftest``: Tests combination BitBake invocations. These tests
+   operate outside the OpenEmbedded build system itself. The
+   ``oe-selftest`` can run all tests by default or can run selected
+   tests or test suites.
+
+   .. note::
+
+      Running
+      oe-selftest
+      requires host packages beyond the "Essential" grouping. See the "
+      Required Packages for the Build Host
+      " section for more information.
+
+Originally, much of this testing was done manually. However, significant
+effort has been made to automate the tests so that more people can use
+them and the Yocto Project development team can run them faster and more
+efficiently.
+
+The Yocto Project's main Autobuilder (https://autobuilder.yoctoproject.org/)
+publicly tests each Yocto Project release's code in the
+:term:`OpenEmbedded-Core (OE-Core)`, Poky, and BitBake repositories. The testing
+occurs for both the current state of the "master" branch and also for
+submitted patches. Testing for submitted patches usually occurs in the
+"ross/mut" branch in the ``poky-contrib`` repository (i.e. the
+master-under-test branch) or in the "master-next" branch in the ``poky``
+repository.
+
+.. note::
+
+   You can find all these branches in the Yocto Project
+   Source Repositories
+   .
+
+Testing within these public branches ensures in a publicly visible way
+that all of the main supposed architectures and recipes in OE-Core
+successfully build and behave properly.
+
+Various features such as ``multilib``, sub architectures (e.g. ``x32``,
+``poky-tiny``, ``musl``, ``no-x11`` and and so forth),
+``bitbake-selftest``, and ``oe-selftest`` are tested as part of the QA
+process of a release. Complete testing and validation for a release
+takes the Autobuilder workers several hours.
+
+.. note::
+
+   The Autobuilder workers are non-homogeneous, which means regular
+   testing across a variety of Linux distributions occurs. The
+   Autobuilder is limited to only testing QEMU-based setups and not real
+   hardware.
+
+Finally, in addition to the Autobuilder's tests, the Yocto Project QA
+team also performs testing on a variety of platforms, which includes
+actual hardware, to ensure expected results.
diff --git a/documentation/ref-manual/ref-release-process.xml b/documentation/ref-manual/ref-release-process.xml
index 5efe17417a..87f5308067 100644
--- a/documentation/ref-manual/ref-release-process.xml
+++ b/documentation/ref-manual/ref-release-process.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-release-process'>
 <title>Yocto Project Releases and the Stable Release Process</title>
diff --git a/documentation/ref-manual/ref-structure.rst b/documentation/ref-manual/ref-structure.rst
new file mode 100644
index 0000000000..48a443331b
--- /dev/null
+++ b/documentation/ref-manual/ref-structure.rst
@@ -0,0 +1,890 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+**************************
+Source Directory Structure
+**************************
+
+The :term:`Source Directory` consists of numerous files,
+directories and subdirectories; understanding their locations and
+contents is key to using the Yocto Project effectively. This chapter
+describes the Source Directory and gives information about those files
+and directories.
+
+For information on how to establish a local Source Directory on your
+development system, see the
+":ref:`dev-manual/dev-manual-start:locating yocto project source files`"
+section in the Yocto Project Development Tasks Manual.
+
+.. note::
+
+   The OpenEmbedded build system does not support file or directory
+   names that contain spaces. Be sure that the Source Directory you use
+   does not contain these types of names.
+
+.. _structure-core:
+
+Top-Level Core Components
+=========================
+
+This section describes the top-level components of the :term:`Source Directory`.
+
+.. _structure-core-bitbake:
+
+``bitbake/``
+------------
+
+This directory includes a copy of BitBake for ease of use. The copy
+usually matches the current stable BitBake release from the BitBake
+project. BitBake, a :term:`Metadata` interpreter, reads the
+Yocto Project Metadata and runs the tasks defined by that data. Failures
+are usually caused by errors in your Metadata and not from BitBake
+itself; consequently, most users do not need to worry about BitBake.
+
+When you run the ``bitbake`` command, the main BitBake executable (which
+resides in the ``bitbake/bin/`` directory) starts. Sourcing the
+environment setup script (i.e. :ref:`structure-core-script`) places
+the ``scripts/`` and ``bitbake/bin/`` directories (in that order) into
+the shell's ``PATH`` environment variable.
+
+For more information on BitBake, see the :doc:`BitBake User Manual
+<bitbake:index>`.
+
+.. _structure-core-build:
+
+``build/``
+----------
+
+This directory contains user configuration files and the output
+generated by the OpenEmbedded build system in its standard configuration
+where the source tree is combined with the output. The :term:`Build Directory`
+is created initially when you ``source``
+the OpenEmbedded build environment setup script (i.e.
+:ref:`structure-core-script`).
+
+It is also possible to place output and configuration files in a
+directory separate from the :term:`Source Directory` by
+providing a directory name when you ``source`` the setup script. For
+information on separating output from your local Source Directory files
+(commonly described as an "out of tree" build), see the
+":ref:`structure-core-script`" section.
+
+.. _handbook:
+
+``documentation/``
+------------------
+
+This directory holds the source for the Yocto Project documentation as
+well as templates and tools that allow you to generate PDF and HTML
+versions of the manuals. Each manual is contained in its own sub-folder;
+for example, the files for this reference manual reside in the
+``ref-manual/`` directory.
+
+.. _structure-core-meta:
+
+``meta/``
+---------
+
+This directory contains the minimal, underlying OpenEmbedded-Core
+metadata. The directory holds recipes, common classes, and machine
+configuration for strictly emulated targets (``qemux86``, ``qemuarm``,
+and so forth.)
+
+.. _structure-core-meta-poky:
+
+``meta-poky/``
+--------------
+
+Designed above the ``meta/`` content, this directory adds just enough
+metadata to define the Poky reference distribution.
+
+.. _structure-core-meta-yocto-bsp:
+
+``meta-yocto-bsp/``
+-------------------
+
+This directory contains the Yocto Project reference hardware Board
+Support Packages (BSPs). For more information on BSPs, see the
+:doc:`../bsp-guide/bsp-guide`.
+
+.. _structure-meta-selftest:
+
+``meta-selftest/``
+------------------
+
+This directory adds additional recipes and append files used by the
+OpenEmbedded selftests to verify the behavior of the build system. You
+do not have to add this layer to your ``bblayers.conf`` file unless you
+want to run the selftests.
+
+.. _structure-meta-skeleton:
+
+``meta-skeleton/``
+------------------
+
+This directory contains template recipes for BSP and kernel development.
+
+.. _structure-core-scripts:
+
+``scripts/``
+------------
+
+This directory contains various integration scripts that implement extra
+functionality in the Yocto Project environment (e.g. QEMU scripts). The
+:ref:`structure-core-script` script prepends this directory to the
+shell's ``PATH`` environment variable.
+
+The ``scripts`` directory has useful scripts that assist in contributing
+back to the Yocto Project, such as ``create-pull-request`` and
+``send-pull-request``.
+
+.. _structure-core-script:
+
+``oe-init-build-env``
+---------------------
+
+This script sets up the OpenEmbedded build environment. Running this
+script with the ``source`` command in a shell makes changes to ``PATH``
+and sets other core BitBake variables based on the current working
+directory. You need to run an environment setup script before running
+BitBake commands. The script uses other scripts within the ``scripts``
+directory to do the bulk of the work.
+
+When you run this script, your Yocto Project environment is set up, a
+:term:`Build Directory` is created, your working
+directory becomes the Build Directory, and you are presented with some
+simple suggestions as to what to do next, including a list of some
+possible targets to build. Here is an example:
+::
+
+   $ source oe-init-build-env
+
+   ### Shell environment set up for builds. ###
+
+   You can now run 'bitbake <target>'
+
+   Common targets are:
+       core-image-minimal
+       core-image-sato
+       meta-toolchain
+       meta-ide-support
+
+   You can also run generated qemu images with a command like 'runqemu qemux86-64'
+
+The default output of the ``oe-init-build-env`` script is from the
+``conf-notes.txt`` file, which is found in the ``meta-poky`` directory
+within the :term:`Source Directory`. If you design a
+custom distribution, you can include your own version of this
+configuration file to mention the targets defined by your distribution.
+See the
+":ref:`dev-manual/dev-manual-common-tasks:creating a custom template configuration directory`"
+section in the Yocto Project Development Tasks Manual for more
+information.
+
+By default, running this script without a Build Directory argument
+creates the ``build/`` directory in your current working directory. If
+you provide a Build Directory argument when you ``source`` the script,
+you direct the OpenEmbedded build system to create a Build Directory of
+your choice. For example, the following command creates a Build
+Directory named ``mybuilds/`` that is outside of the :term:`Source Directory`:
+::
+
+   $ source OE_INIT_FILE ~/mybuilds
+
+The OpenEmbedded build system uses the template configuration files, which
+are found by default in the ``meta-poky/conf/`` directory in the Source
+Directory. See the
+":ref:`dev-manual/dev-manual-common-tasks:creating a custom template configuration directory`"
+section in the Yocto Project Development Tasks Manual for more
+information.
+
+.. note::
+
+   The OpenEmbedded build system does not support file or directory
+   names that contain spaces. If you attempt to run the
+   OE_INIT_FILE
+   script from a Source Directory that contains spaces in either the
+   filenames or directory names, the script returns an error indicating
+   no such file or directory. Be sure to use a Source Directory free of
+   names containing spaces.
+
+.. _structure-basic-top-level:
+
+``LICENSE, README, and README.hardware``
+----------------------------------------
+
+These files are standard top-level files.
+
+.. _structure-build:
+
+The Build Directory - ``build/``
+================================
+
+The OpenEmbedded build system creates the :term:`Build Directory`
+when you run the build environment setup
+script :ref:`structure-core-script`. If you do not give the Build
+Directory a specific name when you run the setup script, the name
+defaults to ``build/``.
+
+For subsequent parsing and processing, the name of the Build directory
+is available via the :term:`TOPDIR` variable.
+
+.. _structure-build-buildhistory:
+
+``build/buildhistory/``
+-----------------------
+
+The OpenEmbedded build system creates this directory when you enable
+build history via the ``buildhistory`` class file. The directory
+organizes build information into image, packages, and SDK
+subdirectories. For information on the build history feature, see the
+":ref:`dev-manual/dev-manual-common-tasks:maintaining build output quality`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _structure-build-conf-local.conf:
+
+``build/conf/local.conf``
+-------------------------
+
+This configuration file contains all the local user configurations for
+your build environment. The ``local.conf`` file contains documentation
+on the various configuration options. Any variable set here overrides
+any variable set elsewhere within the environment unless that variable
+is hard-coded within a file (e.g. by using '=' instead of '?='). Some
+variables are hard-coded for various reasons but such variables are
+relatively rare.
+
+At a minimum, you would normally edit this file to select the target
+``MACHINE``, which package types you wish to use
+(:term:`PACKAGE_CLASSES`), and the location from
+which you want to access downloaded files (``DL_DIR``).
+
+If ``local.conf`` is not present when you start the build, the
+OpenEmbedded build system creates it from ``local.conf.sample`` when you
+``source`` the top-level build environment setup script
+:ref:`structure-core-script`.
+
+The source ``local.conf.sample`` file used depends on the
+``$TEMPLATECONF`` script variable, which defaults to ``meta-poky/conf/``
+when you are building from the Yocto Project development environment,
+and to ``meta/conf/`` when you are building from the OpenEmbedded-Core
+environment. Because the script variable points to the source of the
+``local.conf.sample`` file, this implies that you can configure your
+build environment from any layer by setting the variable in the
+top-level build environment setup script as follows:
+::
+
+   TEMPLATECONF=your_layer/conf
+
+Once the build process gets the sample
+file, it uses ``sed`` to substitute final
+``${``\ :term:`OEROOT`\ ``}`` values for all
+``##OEROOT##`` values.
+
+.. note::
+
+   You can see how the
+   TEMPLATECONF
+   variable is used by looking at the
+   scripts/oe-setup-builddir
+   script in the
+   Source Directory
+   . You can find the Yocto Project version of the
+   local.conf.sample
+   file in the
+   meta-poky/conf
+   directory.
+
+.. _structure-build-conf-bblayers.conf:
+
+``build/conf/bblayers.conf``
+----------------------------
+
+This configuration file defines
+:ref:`layers <dev-manual/dev-manual-common-tasks:understanding and creating layers>`,
+which are directory trees, traversed (or walked) by BitBake. The
+``bblayers.conf`` file uses the :term:`BBLAYERS`
+variable to list the layers BitBake tries to find.
+
+If ``bblayers.conf`` is not present when you start the build, the
+OpenEmbedded build system creates it from ``bblayers.conf.sample`` when
+you ``source`` the top-level build environment setup script (i.e.
+:ref:`structure-core-script`).
+
+As with the ``local.conf`` file, the source ``bblayers.conf.sample``
+file used depends on the ``$TEMPLATECONF`` script variable, which
+defaults to ``meta-poky/conf/`` when you are building from the Yocto
+Project development environment, and to ``meta/conf/`` when you are
+building from the OpenEmbedded-Core environment. Because the script
+variable points to the source of the ``bblayers.conf.sample`` file, this
+implies that you can base your build from any layer by setting the
+variable in the top-level build environment setup script as follows:
+::
+
+   TEMPLATECONF=your_layer/conf
+
+Once the build process gets the sample file, it uses ``sed`` to substitute final
+``${``\ :term:`OEROOT`\ ``}`` values for all ``##OEROOT##`` values.
+
+.. note::
+
+   You can see how the
+   TEMPLATECONF
+   variable
+   scripts/oe-setup-builddir
+   script in the
+   Source Directory
+   . You can find the Yocto Project version of the
+   bblayers.conf.sample
+   file in the
+   meta-poky/conf/
+   directory.
+
+.. _structure-build-conf-sanity_info:
+
+``build/cache/sanity_info``
+---------------------------
+
+This file indicates the state of the sanity checks and is created during
+the build.
+
+.. _structure-build-downloads:
+
+``build/downloads/``
+--------------------
+
+This directory contains downloaded upstream source tarballs. You can
+reuse the directory for multiple builds or move the directory to another
+location. You can control the location of this directory through the
+``DL_DIR`` variable.
+
+.. _structure-build-sstate-cache:
+
+``build/sstate-cache/``
+-----------------------
+
+This directory contains the shared state cache. You can reuse the
+directory for multiple builds or move the directory to another location.
+You can control the location of this directory through the
+``SSTATE_DIR`` variable.
+
+.. _structure-build-tmp:
+
+``build/tmp/``
+--------------
+
+The OpenEmbedded build system creates and uses this directory for all
+the build system's output. The :term:`TMPDIR` variable
+points to this directory.
+
+BitBake creates this directory if it does not exist. As a last resort,
+to clean up a build and start it from scratch (other than the
+downloads), you can remove everything in the ``tmp`` directory or get
+rid of the directory completely. If you do, you should also completely
+remove the ``build/sstate-cache`` directory.
+
+.. _structure-build-tmp-buildstats:
+
+``build/tmp/buildstats/``
+-------------------------
+
+This directory stores the build statistics.
+
+.. _structure-build-tmp-cache:
+
+``build/tmp/cache/``
+--------------------
+
+When BitBake parses the metadata (recipes and configuration files), it
+caches the results in ``build/tmp/cache/`` to speed up future builds.
+The results are stored on a per-machine basis.
+
+During subsequent builds, BitBake checks each recipe (together with, for
+example, any files included or appended to it) to see if they have been
+modified. Changes can be detected, for example, through file
+modification time (mtime) changes and hashing of file contents. If no
+changes to the file are detected, then the parsed result stored in the
+cache is reused. If the file has changed, it is reparsed.
+
+.. _structure-build-tmp-deploy:
+
+``build/tmp/deploy/``
+---------------------
+
+This directory contains any "end result" output from the OpenEmbedded
+build process. The :term:`DEPLOY_DIR` variable points
+to this directory. For more detail on the contents of the ``deploy``
+directory, see the
+":ref:`images-dev-environment`" and
+":ref:`sdk-dev-environment`" sections in the Yocto
+Project Overview and Concepts Manual.
+
+.. _structure-build-tmp-deploy-deb:
+
+``build/tmp/deploy/deb/``
+-------------------------
+
+This directory receives any ``.deb`` packages produced by the build
+process. The packages are sorted into feeds for different architecture
+types.
+
+.. _structure-build-tmp-deploy-rpm:
+
+``build/tmp/deploy/rpm/``
+-------------------------
+
+This directory receives any ``.rpm`` packages produced by the build
+process. The packages are sorted into feeds for different architecture
+types.
+
+.. _structure-build-tmp-deploy-ipk:
+
+``build/tmp/deploy/ipk/``
+-------------------------
+
+This directory receives ``.ipk`` packages produced by the build process.
+
+.. _structure-build-tmp-deploy-licenses:
+
+``build/tmp/deploy/licenses/``
+------------------------------
+
+This directory receives package licensing information. For example, the
+directory contains sub-directories for ``bash``, ``busybox``, and
+``glibc`` (among others) that in turn contain appropriate ``COPYING``
+license files with other licensing information. For information on
+licensing, see the
+":ref:`dev-manual/dev-manual-common-tasks:maintaining open source license compliance during your product's lifecycle`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _structure-build-tmp-deploy-images:
+
+``build/tmp/deploy/images/``
+----------------------------
+
+This directory is populated with the basic output objects of the build
+(think of them as the "generated artifacts" of the build process),
+including things like the boot loader image, kernel, root filesystem and
+more. If you want to flash the resulting image from a build onto a
+device, look here for the necessary components.
+
+Be careful when deleting files in this directory. You can safely delete
+old images from this directory (e.g. ``core-image-*``). However, the
+kernel (``*zImage*``, ``*uImage*``, etc.), bootloader and other
+supplementary files might be deployed here prior to building an image.
+Because these files are not directly produced from the image, if you
+delete them they will not be automatically re-created when you build the
+image again.
+
+If you do accidentally delete files here, you will need to force them to
+be re-created. In order to do that, you will need to know the target
+that produced them. For example, these commands rebuild and re-create
+the kernel files:
+::
+
+   $ bitbake -c clean virtual/kernel
+   $ bitbake virtual/kernel
+
+.. _structure-build-tmp-deploy-sdk:
+
+``build/tmp/deploy/sdk/``
+-------------------------
+
+The OpenEmbedded build system creates this directory to hold toolchain
+installer scripts which, when executed, install the sysroot that matches
+your target hardware. You can find out more about these installers in
+the ":ref:`sdk-manual/sdk-appendix-obtain:building an sdk installer`"
+section in the Yocto Project Application Development and the Extensible
+Software Development Kit (eSDK) manual.
+
+.. _structure-build-tmp-sstate-control:
+
+``build/tmp/sstate-control/``
+-----------------------------
+
+The OpenEmbedded build system uses this directory for the shared state
+manifest files. The shared state code uses these files to record the
+files installed by each sstate task so that the files can be removed
+when cleaning the recipe or when a newer version is about to be
+installed. The build system also uses the manifests to detect and
+produce a warning when files from one task are overwriting those from
+another.
+
+.. _structure-build-tmp-sysroots-components:
+
+``build/tmp/sysroots-components/``
+----------------------------------
+
+This directory is the location of the sysroot contents that the task
+:ref:`ref-tasks-prepare_recipe_sysroot`
+links or copies into the recipe-specific sysroot for each recipe listed
+in :term:`DEPENDS`. Population of this directory is
+handled through shared state, while the path is specified by the
+:term:`COMPONENTS_DIR` variable. Apart from a few
+unusual circumstances, handling of the ``sysroots-components`` directory
+should be automatic, and recipes should not directly reference
+``build/tmp/sysroots-components``.
+
+.. _structure-build-tmp-sysroots:
+
+``build/tmp/sysroots/``
+-----------------------
+
+Previous versions of the OpenEmbedded build system used to create a
+global shared sysroot per machine along with a native sysroot. Beginning
+with the DISTRO version of the Yocto Project, sysroots exist in
+recipe-specific :term:`WORKDIR` directories. Thus, the
+``build/tmp/sysroots/`` directory is unused.
+
+.. note::
+
+   The
+   build/tmp/sysroots/
+   directory can still be populated using the
+   bitbake build-sysroots
+   command and can be used for compatibility in some cases. However, in
+   general it is not recommended to populate this directory. Individual
+   recipe-specific sysroots should be used.
+
+.. _structure-build-tmp-stamps:
+
+``build/tmp/stamps/``
+---------------------
+
+This directory holds information that BitBake uses for accounting
+purposes to track what tasks have run and when they have run. The
+directory is sub-divided by architecture, package name, and version.
+Following is an example:
+stamps/all-poky-linux/distcc-config/1.0-r0.do_build-2fdd....2do Although
+the files in the directory are empty of data, BitBake uses the filenames
+and timestamps for tracking purposes.
+
+For information on how BitBake uses stamp files to determine if a task
+should be rerun, see the
+":ref:`overview-manual/overview-manual-concepts:stamp files and the rerunning of tasks`"
+section in the Yocto Project Overview and Concepts Manual.
+
+.. _structure-build-tmp-log:
+
+``build/tmp/log/``
+------------------
+
+This directory contains general logs that are not otherwise placed using
+the package's ``WORKDIR``. Examples of logs are the output from the
+``do_check_pkg`` or ``do_distro_check`` tasks. Running a build does not
+necessarily mean this directory is created.
+
+.. _structure-build-tmp-work:
+
+``build/tmp/work/``
+-------------------
+
+This directory contains architecture-specific work sub-directories for
+packages built by BitBake. All tasks execute from the appropriate work
+directory. For example, the source for a particular package is unpacked,
+patched, configured and compiled all within its own work directory.
+Within the work directory, organization is based on the package group
+and version for which the source is being compiled as defined by the
+:term:`WORKDIR`.
+
+It is worth considering the structure of a typical work directory. As an
+example, consider ``linux-yocto-kernel-3.0`` on the machine ``qemux86``
+built within the Yocto Project. For this package, a work directory of
+``tmp/work/qemux86-poky-linux/linux-yocto/3.0+git1+<.....>``, referred
+to as the ``WORKDIR``, is created. Within this directory, the source is
+unpacked to ``linux-qemux86-standard-build`` and then patched by Quilt.
+(See the ":ref:`using-a-quilt-workflow`" section in
+the Yocto Project Development Tasks Manual for more information.) Within
+the ``linux-qemux86-standard-build`` directory, standard Quilt
+directories ``linux-3.0/patches`` and ``linux-3.0/.pc`` are created, and
+standard Quilt commands can be used.
+
+There are other directories generated within ``WORKDIR``. The most
+important directory is ``WORKDIR/temp/``, which has log files for each
+task (``log.do_*.pid``) and contains the scripts BitBake runs for each
+task (``run.do_*.pid``). The ``WORKDIR/image/`` directory is where "make
+install" places its output that is then split into sub-packages within
+``WORKDIR/packages-split/``.
+
+.. _structure-build-tmp-work-tunearch-recipename-version:
+
+``build/tmp/work/tunearch/recipename/version/``
+-----------------------------------------------
+
+The recipe work directory - ``${WORKDIR}``.
+
+As described earlier in the
+"```build/tmp/sysroots/`` <#structure-build-tmp-sysroots>`__" section,
+beginning with the DISTRO release of the Yocto Project, the OpenEmbedded
+build system builds each recipe in its own work directory (i.e.
+:term:`WORKDIR`). The path to the work directory is
+constructed using the architecture of the given build (e.g.
+:term:`TUNE_PKGARCH`,
+:term:`MACHINE_ARCH`, or "allarch"), the recipe
+name, and the version of the recipe (i.e.
+:term:`PE`\ ``:``\ :term:`PV`\ ``-``\ :term:`PR`).
+
+A number of key subdirectories exist within each recipe work directory:
+
+-  ``${WORKDIR}/temp``: Contains the log files of each task executed for
+   this recipe, the "run" files for each executed task, which contain
+   the code run, and a ``log.task_order`` file, which lists the order in
+   which tasks were executed.
+
+-  ``${WORKDIR}/image``: Contains the output of the
+   :ref:`ref-tasks-install` task, which corresponds to
+   the ``${``\ :term:`D`\ ``}`` variable in that task.
+
+-  ``${WORKDIR}/pseudo``: Contains the pseudo database and log for any
+   tasks executed under pseudo for the recipe.
+
+-  ``${WORKDIR}/sysroot-destdir``: Contains the output of the
+   :ref:`ref-tasks-populate_sysroot` task.
+
+-  ``${WORKDIR}/package``: Contains the output of the
+   :ref:`ref-tasks-package` task before the output is
+   split into individual packages.
+
+-  ``${WORKDIR}/packages-split``: Contains the output of the
+   ``do_package`` task after the output has been split into individual
+   packages. Subdirectories exist for each individual package created by
+   the recipe.
+
+-  ``${WORKDIR}/recipe-sysroot``: A directory populated with the target
+   dependencies of the recipe. This directory looks like the target
+   filesystem and contains libraries that the recipe might need to link
+   against (e.g. the C library).
+
+-  ``${WORKDIR}/recipe-sysroot-native``: A directory populated with the
+   native dependencies of the recipe. This directory contains the tools
+   the recipe needs to build (e.g. the compiler, Autoconf, libtool, and
+   so forth).
+
+-  ``${WORKDIR}/build``: This subdirectory applies only to recipes that
+   support builds where the source is separate from the build artifacts.
+   The OpenEmbedded build system uses this directory as a separate build
+   directory (i.e. ``${``\ :term:`B`\ ``}``).
+
+.. _structure-build-work-shared:
+
+``build/tmp/work-shared/``
+--------------------------
+
+For efficiency, the OpenEmbedded build system creates and uses this
+directory to hold recipes that share a work directory with other
+recipes. In practice, this is only used for ``gcc`` and its variants
+(e.g. ``gcc-cross``, ``libgcc``, ``gcc-runtime``, and so forth).
+
+.. _structure-meta:
+
+The Metadata - ``meta/``
+========================
+
+As mentioned previously, :term:`Metadata` is the core of the
+Yocto Project. Metadata has several important subdivisions:
+
+.. _structure-meta-classes:
+
+``meta/classes/``
+-----------------
+
+This directory contains the ``*.bbclass`` files. Class files are used to
+abstract common code so it can be reused by multiple packages. Every
+package inherits the ``base.bbclass`` file. Examples of other important
+classes are ``autotools.bbclass``, which in theory allows any
+Autotool-enabled package to work with the Yocto Project with minimal
+effort. Another example is ``kernel.bbclass`` that contains common code
+and functions for working with the Linux kernel. Functions like image
+generation or packaging also have their specific class files such as
+``image.bbclass``, ``rootfs_*.bbclass`` and ``package*.bbclass``.
+
+For reference information on classes, see the
+":ref:`ref-manual/ref-classes:Classes`" chapter.
+
+.. _structure-meta-conf:
+
+``meta/conf/``
+--------------
+
+This directory contains the core set of configuration files that start
+from ``bitbake.conf`` and from which all other configuration files are
+included. See the include statements at the end of the ``bitbake.conf``
+file and you will note that even ``local.conf`` is loaded from there.
+While ``bitbake.conf`` sets up the defaults, you can often override
+these by using the (``local.conf``) file, machine file or the
+distribution configuration file.
+
+.. _structure-meta-conf-machine:
+
+``meta/conf/machine/``
+----------------------
+
+This directory contains all the machine configuration files. If you set
+``MACHINE = "qemux86"``, the OpenEmbedded build system looks for a
+``qemux86.conf`` file in this directory. The ``include`` directory
+contains various data common to multiple machines. If you want to add
+support for a new machine to the Yocto Project, look in this directory.
+
+.. _structure-meta-conf-distro:
+
+``meta/conf/distro/``
+---------------------
+
+The contents of this directory controls any distribution-specific
+configurations. For the Yocto Project, the ``defaultsetup.conf`` is the
+main file here. This directory includes the versions and the ``SRCDATE``
+definitions for applications that are configured here. An example of an
+alternative configuration might be ``poky-bleeding.conf``. Although this
+file mainly inherits its configuration from Poky.
+
+.. _structure-meta-conf-machine-sdk:
+
+``meta/conf/machine-sdk/``
+--------------------------
+
+The OpenEmbedded build system searches this directory for configuration
+files that correspond to the value of
+:term:`SDKMACHINE`. By default, 32-bit and 64-bit x86
+files ship with the Yocto Project that support some SDK hosts. However,
+it is possible to extend that support to other SDK hosts by adding
+additional configuration files in this subdirectory within another
+layer.
+
+.. _structure-meta-files:
+
+``meta/files/``
+---------------
+
+This directory contains common license files and several text files used
+by the build system. The text files contain minimal device information
+and lists of files and directories with known permissions.
+
+.. _structure-meta-lib:
+
+``meta/lib/``
+-------------
+
+This directory contains OpenEmbedded Python library code used during the
+build process.
+
+.. _structure-meta-recipes-bsp:
+
+``meta/recipes-bsp/``
+---------------------
+
+This directory contains anything linking to specific hardware or
+hardware configuration information such as "u-boot" and "grub".
+
+.. _structure-meta-recipes-connectivity:
+
+``meta/recipes-connectivity/``
+------------------------------
+
+This directory contains libraries and applications related to
+communication with other devices.
+
+.. _structure-meta-recipes-core:
+
+``meta/recipes-core/``
+----------------------
+
+This directory contains what is needed to build a basic working Linux
+image including commonly used dependencies.
+
+.. _structure-meta-recipes-devtools:
+
+``meta/recipes-devtools/``
+--------------------------
+
+This directory contains tools that are primarily used by the build
+system. The tools, however, can also be used on targets.
+
+.. _structure-meta-recipes-extended:
+
+``meta/recipes-extended/``
+--------------------------
+
+This directory contains non-essential applications that add features
+compared to the alternatives in core. You might need this directory for
+full tool functionality or for Linux Standard Base (LSB) compliance.
+
+.. _structure-meta-recipes-gnome:
+
+``meta/recipes-gnome/``
+-----------------------
+
+This directory contains all things related to the GTK+ application
+framework.
+
+.. _structure-meta-recipes-graphics:
+
+``meta/recipes-graphics/``
+--------------------------
+
+This directory contains X and other graphically related system
+libraries.
+
+.. _structure-meta-recipes-kernel:
+
+``meta/recipes-kernel/``
+------------------------
+
+This directory contains the kernel and generic applications and
+libraries that have strong kernel dependencies.
+
+.. _structure-meta-recipes-lsb4:
+
+``meta/recipes-lsb4/``
+----------------------
+
+This directory contains recipes specifically added to support the Linux
+Standard Base (LSB) version 4.x.
+
+.. _structure-meta-recipes-multimedia:
+
+``meta/recipes-multimedia/``
+----------------------------
+
+This directory contains codecs and support utilities for audio, images
+and video.
+
+.. _structure-meta-recipes-rt:
+
+``meta/recipes-rt/``
+--------------------
+
+This directory contains package and image recipes for using and testing
+the ``PREEMPT_RT`` kernel.
+
+.. _structure-meta-recipes-sato:
+
+``meta/recipes-sato/``
+----------------------
+
+This directory contains the Sato demo/reference UI/UX and its associated
+applications and configuration data.
+
+.. _structure-meta-recipes-support:
+
+``meta/recipes-support/``
+-------------------------
+
+This directory contains recipes used by other recipes, but that are not
+directly included in images (i.e. dependencies of other recipes).
+
+.. _structure-meta-site:
+
+``meta/site/``
+--------------
+
+This directory contains a list of cached results for various
+architectures. Because certain "autoconf" test results cannot be
+determined when cross-compiling due to the tests not able to run on a
+live system, the information in this directory is passed to "autoconf"
+for the various architectures.
+
+.. _structure-meta-recipes-txt:
+
+``meta/recipes.txt``
+--------------------
+
+This file is a description of the contents of ``recipes-*``.
diff --git a/documentation/ref-manual/ref-structure.xml b/documentation/ref-manual/ref-structure.xml
index 27f17dd919..8588e9c2dd 100644
--- a/documentation/ref-manual/ref-structure.xml
+++ b/documentation/ref-manual/ref-structure.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-structure'>
 
diff --git a/documentation/ref-manual/ref-style.css b/documentation/ref-manual/ref-style.css
index 7077e4b70d..622ceb8f7e 100644
--- a/documentation/ref-manual/ref-style.css
+++ b/documentation/ref-manual/ref-style.css
@@ -1,4 +1,7 @@
 /*
+
+   SPDX-License-Identifier: CC-BY-2.0-UK
+
    Generic XHTML / DocBook XHTML CSS Stylesheet.
 
    Browser wrangling and typographic design by
diff --git a/documentation/ref-manual/ref-system-requirements.rst b/documentation/ref-manual/ref-system-requirements.rst
new file mode 100644
index 0000000000..56218e4ebb
--- /dev/null
+++ b/documentation/ref-manual/ref-system-requirements.rst
@@ -0,0 +1,437 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+*******************
+System Requirements
+*******************
+
+Welcome to the Yocto Project Reference Manual! This manual provides
+reference information for the current release of the Yocto Project, and
+is most effectively used after you have an understanding of the basics
+of the Yocto Project. The manual is neither meant to be read as a
+starting point to the Yocto Project, nor read from start to finish.
+Rather, use this manual to find variable definitions, class
+descriptions, and so forth as needed during the course of using the
+Yocto Project.
+
+For introductory information on the Yocto Project, see the
+:yocto_home:`Yocto Project Website <>` and the
+":ref:`overview-manual/overview-manual-development-environment:the yocto project development environment`"
+chapter in the Yocto Project Overview and Concepts Manual.
+
+If you want to use the Yocto Project to quickly build an image without
+having to understand concepts, work through the
+:doc:`../brief-yoctoprojectqs/brief-yoctoprojectqs` document. You can find "how-to"
+information in the :doc:`../dev-manual/dev-manual`. You can find Yocto Project overview
+and conceptual information in the :doc:`../overview-manual/overview-manual`.
+
+.. note::
+
+   For more information about the Yocto Project Documentation set, see
+   the "
+   Links and Related Documentation
+   " section.
+
+.. _detailed-supported-distros:
+
+Supported Linux Distributions
+=============================
+
+Currently, the Yocto Project is supported on the following
+distributions:
+
+-  Ubuntu 16.04 (LTS)
+
+-  Ubuntu 18.04 (LTS)
+
+-  Ubuntu 20.04
+
+-  Fedora 30
+
+-  Fedora 31
+
+-  Fedora 32
+
+-  CentOS 7.x
+
+-  CentOS 8.x
+
+-  Debian GNU/Linux 8.x (Jessie)
+
+-  Debian GNU/Linux 9.x (Stretch)
+
+-  Debian GNU/Linux 10.x (Buster)
+
+-  OpenSUSE Leap 15.1
+
+
+.. note::
+
+   -  While the Yocto Project Team attempts to ensure all Yocto Project
+      releases are one hundred percent compatible with each officially
+      supported Linux distribution, instances might exist where you
+      encounter a problem while using the Yocto Project on a specific
+      distribution.
+
+   -  Yocto Project releases are tested against the stable Linux
+      distributions in the above list. The Yocto Project should work
+      on other distributions but validation is not performed against
+      them.
+
+   -  In particular, the Yocto Project does not support and currently
+      has no plans to support rolling-releases or development
+      distributions due to their constantly changing nature. We welcome
+      patches and bug reports, but keep in mind that our priority is on
+      the supported platforms listed below.
+
+   -  You may use Windows Subsystem For Linux v2 to set up a build host
+      using Windows 10, but validation is not performed against build
+      hosts using WSLv2.
+
+   -  The Yocto Project is not compatible with WSLv1, it is
+      compatible but not officially supported nor validated with
+      WSLv2, if you still decide to use WSL please upgrade to WSLv2.
+
+   -  If you encounter problems, please go to `Yocto Project
+      Bugzilla <http://bugzilla.yoctoproject.org>`__ and submit a bug. We are
+      interested in hearing about your experience. For information on
+      how to submit a bug, see the Yocto Project
+      :yocto_wiki:`Bugzilla wiki page </wiki/Bugzilla_Configuration_and_Bug_Tracking>`
+      and the ":ref:`dev-manual/dev-manual-common-tasks:submitting a defect against the yocto project`"
+      section in the Yocto Project Development Tasks Manual.
+
+
+Required Packages for the Build Host
+====================================
+
+The list of packages you need on the host development system can be
+large when covering all build scenarios using the Yocto Project. This
+section describes required packages according to Linux distribution and
+function.
+
+.. _ubuntu-packages:
+
+Ubuntu and Debian
+-----------------
+
+The following list shows the required packages by function given a
+supported Ubuntu or Debian Linux distribution:
+
+.. note::
+
+   -  If your build system has the ``oss4-dev`` package installed, you
+      might experience QEMU build failures due to the package installing
+      its own custom ``/usr/include/linux/soundcard.h`` on the Debian
+      system. If you run into this situation, either of the following
+      solutions exist:
+      ::
+
+         $ sudo apt-get build-dep qemu
+         $ sudo apt-get remove oss4-dev
+
+   -  For Debian-8, ``python3-git`` and ``pylint3`` are no longer
+      available via ``apt-get``.
+      ::
+
+         $ sudo pip3 install GitPython pylint==1.9.5
+
+-  *Essentials:* Packages needed to build an image on a headless system:
+   ::
+
+      $ sudo apt-get install &UBUNTU_HOST_PACKAGES_ESSENTIAL;
+
+-  *Documentation:* Packages needed if you are going to build out the
+   Yocto Project documentation manuals:
+   ::
+
+      $ sudo apt-get install make xsltproc docbook-utils fop dblatex xmlto
+
+Fedora Packages
+---------------
+
+The following list shows the required packages by function given a
+supported Fedora Linux distribution:
+
+-  *Essentials:* Packages needed to build an image for a headless
+   system:
+   ::
+
+      $ sudo dnf install &FEDORA_HOST_PACKAGES_ESSENTIAL;
+
+-  *Documentation:* Packages needed if you are going to build out the
+   Yocto Project documentation manuals:
+   ::
+
+      $ sudo dnf install  docbook-style-dsssl docbook-style-xsl \
+      docbook-dtds docbook-utils fop libxslt dblatex xmlto
+
+openSUSE Packages
+-----------------
+
+The following list shows the required packages by function given a
+supported openSUSE Linux distribution:
+
+-  *Essentials:* Packages needed to build an image for a headless
+   system:
+   ::
+
+      $ sudo zypper install &OPENSUSE_HOST_PACKAGES_ESSENTIAL;
+
+-  *Documentation:* Packages needed if you are going to build out the
+   Yocto Project documentation manuals: $ sudo zypper install dblatex
+   xmlto
+
+CentOS-7 Packages
+-----------------
+
+The following list shows the required packages by function given a
+supported CentOS-7 Linux distribution:
+
+-  *Essentials:* Packages needed to build an image for a headless
+   system:
+   ::
+
+      $ sudo yum install &CENTOS7_HOST_PACKAGES_ESSENTIAL;
+
+   .. note::
+
+      -  Extra Packages for Enterprise Linux (i.e. ``epel-release``) is
+         a collection of packages from Fedora built on RHEL/CentOS for
+         easy installation of packages not included in enterprise Linux
+         by default. You need to install these packages separately.
+
+      -  The ``makecache`` command consumes additional Metadata from
+         ``epel-release``.
+
+-  *Documentation:* Packages needed if you are going to build out the
+   Yocto Project documentation manuals:
+   ::
+
+      $ sudo yum install docbook-style-dsssl docbook-style-xsl \
+      docbook-dtds docbook-utils fop libxslt dblatex xmlto
+
+CentOS-8 Packages
+-----------------
+
+The following list shows the required packages by function given a
+supported CentOS-8 Linux distribution:
+
+-  *Essentials:* Packages needed to build an image for a headless
+   system:
+   ::
+
+      $ sudo dnf install &CENTOS8_HOST_PACKAGES_ESSENTIAL;
+
+   .. note::
+
+      -  Extra Packages for Enterprise Linux (i.e. ``epel-release``) is
+         a collection of packages from Fedora built on RHEL/CentOS for
+         easy installation of packages not included in enterprise Linux
+         by default. You need to install these packages separately.
+
+      -  The ``PowerTools`` repo provides additional packages such as
+         ``rpcgen`` and ``texinfo``.
+
+      -  The ``makecache`` command consumes additional Metadata from
+         ``epel-release``.
+
+-  *Documentation:* Packages needed if you are going to build out the
+   Yocto Project documentation manuals:
+   ::
+
+      $ sudo dnf install docbook-style-dsssl docbook-style-xsl \\
+      docbook-dtds docbook-utils fop libxslt dblatex xmlto
+
+Required Git, tar, Python and gcc Versions
+==========================================
+
+In order to use the build system, your host development system must meet
+the following version requirements for Git, tar, and Python:
+
+-  Git 1.8.3.1 or greater
+
+-  tar 1.28 or greater
+
+-  Python 3.5.0 or greater
+
+If your host development system does not meet all these requirements,
+you can resolve this by installing a ``buildtools`` tarball that
+contains these tools. You can get the tarball one of two ways: download
+a pre-built tarball or use BitBake to build the tarball.
+
+In addition, your host development system must meet the following
+version requirement for gcc:
+
+-  gcc 5.0 or greater
+
+If your host development system does not meet this requirement, you can
+resolve this by installing a ``buildtools-extended`` tarball that
+contains additional tools, the equivalent of ``buildtools-essential``.
+
+Installing a Pre-Built ``buildtools`` Tarball with ``install-buildtools`` script
+--------------------------------------------------------------------------------
+
+The ``install-buildtools`` script is the easiest of the three methods by
+which you can get these tools. It downloads a pre-built buildtools
+installer and automatically installs the tools for you:
+
+1. Execute the ``install-buildtools`` script. Here is an example:
+   ::
+
+      $ cd poky
+      $ scripts/install-buildtools --without-extended-buildtools \
+        --base-url https://downloads.yoctoproject.org/releases/yocto \
+        --release yocto-&DISTRO; \
+        --installer-version &DISTRO;
+
+   During execution, the buildtools tarball will be downloaded, the
+   checksum of the download will be verified, the installer will be run
+   for you, and some basic checks will be run to to make sure the
+   installation is functional.
+
+   To avoid the need of ``sudo`` privileges, the ``install-buildtools``
+   script will by default tell the installer to install in:
+   ::
+
+      /path/to/poky/buildtools
+
+   If your host development system needs the additional tools provided
+   in the ``buildtools-extended`` tarball, you can instead execute the
+   ``install-buildtools`` script with the default parameters:
+   ::
+
+      $ cd poky
+      $ scripts/install-buildtools
+
+2. Source the tools environment setup script by using a command like the
+   following:
+   ::
+
+      $ source /path/to/poky/buildtools/environment-setup-x86_64-pokysdk-linux
+
+   Of course, you need to supply your installation directory and be sure to
+   use the right file (i.e. i586 or x86_64).
+
+   After you have sourced the setup script, the tools are added to
+   ``PATH`` and any other environment variables required to run the
+   tools are initialized. The results are working versions versions of
+   Git, tar, Python and ``chrpath``. And in the case of the
+   ``buildtools-extended`` tarball, additional working versions of tools
+   including ``gcc``, ``make`` and the other tools included in
+   ``packagegroup-core-buildessential``.
+
+Downloading a Pre-Built ``buildtools`` Tarball
+----------------------------------------------
+
+Downloading and running a pre-built buildtools installer is the easiest
+of the two methods by which you can get these tools:
+
+1. Locate and download the ``*.sh`` at &YOCTO_RELEASE_DL_URL;/buildtools/
+
+2. Execute the installation script. Here is an example for the
+   traditional installer:
+   ::
+
+      $ sh ~/Downloads/x86_64-buildtools-nativesdk-standalone-DISTRO.sh
+
+   Here is an example for the extended installer:
+   ::
+
+      $ sh ~/Downloads/x86_64-buildtools-extended-nativesdk-standalone-DISTRO.sh
+
+   During execution, a prompt appears that allows you to choose the
+   installation directory. For example, you could choose the following:
+   /home/your-username/buildtools
+
+3. Source the tools environment setup script by using a command like the
+   following:
+   ::
+
+      $ source /home/your_username/buildtools/environment-setup-i586-poky-linux
+
+   Of
+   course, you need to supply your installation directory and be sure to
+   use the right file (i.e. i585 or x86-64).
+
+   After you have sourced the setup script, the tools are added to
+   ``PATH`` and any other environment variables required to run the
+   tools are initialized. The results are working versions versions of
+   Git, tar, Python and ``chrpath``. And in the case of the
+   ``buildtools-extended`` tarball, additional working versions of tools
+   including ``gcc``, ``make`` and the other tools included in
+   ``packagegroup-core-buildessential``.
+
+Building Your Own ``buildtools`` Tarball
+----------------------------------------
+
+Building and running your own buildtools installer applies only when you
+have a build host that can already run BitBake. In this case, you use
+that machine to build the ``.sh`` file and then take steps to transfer
+and run it on a machine that does not meet the minimal Git, tar, and
+Python (or gcc) requirements.
+
+Here are the steps to take to build and run your own buildtools
+installer:
+
+1. On the machine that is able to run BitBake, be sure you have set up
+   your build environment with the setup script
+   (:ref:`structure-core-script`).
+
+2. Run the BitBake command to build the tarball:
+   ::
+
+      $ bitbake buildtools-tarball
+
+   or run the BitBake command to build the extended tarball:
+   ::
+
+      $ bitbake buildtools-extended-tarball
+
+   .. note::
+
+      The
+      SDKMACHINE
+      variable in your
+      local.conf
+      file determines whether you build tools for a 32-bit or 64-bit
+      system.
+
+   Once the build completes, you can find the ``.sh`` file that installs
+   the tools in the ``tmp/deploy/sdk`` subdirectory of the
+   :term:`Build Directory`. The installer file has the string
+   "buildtools" (or "buildtools-extended") in the name.
+
+3. Transfer the ``.sh`` file from the build host to the machine that
+   does not meet the Git, tar, or Python (or gcc) requirements.
+
+4. On the machine that does not meet the requirements, run the ``.sh``
+   file to install the tools. Here is an example for the traditional
+   installer:
+   ::
+
+      $ sh ~/Downloads/x86_64-buildtools-nativesdk-standalone-&DISTRO;.sh
+
+   Here is an example for the extended installer:
+   ::
+
+      $ sh ~/Downloads/x86_64-buildtools-extended-nativesdk-standalone-&DISTRO;.sh
+
+   During execution, a prompt appears that allows you to choose the
+   installation directory. For example, you could choose the following:
+   /home/your_username/buildtools
+
+5. Source the tools environment setup script by using a command like the
+   following:
+   ::
+
+      $ source /home/your_username/buildtools/environment-setup-x86_64-poky-linux
+
+   Of course, you need to supply your installation directory and be sure to
+   use the right file (i.e. i586 or x86_64).
+
+   After you have sourced the setup script, the tools are added to
+   ``PATH`` and any other environment variables required to run the
+   tools are initialized. The results are working versions versions of
+   Git, tar, Python and ``chrpath``. And in the case of the
+   ``buildtools-extended`` tarball, additional working versions of tools
+   including ``gcc``, ``make`` and the other tools included in
+   ``packagegroup-core-buildessential``.
diff --git a/documentation/ref-manual/ref-system-requirements.xml b/documentation/ref-manual/ref-system-requirements.xml
index c6e1eb9716..ac8b0032db 100644
--- a/documentation/ref-manual/ref-system-requirements.xml
+++ b/documentation/ref-manual/ref-system-requirements.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-manual-system-requirements'>
 <title>System Requirements</title>
@@ -93,14 +94,12 @@
             <itemizedlist>
                 <listitem><para>Ubuntu 16.04 (LTS)</para></listitem>
                 <listitem><para>Ubuntu 18.04 (LTS)</para></listitem>
-                <listitem><para>Ubuntu 19.04</para></listitem>
                 <listitem><para>Ubuntu 20.04</para></listitem>
-                <listitem><para>Fedora 28</para></listitem>
-                <listitem><para>Fedora 29</para></listitem>
                 <listitem><para>Fedora 30</para></listitem>
                 <listitem><para>Fedora 31</para></listitem>
                 <listitem><para>Fedora 32</para></listitem>
                 <listitem><para>CentOS 7.x</para></listitem>
+                <listitem><para>CentOS 8.x</para></listitem>
                 <listitem><para>Debian GNU/Linux 8.x (Jessie)</para></listitem>
                 <listitem><para>Debian GNU/Linux 9.x (Stretch)</para></listitem>
                 <listitem><para>Debian GNU/Linux 10.x (Buster)</para></listitem>
diff --git a/documentation/ref-manual/ref-tasks.rst b/documentation/ref-manual/ref-tasks.rst
new file mode 100644
index 0000000000..dcdff05dce
--- /dev/null
+++ b/documentation/ref-manual/ref-tasks.rst
@@ -0,0 +1,875 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+*****
+Tasks
+*****
+
+Tasks are units of execution for BitBake. Recipes (``.bb`` files) use
+tasks to complete configuring, compiling, and packaging software. This
+chapter provides a reference of the tasks defined in the OpenEmbedded
+build system.
+
+Normal Recipe Build Tasks
+=========================
+
+The following sections describe normal tasks associated with building a
+recipe. For more information on tasks and dependencies, see the
+":ref:`Tasks <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:tasks>`" and
+":ref:`Dependencies <bitbake:bitbake-user-manual/bitbake-user-manual-execution:dependencies>`" sections in the
+BitBake User Manual.
+
+.. _ref-tasks-build:
+
+``do_build``
+------------
+
+The default task for all recipes. This task depends on all other normal
+tasks required to build a recipe.
+
+.. _ref-tasks-compile:
+
+``do_compile``
+--------------
+
+Compiles the source code. This task runs with the current working
+directory set to ``${``\ :term:`B`\ ``}``.
+
+The default behavior of this task is to run the ``oe_runmake`` function
+if a makefile (``Makefile``, ``makefile``, or ``GNUmakefile``) is found.
+If no such file is found, the ``do_compile`` task does nothing.
+
+.. _ref-tasks-compile_ptest_base:
+
+``do_compile_ptest_base``
+-------------------------
+
+Compiles the runtime test suite included in the software being built.
+
+.. _ref-tasks-configure:
+
+``do_configure``
+----------------
+
+Configures the source by enabling and disabling any build-time and
+configuration options for the software being built. The task runs with
+the current working directory set to ``${``\ :term:`B`\ ``}``.
+
+The default behavior of this task is to run ``oe_runmake clean`` if a
+makefile (``Makefile``, ``makefile``, or ``GNUmakefile``) is found and
+:term:`CLEANBROKEN` is not set to "1". If no such
+file is found or the ``CLEANBROKEN`` variable is set to "1", the
+``do_configure`` task does nothing.
+
+.. _ref-tasks-configure_ptest_base:
+
+``do_configure_ptest_base``
+---------------------------
+
+Configures the runtime test suite included in the software being built.
+
+.. _ref-tasks-deploy:
+
+``do_deploy``
+-------------
+
+Writes output files that are to be deployed to
+``${``\ :term:`DEPLOY_DIR_IMAGE`\ ``}``. The
+task runs with the current working directory set to
+``${``\ :term:`B`\ ``}``.
+
+Recipes implementing this task should inherit the
+:ref:`deploy <ref-classes-deploy>` class and should write the output
+to ``${``\ :term:`DEPLOYDIR`\ ``}``, which is not to be
+confused with ``${DEPLOY_DIR}``. The ``deploy`` class sets up
+``do_deploy`` as a shared state (sstate) task that can be accelerated
+through sstate use. The sstate mechanism takes care of copying the
+output from ``${DEPLOYDIR}`` to ``${DEPLOY_DIR_IMAGE}``.
+
+.. note::
+
+   Do not write the output directly to
+   ${DEPLOY_DIR_IMAGE}
+   , as this causes the sstate mechanism to malfunction.
+
+The ``do_deploy`` task is not added as a task by default and
+consequently needs to be added manually. If you want the task to run
+after :ref:`ref-tasks-compile`, you can add it by doing
+the following: addtask deploy after do_compile Adding ``do_deploy``
+after other tasks works the same way.
+
+.. note::
+
+   You do not need to add
+   before do_build
+   to the
+   addtask
+   command (though it is harmless), because the
+   base
+   class contains the following:
+   ::
+
+           do_build[recrdeptask] += "do_deploy"
+
+
+   See the "
+   Dependencies
+   " section in the BitBake User Manual for more information.
+
+If the ``do_deploy`` task re-executes, any previous output is removed
+(i.e. "cleaned").
+
+.. _ref-tasks-fetch:
+
+``do_fetch``
+------------
+
+Fetches the source code. This task uses the
+:term:`SRC_URI` variable and the argument's prefix to
+determine the correct :ref:`fetcher <bitbake:bb-fetchers>`
+module.
+
+.. _ref-tasks-image:
+
+``do_image``
+------------
+
+Starts the image generation process. The ``do_image`` task runs after
+the OpenEmbedded build system has run the
+:ref:`ref-tasks-rootfs` task during which packages are
+identified for installation into the image and the root filesystem is
+created, complete with post-processing.
+
+The ``do_image`` task performs pre-processing on the image through the
+:term:`IMAGE_PREPROCESS_COMMAND` and
+dynamically generates supporting ``do_image_*`` tasks as needed.
+
+For more information on image creation, see the ":ref:`image-generation-dev-environment`"
+section in the Yocto Project Overview and Concepts Manual.
+
+.. _ref-tasks-image-complete:
+
+``do_image_complete``
+---------------------
+
+Completes the image generation process. The ``do_image_complete`` task
+runs after the OpenEmbedded build system has run the
+:ref:`ref-tasks-image` task during which image
+pre-processing occurs and through dynamically generated ``do_image_*``
+tasks the image is constructed.
+
+The ``do_image_complete`` task performs post-processing on the image
+through the
+:term:`IMAGE_POSTPROCESS_COMMAND`.
+
+For more information on image creation, see the
+":ref:`image-generation-dev-environment`"
+section in the Yocto Project Overview and Concepts Manual.
+
+.. _ref-tasks-install:
+
+``do_install``
+--------------
+
+Copies files that are to be packaged into the holding area
+``${``\ :term:`D`\ ``}``. This task runs with the current
+working directory set to ``${``\ :term:`B`\ ``}``, which is the
+compilation directory. The ``do_install`` task, as well as other tasks
+that either directly or indirectly depend on the installed files (e.g.
+:ref:`ref-tasks-package`, ``do_package_write_*``, and
+:ref:`ref-tasks-rootfs`), run under
+:ref:`fakeroot <overview-manual/overview-manual-concepts:fakeroot and pseudo>`.
+
+.. note::
+
+   When installing files, be careful not to set the owner and group IDs
+   of the installed files to unintended values. Some methods of copying
+   files, notably when using the recursive ``cp`` command, can preserve
+   the UID and/or GID of the original file, which is usually not what
+   you want. The ``host-user-contaminated`` QA check checks for files
+   that probably have the wrong ownership.
+
+   Safe methods for installing files include the following:
+
+   -  The ``install`` utility. This utility is the preferred method.
+
+   -  The ``cp`` command with the "--no-preserve=ownership" option.
+
+   -  The ``tar`` command with the "--no-same-owner" option. See the
+      ``bin_package.bbclass`` file in the ``meta/classes`` directory of
+      the :term:`Source Directory` for an example.
+
+.. _ref-tasks-install_ptest_base:
+
+``do_install_ptest_base``
+-------------------------
+
+Copies the runtime test suite files from the compilation directory to a
+holding area.
+
+.. _ref-tasks-package:
+
+``do_package``
+--------------
+
+Analyzes the content of the holding area
+``${``\ :term:`D`\ ``}`` and splits the content into subsets
+based on available packages and files. This task makes use of the
+:term:`PACKAGES` and :term:`FILES`
+variables.
+
+The ``do_package`` task, in conjunction with the
+:ref:`ref-tasks-packagedata` task, also saves some
+important package metadata. For additional information, see the
+:term:`PKGDESTWORK` variable and the
+":ref:`overview-manual/overview-manual-concepts:automatically added runtime dependencies`"
+section in the Yocto Project Overview and Concepts Manual.
+
+.. _ref-tasks-package_qa:
+
+``do_package_qa``
+-----------------
+
+Runs QA checks on packaged files. For more information on these checks,
+see the :ref:`insane <ref-classes-insane>` class.
+
+.. _ref-tasks-package_write_deb:
+
+``do_package_write_deb``
+------------------------
+
+Creates Debian packages (i.e. ``*.deb`` files) and places them in the
+``${``\ :term:`DEPLOY_DIR_DEB`\ ``}`` directory in
+the package feeds area. For more information, see the
+":ref:`package-feeds-dev-environment`" section in
+the Yocto Project Overview and Concepts Manual.
+
+.. _ref-tasks-package_write_ipk:
+
+``do_package_write_ipk``
+------------------------
+
+Creates IPK packages (i.e. ``*.ipk`` files) and places them in the
+``${``\ :term:`DEPLOY_DIR_IPK`\ ``}`` directory in
+the package feeds area. For more information, see the
+":ref:`package-feeds-dev-environment`" section in
+the Yocto Project Overview and Concepts Manual.
+
+.. _ref-tasks-package_write_rpm:
+
+``do_package_write_rpm``
+------------------------
+
+Creates RPM packages (i.e. ``*.rpm`` files) and places them in the
+``${``\ :term:`DEPLOY_DIR_RPM`\ ``}`` directory in
+the package feeds area. For more information, see the
+":ref:`package-feeds-dev-environment`" section in
+the Yocto Project Overview and Concepts Manual.
+
+.. _ref-tasks-package_write_tar:
+
+``do_package_write_tar``
+------------------------
+
+Creates tarballs and places them in the
+``${``\ :term:`DEPLOY_DIR_TAR`\ ``}`` directory in
+the package feeds area. For more information, see the
+":ref:`package-feeds-dev-environment`" section in
+the Yocto Project Overview and Concepts Manual.
+
+.. _ref-tasks-packagedata:
+
+``do_packagedata``
+------------------
+
+Saves package metadata generated by the
+:ref:`ref-tasks-package` task in
+:term:`PKGDATA_DIR` to make it available globally.
+
+.. _ref-tasks-patch:
+
+``do_patch``
+------------
+
+Locates patch files and applies them to the source code.
+
+After fetching and unpacking source files, the build system uses the
+recipe's :term:`SRC_URI` statements
+to locate and apply patch files to the source code.
+
+.. note::
+
+   The build system uses the
+   FILESPATH
+   variable to determine the default set of directories when searching
+   for patches.
+
+Patch files, by default, are ``*.patch`` and ``*.diff`` files created
+and kept in a subdirectory of the directory holding the recipe file. For
+example, consider the
+:yocto_git:`bluez5 </cgit/cgit.cgi/poky/tree/meta/recipes-connectivity/bluez5>`
+recipe from the OE-Core layer (i.e. ``poky/meta``):
+::
+
+   poky/meta/recipes-connectivity/bluez5
+
+This recipe has two patch files located here:
+::
+
+   poky/meta/recipes-connectivity/bluez5/bluez5
+
+In the ``bluez5`` recipe, the ``SRC_URI`` statements point to the source
+and patch files needed to build the package.
+
+.. note::
+
+   In the case for the
+   bluez5_5.48.bb
+   recipe, the
+   SRC_URI
+   statements are from an include file
+   bluez5.inc
+   .
+
+As mentioned earlier, the build system treats files whose file types are
+``.patch`` and ``.diff`` as patch files. However, you can use the
+"apply=yes" parameter with the ``SRC_URI`` statement to indicate any
+file as a patch file:
+::
+
+   SRC_URI = " \\
+       git://path_to_repo/some_package \\
+       file://file;apply=yes \\
+       "
+
+Conversely, if you have a directory full of patch files and you want to
+exclude some so that the ``do_patch`` task does not apply them during
+the patch phase, you can use the "apply=no" parameter with the
+``SRC_URI`` statement:
+::
+
+   SRC_URI = " \
+       git://path_to_repo/some_package \
+       file://path_to_lots_of_patch_files \
+       file://path_to_lots_of_patch_files/patch_file5;apply=no \
+       "
+
+In the
+previous example, assuming all the files in the directory holding the
+patch files end with either ``.patch`` or ``.diff``, every file would be
+applied as a patch by default except for the patch_file5 patch.
+
+You can find out more about the patching process in the
+":ref:`patching-dev-environment`" section in
+the Yocto Project Overview and Concepts Manual and the
+":ref:`new-recipe-patching-code`" section in the
+Yocto Project Development Tasks Manual.
+
+.. _ref-tasks-populate_lic:
+
+``do_populate_lic``
+-------------------
+
+Writes license information for the recipe that is collected later when
+the image is constructed.
+
+.. _ref-tasks-populate_sdk:
+
+``do_populate_sdk``
+-------------------
+
+Creates the file and directory structure for an installable SDK. See the
+":ref:`sdk-generation-dev-environment`"
+section in the Yocto Project Overview and Concepts Manual for more
+information.
+
+.. _ref-tasks-populate_sdk_ext:
+
+``do_populate_sdk_ext``
+-----------------------
+
+Creates the file and directory structure for an installable extensible 
+SDK (eSDK). See the ":ref:`sdk-generation-dev-environment`"
+section in the Yocto Project Overview and Concepts Manual for more
+information.
+
+
+.. _ref-tasks-populate_sysroot:
+
+``do_populate_sysroot``
+-----------------------
+
+Stages (copies) a subset of the files installed by the
+:ref:`ref-tasks-install` task into the appropriate
+sysroot. For information on how to access these files from other
+recipes, see the :term:`STAGING_DIR* <STAGING_DIR_HOST>` variables.
+Directories that would typically not be needed by other recipes at build
+time (e.g. ``/etc``) are not copied by default.
+
+For information on what directories are copied by default, see the
+:term:`SYSROOT_DIRS* <SYSROOT_DIRS>` variables. You can change
+these variables inside your recipe if you need to make additional (or
+fewer) directories available to other recipes at build time.
+
+The ``do_populate_sysroot`` task is a shared state (sstate) task, which
+means that the task can be accelerated through sstate use. Realize also
+that if the task is re-executed, any previous output is removed (i.e.
+"cleaned").
+
+.. _ref-tasks-prepare_recipe_sysroot:
+
+``do_prepare_recipe_sysroot``
+-----------------------------
+
+Installs the files into the individual recipe specific sysroots (i.e.
+``recipe-sysroot`` and ``recipe-sysroot-native`` under
+``${``\ :term:`WORKDIR`\ ``}`` based upon the
+dependencies specified by :term:`DEPENDS`). See the
+":ref:`staging <ref-classes-staging>`" class for more information.
+
+.. _ref-tasks-rm_work:
+
+``do_rm_work``
+--------------
+
+Removes work files after the OpenEmbedded build system has finished with
+them. You can learn more by looking at the
+":ref:`rm_work.bbclass <ref-classes-rm-work>`" section.
+
+.. _ref-tasks-unpack:
+
+``do_unpack``
+-------------
+
+Unpacks the source code into a working directory pointed to by
+``${``\ :term:`WORKDIR`\ ``}``. The :term:`S`
+variable also plays a role in where unpacked source files ultimately
+reside. For more information on how source files are unpacked, see the
+":ref:`source-fetching-dev-environment`"
+section in the Yocto Project Overview and Concepts Manual and also see
+the ``WORKDIR`` and ``S`` variable descriptions.
+
+Manually Called Tasks
+=====================
+
+These tasks are typically manually triggered (e.g. by using the
+``bitbake -c`` command-line option):
+
+.. _ref-tasks-checkpkg:
+
+``do_checkpkg``
+---------------
+
+Provides information about the recipe including its upstream version and
+status. The upstream version and status reveals whether or not a version
+of the recipe exists upstream and a status of not updated, updated, or
+unknown.
+
+To check the upstream version and status of a recipe, use the following
+devtool commands:
+::
+
+   $ devtool latest-version
+   $ devtool check-upgrade-status
+
+See the ":ref:`ref-manual/ref-devtool-reference:\`\`devtool\`\` quick reference`"
+chapter for more information on
+``devtool``. See the ":ref:`devtool-checking-on-the-upgrade-status-of-a-recipe`"
+section for information on checking the upgrade status of a recipe.
+
+To build the ``checkpkg`` task, use the ``bitbake`` command with the
+"-c" option and task name:
+::
+
+   $ bitbake core-image-minimal -c checkpkg
+
+By default, the results are stored in :term:`$LOG_DIR <LOG_DIR>` (e.g.
+``$BUILD_DIR/tmp/log``).
+
+.. _ref-tasks-checkuri:
+
+``do_checkuri``
+---------------
+
+Validates the :term:`SRC_URI` value.
+
+.. _ref-tasks-clean:
+
+``do_clean``
+------------
+
+Removes all output files for a target from the
+:ref:`ref-tasks-unpack` task forward (i.e. ``do_unpack``,
+:ref:`ref-tasks-configure`,
+:ref:`ref-tasks-compile`,
+:ref:`ref-tasks-install`, and
+:ref:`ref-tasks-package`).
+
+You can run this task using BitBake as follows:
+::
+
+   $ bitbake -c clean recipe
+
+Running this task does not remove the
+:ref:`sstate <overview-manual/overview-manual-concepts:shared state cache>` cache files.
+Consequently, if no changes have been made and the recipe is rebuilt
+after cleaning, output files are simply restored from the sstate cache.
+If you want to remove the sstate cache files for the recipe, you need to
+use the :ref:`ref-tasks-cleansstate` task instead
+(i.e. ``bitbake -c cleansstate`` recipe).
+
+.. _ref-tasks-cleanall:
+
+``do_cleanall``
+---------------
+
+Removes all output files, shared state
+(:ref:`sstate <overview-manual/overview-manual-concepts:shared state cache>`) cache, and
+downloaded source files for a target (i.e. the contents of
+:term:`DL_DIR`). Essentially, the ``do_cleanall`` task is
+identical to the :ref:`ref-tasks-cleansstate` task
+with the added removal of downloaded source files.
+
+You can run this task using BitBake as follows:
+::
+
+   $ bitbake -c cleanall recipe
+
+Typically, you would not normally use the ``cleanall`` task. Do so only
+if you want to start fresh with the :ref:`ref-tasks-fetch`
+task.
+
+.. _ref-tasks-cleansstate:
+
+``do_cleansstate``
+------------------
+
+Removes all output files and shared state
+(:ref:`sstate <overview-manual/overview-manual-concepts:shared state cache>`) cache for a
+target. Essentially, the ``do_cleansstate`` task is identical to the
+:ref:`ref-tasks-clean` task with the added removal of
+shared state (`:ref:`sstate <overview-manual/overview-manual-concepts:shared state cache>`)
+cache.
+
+You can run this task using BitBake as follows:
+::
+
+   $ bitbake -c cleansstate recipe
+
+When you run the ``do_cleansstate`` task, the OpenEmbedded build system
+no longer uses any sstate. Consequently, building the recipe from
+scratch is guaranteed.
+
+.. note::
+
+   The
+   do_cleansstate
+   task cannot remove sstate from a remote sstate mirror. If you need to
+   build a target from scratch using remote mirrors, use the "-f" option
+   as follows:
+   ::
+
+      $ bitbake -f -c do_cleansstate target
+
+
+.. _ref-tasks-devpyshell:
+
+``do_devpyshell``
+-----------------
+
+Starts a shell in which an interactive Python interpreter allows you to
+interact with the BitBake build environment. From within this shell, you
+can directly examine and set bits from the data store and execute
+functions as if within the BitBake environment. See the ":ref:`platdev-appdev-devpyshell`" section in
+the Yocto Project Development Tasks Manual for more information about
+using ``devpyshell``.
+
+.. _ref-tasks-devshell:
+
+``do_devshell``
+---------------
+
+Starts a shell whose environment is set up for development, debugging,
+or both. See the ":ref:`platdev-appdev-devshell`" section in the
+Yocto Project Development Tasks Manual for more information about using
+``devshell``.
+
+.. _ref-tasks-listtasks:
+
+``do_listtasks``
+----------------
+
+Lists all defined tasks for a target.
+
+.. _ref-tasks-package_index:
+
+``do_package_index``
+--------------------
+
+Creates or updates the index in the `:ref:`package-feeds-dev-environment` area.
+
+.. note::
+
+   This task is not triggered with the
+   bitbake -c
+   command-line option as are the other tasks in this section. Because
+   this task is specifically for the
+   package-index
+   recipe, you run it using
+   bitbake package-index
+   .
+
+Image-Related Tasks
+===================
+
+The following tasks are applicable to image recipes.
+
+.. _ref-tasks-bootimg:
+
+``do_bootimg``
+--------------
+
+Creates a bootable live image. See the
+:term:`IMAGE_FSTYPES` variable for additional
+information on live image types.
+
+.. _ref-tasks-bundle_initramfs:
+
+``do_bundle_initramfs``
+-----------------------
+
+Combines an initial RAM disk (initramfs) image and kernel together to
+form a single image. The
+:term:`CONFIG_INITRAMFS_SOURCE` variable
+has some more information about these types of images.
+
+.. _ref-tasks-rootfs:
+
+``do_rootfs``
+-------------
+
+Creates the root filesystem (file and directory structure) for an image.
+See the ":ref:`image-generation-dev-environment`"
+section in the Yocto Project Overview and Concepts Manual for more
+information on how the root filesystem is created.
+
+.. _ref-tasks-testimage:
+
+``do_testimage``
+----------------
+
+Boots an image and performs runtime tests within the image. For
+information on automatically testing images, see the
+":ref:`dev-manual/dev-manual-common-tasks:performing automated runtime testing`"
+section in the Yocto Project Development Tasks Manual.
+
+.. _ref-tasks-testimage_auto:
+
+``do_testimage_auto``
+---------------------
+
+Boots an image and performs runtime tests within the image immediately
+after it has been built. This task is enabled when you set
+:term:`TESTIMAGE_AUTO` equal to "1".
+
+For information on automatically testing images, see the
+":ref:`dev-manual/dev-manual-common-tasks:performing automated runtime testing`"
+section in the Yocto Project Development Tasks Manual.
+
+Kernel-Related Tasks
+====================
+
+The following tasks are applicable to kernel recipes. Some of these
+tasks (e.g. the :ref:`ref-tasks-menuconfig` task) are
+also applicable to recipes that use Linux kernel style configuration
+such as the BusyBox recipe.
+
+.. _ref-tasks-compile_kernelmodules:
+
+``do_compile_kernelmodules``
+----------------------------
+
+Runs the step that builds the kernel modules (if needed). Building a
+kernel consists of two steps: 1) the kernel (``vmlinux``) is built, and
+2) the modules are built (i.e. ``make modules``).
+
+.. _ref-tasks-diffconfig:
+
+``do_diffconfig``
+-----------------
+
+When invoked by the user, this task creates a file containing the
+differences between the original config as produced by
+:ref:`ref-tasks-kernel_configme` task and the
+changes made by the user with other methods (i.e. using
+(:ref:`ref-tasks-kernel_menuconfig`). Once the
+file of differences is created, it can be used to create a config
+fragment that only contains the differences. You can invoke this task
+from the command line as follows:
+::
+
+   $ bitbake linux-yocto -c diffconfig
+
+For more information, see the
+":ref:`kernel-dev/kernel-dev-common:creating configuration fragments`"
+section in the Yocto Project Linux Kernel Development Manual.
+
+.. _ref-tasks-kernel_checkout:
+
+``do_kernel_checkout``
+----------------------
+
+Converts the newly unpacked kernel source into a form with which the
+OpenEmbedded build system can work. Because the kernel source can be
+fetched in several different ways, the ``do_kernel_checkout`` task makes
+sure that subsequent tasks are given a clean working tree copy of the
+kernel with the correct branches checked out.
+
+.. _ref-tasks-kernel_configcheck:
+
+``do_kernel_configcheck``
+-------------------------
+
+Validates the configuration produced by the
+:ref:`ref-tasks-kernel_menuconfig` task. The
+``do_kernel_configcheck`` task produces warnings when a requested
+configuration does not appear in the final ``.config`` file or when you
+override a policy configuration in a hardware configuration fragment.
+You can run this task explicitly and view the output by using the
+following command:
+::
+
+   $ bitbake linux-yocto -c kernel_configcheck -f
+
+For more information, see the
+":ref:`kernel-dev/kernel-dev-common:validating configuration`"
+section in the Yocto Project Linux Kernel Development Manual.
+
+.. _ref-tasks-kernel_configme:
+
+``do_kernel_configme``
+----------------------
+
+After the kernel is patched by the :ref:`ref-tasks-patch`
+task, the ``do_kernel_configme`` task assembles and merges all the
+kernel config fragments into a merged configuration that can then be
+passed to the kernel configuration phase proper. This is also the time
+during which user-specified defconfigs are applied if present, and where
+configuration modes such as ``--allnoconfig`` are applied.
+
+.. _ref-tasks-kernel_menuconfig:
+
+``do_kernel_menuconfig``
+------------------------
+
+Invoked by the user to manipulate the ``.config`` file used to build a
+linux-yocto recipe. This task starts the Linux kernel configuration
+tool, which you then use to modify the kernel configuration.
+
+.. note::
+
+   You can also invoke this tool from the command line as follows:
+   ::
+
+           $ bitbake linux-yocto -c menuconfig
+
+
+See the ":ref:`kernel-dev/kernel-dev-common:using \`\`menuconfig\`\``"
+section in the Yocto Project Linux Kernel Development Manual for more
+information on this configuration tool.
+
+.. _ref-tasks-kernel_metadata:
+
+``do_kernel_metadata``
+----------------------
+
+Collects all the features required for a given kernel build, whether the
+features come from :term:`SRC_URI` or from Git
+repositories. After collection, the ``do_kernel_metadata`` task
+processes the features into a series of config fragments and patches,
+which can then be applied by subsequent tasks such as
+:ref:`ref-tasks-patch` and
+:ref:`ref-tasks-kernel_configme`.
+
+.. _ref-tasks-menuconfig:
+
+``do_menuconfig``
+-----------------
+
+Runs ``make menuconfig`` for the kernel. For information on
+``menuconfig``, see the
+":ref:`kernel-dev/kernel-dev-common:using \`\`menuconfig\`\``"
+section in the Yocto Project Linux Kernel Development Manual.
+
+.. _ref-tasks-savedefconfig:
+
+``do_savedefconfig``
+--------------------
+
+When invoked by the user, creates a defconfig file that can be used
+instead of the default defconfig. The saved defconfig contains the
+differences between the default defconfig and the changes made by the
+user using other methods (i.e. the
+:ref:`ref-tasks-kernel_menuconfig` task. You
+can invoke the task using the following command:
+::
+
+   $ bitbake linux-yocto -c savedefconfig
+
+.. _ref-tasks-shared_workdir:
+
+``do_shared_workdir``
+---------------------
+
+After the kernel has been compiled but before the kernel modules have
+been compiled, this task copies files required for module builds and
+which are generated from the kernel build into the shared work
+directory. With these copies successfully copied, the
+:ref:`ref-tasks-compile_kernelmodules` task
+can successfully build the kernel modules in the next step of the build.
+
+.. _ref-tasks-sizecheck:
+
+``do_sizecheck``
+----------------
+
+After the kernel has been built, this task checks the size of the
+stripped kernel image against
+:term:`KERNEL_IMAGE_MAXSIZE`. If that
+variable was set and the size of the stripped kernel exceeds that size,
+the kernel build produces a warning to that effect.
+
+.. _ref-tasks-strip:
+
+``do_strip``
+------------
+
+If ``KERNEL_IMAGE_STRIP_EXTRA_SECTIONS`` is defined, this task strips
+the sections named in that variable from ``vmlinux``. This stripping is
+typically used to remove nonessential sections such as ``.comment``
+sections from a size-sensitive configuration.
+
+.. _ref-tasks-validate_branches:
+
+``do_validate_branches``
+------------------------
+
+After the kernel is unpacked but before it is patched, this task makes
+sure that the machine and metadata branches as specified by the
+:term:`SRCREV` variables actually exist on the specified
+branches. If these branches do not exist and
+:term:`AUTOREV` is not being used, the
+``do_validate_branches`` task fails during the build.
+
+Miscellaneous Tasks
+===================
+
+The following sections describe miscellaneous tasks.
+
+.. _ref-tasks-spdx:
+
+``do_spdx``
+-----------
+
+A build stage that takes the source code and scans it on a remote
+FOSSOLOGY server in order to produce an SPDX document. This task applies
+only to the :ref:`spdx <ref-classes-spdx>` class.
diff --git a/documentation/ref-manual/ref-tasks.xml b/documentation/ref-manual/ref-tasks.xml
index 011e0d7496..5b09b3f2e8 100644
--- a/documentation/ref-manual/ref-tasks.xml
+++ b/documentation/ref-manual/ref-tasks.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-tasks'>
 <title>Tasks</title>
diff --git a/documentation/ref-manual/ref-terms.rst b/documentation/ref-manual/ref-terms.rst
new file mode 100644
index 0000000000..600cc23c3e
--- /dev/null
+++ b/documentation/ref-manual/ref-terms.rst
@@ -0,0 +1,397 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+*******************
+Yocto Project Terms
+*******************
+
+Following is a list of terms and definitions users new to the Yocto Project
+development environment might find helpful. While some of these terms are
+universal, the list includes them just in case:
+
+.. glossary::
+
+   Append Files
+      Files that append build information to a recipe file.  Append files are
+      known as BitBake append files and ``.bbappend`` files. The OpenEmbedded
+      build system expects every append file to have a corresponding recipe
+      (``.bb``) file. Furthermore, the append file and corresponding recipe file
+      must use the same root filename.  The filenames can differ only in the
+      file type suffix used (e.g. ``formfactor_0.0.bb`` and
+      ``formfactor_0.0.bbappend``).
+
+      Information in append files extends or overrides the information in the
+      similarly-named recipe file. For an example of an append file in use, see
+      the ":ref:`dev-manual/dev-manual-common-tasks:Using .bbappend Files in
+      Your Layer`" section in the Yocto Project Development Tasks Manual.
+
+      When you name an append file, you can use the "``%``" wildcard character
+      to allow for matching recipe names. For example, suppose you have an
+      append file named as follows:
+      ::
+      
+         busybox_1.21.%.bbappend
+
+      That append file
+      would match any ``busybox_1.21.``\ x\ ``.bb`` version of the recipe. So,
+      the append file would match any of the following recipe names:
+
+      .. code-block:: shell
+
+         busybox_1.21.1.bb
+         busybox_1.21.2.bb
+         busybox_1.21.3.bb
+         busybox_1.21.10.bb
+         busybox_1.21.25.bb
+
+      .. note::
+
+         The use of the " % " character is limited in that it only works
+         directly in front of the .bbappend portion of the append file's
+         name. You cannot use the wildcard character in any other location of
+         the name.
+
+   BitBake
+      The task executor and scheduler used by the OpenEmbedded build system to
+      build images. For more information on BitBake, see the :doc:`BitBake User
+      Manual <bitbake:index>`.
+
+   Board Support Package (BSP)
+      A group of drivers, definitions, and other components that provide support
+      for a specific hardware configuration. For more information on BSPs, see
+      the :ref:`bsp-guide/bsp-guide:Yocto Project Board Support Package
+      Developer's Guide`.
+
+   Build Directory
+      This term refers to the area used by the OpenEmbedded build system for
+      builds. The area is created when you ``source`` the setup environment
+      script that is found in the Source Directory
+      (i.e. :ref:`ref-manual/ref-structure:\`\`oe-init-build-env\`\``). The
+      :term:`TOPDIR` variable points to the Build Directory.
+
+      You have a lot of flexibility when creating the Build Directory.
+      Following are some examples that show how to create the directory.  The
+      examples assume your :term:`Source Directory` is named ``poky``:
+
+         -  Create the Build Directory inside your Source Directory and let
+            the name of the Build Directory default to ``build``:
+
+            .. code-block:: shell
+
+               $ cd $HOME/poky
+               $ source oe-init-build-env
+
+         -  Create the Build Directory inside your home directory and
+            specifically name it ``test-builds``:
+
+            .. code-block:: shell
+
+               $ cd $HOME
+               $ source poky/oe-init-build-env test-builds
+
+         -  Provide a directory path and specifically name the Build
+            Directory. Any intermediate folders in the pathname must exist.
+            This next example creates a Build Directory named
+            ``YP-POKYVERSION`` in your home directory within the existing
+            directory ``mybuilds``:
+
+            .. code-block:: shell
+
+               $ cd $HOME
+               $ source $HOME/poky/oe-init-build-env $HOME/mybuilds/YP-POKYVERSION
+
+      .. note::
+
+         By default, the Build Directory contains :term:`TMPDIR` , which is a
+         temporary directory the build system uses for its work. TMPDIR cannot
+         be under NFS. Thus, by default, the Build Directory cannot be under
+         NFS. However, if you need the Build Directory to be under NFS, you can
+         set this up by setting TMPDIR in your local.conf file to use a local
+         drive. Doing so effectively separates TMPDIR from TOPDIR , which is the
+         Build Directory.
+
+   Build Host
+      The system used to build images in a Yocto Project Development
+      environment. The build system is sometimes referred to as the development
+      host.
+
+   Classes
+      Files that provide for logic encapsulation and inheritance so that
+      commonly used patterns can be defined once and then easily used in
+      multiple recipes. For reference information on the Yocto Project classes,
+      see the ":ref:`ref-manual/ref-classes:Classes`" chapter. Class files end with the
+      ``.bbclass`` filename extension.
+
+   Configuration File
+      Files that hold global definitions of variables, user-defined variables,
+      and hardware configuration information. These files tell the OpenEmbedded
+      build system what to build and what to put into the image to support a
+      particular platform.
+
+      Configuration files end with a ``.conf`` filename extension. The
+      :file:`conf/local.conf` configuration file in the :term:`Build Directory`
+      contains user-defined variables that affect every build. The
+      :file:`meta-poky/conf/distro/poky.conf` configuration file defines Yocto
+      "distro" configuration variables used only when building with this
+      policy. Machine configuration files, which are located throughout the
+      :term:`Source Directory`, define variables for specific hardware and are
+      only used when building for that target (e.g. the
+      :file:`machine/beaglebone.conf` configuration file defines variables for
+      the Texas Instruments ARM Cortex-A8 development board).
+
+   Container Layer
+      Layers that hold other layers. An example of a container layer is
+      OpenEmbedded's `meta-openembedded
+      <https://github.com/openembedded/meta-openembedded>`_ layer. The
+      ``meta-openembedded`` layer contains many ``meta-*`` layers.
+
+   Cross-Development Toolchain
+      In general, a cross-development toolchain is a collection of software
+      development tools and utilities that run on one architecture and allow you
+      to develop software for a different, or targeted, architecture. These
+      toolchains contain cross-compilers, linkers, and debuggers that are
+      specific to the target architecture.
+
+      The Yocto Project supports two different cross-development toolchains:
+
+      - A toolchain only used by and within BitBake when building an image for a
+        target architecture.
+
+      - A relocatable toolchain used outside of BitBake by developers when
+        developing applications that will run on a targeted device.
+
+      Creation of these toolchains is simple and automated. For information on
+      toolchain concepts as they apply to the Yocto Project, see the
+      ":ref:`overview-manual/overview-manual-concepts:Cross-Development
+      Toolchain Generation`" section in the Yocto Project Overview and Concepts
+      Manual. You can also find more information on using the relocatable
+      toolchain in the :ref:`sdk-manual/sdk-manual:Yocto Project Application
+      Development and the Extensible Software Development Kit (eSDK)` manual.
+
+   Extensible Software Development Kit (eSDK)
+      A custom SDK for application developers. This eSDK allows developers to
+      incorporate their library and programming changes back into the image to
+      make their code available to other application developers.
+
+      For information on the eSDK, see the :ref:`sdk-manual/sdk-manual:Yocto
+      Project Application Development and the Extensible Software Development
+      Kit (eSDK)` manual.
+
+   Image
+      An image is an artifact of the BitBake build process given a collection of
+      recipes and related Metadata. Images are the binary output that run on
+      specific hardware or QEMU and are used for specific use-cases. For a list
+      of the supported image types that the Yocto Project provides, see the
+      ":ref:`ref-manual/ref-images:Images`" chapter.
+
+   Layer
+      A collection of related recipes. Layers allow you to consolidate related
+      metadata to customize your build. Layers also isolate information used
+      when building for multiple architectures.  Layers are hierarchical in
+      their ability to override previous specifications. You can include any
+      number of available layers from the Yocto Project and customize the build
+      by adding your layers after them. You can search the Layer Index for
+      layers used within Yocto Project.
+
+      For introductory information on layers, see the
+      ":ref:`overview-manual/overview-manual-yp-intro:The Yocto Project Layer
+      Model`" section in the Yocto Project Overview and Concepts Manual. For
+      more detailed information on layers, see the
+      ":ref:`dev-manual/dev-manual-common-tasks:Understanding and Creating
+      Layers`" section in the Yocto Project Development Tasks Manual. For a
+      discussion specifically on BSP Layers, see the ":ref:`bsp-guide/bsp:BSP
+      Layers`" section in the Yocto Project Board Support Packages (BSP)
+      Developer's Guide.
+
+   Metadata
+      A key element of the Yocto Project is the Metadata that
+      is used to construct a Linux distribution and is contained in the
+      files that the :term:`OpenEmbedded Build System`
+      parses when building an image. In general, Metadata includes recipes,
+      configuration files, and other information that refers to the build
+      instructions themselves, as well as the data used to control what
+      things get built and the effects of the build. Metadata also includes
+      commands and data used to indicate what versions of software are
+      used, from where they are obtained, and changes or additions to the
+      software itself (patches or auxiliary files) that are used to fix
+      bugs or customize the software for use in a particular situation.
+      OpenEmbedded-Core is an important set of validated metadata.
+
+      In the context of the kernel ("kernel Metadata"), the term refers to
+      the kernel config fragments and features contained in the
+      :yocto_git:`yocto-kernel-cache </cgit/cgit.cgi/yocto-kernel-cache>`
+      Git repository.
+
+   OpenEmbedded-Core (OE-Core)
+      OE-Core is metadata comprised of
+      foundational recipes, classes, and associated files that are meant to
+      be common among many different OpenEmbedded-derived systems,
+      including the Yocto Project. OE-Core is a curated subset of an
+      original repository developed by the OpenEmbedded community that has
+      been pared down into a smaller, core set of continuously validated
+      recipes. The result is a tightly controlled and an quality-assured
+      core set of recipes.
+
+      You can see the Metadata in the ``meta`` directory of the Yocto
+      Project :yocto_git:`Source Repositories <>`.
+
+   OpenEmbedded Build System
+      The build system specific to the Yocto
+      Project. The OpenEmbedded build system is based on another project
+      known as "Poky", which uses :term:`BitBake` as the task
+      executor. Throughout the Yocto Project documentation set, the
+      OpenEmbedded build system is sometimes referred to simply as "the
+      build system". If other build systems, such as a host or target build
+      system are referenced, the documentation clearly states the
+      difference.
+
+      .. note::
+
+         For some historical information about Poky, see the
+         Poky
+         term.
+
+   Package
+      In the context of the Yocto Project, this term refers to a
+      recipe's packaged output produced by BitBake (i.e. a "baked recipe").
+      A package is generally the compiled binaries produced from the
+      recipe's sources. You "bake" something by running it through BitBake.
+
+      It is worth noting that the term "package" can, in general, have
+      subtle meanings. For example, the packages referred to in the
+      "`Required Packages for the Build
+      Host <#required-packages-for-the-build-host>`__" section are compiled
+      binaries that, when installed, add functionality to your Linux
+      distribution.
+
+      Another point worth noting is that historically within the Yocto
+      Project, recipes were referred to as packages - thus, the existence
+      of several BitBake variables that are seemingly mis-named, (e.g.
+      :term:`PR`, :term:`PV`, and
+      :term:`PE`).
+
+   Package Groups
+      Arbitrary groups of software Recipes. You use
+      package groups to hold recipes that, when built, usually accomplish a
+      single task. For example, a package group could contain the recipes
+      for a company's proprietary or value-add software. Or, the package
+      group could contain the recipes that enable graphics. A package group
+      is really just another recipe. Because package group files are
+      recipes, they end with the ``.bb`` filename extension.
+
+   Poky
+      Poky, which is pronounced *Pock*-ee, is a reference embedded
+      distribution and a reference test configuration. Poky provides the
+      following:
+
+      -  A base-level functional distro used to illustrate how to customize
+         a distribution.
+
+      -  A means by which to test the Yocto Project components (i.e. Poky
+         is used to validate the Yocto Project).
+
+      -  A vehicle through which you can download the Yocto Project.
+
+      Poky is not a product level distro. Rather, it is a good starting
+      point for customization.
+
+      .. note::
+
+         Poky began as an open-source project initially developed by
+         OpenedHand. OpenedHand developed Poky from the existing
+         OpenEmbedded build system to create a commercially supportable
+         build system for embedded Linux. After Intel Corporation acquired
+         OpenedHand, the poky project became the basis for the Yocto
+         Project's build system.
+
+   Recipe
+      A set of instructions for building packages. A recipe
+      describes where you get source code, which patches to apply, how to
+      configure the source, how to compile it and so on. Recipes also
+      describe dependencies for libraries or for other recipes. Recipes
+      represent the logical unit of execution, the software to build, the
+      images to build, and use the ``.bb`` file extension.
+
+   Reference Kit
+      A working example of a system, which includes a
+      :term:`BSP<Board Support Package (BSP)>` as well as a
+      :term:`build host<Build Host>` and other components, that can
+      work on specific hardware.
+
+   Source Directory
+     This term refers to the directory structure
+     created as a result of creating a local copy of the ``poky`` Git
+     repository ``git://git.yoctoproject.org/poky`` or expanding a
+     released ``poky`` tarball.
+
+     .. note::
+
+        Creating a local copy of the
+        poky
+        Git repository is the recommended method for setting up your
+        Source Directory.
+
+     Sometimes you might hear the term "poky directory" used to refer to
+     this directory structure.
+
+     .. note::
+
+        The OpenEmbedded build system does not support file or directory
+        names that contain spaces. Be sure that the Source Directory you
+        use does not contain these types of names.
+
+     The Source Directory contains BitBake, Documentation, Metadata and
+     other files that all support the Yocto Project. Consequently, you
+     must have the Source Directory in place on your development system in
+     order to do any development using the Yocto Project.
+
+     When you create a local copy of the Git repository, you can name the
+     repository anything you like. Throughout much of the documentation,
+     "poky" is used as the name of the top-level folder of the local copy
+     of the poky Git repository. So, for example, cloning the ``poky`` Git
+     repository results in a local Git repository whose top-level folder
+     is also named "poky".
+
+     While it is not recommended that you use tarball expansion to set up
+     the Source Directory, if you do, the top-level directory name of the
+     Source Directory is derived from the Yocto Project release tarball.
+     For example, downloading and unpacking
+     :yocto_dl:`/releases/yocto/&DISTRO_REL_TAG;/&YOCTO_POKY;.tar.bz2`
+     results in a Source Directory whose root folder is named ``poky``.
+
+     It is important to understand the differences between the Source
+     Directory created by unpacking a released tarball as compared to
+     cloning ``git://git.yoctoproject.org/poky``. When you unpack a
+     tarball, you have an exact copy of the files based on the time of
+     release - a fixed release point. Any changes you make to your local
+     files in the Source Directory are on top of the release and will
+     remain local only. On the other hand, when you clone the ``poky`` Git
+     repository, you have an active development repository with access to
+     the upstream repository's branches and tags. In this case, any local
+     changes you make to the local Source Directory can be later applied
+     to active development branches of the upstream ``poky`` Git
+     repository.
+
+     For more information on concepts related to Git repositories,
+     branches, and tags, see the
+     ":ref:`overview-manual/overview-manual-development-environment:repositories, tags, and branches`"
+     section in the Yocto Project Overview and Concepts Manual.
+
+   Task
+      A unit of execution for BitBake (e.g.
+      :ref:`ref-tasks-compile`,
+      :ref:`ref-tasks-fetch`,
+      :ref:`ref-tasks-patch`, and so forth).
+
+   Toaster
+      A web interface to the Yocto Project's :term:`OpenEmbedded Build System`.
+      The interface enables you to
+      configure and run your builds. Information about builds is collected
+      and stored in a database. For information on Toaster, see the
+      :doc:`../toaster-manual/toaster-manual`.
+
+   Upstream
+      A reference to source code or repositories that are not
+      local to the development system but located in a master area that is
+      controlled by the maintainer of the source code. For example, in
+      order for a developer to work on a particular piece of code, they
+      need to first get a copy of it from an "upstream" source.
diff --git a/documentation/ref-manual/ref-terms.xml b/documentation/ref-manual/ref-terms.xml
index 722fa7ee27..2a0452bd78 100644
--- a/documentation/ref-manual/ref-terms.xml
+++ b/documentation/ref-manual/ref-terms.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-terms'>
 <title>Yocto Project Terms</title>
@@ -364,7 +365,7 @@
                 You use package groups to hold recipes that, when built,
                 usually accomplish a single task.
                 For example, a package group could contain the recipes for a
-                company’s proprietary or value-add software.
+                company's proprietary or value-add software.
                 Or, the package group could contain the recipes that enable
                 graphics.
                 A package group is really just another recipe.
diff --git a/documentation/ref-manual/ref-variables.rst b/documentation/ref-manual/ref-variables.rst
new file mode 100644
index 0000000000..c49c208bc0
--- /dev/null
+++ b/documentation/ref-manual/ref-variables.rst
@@ -0,0 +1,8899 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+******************
+Variables Glossary
+******************
+
+This chapter lists common variables used in the OpenEmbedded build
+system and gives an overview of their function and contents.
+
+`A <#var-ABIEXTENSION>`__ :term:`B` `C <#var-CACHE>`__
+:term:`D` `E <#var-EFI_PROVIDER>`__ `F <#var-FEATURE_PACKAGES>`__
+`G <#var-GCCPIE>`__ `H <#var-HOMEPAGE>`__ `I <#var-ICECC_DISABLED>`__
+`K <#var-KARCH>`__ `L <#var-LABELS>`__ `M <#var-MACHINE>`__
+`N <#var-NATIVELSBSTRING>`__ `O <#var-OBJCOPY>`__ :term:`P`
+`R <#var-RANLIB>`__ :term:`S` :term:`T`
+`U <#var-UBOOT_CONFIG>`__ `V <#var-VOLATILE_LOG_DIR>`__
+`W <#var-WARN_QA>`__ `X <#var-XSERVER>`__
+
+.. glossary::
+
+   ABIEXTENSION
+      Extension to the Application Binary Interface (ABI) field of the GNU
+      canonical architecture name (e.g. "eabi").
+
+      ABI extensions are set in the machine include files. For example, the
+      ``meta/conf/machine/include/arm/arch-arm.inc`` file sets the
+      following extension:
+      ::
+
+         ABIEXTENSION = "eabi"
+
+   ALLOW_EMPTY
+      Specifies whether to produce an output package even if it is empty.
+      By default, BitBake does not produce empty packages. This default
+      behavior can cause issues when there is an
+      :term:`RDEPENDS` or some other hard runtime
+      requirement on the existence of the package.
+
+      Like all package-controlling variables, you must always use them in
+      conjunction with a package name override, as in:
+      ::
+
+         ALLOW_EMPTY_${PN} = "1"
+         ALLOW_EMPTY_${PN}-dev = "1"
+         ALLOW_EMPTY_${PN}-staticdev = "1"
+
+   ALTERNATIVE
+      Lists commands in a package that need an alternative binary naming
+      scheme. Sometimes the same command is provided in multiple packages.
+      When this occurs, the OpenEmbedded build system needs to use the
+      alternatives system to create a different binary naming scheme so the
+      commands can co-exist.
+
+      To use the variable, list out the package's commands that also exist
+      as part of another package. For example, if the ``busybox`` package
+      has four commands that also exist as part of another package, you
+      identify them as follows:
+      ::
+
+         ALTERNATIVE_busybox = "sh sed test bracket"
+
+      For more information on the alternatives system, see the
+      ":ref:`update-alternatives.bbclass <ref-classes-update-alternatives>`"
+      section.
+
+   ALTERNATIVE_LINK_NAME
+      Used by the alternatives system to map duplicated commands to actual
+      locations. For example, if the ``bracket`` command provided by the
+      ``busybox`` package is duplicated through another package, you must
+      use the ``ALTERNATIVE_LINK_NAME`` variable to specify the actual
+      location:
+      ::
+
+         ALTERNATIVE_LINK_NAME[bracket] = "/usr/bin/["
+
+      In this example, the binary for the ``bracket`` command (i.e. ``[``)
+      from the ``busybox`` package resides in ``/usr/bin/``.
+
+      .. note::
+
+         If ALTERNATIVE_LINK_NAME is not defined, it defaults to ${bindir}/ name.
+
+      For more information on the alternatives system, see the
+      ":ref:`update-alternatives.bbclass <ref-classes-update-alternatives>`"
+      section.
+
+   ALTERNATIVE_PRIORITY
+      Used by the alternatives system to create default priorities for
+      duplicated commands. You can use the variable to create a single
+      default regardless of the command name or package, a default for
+      specific duplicated commands regardless of the package, or a default
+      for specific commands tied to particular packages. Here are the
+      available syntax forms:
+      ::
+
+         ALTERNATIVE_PRIORITY = "priority"
+         ALTERNATIVE_PRIORITY[name] = "priority"
+         ALTERNATIVE_PRIORITY_pkg[name] = "priority"
+
+      For more information on the alternatives system, see the
+      ":ref:`update-alternatives.bbclass <ref-classes-update-alternatives>`"
+      section.
+
+   ALTERNATIVE_TARGET
+      Used by the alternatives system to create default link locations for
+      duplicated commands. You can use the variable to create a single
+      default location for all duplicated commands regardless of the
+      command name or package, a default for specific duplicated commands
+      regardless of the package, or a default for specific commands tied to
+      particular packages. Here are the available syntax forms:
+      ::
+
+         ALTERNATIVE_TARGET = "target"
+         ALTERNATIVE_TARGET[name] = "target"
+         ALTERNATIVE_TARGET_pkg[name] = "target"
+
+      .. note::
+
+         If ``ALTERNATIVE_TARGET`` is not defined, it inherits the value
+         from the :term:`ALTERNATIVE_LINK_NAME` variable.
+
+         If ``ALTERNATIVE_LINK_NAME`` and ``ALTERNATIVE_TARGET`` are the
+         same, the target for ``ALTERNATIVE_TARGET`` has "``.{BPN}``"
+         appended to it.
+
+         Finally, if the file referenced has not been renamed, the
+         alternatives system will rename it to avoid the need to rename
+         alternative files in the :ref:`ref-tasks-install`
+         task while retaining support for the command if necessary.
+
+      For more information on the alternatives system, see the
+      ":ref:`update-alternatives.bbclass <ref-classes-update-alternatives>`"
+      section.
+
+   APPEND
+      An override list of append strings for each target specified with
+      :term:`LABELS`.
+
+      See the :ref:`grub-efi <ref-classes-grub-efi>` class for more
+      information on how this variable is used.
+
+   AR
+      The minimal command and arguments used to run ``ar``.
+
+   ARCHIVER_MODE
+      When used with the :ref:`archiver <ref-classes-archiver>` class,
+      determines the type of information used to create a released archive.
+      You can use this variable to create archives of patched source,
+      original source, configured source, and so forth by employing the
+      following variable flags (varflags):
+      ::
+
+         ARCHIVER_MODE[src] = "original"                   # Uses original (unpacked) source files.
+         ARCHIVER_MODE[src] = "patched"                    # Uses patched source files. This is the default.
+         ARCHIVER_MODE[src] = "configured"                 # Uses configured source files.
+         ARCHIVER_MODE[diff] = "1"                         # Uses patches between do_unpack and do_patch.
+         ARCHIVER_MODE[diff-exclude] ?= "file file ..."    # Lists files and directories to exclude from diff.
+         ARCHIVER_MODE[dumpdata] = "1"                     # Uses environment data.
+         ARCHIVER_MODE[recipe] = "1"                       # Uses recipe and include files.
+         ARCHIVER_MODE[srpm] = "1"                         # Uses RPM package files.
+
+      For information on how the variable works, see the
+      ``meta/classes/archiver.bbclass`` file in the :term:`Source Directory`.
+
+   AS
+      Minimal command and arguments needed to run the assembler.
+
+   ASSUME_PROVIDED
+      Lists recipe names (:term:`PN` values) BitBake does not
+      attempt to build. Instead, BitBake assumes these recipes have already
+      been built.
+
+      In OpenEmbedded-Core, ``ASSUME_PROVIDED`` mostly specifies native
+      tools that should not be built. An example is ``git-native``, which
+      when specified, allows for the Git binary from the host to be used
+      rather than building ``git-native``.
+
+   ASSUME_SHLIBS
+      Provides additional ``shlibs`` provider mapping information, which
+      adds to or overwrites the information provided automatically by the
+      system. Separate multiple entries using spaces.
+
+      As an example, use the following form to add an ``shlib`` provider of
+      shlibname in packagename with the optional version:
+      ::
+
+         shlibname:packagename[_version]
+
+      Here is an example that adds a shared library named ``libEGL.so.1``
+      as being provided by the ``libegl-implementation`` package:
+      ::
+
+         ASSUME_SHLIBS = "libEGL.so.1:libegl-implementation"
+
+   AUTHOR
+      The email address used to contact the original author or authors in
+      order to send patches and forward bugs.
+
+   AUTO_LIBNAME_PKGS
+      When the :ref:`debian <ref-classes-debian>` class is inherited,
+      which is the default behavior, ``AUTO_LIBNAME_PKGS`` specifies which
+      packages should be checked for libraries and renamed according to
+      Debian library package naming.
+
+      The default value is "${PACKAGES}", which causes the debian class to
+      act on all packages that are explicitly generated by the recipe.
+
+   AUTO_SYSLINUXMENU
+      Enables creating an automatic menu for the syslinux bootloader. You
+      must set this variable in your recipe. The
+      :ref:`syslinux <ref-classes-syslinux>` class checks this variable.
+
+   AUTOREV
+      When ``SRCREV`` is set to the value of this variable, it specifies to
+      use the latest source revision in the repository. Here is an example:
+      ::
+
+         SRCREV = "${AUTOREV}"
+
+      If you use the previous statement to retrieve the latest version of
+      software, you need to be sure :term:`PV` contains
+      ``${``\ :term:`SRCPV`\ ``}``. For example, suppose you
+      have a kernel recipe that inherits the
+      :ref:`kernel <ref-classes-kernel>` class and you use the previous
+      statement. In this example, ``${SRCPV}`` does not automatically get
+      into ``PV``. Consequently, you need to change ``PV`` in your recipe
+      so that it does contain ``${SRCPV}``.
+
+      For more information see the
+      ":ref:`dev-manual/dev-manual-common-tasks:automatically incrementing a package version number`"
+      section in the Yocto Project Development Tasks Manual.
+
+   AVAILABLE_LICENSES
+      List of licenses found in the directories specified by
+      :term:`COMMON_LICENSE_DIR` and
+      :term:`LICENSE_PATH`.
+
+      .. note::
+
+         It is assumed that all changes to
+         COMMON_LICENSE_DIR
+         and
+         LICENSE_PATH
+         have been done before
+         AVAILABLE_LICENSES
+         is defined (in
+         license.bbclass
+         ).
+
+   AVAILTUNES
+      The list of defined CPU and Application Binary Interface (ABI)
+      tunings (i.e. "tunes") available for use by the OpenEmbedded build
+      system.
+
+      The list simply presents the tunes that are available. Not all tunes
+      may be compatible with a particular machine configuration, or with
+      each other in a
+      :ref:`Multilib <dev-manual/dev-manual-common-tasks:combining multiple versions of library files into one image>`
+      configuration.
+
+      To add a tune to the list, be sure to append it with spaces using the
+      "+=" BitBake operator. Do not simply replace the list by using the
+      "=" operator. See the
+      ":ref:`Basic Syntax <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:basic syntax>`" section in the BitBake
+      User Manual for more information.
+
+   B
+      The directory within the :term:`Build Directory` in
+      which the OpenEmbedded build system places generated objects during a
+      recipe's build process. By default, this directory is the same as the
+      :term:`S` directory, which is defined as:
+      ::
+
+         S = "${WORKDIR}/${BP}"
+
+      You can separate the (``S``) directory and the directory pointed to
+      by the ``B`` variable. Most Autotools-based recipes support
+      separating these directories. The build system defaults to using
+      separate directories for ``gcc`` and some kernel recipes.
+
+   BAD_RECOMMENDATIONS
+      Lists "recommended-only" packages to not install. Recommended-only
+      packages are packages installed only through the
+      :term:`RRECOMMENDS` variable. You can prevent any
+      of these "recommended" packages from being installed by listing them
+      with the ``BAD_RECOMMENDATIONS`` variable:
+      ::
+
+         BAD_RECOMMENDATIONS = "package_name package_name package_name ..."
+
+      You can set this variable globally in your ``local.conf`` file or you
+      can attach it to a specific image recipe by using the recipe name
+      override:
+      ::
+
+         BAD_RECOMMENDATIONS_pn-target_image = "package_name"
+
+      It is important to realize that if you choose to not install packages
+      using this variable and some other packages are dependent on them
+      (i.e. listed in a recipe's :term:`RDEPENDS`
+      variable), the OpenEmbedded build system ignores your request and
+      will install the packages to avoid dependency errors.
+
+      Support for this variable exists only when using the IPK and RPM
+      packaging backend. Support does not exist for DEB.
+
+      See the :term:`NO_RECOMMENDATIONS` and the
+      :term:`PACKAGE_EXCLUDE` variables for related
+      information.
+
+   BASE_LIB
+      The library directory name for the CPU or Application Binary
+      Interface (ABI) tune. The ``BASE_LIB`` applies only in the Multilib
+      context. See the ":ref:`dev-manual/dev-manual-common-tasks:combining multiple versions of library files into one image`"
+      section in the Yocto Project Development Tasks Manual for information
+      on Multilib.
+
+      The ``BASE_LIB`` variable is defined in the machine include files in
+      the :term:`Source Directory`. If Multilib is not
+      being used, the value defaults to "lib".
+
+   BASE_WORKDIR
+      Points to the base of the work directory for all recipes. The default
+      value is "${TMPDIR}/work".
+
+   BB_ALLOWED_NETWORKS
+      Specifies a space-delimited list of hosts that the fetcher is allowed
+      to use to obtain the required source code. Following are
+      considerations surrounding this variable:
+
+      -  This host list is only used if ``BB_NO_NETWORK`` is either not set
+         or set to "0".
+
+      -  Limited support for wildcard matching against the beginning of
+         host names exists. For example, the following setting matches
+         ``git.gnu.org``, ``ftp.gnu.org``, and ``foo.git.gnu.org``.
+         ::
+
+            BB_ALLOWED_NETWORKS = "*.gnu.org"
+
+         .. note::
+
+            The use of the "``*``" character only works at the beginning of
+            a host name and it must be isolated from the remainder of the
+            host name. You cannot use the wildcard character in any other
+            location of the name or combined with the front part of the
+            name.
+
+            For example, ``*.foo.bar`` is supported, while ``*aa.foo.bar``
+            is not.
+
+      -  Mirrors not in the host list are skipped and logged in debug.
+
+      -  Attempts to access networks not in the host list cause a failure.
+
+      Using ``BB_ALLOWED_NETWORKS`` in conjunction with
+      :term:`PREMIRRORS` is very useful. Adding the host
+      you want to use to ``PREMIRRORS`` results in the source code being
+      fetched from an allowed location and avoids raising an error when a
+      host that is not allowed is in a :term:`SRC_URI`
+      statement. This is because the fetcher does not attempt to use the
+      host listed in ``SRC_URI`` after a successful fetch from the
+      ``PREMIRRORS`` occurs.
+
+   BB_DANGLINGAPPENDS_WARNONLY
+      Defines how BitBake handles situations where an append file
+      (``.bbappend``) has no corresponding recipe file (``.bb``). This
+      condition often occurs when layers get out of sync (e.g. ``oe-core``
+      bumps a recipe version and the old recipe no longer exists and the
+      other layer has not been updated to the new version of the recipe
+      yet).
+
+      The default fatal behavior is safest because it is the sane reaction
+      given something is out of sync. It is important to realize when your
+      changes are no longer being applied.
+
+      You can change the default behavior by setting this variable to "1",
+      "yes", or "true" in your ``local.conf`` file, which is located in the
+      :term:`Build Directory`: Here is an example:
+      ::
+
+         BB_DANGLINGAPPENDS_WARNONLY = "1"
+
+   BB_DISKMON_DIRS
+      Monitors disk space and available inodes during the build and allows
+      you to control the build based on these parameters.
+
+      Disk space monitoring is disabled by default. To enable monitoring,
+      add the ``BB_DISKMON_DIRS`` variable to your ``conf/local.conf`` file
+      found in the :term:`Build Directory`. Use the
+      following form:
+      ::
+
+         BB_DISKMON_DIRS = "action,dir,threshold [...]"
+
+         where:
+
+            action is:
+               ABORT:     Immediately abort the build when
+                          a threshold is broken.
+               STOPTASKS: Stop the build after the currently
+                          executing tasks have finished when
+                          a threshold is broken.
+               WARN:      Issue a warning but continue the
+                          build when a threshold is broken.
+                          Subsequent warnings are issued as
+                          defined by the BB_DISKMON_WARNINTERVAL
+                          variable, which must be defined in
+                          the conf/local.conf file.
+
+            dir is:
+               Any directory you choose. You can specify one or
+               more directories to monitor by separating the
+               groupings with a space.  If two directories are
+               on the same device, only the first directory
+               is monitored.
+
+            threshold is:
+               Either the minimum available disk space,
+               the minimum number of free inodes, or
+               both.  You must specify at least one.  To
+               omit one or the other, simply omit the value.
+               Specify the threshold using G, M, K for Gbytes,
+               Mbytes, and Kbytes, respectively. If you do
+               not specify G, M, or K, Kbytes is assumed by
+               default.  Do not use GB, MB, or KB.
+
+      Here are some examples:
+      ::
+
+         BB_DISKMON_DIRS = "ABORT,${TMPDIR},1G,100K WARN,${SSTATE_DIR},1G,100K"
+         BB_DISKMON_DIRS = "STOPTASKS,${TMPDIR},1G"
+         BB_DISKMON_DIRS = "ABORT,${TMPDIR},,100K"
+
+      The first example works only if you also provide the
+      :term:`BB_DISKMON_WARNINTERVAL`
+      variable in the ``conf/local.conf``. This example causes the build
+      system to immediately abort when either the disk space in
+      ``${TMPDIR}`` drops below 1 Gbyte or the available free inodes drops
+      below 100 Kbytes. Because two directories are provided with the
+      variable, the build system also issue a warning when the disk space
+      in the ``${SSTATE_DIR}`` directory drops below 1 Gbyte or the number
+      of free inodes drops below 100 Kbytes. Subsequent warnings are issued
+      during intervals as defined by the ``BB_DISKMON_WARNINTERVAL``
+      variable.
+
+      The second example stops the build after all currently executing
+      tasks complete when the minimum disk space in the ``${TMPDIR}``
+      directory drops below 1 Gbyte. No disk monitoring occurs for the free
+      inodes in this case.
+
+      The final example immediately aborts the build when the number of
+      free inodes in the ``${TMPDIR}`` directory drops below 100 Kbytes. No
+      disk space monitoring for the directory itself occurs in this case.
+
+   BB_DISKMON_WARNINTERVAL
+      Defines the disk space and free inode warning intervals. To set these
+      intervals, define the variable in your ``conf/local.conf`` file in
+      the :term:`Build Directory`.
+
+      If you are going to use the ``BB_DISKMON_WARNINTERVAL`` variable, you
+      must also use the :term:`BB_DISKMON_DIRS`
+      variable and define its action as "WARN". During the build,
+      subsequent warnings are issued each time disk space or number of free
+      inodes further reduces by the respective interval.
+
+      If you do not provide a ``BB_DISKMON_WARNINTERVAL`` variable and you
+      do use ``BB_DISKMON_DIRS`` with the "WARN" action, the disk
+      monitoring interval defaults to the following:
+      ::
+
+         BB_DISKMON_WARNINTERVAL = "50M,5K"
+
+      When specifying the variable in your configuration file, use the
+      following form:
+      ::
+
+         BB_DISKMON_WARNINTERVAL = "disk_space_interval,disk_inode_interval"
+
+         where:
+
+            disk_space_interval is:
+               An interval of memory expressed in either
+               G, M, or K for Gbytes, Mbytes, or Kbytes,
+               respectively. You cannot use GB, MB, or KB.
+
+            disk_inode_interval is:
+               An interval of free inodes expressed in either
+               G, M, or K for Gbytes, Mbytes, or Kbytes,
+               respectively. You cannot use GB, MB, or KB.
+
+      Here is an example:
+      ::
+
+         BB_DISKMON_DIRS = "WARN,${SSTATE_DIR},1G,100K"
+         BB_DISKMON_WARNINTERVAL = "50M,5K"
+
+      These variables cause the
+      OpenEmbedded build system to issue subsequent warnings each time the
+      available disk space further reduces by 50 Mbytes or the number of
+      free inodes further reduces by 5 Kbytes in the ``${SSTATE_DIR}``
+      directory. Subsequent warnings based on the interval occur each time
+      a respective interval is reached beyond the initial warning (i.e. 1
+      Gbytes and 100 Kbytes).
+
+   BB_GENERATE_MIRROR_TARBALLS
+      Causes tarballs of the source control repositories (e.g. Git
+      repositories), including metadata, to be placed in the
+      :term:`DL_DIR` directory.
+
+      For performance reasons, creating and placing tarballs of these
+      repositories is not the default action by the OpenEmbedded build
+      system.
+      ::
+
+         BB_GENERATE_MIRROR_TARBALLS = "1"
+
+      Set this variable in your
+      ``local.conf`` file in the :term:`Build Directory`.
+
+      Once you have the tarballs containing your source files, you can
+      clean up your ``DL_DIR`` directory by deleting any Git or other
+      source control work directories.
+
+   BB_NUMBER_THREADS
+      The maximum number of tasks BitBake should run in parallel at any one
+      time. The OpenEmbedded build system automatically configures this
+      variable to be equal to the number of cores on the build system. For
+      example, a system with a dual core processor that also uses
+      hyper-threading causes the ``BB_NUMBER_THREADS`` variable to default
+      to "4".
+
+      For single socket systems (i.e. one CPU), you should not have to
+      override this variable to gain optimal parallelism during builds.
+      However, if you have very large systems that employ multiple physical
+      CPUs, you might want to make sure the ``BB_NUMBER_THREADS`` variable
+      is not set higher than "20".
+
+      For more information on speeding up builds, see the
+      ":ref:`dev-manual/dev-manual-common-tasks:speeding up a build`"
+      section in the Yocto Project Development Tasks Manual.
+
+   BB_SERVER_TIMEOUT
+      Specifies the time (in seconds) after which to unload the BitBake
+      server due to inactivity. Set ``BB_SERVER_TIMEOUT`` to determine how
+      long the BitBake server stays resident between invocations.
+
+      For example, the following statement in your ``local.conf`` file
+      instructs the server to be unloaded after 20 seconds of inactivity:
+      ::
+
+         BB_SERVER_TIMEOUT = "20"
+
+      If you want the server to never be unloaded,
+      set ``BB_SERVER_TIMEOUT`` to "-1".
+
+   BBCLASSEXTEND
+      Allows you to extend a recipe so that it builds variants of the
+      software. Common variants for recipes exist such as "natives" like
+      ``quilt-native``, which is a copy of Quilt built to run on the build
+      system; "crosses" such as ``gcc-cross``, which is a compiler built to
+      run on the build machine but produces binaries that run on the target
+      :term:`MACHINE`; "nativesdk", which targets the SDK
+      machine instead of ``MACHINE``; and "mulitlibs" in the form
+      "``multilib:``\ multilib_name".
+
+      To build a different variant of the recipe with a minimal amount of
+      code, it usually is as simple as adding the following to your recipe:
+      ::
+
+         BBCLASSEXTEND =+ "native nativesdk"
+         BBCLASSEXTEND =+ "multilib:multilib_name"
+
+      .. note::
+
+         Internally, the ``BBCLASSEXTEND`` mechanism generates recipe
+         variants by rewriting variable values and applying overrides such
+         as ``_class-native``. For example, to generate a native version of
+         a recipe, a :term:`DEPENDS` on "foo" is rewritten
+         to a ``DEPENDS`` on "foo-native".
+
+         Even when using ``BBCLASSEXTEND``, the recipe is only parsed once.
+         Parsing once adds some limitations. For example, it is not
+         possible to include a different file depending on the variant,
+         since ``include`` statements are processed when the recipe is
+         parsed.
+
+   BBFILE_COLLECTIONS
+      Lists the names of configured layers. These names are used to find
+      the other ``BBFILE_*`` variables. Typically, each layer will append
+      its name to this variable in its ``conf/layer.conf`` file.
+
+   BBFILE_PATTERN
+      Variable that expands to match files from
+      :term:`BBFILES` in a particular layer. This variable
+      is used in the ``conf/layer.conf`` file and must be suffixed with the
+      name of the specific layer (e.g. ``BBFILE_PATTERN_emenlow``).
+
+   BBFILE_PRIORITY
+      Assigns the priority for recipe files in each layer.
+
+      This variable is useful in situations where the same recipe appears
+      in more than one layer. Setting this variable allows you to
+      prioritize a layer against other layers that contain the same recipe
+      - effectively letting you control the precedence for the multiple
+      layers. The precedence established through this variable stands
+      regardless of a recipe's version (:term:`PV` variable). For
+      example, a layer that has a recipe with a higher ``PV`` value but for
+      which the ``BBFILE_PRIORITY`` is set to have a lower precedence still
+      has a lower precedence.
+
+      A larger value for the ``BBFILE_PRIORITY`` variable results in a
+      higher precedence. For example, the value 6 has a higher precedence
+      than the value 5. If not specified, the ``BBFILE_PRIORITY`` variable
+      is set based on layer dependencies (see the ``LAYERDEPENDS`` variable
+      for more information. The default priority, if unspecified for a
+      layer with no dependencies, is the lowest defined priority + 1 (or 1
+      if no priorities are defined).
+
+      .. tip::
+
+         You can use the command
+         bitbake-layers show-layers
+         to list all configured layers along with their priorities.
+
+   BBFILES
+      A space-separated list of recipe files BitBake uses to build
+      software.
+
+      When specifying recipe files, you can pattern match using Python's
+      `glob <https://docs.python.org/3/library/glob.html>`_ syntax.
+      For details on the syntax, see the documentation by following the
+      previous link.
+
+   BBFILES_DYNAMIC
+      Activates content when identified layers are present. You identify
+      the layers by the collections that the layers define.
+
+      Use the ``BBFILES_DYNAMIC`` variable to avoid ``.bbappend`` files
+      whose corresponding ``.bb`` file is in a layer that attempts to
+      modify other layers through ``.bbappend`` but does not want to
+      introduce a hard dependency on those other layers.
+
+      Use the following form for ``BBFILES_DYNAMIC``:
+      collection_name:filename_pattern The following example identifies two
+      collection names and two filename patterns:
+      ::
+
+         BBFILES_DYNAMIC += " \
+            clang-layer:${LAYERDIR}/bbappends/meta-clang/*/*/*.bbappend \
+            core:${LAYERDIR}/bbappends/openembedded-core/meta/*/*/*.bbappend \
+            "
+
+      This next example shows an error message that occurs because invalid
+      entries are found, which cause parsing to abort:
+      ::
+
+         ERROR: BBFILES_DYNAMIC entries must be of the form <collection name>:<filename pattern>, not:
+             /work/my-layer/bbappends/meta-security-isafw/*/*/*.bbappend
+             /work/my-layer/bbappends/openembedded-core/meta/*/*/*.bbappend
+
+   BBINCLUDELOGS
+      Variable that controls how BitBake displays logs on build failure.
+
+   BBINCLUDELOGS_LINES
+      If :term:`BBINCLUDELOGS` is set, specifies the
+      maximum number of lines from the task log file to print when
+      reporting a failed task. If you do not set ``BBINCLUDELOGS_LINES``,
+      the entire log is printed.
+
+   BBLAYERS
+      Lists the layers to enable during the build. This variable is defined
+      in the ``bblayers.conf`` configuration file in the :term:`Build Directory`.
+      Here is an example:
+      ::
+
+         BBLAYERS = " \
+             /home/scottrif/poky/meta \ /home/scottrif/poky/meta-poky \
+             /home/scottrif/poky/meta-yocto-bsp \
+             /home/scottrif/poky/meta-mykernel \
+             "
+
+      This example enables four layers, one of which is a custom,
+      user-defined layer named ``meta-mykernel``.
+
+   BBMASK
+      Prevents BitBake from processing recipes and recipe append files.
+
+      You can use the ``BBMASK`` variable to "hide" these ``.bb`` and
+      ``.bbappend`` files. BitBake ignores any recipe or recipe append
+      files that match any of the expressions. It is as if BitBake does not
+      see them at all. Consequently, matching files are not parsed or
+      otherwise used by BitBake.
+
+      The values you provide are passed to Python's regular expression
+      compiler. Consequently, the syntax follows Python's Regular
+      Expression (re) syntax. The expressions are compared against the full
+      paths to the files. For complete syntax information, see Python's
+      documentation at https://docs.python.org/3/library/re.html#regular-expression-syntax.
+
+      The following example uses a complete regular expression to tell
+      BitBake to ignore all recipe and recipe append files in the
+      ``meta-ti/recipes-misc/`` directory:
+      ::
+
+         BBMASK = "meta-ti/recipes-misc/"
+
+      If you want to mask out multiple directories or recipes, you can
+      specify multiple regular expression fragments. This next example
+      masks out multiple directories and individual recipes: ::
+
+         BBMASK += "/meta-ti/recipes-misc/ meta-ti/recipes-ti/packagegroup/"
+         BBMASK += "/meta-oe/recipes-support/"
+         BBMASK += "/meta-foo/.*/openldap"
+         BBMASK += "opencv.*\.bbappend"
+         BBMASK += "lzma"
+
+      .. note::
+
+         When specifying a directory name, use the trailing slash character
+         to ensure you match just that directory name.
+
+   BBMULTICONFIG
+      Specifies each additional separate configuration when you are
+      building targets with multiple configurations. Use this variable in
+      your ``conf/local.conf`` configuration file. Specify a
+      multiconfigname for each configuration file you are using. For
+      example, the following line specifies three configuration files:
+      ::
+
+         BBMULTICONFIG = "configA configB configC"
+
+      Each configuration file you
+      use must reside in the :term:`Build Directory`
+      ``conf/multiconfig`` directory (e.g.
+      build_directory\ ``/conf/multiconfig/configA.conf``).
+
+      For information on how to use ``BBMULTICONFIG`` in an environment
+      that supports building targets with multiple configurations, see the
+      ":ref:`dev-building-images-for-multiple-targets-using-multiple-configurations`"
+      section in the Yocto Project Development Tasks Manual.
+
+   BBPATH
+      Used by BitBake to locate ``.bbclass`` and configuration files. This
+      variable is analogous to the ``PATH`` variable.
+
+      .. note::
+
+         If you run BitBake from a directory outside of the
+         Build Directory
+         , you must be sure to set
+         BBPATH
+         to point to the Build Directory. Set the variable as you would any
+         environment variable and then run BitBake:
+         ::
+
+                 $ BBPATH = "build_directory"
+                 $ export BBPATH
+                 $ bitbake target
+
+
+   BBSERVER
+      If defined in the BitBake environment, ``BBSERVER`` points to the
+      BitBake remote server.
+
+      Use the following format to export the variable to the BitBake
+      environment:
+      ::
+
+         export BBSERVER=localhost:$port
+
+      By default, ``BBSERVER`` also appears in
+      :term:`bitbake:BB_HASHBASE_WHITELIST`.
+      Consequently, ``BBSERVER`` is excluded from checksum and dependency
+      data.
+
+   BINCONFIG
+      When inheriting the
+      :ref:`binconfig-disabled <ref-classes-binconfig-disabled>` class,
+      this variable specifies binary configuration scripts to disable in
+      favor of using ``pkg-config`` to query the information. The
+      ``binconfig-disabled`` class will modify the specified scripts to
+      return an error so that calls to them can be easily found and
+      replaced.
+
+      To add multiple scripts, separate them by spaces. Here is an example
+      from the ``libpng`` recipe:
+      ::
+
+         BINCONFIG = "${bindir}/libpng-config ${bindir}/libpng16-config"
+
+   BINCONFIG_GLOB
+      When inheriting the :ref:`binconfig <ref-classes-binconfig>` class,
+      this variable specifies a wildcard for configuration scripts that
+      need editing. The scripts are edited to correct any paths that have
+      been set up during compilation so that they are correct for use when
+      installed into the sysroot and called by the build processes of other
+      recipes.
+
+      .. note::
+
+         The
+         BINCONFIG_GLOB
+         variable uses
+         shell globbing
+         , which is recognition and expansion of wildcards during pattern
+         matching. Shell globbing is very similar to
+         fnmatch
+         and
+         glob
+         .
+
+      For more information on how this variable works, see
+      ``meta/classes/binconfig.bbclass`` in the :term:`Source Directory`.
+      You can also find general
+      information on the class in the
+      ":ref:`binconfig.bbclass <ref-classes-binconfig>`" section.
+
+   BP
+      The base recipe name and version but without any special recipe name
+      suffix (i.e. ``-native``, ``lib64-``, and so forth). ``BP`` is
+      comprised of the following:
+      ::
+
+         ${BPN}-${PV}
+
+   BPN
+      This variable is a version of the :term:`PN` variable with
+      common prefixes and suffixes removed, such as ``nativesdk-``,
+      ``-cross``, ``-native``, and multilib's ``lib64-`` and ``lib32-``.
+      The exact lists of prefixes and suffixes removed are specified by the
+      :term:`MLPREFIX` and
+      :term:`SPECIAL_PKGSUFFIX` variables,
+      respectively.
+
+   BUGTRACKER
+      Specifies a URL for an upstream bug tracking website for a recipe.
+      The OpenEmbedded build system does not use this variable. Rather, the
+      variable is a useful pointer in case a bug in the software being
+      built needs to be manually reported.
+
+   BUILD_ARCH
+      Specifies the architecture of the build host (e.g. ``i686``). The
+      OpenEmbedded build system sets the value of ``BUILD_ARCH`` from the
+      machine name reported by the ``uname`` command.
+
+   BUILD_AS_ARCH
+      Specifies the architecture-specific assembler flags for the build
+      host. By default, the value of ``BUILD_AS_ARCH`` is empty.
+
+   BUILD_CC_ARCH
+      Specifies the architecture-specific C compiler flags for the build
+      host. By default, the value of ``BUILD_CC_ARCH`` is empty.
+
+   BUILD_CCLD
+      Specifies the linker command to be used for the build host when the C
+      compiler is being used as the linker. By default, ``BUILD_CCLD``
+      points to GCC and passes as arguments the value of
+      :term:`BUILD_CC_ARCH`, assuming
+      ``BUILD_CC_ARCH`` is set.
+
+   BUILD_CFLAGS
+      Specifies the flags to pass to the C compiler when building for the
+      build host. When building in the ``-native`` context,
+      :term:`CFLAGS` is set to the value of this variable by
+      default.
+
+   BUILD_CPPFLAGS
+      Specifies the flags to pass to the C preprocessor (i.e. to both the C
+      and the C++ compilers) when building for the build host. When
+      building in the ``-native`` context, :term:`CPPFLAGS`
+      is set to the value of this variable by default.
+
+   BUILD_CXXFLAGS
+      Specifies the flags to pass to the C++ compiler when building for the
+      build host. When building in the ``-native`` context,
+      :term:`CXXFLAGS` is set to the value of this variable
+      by default.
+
+   BUILD_FC
+      Specifies the Fortran compiler command for the build host. By
+      default, ``BUILD_FC`` points to Gfortran and passes as arguments the
+      value of :term:`BUILD_CC_ARCH`, assuming
+      ``BUILD_CC_ARCH`` is set.
+
+   BUILD_LD
+      Specifies the linker command for the build host. By default,
+      ``BUILD_LD`` points to the GNU linker (ld) and passes as arguments
+      the value of :term:`BUILD_LD_ARCH`, assuming
+      ``BUILD_LD_ARCH`` is set.
+
+   BUILD_LD_ARCH
+      Specifies architecture-specific linker flags for the build host. By
+      default, the value of ``BUILD_LD_ARCH`` is empty.
+
+   BUILD_LDFLAGS
+      Specifies the flags to pass to the linker when building for the build
+      host. When building in the ``-native`` context,
+      :term:`LDFLAGS` is set to the value of this variable
+      by default.
+
+   BUILD_OPTIMIZATION
+      Specifies the optimization flags passed to the C compiler when
+      building for the build host or the SDK. The flags are passed through
+      the :term:`BUILD_CFLAGS` and
+      :term:`BUILDSDK_CFLAGS` default values.
+
+      The default value of the ``BUILD_OPTIMIZATION`` variable is "-O2
+      -pipe".
+
+   BUILD_OS
+      Specifies the operating system in use on the build host (e.g.
+      "linux"). The OpenEmbedded build system sets the value of
+      ``BUILD_OS`` from the OS reported by the ``uname`` command - the
+      first word, converted to lower-case characters.
+
+   BUILD_PREFIX
+      The toolchain binary prefix used for native recipes. The OpenEmbedded
+      build system uses the ``BUILD_PREFIX`` value to set the
+      :term:`TARGET_PREFIX` when building for
+      ``native`` recipes.
+
+   BUILD_STRIP
+      Specifies the command to be used to strip debugging symbols from
+      binaries produced for the build host. By default, ``BUILD_STRIP``
+      points to
+      ``${``\ :term:`BUILD_PREFIX`\ ``}strip``.
+
+   BUILD_SYS
+      Specifies the system, including the architecture and the operating
+      system, to use when building for the build host (i.e. when building
+      ``native`` recipes).
+
+      The OpenEmbedded build system automatically sets this variable based
+      on :term:`BUILD_ARCH`,
+      :term:`BUILD_VENDOR`, and
+      :term:`BUILD_OS`. You do not need to set the
+      ``BUILD_SYS`` variable yourself.
+
+   BUILD_VENDOR
+      Specifies the vendor name to use when building for the build host.
+      The default value is an empty string ("").
+
+   BUILDDIR
+      Points to the location of the :term:`Build Directory`.
+      You can define this directory indirectly through the
+      ````` <#structure-core-script>`__ script by passing in a Build
+      Directory path when you run the script. If you run the script and do
+      not provide a Build Directory path, the ``BUILDDIR`` defaults to
+      ``build`` in the current directory.
+
+   BUILDHISTORY_COMMIT
+      When inheriting the :ref:`buildhistory <ref-classes-buildhistory>`
+      class, this variable specifies whether or not to commit the build
+      history output in a local Git repository. If set to "1", this local
+      repository will be maintained automatically by the ``buildhistory``
+      class and a commit will be created on every build for changes to each
+      top-level subdirectory of the build history output (images, packages,
+      and sdk). If you want to track changes to build history over time,
+      you should set this value to "1".
+
+      By default, the ``buildhistory`` class does not commit the build
+      history output in a local Git repository:
+      ::
+
+         BUILDHISTORY_COMMIT ?= "0"
+
+   BUILDHISTORY_COMMIT_AUTHOR
+      When inheriting the :ref:`buildhistory <ref-classes-buildhistory>`
+      class, this variable specifies the author to use for each Git commit.
+      In order for the ``BUILDHISTORY_COMMIT_AUTHOR`` variable to work, the
+      :term:`BUILDHISTORY_COMMIT` variable must
+      be set to "1".
+
+      Git requires that the value you provide for the
+      ``BUILDHISTORY_COMMIT_AUTHOR`` variable takes the form of "name
+      email@host". Providing an email address or host that is not valid
+      does not produce an error.
+
+      By default, the ``buildhistory`` class sets the variable as follows:
+      ::
+
+         BUILDHISTORY_COMMIT_AUTHOR ?= "buildhistory <buildhistory@${DISTRO}>"
+
+   BUILDHISTORY_DIR
+      When inheriting the :ref:`buildhistory <ref-classes-buildhistory>`
+      class, this variable specifies the directory in which build history
+      information is kept. For more information on how the variable works,
+      see the ``buildhistory.class``.
+
+      By default, the ``buildhistory`` class sets the directory as follows:
+      ::
+
+         BUILDHISTORY_DIR ?= "${TOPDIR}/buildhistory"
+
+   BUILDHISTORY_FEATURES
+      When inheriting the :ref:`buildhistory <ref-classes-buildhistory>`
+      class, this variable specifies the build history features to be
+      enabled. For more information on how build history works, see the
+      ":ref:`dev-manual/dev-manual-common-tasks:maintaining build output quality`"
+      section in the Yocto Project Development Tasks Manual.
+
+      You can specify these features in the form of a space-separated list:
+
+      -  *image:* Analysis of the contents of images, which includes the
+         list of installed packages among other things.
+
+      -  *package:* Analysis of the contents of individual packages.
+
+      -  *sdk:* Analysis of the contents of the software development kit
+         (SDK).
+
+      -  *task:* Save output file signatures for
+         :ref:`shared state <overview-manual/overview-manual-concepts:shared state cache>`
+         (sstate) tasks.
+         This saves one file per task and lists the SHA-256 checksums for
+         each file staged (i.e. the output of the task).
+
+      By default, the ``buildhistory`` class enables the following
+      features:
+      ::
+
+         BUILDHISTORY_FEATURES ?= "image package sdk"
+
+   BUILDHISTORY_IMAGE_FILES
+      When inheriting the :ref:`buildhistory <ref-classes-buildhistory>`
+      class, this variable specifies a list of paths to files copied from
+      the image contents into the build history directory under an
+      "image-files" directory in the directory for the image, so that you
+      can track the contents of each file. The default is to copy
+      ``/etc/passwd`` and ``/etc/group``, which allows you to monitor for
+      changes in user and group entries. You can modify the list to include
+      any file. Specifying an invalid path does not produce an error.
+      Consequently, you can include files that might not always be present.
+
+      By default, the ``buildhistory`` class provides paths to the
+      following files:
+      ::
+
+         BUILDHISTORY_IMAGE_FILES ?= "/etc/passwd /etc/group"
+
+   BUILDHISTORY_PUSH_REPO
+      When inheriting the :ref:`buildhistory <ref-classes-buildhistory>`
+      class, this variable optionally specifies a remote repository to
+      which build history pushes Git changes. In order for
+      ``BUILDHISTORY_PUSH_REPO`` to work,
+      :term:`BUILDHISTORY_COMMIT` must be set to
+      "1".
+
+      The repository should correspond to a remote address that specifies a
+      repository as understood by Git, or alternatively to a remote name
+      that you have set up manually using ``git remote`` within the local
+      repository.
+
+      By default, the ``buildhistory`` class sets the variable as follows:
+      ::
+
+         BUILDHISTORY_PUSH_REPO ?= ""
+
+   BUILDSDK_CFLAGS
+      Specifies the flags to pass to the C compiler when building for the
+      SDK. When building in the ``nativesdk-`` context,
+      :term:`CFLAGS` is set to the value of this variable by
+      default.
+
+   BUILDSDK_CPPFLAGS
+      Specifies the flags to pass to the C pre-processor (i.e. to both the
+      C and the C++ compilers) when building for the SDK. When building in
+      the ``nativesdk-`` context, :term:`CPPFLAGS` is set
+      to the value of this variable by default.
+
+   BUILDSDK_CXXFLAGS
+      Specifies the flags to pass to the C++ compiler when building for the
+      SDK. When building in the ``nativesdk-`` context,
+      :term:`CXXFLAGS` is set to the value of this variable
+      by default.
+
+   BUILDSDK_LDFLAGS
+      Specifies the flags to pass to the linker when building for the SDK.
+      When building in the ``nativesdk-`` context,
+      :term:`LDFLAGS` is set to the value of this variable
+      by default.
+
+   BUILDSTATS_BASE
+      Points to the location of the directory that holds build statistics
+      when you use and enable the
+      :ref:`buildstats <ref-classes-buildstats>` class. The
+      ``BUILDSTATS_BASE`` directory defaults to
+      ``${``\ :term:`TMPDIR`\ ``}/buildstats/``.
+
+   BUSYBOX_SPLIT_SUID
+      For the BusyBox recipe, specifies whether to split the output
+      executable file into two parts: one for features that require
+      ``setuid root``, and one for the remaining features (i.e. those that
+      do not require ``setuid root``).
+
+      The ``BUSYBOX_SPLIT_SUID`` variable defaults to "1", which results in
+      splitting the output executable file. Set the variable to "0" to get
+      a single output executable file.
+
+   CACHE
+      Specifies the directory BitBake uses to store a cache of the
+      :term:`Metadata` so it does not need to be parsed every time
+      BitBake is started.
+
+   CC
+      The minimal command and arguments used to run the C compiler.
+
+   CFLAGS
+      Specifies the flags to pass to the C compiler. This variable is
+      exported to an environment variable and thus made visible to the
+      software being built during the compilation step.
+
+      Default initialization for ``CFLAGS`` varies depending on what is
+      being built:
+
+      -  :term:`TARGET_CFLAGS` when building for the
+         target
+
+      -  :term:`BUILD_CFLAGS` when building for the
+         build host (i.e. ``-native``)
+
+      -  :term:`BUILDSDK_CFLAGS` when building for
+         an SDK (i.e. ``nativesdk-``)
+
+   CLASSOVERRIDE
+      An internal variable specifying the special class override that
+      should currently apply (e.g. "class-target", "class-native", and so
+      forth). The classes that use this variable (e.g.
+      :ref:`native <ref-classes-native>`,
+      :ref:`nativesdk <ref-classes-nativesdk>`, and so forth) set the
+      variable to appropriate values.
+
+      .. note::
+
+         CLASSOVERRIDE
+         gets its default "class-target" value from the
+         bitbake.conf
+         file.
+
+      As an example, the following override allows you to install extra
+      files, but only when building for the target:
+      ::
+
+         do_install_append_class-target() {
+             install my-extra-file ${D}${sysconfdir}
+         }
+
+      Here is an example where ``FOO`` is set to
+      "native" when building for the build host, and to "other" when not
+      building for the build host:
+      ::
+
+         FOO_class-native = "native"
+         FOO = "other"
+
+      The underlying mechanism behind ``CLASSOVERRIDE`` is simply
+      that it is included in the default value of
+      :term:`OVERRIDES`.
+
+   CLEANBROKEN
+      If set to "1" within a recipe, ``CLEANBROKEN`` specifies that the
+      ``make clean`` command does not work for the software being built.
+      Consequently, the OpenEmbedded build system will not try to run
+      ``make clean`` during the :ref:`ref-tasks-configure`
+      task, which is the default behavior.
+
+   COMBINED_FEATURES
+      Provides a list of hardware features that are enabled in both
+      :term:`MACHINE_FEATURES` and
+      :term:`DISTRO_FEATURES`. This select list of
+      features contains features that make sense to be controlled both at
+      the machine and distribution configuration level. For example, the
+      "bluetooth" feature requires hardware support but should also be
+      optional at the distribution level, in case the hardware supports
+      Bluetooth but you do not ever intend to use it.
+
+   COMMON_LICENSE_DIR
+      Points to ``meta/files/common-licenses`` in the
+      :term:`Source Directory`, which is where generic license
+      files reside.
+
+   COMPATIBLE_HOST
+      A regular expression that resolves to one or more hosts (when the
+      recipe is native) or one or more targets (when the recipe is
+      non-native) with which a recipe is compatible. The regular expression
+      is matched against :term:`HOST_SYS`. You can use the
+      variable to stop recipes from being built for classes of systems with
+      which the recipes are not compatible. Stopping these builds is
+      particularly useful with kernels. The variable also helps to increase
+      parsing speed since the build system skips parsing recipes not
+      compatible with the current system.
+
+   COMPATIBLE_MACHINE
+      A regular expression that resolves to one or more target machines
+      with which a recipe is compatible. The regular expression is matched
+      against :term:`MACHINEOVERRIDES`. You can use
+      the variable to stop recipes from being built for machines with which
+      the recipes are not compatible. Stopping these builds is particularly
+      useful with kernels. The variable also helps to increase parsing
+      speed since the build system skips parsing recipes not compatible
+      with the current machine.
+
+   COMPLEMENTARY_GLOB
+      Defines wildcards to match when installing a list of complementary
+      packages for all the packages explicitly (or implicitly) installed in
+      an image.
+
+      .. note::
+
+         The
+         COMPLEMENTARY_GLOB
+         variable uses Unix filename pattern matching (
+         fnmatch
+         ), which is similar to the Unix style pathname pattern expansion (
+         glob
+         ).
+
+      The resulting list of complementary packages is associated with an
+      item that can be added to
+      :term:`IMAGE_FEATURES`. An example usage of
+      this is the "dev-pkgs" item that when added to ``IMAGE_FEATURES``
+      will install -dev packages (containing headers and other development
+      files) for every package in the image.
+
+      To add a new feature item pointing to a wildcard, use a variable flag
+      to specify the feature item name and use the value to specify the
+      wildcard. Here is an example:
+      ::
+
+         COMPLEMENTARY_GLOB[dev-pkgs] = '*-dev'
+
+   COMPONENTS_DIR
+      Stores sysroot components for each recipe. The OpenEmbedded build
+      system uses ``COMPONENTS_DIR`` when constructing recipe-specific
+      sysroots for other recipes.
+
+      The default is
+      "``${``\ :term:`STAGING_DIR`\ ``}-components``."
+      (i.e.
+      "``${``\ :term:`TMPDIR`\ ``}/sysroots-components``").
+
+   CONF_VERSION
+      Tracks the version of the local configuration file (i.e.
+      ``local.conf``). The value for ``CONF_VERSION`` increments each time
+      ``build/conf/`` compatibility changes.
+
+   CONFFILES
+      Identifies editable or configurable files that are part of a package.
+      If the Package Management System (PMS) is being used to update
+      packages on the target system, it is possible that configuration
+      files you have changed after the original installation and that you
+      now want to remain unchanged are overwritten. In other words,
+      editable files might exist in the package that you do not want reset
+      as part of the package update process. You can use the ``CONFFILES``
+      variable to list the files in the package that you wish to prevent
+      the PMS from overwriting during this update process.
+
+      To use the ``CONFFILES`` variable, provide a package name override
+      that identifies the resulting package. Then, provide a
+      space-separated list of files. Here is an example:
+      ::
+
+         CONFFILES_${PN} += "${sysconfdir}/file1 \
+             ${sysconfdir}/file2 ${sysconfdir}/file3"
+
+      A relationship exists between the ``CONFFILES`` and ``FILES``
+      variables. The files listed within ``CONFFILES`` must be a subset of
+      the files listed within ``FILES``. Because the configuration files
+      you provide with ``CONFFILES`` are simply being identified so that
+      the PMS will not overwrite them, it makes sense that the files must
+      already be included as part of the package through the ``FILES``
+      variable.
+
+      .. note::
+
+         When specifying paths as part of the
+         CONFFILES
+         variable, it is good practice to use appropriate path variables.
+         For example,
+         ${sysconfdir}
+         rather than
+         /etc
+         or
+         ${bindir}
+         rather than
+         /usr/bin
+         . You can find a list of these variables at the top of the
+         meta/conf/bitbake.conf
+         file in the
+         Source Directory
+         .
+
+   CONFIG_INITRAMFS_SOURCE
+      Identifies the initial RAM filesystem (initramfs) source files. The
+      OpenEmbedded build system receives and uses this kernel Kconfig
+      variable as an environment variable. By default, the variable is set
+      to null ("").
+
+      The ``CONFIG_INITRAMFS_SOURCE`` can be either a single cpio archive
+      with a ``.cpio`` suffix or a space-separated list of directories and
+      files for building the initramfs image. A cpio archive should contain
+      a filesystem archive to be used as an initramfs image. Directories
+      should contain a filesystem layout to be included in the initramfs
+      image. Files should contain entries according to the format described
+      by the ``usr/gen_init_cpio`` program in the kernel tree.
+
+      If you specify multiple directories and files, the initramfs image
+      will be the aggregate of all of them.
+
+      For information on creating an initramfs, see the
+      ":ref:`building-an-initramfs-image`" section
+      in the Yocto Project Development Tasks Manual.
+
+   CONFIG_SITE
+      A list of files that contains ``autoconf`` test results relevant to
+      the current build. This variable is used by the Autotools utilities
+      when running ``configure``.
+
+   CONFIGURE_FLAGS
+      The minimal arguments for GNU configure.
+
+   CONFLICT_DISTRO_FEATURES
+      When inheriting the
+      :ref:`distro_features_check <ref-classes-distro_features_check>`
+      class, this variable identifies distribution features that would be
+      in conflict should the recipe be built. In other words, if the
+      ``CONFLICT_DISTRO_FEATURES`` variable lists a feature that also
+      appears in ``DISTRO_FEATURES`` within the current configuration, an
+      error occurs and the build stops.
+
+   COPYLEFT_LICENSE_EXCLUDE
+      A space-separated list of licenses to exclude from the source
+      archived by the :ref:`archiver <ref-classes-archiver>` class. In
+      other words, if a license in a recipe's
+      :term:`LICENSE` value is in the value of
+      ``COPYLEFT_LICENSE_EXCLUDE``, then its source is not archived by the
+      class.
+
+      .. note::
+
+         The
+         COPYLEFT_LICENSE_EXCLUDE
+         variable takes precedence over the
+         COPYLEFT_LICENSE_INCLUDE
+         variable.
+
+      The default value, which is "CLOSED Proprietary", for
+      ``COPYLEFT_LICENSE_EXCLUDE`` is set by the
+      :ref:`copyleft_filter <ref-classes-copyleft_filter>` class, which
+      is inherited by the ``archiver`` class.
+
+   COPYLEFT_LICENSE_INCLUDE
+      A space-separated list of licenses to include in the source archived
+      by the :ref:`archiver <ref-classes-archiver>` class. In other
+      words, if a license in a recipe's :term:`LICENSE`
+      value is in the value of ``COPYLEFT_LICENSE_INCLUDE``, then its
+      source is archived by the class.
+
+      The default value is set by the
+      :ref:`copyleft_filter <ref-classes-copyleft_filter>` class, which
+      is inherited by the ``archiver`` class. The default value includes
+      "GPL*", "LGPL*", and "AGPL*".
+
+   COPYLEFT_PN_EXCLUDE
+      A list of recipes to exclude in the source archived by the
+      :ref:`archiver <ref-classes-archiver>` class. The
+      ``COPYLEFT_PN_EXCLUDE`` variable overrides the license inclusion and
+      exclusion caused through the
+      :term:`COPYLEFT_LICENSE_INCLUDE` and
+      :term:`COPYLEFT_LICENSE_EXCLUDE`
+      variables, respectively.
+
+      The default value, which is "" indicating to not explicitly exclude
+      any recipes by name, for ``COPYLEFT_PN_EXCLUDE`` is set by the
+      :ref:`copyleft_filter <ref-classes-copyleft_filter>` class, which
+      is inherited by the ``archiver`` class.
+
+   COPYLEFT_PN_INCLUDE
+      A list of recipes to include in the source archived by the
+      :ref:`archiver <ref-classes-archiver>` class. The
+      ``COPYLEFT_PN_INCLUDE`` variable overrides the license inclusion and
+      exclusion caused through the
+      :term:`COPYLEFT_LICENSE_INCLUDE` and
+      :term:`COPYLEFT_LICENSE_EXCLUDE`
+      variables, respectively.
+
+      The default value, which is "" indicating to not explicitly include
+      any recipes by name, for ``COPYLEFT_PN_INCLUDE`` is set by the
+      :ref:`copyleft_filter <ref-classes-copyleft_filter>` class, which
+      is inherited by the ``archiver`` class.
+
+   COPYLEFT_RECIPE_TYPES
+      A space-separated list of recipe types to include in the source
+      archived by the :ref:`archiver <ref-classes-archiver>` class.
+      Recipe types are ``target``, ``native``, ``nativesdk``, ``cross``,
+      ``crosssdk``, and ``cross-canadian``.
+
+      The default value, which is "target*", for ``COPYLEFT_RECIPE_TYPES``
+      is set by the :ref:`copyleft_filter <ref-classes-copyleft_filter>`
+      class, which is inherited by the ``archiver`` class.
+
+   COPY_LIC_DIRS
+      If set to "1" along with the
+      :term:`COPY_LIC_MANIFEST` variable, the
+      OpenEmbedded build system copies into the image the license files,
+      which are located in ``/usr/share/common-licenses``, for each
+      package. The license files are placed in directories within the image
+      itself during build time.
+
+      .. note::
+
+         The
+         COPY_LIC_DIRS
+         does not offer a path for adding licenses for newly installed
+         packages to an image, which might be most suitable for read-only
+         filesystems that cannot be upgraded. See the
+         LICENSE_CREATE_PACKAGE
+         variable for additional information. You can also reference the "
+         Providing License Text
+         " section in the Yocto Project Development Tasks Manual for
+         information on providing license text.
+
+   COPY_LIC_MANIFEST
+      If set to "1", the OpenEmbedded build system copies the license
+      manifest for the image to
+      ``/usr/share/common-licenses/license.manifest`` within the image
+      itself during build time.
+
+      .. note::
+
+         The
+         COPY_LIC_MANIFEST
+         does not offer a path for adding licenses for newly installed
+         packages to an image, which might be most suitable for read-only
+         filesystems that cannot be upgraded. See the
+         LICENSE_CREATE_PACKAGE
+         variable for additional information. You can also reference the "
+         Providing License Text
+         " section in the Yocto Project Development Tasks Manual for
+         information on providing license text.
+
+   CORE_IMAGE_EXTRA_INSTALL
+      Specifies the list of packages to be added to the image. You should
+      only set this variable in the ``local.conf`` configuration file found
+      in the :term:`Build Directory`.
+
+      This variable replaces ``POKY_EXTRA_INSTALL``, which is no longer
+      supported.
+
+   COREBASE
+      Specifies the parent directory of the OpenEmbedded-Core Metadata
+      layer (i.e. ``meta``).
+
+      It is an important distinction that ``COREBASE`` points to the parent
+      of this layer and not the layer itself. Consider an example where you
+      have cloned the Poky Git repository and retained the ``poky`` name
+      for your local copy of the repository. In this case, ``COREBASE``
+      points to the ``poky`` folder because it is the parent directory of
+      the ``poky/meta`` layer.
+
+   COREBASE_FILES
+      Lists files from the :term:`COREBASE` directory that
+      should be copied other than the layers listed in the
+      ``bblayers.conf`` file. The ``COREBASE_FILES`` variable exists for
+      the purpose of copying metadata from the OpenEmbedded build system
+      into the extensible SDK.
+
+      Explicitly listing files in ``COREBASE`` is needed because it
+      typically contains build directories and other files that should not
+      normally be copied into the extensible SDK. Consequently, the value
+      of ``COREBASE_FILES`` is used in order to only copy the files that
+      are actually needed.
+
+   CPP
+      The minimal command and arguments used to run the C preprocessor.
+
+   CPPFLAGS
+      Specifies the flags to pass to the C pre-processor (i.e. to both the
+      C and the C++ compilers). This variable is exported to an environment
+      variable and thus made visible to the software being built during the
+      compilation step.
+
+      Default initialization for ``CPPFLAGS`` varies depending on what is
+      being built:
+
+      -  :term:`TARGET_CPPFLAGS` when building for
+         the target
+
+      -  :term:`BUILD_CPPFLAGS` when building for the
+         build host (i.e. ``-native``)
+
+      -  :term:`BUILDSDK_CPPFLAGS` when building
+         for an SDK (i.e. ``nativesdk-``)
+
+   CROSS_COMPILE
+      The toolchain binary prefix for the target tools. The
+      ``CROSS_COMPILE`` variable is the same as the
+      :term:`TARGET_PREFIX` variable.
+
+      .. note::
+
+         The OpenEmbedded build system sets the
+         CROSS_COMPILE
+         variable only in certain contexts (e.g. when building for kernel
+         and kernel module recipes).
+
+   CVSDIR
+      The directory in which files checked out under the CVS system are
+      stored.
+
+   CXX
+      The minimal command and arguments used to run the C++ compiler.
+
+   CXXFLAGS
+      Specifies the flags to pass to the C++ compiler. This variable is
+      exported to an environment variable and thus made visible to the
+      software being built during the compilation step.
+
+      Default initialization for ``CXXFLAGS`` varies depending on what is
+      being built:
+
+      -  :term:`TARGET_CXXFLAGS` when building for
+         the target
+
+      -  :term:`BUILD_CXXFLAGS` when building for the
+         build host (i.e. ``-native``)
+
+      -  :term:`BUILDSDK_CXXFLAGS` when building
+         for an SDK (i.e. ``nativesdk-``)
+
+   D
+      The destination directory. The location in the :term:`Build Directory`
+      where components are installed by the
+      :ref:`ref-tasks-install` task. This location defaults
+      to:
+      ::
+
+         ${WORKDIR}/image
+
+      .. note::
+
+         Tasks that read from or write to this directory should run under
+         fakeroot
+         .
+
+   DATE
+      The date the build was started. Dates appear using the year, month,
+      and day (YMD) format (e.g. "20150209" for February 9th, 2015).
+
+   DATETIME
+      The date and time on which the current build started. The format is
+      suitable for timestamps.
+
+   DEBIAN_NOAUTONAME
+      When the :ref:`debian <ref-classes-debian>` class is inherited,
+      which is the default behavior, ``DEBIAN_NOAUTONAME`` specifies a
+      particular package should not be renamed according to Debian library
+      package naming. You must use the package name as an override when you
+      set this variable. Here is an example from the ``fontconfig`` recipe:
+      ::
+
+         DEBIAN_NOAUTONAME_fontconfig-utils = "1"
+
+   DEBIANNAME
+      When the :ref:`debian <ref-classes-debian>` class is inherited,
+      which is the default behavior, ``DEBIANNAME`` allows you to override
+      the library name for an individual package. Overriding the library
+      name in these cases is rare. You must use the package name as an
+      override when you set this variable. Here is an example from the
+      ``dbus`` recipe:
+      ::
+
+         DEBIANNAME_${PN} = "dbus-1"
+
+   DEBUG_BUILD
+      Specifies to build packages with debugging information. This
+      influences the value of the ``SELECTED_OPTIMIZATION`` variable.
+
+   DEBUG_OPTIMIZATION
+      The options to pass in ``TARGET_CFLAGS`` and ``CFLAGS`` when
+      compiling a system for debugging. This variable defaults to "-O
+      -fno-omit-frame-pointer ${DEBUG_FLAGS} -pipe".
+
+   DEFAULT_PREFERENCE
+      Specifies a weak bias for recipe selection priority.
+
+      The most common usage of this is variable is to set it to "-1" within
+      a recipe for a development version of a piece of software. Using the
+      variable in this way causes the stable version of the recipe to build
+      by default in the absence of ``PREFERRED_VERSION`` being used to
+      build the development version.
+
+      .. note::
+
+         The bias provided by
+         DEFAULT_PREFERENCE
+         is weak and is overridden by
+         BBFILE_PRIORITY
+         if that variable is different between two layers that contain
+         different versions of the same recipe.
+
+   DEFAULTTUNE
+      The default CPU and Application Binary Interface (ABI) tunings (i.e.
+      the "tune") used by the OpenEmbedded build system. The
+      ``DEFAULTTUNE`` helps define
+      :term:`TUNE_FEATURES`.
+
+      The default tune is either implicitly or explicitly set by the
+      machine (:term:`MACHINE`). However, you can override
+      the setting using available tunes as defined with
+      :term:`AVAILTUNES`.
+
+   DEPENDS
+      Lists a recipe's build-time dependencies. These are dependencies on
+      other recipes whose contents (e.g. headers and shared libraries) are
+      needed by the recipe at build time.
+
+      As an example, consider a recipe ``foo`` that contains the following
+      assignment:
+      ::
+
+          DEPENDS = "bar"
+
+      The practical effect of the previous
+      assignment is that all files installed by bar will be available in
+      the appropriate staging sysroot, given by the
+      :term:`STAGING_DIR* <STAGING_DIR>` variables, by the time the
+      :ref:`ref-tasks-configure` task for ``foo`` runs.
+      This mechanism is implemented by having ``do_configure`` depend on
+      the :ref:`ref-tasks-populate_sysroot` task of
+      each recipe listed in ``DEPENDS``, through a
+      ``[``\ :ref:`deptask <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:variable flags>`\ ``]``
+      declaration in the :ref:`base <ref-classes-base>` class.
+
+      .. note::
+
+         It seldom is necessary to reference, for example,
+         STAGING_DIR_HOST
+         explicitly. The standard classes and build-related variables are
+         configured to automatically use the appropriate staging sysroots.
+
+      As another example, ``DEPENDS`` can also be used to add utilities
+      that run on the build machine during the build. For example, a recipe
+      that makes use of a code generator built by the recipe ``codegen``
+      might have the following:
+      ::
+
+         DEPENDS = "codegen-native"
+
+      For more
+      information, see the :ref:`native <ref-classes-native>` class and
+      the :term:`EXTRANATIVEPATH` variable.
+
+      .. note::
+
+         -  ``DEPENDS`` is a list of recipe names. Or, to be more precise,
+            it is a list of :term:`PROVIDES` names, which
+            usually match recipe names. Putting a package name such as
+            "foo-dev" in ``DEPENDS`` does not make sense. Use "foo"
+            instead, as this will put files from all the packages that make
+            up ``foo``, which includes those from ``foo-dev``, into the
+            sysroot.
+
+         -  One recipe having another recipe in ``DEPENDS`` does not by
+            itself add any runtime dependencies between the packages
+            produced by the two recipes. However, as explained in the
+            ":ref:`overview-manual/overview-manual-concepts:automatically added runtime dependencies`"
+            section in the Yocto Project Overview and Concepts Manual,
+            runtime dependencies will often be added automatically, meaning
+            ``DEPENDS`` alone is sufficient for most recipes.
+
+         -  Counterintuitively, ``DEPENDS`` is often necessary even for
+            recipes that install precompiled components. For example, if
+            ``libfoo`` is a precompiled library that links against
+            ``libbar``, then linking against ``libfoo`` requires both
+            ``libfoo`` and ``libbar`` to be available in the sysroot.
+            Without a ``DEPENDS`` from the recipe that installs ``libfoo``
+            to the recipe that installs ``libbar``, other recipes might
+            fail to link against ``libfoo``.
+
+      For information on runtime dependencies, see the
+      :term:`RDEPENDS` variable. You can also see the
+      ":ref:`Tasks <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:tasks>`" and
+      ":ref:`Dependencies <bitbake:bitbake-user-manual/bitbake-user-manual-execution:dependencies>`" sections in the
+      BitBake User Manual for additional information on tasks and
+      dependencies.
+
+   DEPLOY_DIR
+      Points to the general area that the OpenEmbedded build system uses to
+      place images, packages, SDKs, and other output files that are ready
+      to be used outside of the build system. By default, this directory
+      resides within the :term:`Build Directory` as
+      ``${TMPDIR}/deploy``.
+
+      For more information on the structure of the Build Directory, see
+      ":ref:`ref-manual/ref-structure:the build directory - \`\`build/\`\``" section.
+      For more detail on the contents of the ``deploy`` directory, see the
+      ":ref:`Images <images-dev-environment>`", ":ref:`Package
+      Feeds <package-feeds-dev-environment>`", and
+      ":ref:`sdk-dev-environment`" sections all in the
+      Yocto Project Overview and Concepts Manual.
+
+   DEPLOY_DIR_DEB
+      Points to the area that the OpenEmbedded build system uses to place
+      Debian packages that are ready to be used outside of the build
+      system. This variable applies only when
+      :term:`PACKAGE_CLASSES` contains
+      "package_deb".
+
+      The BitBake configuration file initially defines the
+      ``DEPLOY_DIR_DEB`` variable as a sub-folder of
+      :term:`DEPLOY_DIR`:
+      ::
+
+         DEPLOY_DIR_DEB = "${DEPLOY_DIR}/deb"
+
+      The :ref:`package_deb <ref-classes-package_deb>` class uses the
+      ``DEPLOY_DIR_DEB`` variable to make sure the
+      :ref:`ref-tasks-package_write_deb` task
+      writes Debian packages into the appropriate folder. For more
+      information on how packaging works, see the ":ref:`Package
+      Feeds <package-feeds-dev-environment>`" section
+      in the Yocto Project Overview and Concepts Manual.
+
+   DEPLOY_DIR_IMAGE
+      Points to the area that the OpenEmbedded build system uses to place
+      images and other associated output files that are ready to be
+      deployed onto the target machine. The directory is machine-specific
+      as it contains the ``${MACHINE}`` name. By default, this directory
+      resides within the :term:`Build Directory` as
+      ``${DEPLOY_DIR}/images/${MACHINE}/``.
+
+      For more information on the structure of the Build Directory, see
+      ":ref:`ref-manual/ref-structure:the build directory - \`\`build/\`\``" section.
+      For more detail on the contents of the ``deploy`` directory, see the
+      ":ref:`Images <images-dev-environment>`" and
+      ":ref:`sdk-dev-environment`" sections both in
+      the Yocto Project Overview and Concepts Manual.
+
+   DEPLOY_DIR_IPK
+      Points to the area that the OpenEmbedded build system uses to place
+      IPK packages that are ready to be used outside of the build system.
+      This variable applies only when
+      :term:`PACKAGE_CLASSES` contains
+      "package_ipk".
+
+      The BitBake configuration file initially defines this variable as a
+      sub-folder of :term:`DEPLOY_DIR`:
+      ::
+
+         DEPLOY_DIR_IPK = "${DEPLOY_DIR}/ipk"
+
+      The :ref:`package_ipk <ref-classes-package_ipk>` class uses the
+      ``DEPLOY_DIR_IPK`` variable to make sure the
+      :ref:`ref-tasks-package_write_ipk` task
+      writes IPK packages into the appropriate folder. For more information
+      on how packaging works, see the ":ref:`Package
+      Feeds <package-feeds-dev-environment>`" section
+      in the Yocto Project Overview and Concepts Manual.
+
+   DEPLOY_DIR_RPM
+      Points to the area that the OpenEmbedded build system uses to place
+      RPM packages that are ready to be used outside of the build system.
+      This variable applies only when
+      :term:`PACKAGE_CLASSES` contains
+      "package_rpm".
+
+      The BitBake configuration file initially defines this variable as a
+      sub-folder of :term:`DEPLOY_DIR`:
+      ::
+
+         DEPLOY_DIR_RPM = "${DEPLOY_DIR}/rpm"
+
+      The :ref:`package_rpm <ref-classes-package_rpm>` class uses the
+      ``DEPLOY_DIR_RPM`` variable to make sure the
+      :ref:`ref-tasks-package_write_rpm` task
+      writes RPM packages into the appropriate folder. For more information
+      on how packaging works, see the ":ref:`Package
+      Feeds <package-feeds-dev-environment>`" section
+      in the Yocto Project Overview and Concepts Manual.
+
+   DEPLOY_DIR_TAR
+      Points to the area that the OpenEmbedded build system uses to place
+      tarballs that are ready to be used outside of the build system. This
+      variable applies only when
+      :term:`PACKAGE_CLASSES` contains
+      "package_tar".
+
+      The BitBake configuration file initially defines this variable as a
+      sub-folder of :term:`DEPLOY_DIR`:
+      ::
+
+         DEPLOY_DIR_TAR = "${DEPLOY_DIR}/tar"
+
+      The :ref:`package_tar <ref-classes-package_tar>` class uses the
+      ``DEPLOY_DIR_TAR`` variable to make sure the
+      :ref:`ref-tasks-package_write_tar` task
+      writes TAR packages into the appropriate folder. For more information
+      on how packaging works, see the ":ref:`Package
+      Feeds <package-feeds-dev-environment>`" section
+      in the Yocto Project Overview and Concepts Manual.
+
+   DEPLOYDIR
+      When inheriting the :ref:`deploy <ref-classes-deploy>` class, the
+      ``DEPLOYDIR`` points to a temporary work area for deployed files that
+      is set in the ``deploy`` class as follows:
+      ::
+
+         DEPLOYDIR = "${WORKDIR}/deploy-${:term:`PN`}"
+
+      Recipes inheriting the ``deploy`` class should copy files to be
+      deployed into ``DEPLOYDIR``, and the class will take care of copying
+      them into :term:`DEPLOY_DIR_IMAGE`
+      afterwards.
+
+   DESCRIPTION
+      The package description used by package managers. If not set,
+      ``DESCRIPTION`` takes the value of the :term:`SUMMARY`
+      variable.
+
+   DISTRO
+      The short name of the distribution. For information on the long name
+      of the distribution, see the :term:`DISTRO_NAME`
+      variable.
+
+      The ``DISTRO`` variable corresponds to a distribution configuration
+      file whose root name is the same as the variable's argument and whose
+      filename extension is ``.conf``. For example, the distribution
+      configuration file for the Poky distribution is named ``poky.conf``
+      and resides in the ``meta-poky/conf/distro`` directory of the
+      :term:`Source Directory`.
+
+      Within that ``poky.conf`` file, the ``DISTRO`` variable is set as
+      follows:
+      ::
+
+         DISTRO = "poky"
+
+      Distribution configuration files are located in a ``conf/distro``
+      directory within the :term:`Metadata` that contains the
+      distribution configuration. The value for ``DISTRO`` must not contain
+      spaces, and is typically all lower-case.
+
+      .. note::
+
+         If the
+         DISTRO
+         variable is blank, a set of default configurations are used, which
+         are specified within
+         meta/conf/distro/defaultsetup.conf
+         also in the Source Directory.
+
+   DISTRO_CODENAME
+      Specifies a codename for the distribution being built.
+
+   DISTRO_EXTRA_RDEPENDS
+      Specifies a list of distro-specific packages to add to all images.
+      This variable takes affect through ``packagegroup-base`` so the
+      variable only really applies to the more full-featured images that
+      include ``packagegroup-base``. You can use this variable to keep
+      distro policy out of generic images. As with all other distro
+      variables, you set this variable in the distro ``.conf`` file.
+
+   DISTRO_EXTRA_RRECOMMENDS
+      Specifies a list of distro-specific packages to add to all images if
+      the packages exist. The packages might not exist or be empty (e.g.
+      kernel modules). The list of packages are automatically installed but
+      you can remove them.
+
+   DISTRO_FEATURES
+      The software support you want in your distribution for various
+      features. You define your distribution features in the distribution
+      configuration file.
+
+      In most cases, the presence or absence of a feature in
+      ``DISTRO_FEATURES`` is translated to the appropriate option supplied
+      to the configure script during the
+      :ref:`ref-tasks-configure` task for recipes that
+      optionally support the feature. For example, specifying "x11" in
+      ``DISTRO_FEATURES``, causes every piece of software built for the
+      target that can optionally support X11 to have its X11 support
+      enabled.
+
+      Two more examples are Bluetooth and NFS support. For a more complete
+      list of features that ships with the Yocto Project and that you can
+      provide with this variable, see the "`Distro
+      Features <#ref-features-distro>`__" section.
+
+   DISTRO_FEATURES_BACKFILL
+      Features to be added to ``DISTRO_FEATURES`` if not also present in
+      ``DISTRO_FEATURES_BACKFILL_CONSIDERED``.
+
+      This variable is set in the ``meta/conf/bitbake.conf`` file. It is
+      not intended to be user-configurable. It is best to just reference
+      the variable to see which distro features are being backfilled for
+      all distro configurations. See the "`Feature
+      Backfilling <#ref-features-backfill>`__" section for more
+      information.
+
+   DISTRO_FEATURES_BACKFILL_CONSIDERED
+      Features from ``DISTRO_FEATURES_BACKFILL`` that should not be
+      backfilled (i.e. added to ``DISTRO_FEATURES``) during the build. See
+      the "`Feature Backfilling <#ref-features-backfill>`__" section for
+      more information.
+
+   DISTRO_FEATURES_DEFAULT
+      A convenience variable that gives you the default list of distro
+      features with the exception of any features specific to the C library
+      (``libc``).
+
+      When creating a custom distribution, you might find it useful to be
+      able to reuse the default
+      :term:`DISTRO_FEATURES` options without the
+      need to write out the full set. Here is an example that uses
+      ``DISTRO_FEATURES_DEFAULT`` from a custom distro configuration file:
+      ::
+
+         DISTRO_FEATURES ?= "${DISTRO_FEATURES_DEFAULT} myfeature"
+
+   DISTRO_FEATURES_FILTER_NATIVE
+      Specifies a list of features that if present in the target
+      :term:`DISTRO_FEATURES` value should be
+      included in ``DISTRO_FEATURES`` when building native recipes. This
+      variable is used in addition to the features filtered using the
+      :term:`DISTRO_FEATURES_NATIVE`
+      variable.
+
+   DISTRO_FEATURES_FILTER_NATIVESDK
+      Specifies a list of features that if present in the target
+      :term:`DISTRO_FEATURES` value should be
+      included in ``DISTRO_FEATURES`` when building nativesdk recipes. This
+      variable is used in addition to the features filtered using the
+      :term:`DISTRO_FEATURES_NATIVESDK`
+      variable.
+
+   DISTRO_FEATURES_NATIVE
+      Specifies a list of features that should be included in
+      :term:`DISTRO_FEATURES` when building native
+      recipes. This variable is used in addition to the features filtered
+      using the
+      :term:`DISTRO_FEATURES_FILTER_NATIVE`
+      variable.
+
+   DISTRO_FEATURES_NATIVESDK
+      Specifies a list of features that should be included in
+      :term:`DISTRO_FEATURES` when building
+      nativesdk recipes. This variable is used in addition to the features
+      filtered using the
+      :term:`DISTRO_FEATURES_FILTER_NATIVESDK`
+      variable.
+
+   DISTRO_NAME
+      The long name of the distribution. For information on the short name
+      of the distribution, see the :term:`DISTRO` variable.
+
+      The ``DISTRO_NAME`` variable corresponds to a distribution
+      configuration file whose root name is the same as the variable's
+      argument and whose filename extension is ``.conf``. For example, the
+      distribution configuration file for the Poky distribution is named
+      ``poky.conf`` and resides in the ``meta-poky/conf/distro`` directory
+      of the :term:`Source Directory`.
+
+      Within that ``poky.conf`` file, the ``DISTRO_NAME`` variable is set
+      as follows:
+      ::
+
+         DISTRO_NAME = "Poky (Yocto Project Reference Distro)"
+
+      Distribution configuration files are located in a ``conf/distro``
+      directory within the :term:`Metadata` that contains the
+      distribution configuration.
+
+      .. note::
+
+         If the
+         DISTRO_NAME
+         variable is blank, a set of default configurations are used, which
+         are specified within
+         meta/conf/distro/defaultsetup.conf
+         also in the Source Directory.
+
+   DISTRO_VERSION
+      The version of the distribution.
+
+   DISTROOVERRIDES
+      A colon-separated list of overrides specific to the current
+      distribution. By default, this list includes the value of
+      :term:`DISTRO`.
+
+      You can extend ``DISTROOVERRIDES`` to add extra overrides that should
+      apply to the distribution.
+
+      The underlying mechanism behind ``DISTROOVERRIDES`` is simply that it
+      is included in the default value of
+      :term:`OVERRIDES`.
+
+   DL_DIR
+      The central download directory used by the build process to store
+      downloads. By default, ``DL_DIR`` gets files suitable for mirroring
+      for everything except Git repositories. If you want tarballs of Git
+      repositories, use the
+      :term:`BB_GENERATE_MIRROR_TARBALLS`
+      variable.
+
+      You can set this directory by defining the ``DL_DIR`` variable in the
+      ``conf/local.conf`` file. This directory is self-maintaining and you
+      should not have to touch it. By default, the directory is
+      ``downloads`` in the :term:`Build Directory`.
+      ::
+
+         #DL_DIR ?= "${TOPDIR}/downloads"
+
+      To specify a different download directory,
+      simply remove the comment from the line and provide your directory.
+
+      During a first build, the system downloads many different source code
+      tarballs from various upstream projects. Downloading can take a
+      while, particularly if your network connection is slow. Tarballs are
+      all stored in the directory defined by ``DL_DIR`` and the build
+      system looks there first to find source tarballs.
+
+      .. note::
+
+         When wiping and rebuilding, you can preserve this directory to
+         speed up this part of subsequent builds.
+
+      You can safely share this directory between multiple builds on the
+      same development machine. For additional information on how the build
+      process gets source files when working behind a firewall or proxy
+      server, see this specific question in the
+      "`FAQ <#how-does-the-yocto-project-obtain-source-code-and-will-it-work-behind-my-firewall-or-proxy-server>`__"
+      chapter. You can also refer to the
+      ":yocto_wiki:`Working Behind a Network Proxy </wiki/Working_Behind_a_Network_Proxy>`"
+      Wiki page.
+
+   DOC_COMPRESS
+      When inheriting the :ref:`compress_doc <ref-classes-compress_doc>`
+      class, this variable sets the compression policy used when the
+      OpenEmbedded build system compresses man pages and info pages. By
+      default, the compression method used is gz (gzip). Other policies
+      available are xz and bz2.
+
+      For information on policies and on how to use this variable, see the
+      comments in the ``meta/classes/compress_doc.bbclass`` file.
+
+   EFI_PROVIDER
+      When building bootable images (i.e. where ``hddimg``, ``iso``, or
+      ``wic.vmdk`` is in :term:`IMAGE_FSTYPES`), the
+      ``EFI_PROVIDER`` variable specifies the EFI bootloader to use. The
+      default is "grub-efi", but "systemd-boot" can be used instead.
+
+      See the :ref:`systemd-boot <ref-classes-systemd-boot>` and
+      :ref:`image-live <ref-classes-image-live>` classes for more
+      information.
+
+   ENABLE_BINARY_LOCALE_GENERATION
+      Variable that controls which locales for ``glibc`` are generated
+      during the build (useful if the target device has 64Mbytes of RAM or
+      less).
+
+   ERR_REPORT_DIR
+      When used with the :ref:`report-error <ref-classes-report-error>`
+      class, specifies the path used for storing the debug files created by
+      the :ref:`error reporting
+      tool <dev-manual/dev-manual-common-tasks:using the error reporting tool>`, which
+      allows you to submit build errors you encounter to a central
+      database. By default, the value of this variable is
+      ``${``\ :term:`LOG_DIR`\ ``}/error-report``.
+
+      You can set ``ERR_REPORT_DIR`` to the path you want the error
+      reporting tool to store the debug files as follows in your
+      ``local.conf`` file:
+      ::
+
+         ERR_REPORT_DIR = "path"
+
+   ERROR_QA
+      Specifies the quality assurance checks whose failures are reported as
+      errors by the OpenEmbedded build system. You set this variable in
+      your distribution configuration file. For a list of the checks you
+      can control with this variable, see the
+      ":ref:`insane.bbclass <ref-classes-insane>`" section.
+
+   EXCLUDE_FROM_SHLIBS
+      Triggers the OpenEmbedded build system's shared libraries resolver to
+      exclude an entire package when scanning for shared libraries.
+
+      .. note::
+
+         The shared libraries resolver's functionality results in part from
+         the internal function
+         package_do_shlibs
+         , which is part of the
+         do_package
+         task. You should be aware that the shared libraries resolver might
+         implicitly define some dependencies between packages.
+
+      The ``EXCLUDE_FROM_SHLIBS`` variable is similar to the
+      :term:`PRIVATE_LIBS` variable, which excludes a
+      package's particular libraries only and not the whole package.
+
+      Use the ``EXCLUDE_FROM_SHLIBS`` variable by setting it to "1" for a
+      particular package:
+      ::
+
+         EXCLUDE_FROM_SHLIBS = "1"
+
+   EXCLUDE_FROM_WORLD
+      Directs BitBake to exclude a recipe from world builds (i.e.
+      ``bitbake world``). During world builds, BitBake locates, parses and
+      builds all recipes found in every layer exposed in the
+      ``bblayers.conf`` configuration file.
+
+      To exclude a recipe from a world build using this variable, set the
+      variable to "1" in the recipe.
+
+      .. note::
+
+         Recipes added to
+         EXCLUDE_FROM_WORLD
+         may still be built during a world build in order to satisfy
+         dependencies of other recipes. Adding a recipe to
+         EXCLUDE_FROM_WORLD
+         only ensures that the recipe is not explicitly added to the list
+         of build targets in a world build.
+
+   EXTENDPE
+      Used with file and pathnames to create a prefix for a recipe's
+      version based on the recipe's :term:`PE` value. If ``PE``
+      is set and greater than zero for a recipe, ``EXTENDPE`` becomes that
+      value (e.g if ``PE`` is equal to "1" then ``EXTENDPE`` becomes "1").
+      If a recipe's ``PE`` is not set (the default) or is equal to zero,
+      ``EXTENDPE`` becomes "".
+
+      See the :term:`STAMP` variable for an example.
+
+   EXTENDPKGV
+      The full package version specification as it appears on the final
+      packages produced by a recipe. The variable's value is normally used
+      to fix a runtime dependency to the exact same version of another
+      package in the same recipe:
+      ::
+
+         RDEPENDS_${PN}-additional-module = "${PN} (= ${EXTENDPKGV})"
+
+      The dependency relationships are intended to force the package
+      manager to upgrade these types of packages in lock-step.
+
+   EXTERNAL_KERNEL_TOOLS
+      When set, the ``EXTERNAL_KERNEL_TOOLS`` variable indicates that these
+      tools are not in the source tree.
+
+      When kernel tools are available in the tree, they are preferred over
+      any externally installed tools. Setting the ``EXTERNAL_KERNEL_TOOLS``
+      variable tells the OpenEmbedded build system to prefer the installed
+      external tools. See the
+      :ref:`kernel-yocto <ref-classes-kernel-yocto>` class in
+      ``meta/classes`` to see how the variable is used.
+
+   EXTERNALSRC
+      When inheriting the :ref:`externalsrc <ref-classes-externalsrc>`
+      class, this variable points to the source tree, which is outside of
+      the OpenEmbedded build system. When set, this variable sets the
+      :term:`S` variable, which is what the OpenEmbedded build
+      system uses to locate unpacked recipe source code.
+
+      For more information on ``externalsrc.bbclass``, see the
+      ":ref:`externalsrc.bbclass <ref-classes-externalsrc>`" section. You
+      can also find information on how to use this variable in the
+      ":ref:`dev-manual/dev-manual-common-tasks:building software from an external source`"
+      section in the Yocto Project Development Tasks Manual.
+
+   EXTERNALSRC_BUILD
+      When inheriting the :ref:`externalsrc <ref-classes-externalsrc>`
+      class, this variable points to the directory in which the recipe's
+      source code is built, which is outside of the OpenEmbedded build
+      system. When set, this variable sets the :term:`B` variable,
+      which is what the OpenEmbedded build system uses to locate the Build
+      Directory.
+
+      For more information on ``externalsrc.bbclass``, see the
+      ":ref:`externalsrc.bbclass <ref-classes-externalsrc>`" section. You
+      can also find information on how to use this variable in the
+      ":ref:`dev-manual/dev-manual-common-tasks:building software from an external source`"
+      section in the Yocto Project Development Tasks Manual.
+
+   EXTRA_AUTORECONF
+      For recipes inheriting the :ref:`autotools <ref-classes-autotools>`
+      class, you can use ``EXTRA_AUTORECONF`` to specify extra options to
+      pass to the ``autoreconf`` command that is executed during the
+      :ref:`ref-tasks-configure` task.
+
+      The default value is "--exclude=autopoint".
+
+   EXTRA_IMAGE_FEATURES
+      A list of additional features to include in an image. When listing
+      more than one feature, separate them with a space.
+
+      Typically, you configure this variable in your ``local.conf`` file,
+      which is found in the :term:`Build Directory`.
+      Although you can use this variable from within a recipe, best
+      practices dictate that you do not.
+
+      .. note::
+
+         To enable primary features from within the image recipe, use the
+         IMAGE_FEATURES
+         variable.
+
+      Here are some examples of features you can add:
+
+        - "dbg-pkgs" - Adds -dbg packages for all installed packages including
+          symbol information for debugging and profiling.
+
+        - "debug-tweaks" - Makes an image suitable for debugging. For example, allows root logins without passwords and
+          enables post-installation logging. See the 'allow-empty-password' and
+          'post-install-logging' features in the "`Image
+          Features <#ref-features-image>`__" section for more information.
+        - "dev-pkgs" - Adds -dev packages for all installed packages. This is
+          useful if you want to develop against the libraries in the image.
+        - "read-only-rootfs" - Creates an image whose root filesystem is
+          read-only. See the
+          ":ref:`dev-manual/dev-manual-common-tasks:creating a read-only root filesystem`"
+          section in the Yocto Project Development Tasks Manual for more
+          information
+        - "tools-debug" - Adds debugging tools such as gdb and strace.
+        - "tools-sdk" - Adds development tools such as gcc, make,
+          pkgconfig and so forth.
+        - "tools-testapps" - Adds useful testing tools
+          such as ts_print, aplay, arecord and so forth.
+
+      For a complete list of image features that ships with the Yocto
+      Project, see the "`Image Features <#ref-features-image>`__" section.
+
+      For an example that shows how to customize your image by using this
+      variable, see the ":ref:`usingpoky-extend-customimage-imagefeatures`"
+      section in the Yocto Project Development Tasks Manual.
+
+   EXTRA_IMAGECMD
+      Specifies additional options for the image creation command that has
+      been specified in :term:`IMAGE_CMD`. When setting
+      this variable, use an override for the associated image type. Here is
+      an example:
+      ::
+
+         EXTRA_IMAGECMD_ext3 ?= "-i 4096"
+
+   EXTRA_IMAGEDEPENDS
+      A list of recipes to build that do not provide packages for
+      installing into the root filesystem.
+
+      Sometimes a recipe is required to build the final image but is not
+      needed in the root filesystem. You can use the ``EXTRA_IMAGEDEPENDS``
+      variable to list these recipes and thus specify the dependencies. A
+      typical example is a required bootloader in a machine configuration.
+
+      .. note::
+
+         To add packages to the root filesystem, see the various
+         \*RDEPENDS and \*RRECOMMENDS
+         variables.
+
+   EXTRANATIVEPATH
+      A list of subdirectories of
+      ``${``\ :term:`STAGING_BINDIR_NATIVE`\ ``}``
+      added to the beginning of the environment variable ``PATH``. As an
+      example, the following prepends
+      "${STAGING_BINDIR_NATIVE}/foo:${STAGING_BINDIR_NATIVE}/bar:" to
+      ``PATH``:
+      ::
+
+         EXTRANATIVEPATH = "foo bar"
+
+   EXTRA_OECMAKE
+      Additional `CMake <https://cmake.org/overview/>`__ options. See the
+      :ref:`cmake <ref-classes-cmake>` class for additional information.
+
+   EXTRA_OECONF
+      Additional ``configure`` script options. See
+      :term:`PACKAGECONFIG_CONFARGS` for
+      additional information on passing configure script options.
+
+   EXTRA_OEMAKE
+      Additional GNU ``make`` options.
+
+      Because the ``EXTRA_OEMAKE`` defaults to "", you need to set the
+      variable to specify any required GNU options.
+
+      :term:`PARALLEL_MAKE` and
+      :term:`PARALLEL_MAKEINST` also make use of
+      ``EXTRA_OEMAKE`` to pass the required flags.
+
+   EXTRA_OESCONS
+      When inheriting the :ref:`scons <ref-classes-scons>` class, this
+      variable specifies additional configuration options you want to pass
+      to the ``scons`` command line.
+
+   EXTRA_USERS_PARAMS
+      When inheriting the :ref:`extrausers <ref-classes-extrausers>`
+      class, this variable provides image level user and group operations.
+      This is a more global method of providing user and group
+      configuration as compared to using the
+      :ref:`useradd <ref-classes-useradd>` class, which ties user and
+      group configurations to a specific recipe.
+
+      The set list of commands you can configure using the
+      ``EXTRA_USERS_PARAMS`` is shown in the ``extrausers`` class. These
+      commands map to the normal Unix commands of the same names:
+      ::
+
+         # EXTRA_USERS_PARAMS = "\
+         # useradd -p '' tester; \
+         # groupadd developers; \
+         # userdel nobody; \
+         # groupdel -g video; \
+         # groupmod -g 1020 developers; \
+         # usermod -s /bin/sh tester; \
+         # "
+
+   FEATURE_PACKAGES
+      Defines one or more packages to include in an image when a specific
+      item is included in :term:`IMAGE_FEATURES`.
+      When setting the value, ``FEATURE_PACKAGES`` should have the name of
+      the feature item as an override. Here is an example:
+      ::
+
+         FEATURE_PACKAGES_widget = "package1 package2"
+
+      In this example, if "widget" were added to ``IMAGE_FEATURES``,
+      package1 and package2 would be included in the image.
+
+      .. note::
+
+         Packages installed by features defined through
+         FEATURE_PACKAGES
+         are often package groups. While similarly named, you should not
+         confuse the
+         FEATURE_PACKAGES
+         variable with package groups, which are discussed elsewhere in the
+         documentation.
+
+   FEED_DEPLOYDIR_BASE_URI
+      Points to the base URL of the server and location within the
+      document-root that provides the metadata and packages required by
+      OPKG to support runtime package management of IPK packages. You set
+      this variable in your ``local.conf`` file.
+
+      Consider the following example:
+      ::
+
+         FEED_DEPLOYDIR_BASE_URI = "http://192.168.7.1/BOARD-dir"
+
+      This example assumes you are serving
+      your packages over HTTP and your databases are located in a directory
+      named ``BOARD-dir``, which is underneath your HTTP server's
+      document-root. In this case, the OpenEmbedded build system generates
+      a set of configuration files for you in your target that work with
+      the feed.
+
+   FILES
+      The list of files and directories that are placed in a package. The
+      :term:`PACKAGES` variable lists the packages
+      generated by a recipe.
+
+      To use the ``FILES`` variable, provide a package name override that
+      identifies the resulting package. Then, provide a space-separated
+      list of files or paths that identify the files you want included as
+      part of the resulting package. Here is an example:
+      ::
+
+         FILES_${PN} += "${bindir}/mydir1 ${bindir}/mydir2/myfile"
+
+      .. note::
+
+         -  When specifying files or paths, you can pattern match using
+            Python's
+            `glob <https://docs.python.org/3/library/glob.html>`_
+            syntax. For details on the syntax, see the documentation by
+            following the previous link.
+
+         -  When specifying paths as part of the ``FILES`` variable, it is
+            good practice to use appropriate path variables. For example,
+            use ``${sysconfdir}`` rather than ``/etc``, or ``${bindir}``
+            rather than ``/usr/bin``. You can find a list of these
+            variables at the top of the ``meta/conf/bitbake.conf`` file in
+            the :term:`Source Directory`. You will also
+            find the default values of the various ``FILES_*`` variables in
+            this file.
+
+      If some of the files you provide with the ``FILES`` variable are
+      editable and you know they should not be overwritten during the
+      package update process by the Package Management System (PMS), you
+      can identify these files so that the PMS will not overwrite them. See
+      the :term:`CONFFILES` variable for information on
+      how to identify these files to the PMS.
+
+   FILES_SOLIBSDEV
+      Defines the file specification to match
+      :term:`SOLIBSDEV`. In other words,
+      ``FILES_SOLIBSDEV`` defines the full path name of the development
+      symbolic link (symlink) for shared libraries on the target platform.
+
+      The following statement from the ``bitbake.conf`` shows how it is
+      set:
+      ::
+
+         FILES_SOLIBSDEV ?= "${base_libdir}/lib*${SOLIBSDEV} ${libdir}/lib*${SOLIBSDEV}"
+
+   FILESEXTRAPATHS
+      Extends the search path the OpenEmbedded build system uses when
+      looking for files and patches as it processes recipes and append
+      files. The default directories BitBake uses when it processes recipes
+      are initially defined by the :term:`FILESPATH`
+      variable. You can extend ``FILESPATH`` variable by using
+      ``FILESEXTRAPATHS``.
+
+      Best practices dictate that you accomplish this by using
+      ``FILESEXTRAPATHS`` from within a ``.bbappend`` file and that you
+      prepend paths as follows:
+      ::
+
+         FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
+
+      In the above example, the build system first
+      looks for files in a directory that has the same name as the
+      corresponding append file.
+
+      .. note::
+
+         When extending ``FILESEXTRAPATHS``, be sure to use the immediate
+         expansion (``:=``) operator. Immediate expansion makes sure that
+         BitBake evaluates :term:`THISDIR` at the time the
+         directive is encountered rather than at some later time when
+         expansion might result in a directory that does not contain the
+         files you need.
+
+         Also, include the trailing separating colon character if you are
+         prepending. The trailing colon character is necessary because you
+         are directing BitBake to extend the path by prepending directories
+         to the search path.
+
+      Here is another common use:
+      ::
+
+         FILESEXTRAPATHS_prepend := "${THISDIR}/files:"
+
+      In this example, the build system extends the
+      ``FILESPATH`` variable to include a directory named ``files`` that is
+      in the same directory as the corresponding append file.
+
+      This next example specifically adds three paths:
+      ::
+
+         FILESEXTRAPATHS_prepend := "path_1:path_2:path_3:"
+
+      A final example shows how you can extend the search path and include
+      a :term:`MACHINE`-specific override, which is useful
+      in a BSP layer:
+      ::
+
+          FILESEXTRAPATHS_prepend_intel-x86-common := "${THISDIR}/${PN}:"
+
+      The previous statement appears in the
+      ``linux-yocto-dev.bbappend`` file, which is found in the
+      :ref:`overview-manual/overview-manual-development-environment:yocto project source repositories` in
+      ``meta-intel/common/recipes-kernel/linux``. Here, the machine
+      override is a special :term:`PACKAGE_ARCH`
+      definition for multiple ``meta-intel`` machines.
+
+      .. note::
+
+         For a layer that supports a single BSP, the override could just be
+         the value of
+         MACHINE
+         .
+
+      By prepending paths in ``.bbappend`` files, you allow multiple append
+      files that reside in different layers but are used for the same
+      recipe to correctly extend the path.
+
+   FILESOVERRIDES
+      A subset of :term:`OVERRIDES` used by the
+      OpenEmbedded build system for creating
+      :term:`FILESPATH`. The ``FILESOVERRIDES`` variable
+      uses overrides to automatically extend the
+      :term:`FILESPATH` variable. For an example of how
+      that works, see the :term:`FILESPATH` variable
+      description. Additionally, you find more information on how overrides
+      are handled in the
+      ":ref:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata:conditional syntax (overrides)`"
+      section of the BitBake User Manual.
+
+      By default, the ``FILESOVERRIDES`` variable is defined as:
+      ::
+
+         FILESOVERRIDES = "${TRANSLATED_TARGET_ARCH}:${MACHINEOVERRIDES}:${DISTROOVERRIDES}"
+
+      .. note::
+
+         Do not hand-edit the
+         FILESOVERRIDES
+         variable. The values match up with expected overrides and are used
+         in an expected manner by the build system.
+
+   FILESPATH
+      The default set of directories the OpenEmbedded build system uses
+      when searching for patches and files.
+
+      During the build process, BitBake searches each directory in
+      ``FILESPATH`` in the specified order when looking for files and
+      patches specified by each ``file://`` URI in a recipe's
+      :term:`SRC_URI` statements.
+
+      The default value for the ``FILESPATH`` variable is defined in the
+      ``base.bbclass`` class found in ``meta/classes`` in the
+      :term:`Source Directory`:
+      ::
+
+         FILESPATH = "${@base_set_filespath(["${FILE_DIRNAME}/${BP}", \
+             "${FILE_DIRNAME}/${BPN}", "${FILE_DIRNAME}/files"], d)}"
+
+      The
+      ``FILESPATH`` variable is automatically extended using the overrides
+      from the :term:`FILESOVERRIDES` variable.
+
+      .. note::
+
+         -  Do not hand-edit the ``FILESPATH`` variable. If you want the
+            build system to look in directories other than the defaults,
+            extend the ``FILESPATH`` variable by using the
+            :term:`FILESEXTRAPATHS` variable.
+
+         -  Be aware that the default ``FILESPATH`` directories do not map
+            to directories in custom layers where append files
+            (``.bbappend``) are used. If you want the build system to find
+            patches or files that reside with your append files, you need
+            to extend the ``FILESPATH`` variable by using the
+            ``FILESEXTRAPATHS`` variable.
+
+      You can take advantage of this searching behavior in useful ways. For
+      example, consider a case where the following directory structure
+      exists for general and machine-specific configurations:
+      ::
+
+         files/defconfig
+         files/MACHINEA/defconfig
+         files/MACHINEB/defconfig
+
+      Also in the example, the ``SRC_URI`` statement contains
+      "file://defconfig". Given this scenario, you can set
+      :term:`MACHINE` to "MACHINEA" and cause the build
+      system to use files from ``files/MACHINEA``. Set ``MACHINE`` to
+      "MACHINEB" and the build system uses files from ``files/MACHINEB``.
+      Finally, for any machine other than "MACHINEA" and "MACHINEB", the
+      build system uses files from ``files/defconfig``.
+
+      You can find out more about the patching process in the
+      ":ref:`patching-dev-environment`" section
+      in the Yocto Project Overview and Concepts Manual and the
+      ":ref:`new-recipe-patching-code`" section in
+      the Yocto Project Development Tasks Manual. See the
+      :ref:`ref-tasks-patch` task as well.
+
+   FILESYSTEM_PERMS_TABLES
+      Allows you to define your own file permissions settings table as part
+      of your configuration for the packaging process. For example, suppose
+      you need a consistent set of custom permissions for a set of groups
+      and users across an entire work project. It is best to do this in the
+      packages themselves but this is not always possible.
+
+      By default, the OpenEmbedded build system uses the ``fs-perms.txt``,
+      which is located in the ``meta/files`` folder in the :term:`Source Directory`.
+      If you create your own file
+      permissions setting table, you should place it in your layer or the
+      distro's layer.
+
+      You define the ``FILESYSTEM_PERMS_TABLES`` variable in the
+      ``conf/local.conf`` file, which is found in the :term:`Build Directory`,
+      to point to your custom
+      ``fs-perms.txt``. You can specify more than a single file permissions
+      setting table. The paths you specify to these files must be defined
+      within the :term:`BBPATH` variable.
+
+      For guidance on how to create your own file permissions settings
+      table file, examine the existing ``fs-perms.txt``.
+
+   FIT_HASH_ALG
+      Specifies the hash algorithm used in creating the FIT Image. For e.g. sha256.
+
+   FIT_SIGN_ALG
+      Specifies the signature algorithm used in creating the FIT Image.
+      For e.g. rsa2048.
+
+   FONT_EXTRA_RDEPENDS
+      When inheriting the :ref:`fontcache <ref-classes-fontcache>` class,
+      this variable specifies the runtime dependencies for font packages.
+      By default, the ``FONT_EXTRA_RDEPENDS`` is set to "fontconfig-utils".
+
+   FONT_PACKAGES
+      When inheriting the :ref:`fontcache <ref-classes-fontcache>` class,
+      this variable identifies packages containing font files that need to
+      be cached by Fontconfig. By default, the ``fontcache`` class assumes
+      that fonts are in the recipe's main package (i.e.
+      ``${``\ :term:`PN`\ ``}``). Use this variable if fonts you
+      need are in a package other than that main package.
+
+   FORCE_RO_REMOVE
+      Forces the removal of the packages listed in ``ROOTFS_RO_UNNEEDED``
+      during the generation of the root filesystem.
+
+      Set the variable to "1" to force the removal of these packages.
+
+   FULL_OPTIMIZATION
+      The options to pass in ``TARGET_CFLAGS`` and ``CFLAGS`` when
+      compiling an optimized system. This variable defaults to "-O2 -pipe
+      ${DEBUG_FLAGS}".
+
+   GCCPIE
+      Enables Position Independent Executables (PIE) within the GNU C
+      Compiler (GCC). Enabling PIE in the GCC makes Return Oriented
+      Programming (ROP) attacks much more difficult to execute.
+
+      By default the ``security_flags.inc`` file enables PIE by setting the
+      variable as follows:
+      ::
+
+         GCCPIE ?= "--enable-default-pie"
+
+   GCCVERSION
+      Specifies the default version of the GNU C Compiler (GCC) used for
+      compilation. By default, ``GCCVERSION`` is set to "8.x" in the
+      ``meta/conf/distro/include/tcmode-default.inc`` include file:
+      ::
+
+         GCCVERSION ?= "8.%"
+
+      You can override this value by setting it in a
+      configuration file such as the ``local.conf``.
+
+   GDB
+      The minimal command and arguments to run the GNU Debugger.
+
+   GITDIR
+      The directory in which a local copy of a Git repository is stored
+      when it is cloned.
+
+   GLIBC_GENERATE_LOCALES
+      Specifies the list of GLIBC locales to generate should you not wish
+      to generate all LIBC locals, which can be time consuming.
+
+      .. note::
+
+         If you specifically remove the locale
+         en_US.UTF-8
+         , you must set
+         IMAGE_LINGUAS
+         appropriately.
+
+      You can set ``GLIBC_GENERATE_LOCALES`` in your ``local.conf`` file.
+      By default, all locales are generated.
+      ::
+
+         GLIBC_GENERATE_LOCALES = "en_GB.UTF-8 en_US.UTF-8"
+
+   GROUPADD_PARAM
+      When inheriting the :ref:`useradd <ref-classes-useradd>` class,
+      this variable specifies for a package what parameters should be
+      passed to the ``groupadd`` command if you wish to add a group to the
+      system when the package is installed.
+
+      Here is an example from the ``dbus`` recipe:
+      ::
+
+         GROUPADD_PARAM_${PN} = "-r netdev"
+
+      For information on the standard Linux shell command
+      ``groupadd``, see http://linux.die.net/man/8/groupadd.
+
+   GROUPMEMS_PARAM
+      When inheriting the :ref:`useradd <ref-classes-useradd>` class,
+      this variable specifies for a package what parameters should be
+      passed to the ``groupmems`` command if you wish to modify the members
+      of a group when the package is installed.
+
+      For information on the standard Linux shell command ``groupmems``,
+      see http://linux.die.net/man/8/groupmems.
+
+   GRUB_GFXSERIAL
+      Configures the GNU GRand Unified Bootloader (GRUB) to have graphics
+      and serial in the boot menu. Set this variable to "1" in your
+      ``local.conf`` or distribution configuration file to enable graphics
+      and serial in the menu.
+
+      See the :ref:`grub-efi <ref-classes-grub-efi>` class for more
+      information on how this variable is used.
+
+   GRUB_OPTS
+      Additional options to add to the GNU GRand Unified Bootloader (GRUB)
+      configuration. Use a semi-colon character (``;``) to separate
+      multiple options.
+
+      The ``GRUB_OPTS`` variable is optional. See the
+      :ref:`grub-efi <ref-classes-grub-efi>` class for more information
+      on how this variable is used.
+
+   GRUB_TIMEOUT
+      Specifies the timeout before executing the default ``LABEL`` in the
+      GNU GRand Unified Bootloader (GRUB).
+
+      The ``GRUB_TIMEOUT`` variable is optional. See the
+      :ref:`grub-efi <ref-classes-grub-efi>` class for more information
+      on how this variable is used.
+
+   GTKIMMODULES_PACKAGES
+      When inheriting the
+      :ref:`gtk-immodules-cache <ref-classes-gtk-immodules-cache>` class,
+      this variable specifies the packages that contain the GTK+ input
+      method modules being installed when the modules are in packages other
+      than the main package.
+
+   HOMEPAGE
+      Website where more information about the software the recipe is
+      building can be found.
+
+   HOST_ARCH
+      The name of the target architecture, which is normally the same as
+      :term:`TARGET_ARCH`. The OpenEmbedded build system
+      supports many architectures. Here is an example list of architectures
+      supported. This list is by no means complete as the architecture is
+      configurable:
+
+      - arm
+      - i586
+      - x86_64
+      - powerpc
+      - powerpc64
+      - mips
+      - mipsel
+
+   HOST_CC_ARCH
+      Specifies architecture-specific compiler flags that are passed to the
+      C compiler.
+
+      Default initialization for ``HOST_CC_ARCH`` varies depending on what
+      is being built:
+
+      -  :term:`TARGET_CC_ARCH` when building for the
+         target
+
+      -  ``BUILD_CC_ARCH`` when building for the build host (i.e.
+         ``-native``)
+
+      -  ``BUILDSDK_CC_ARCH`` when building for an SDK (i.e.
+         ``nativesdk-``)
+
+   HOST_OS
+      Specifies the name of the target operating system, which is normally
+      the same as the :term:`TARGET_OS`. The variable can
+      be set to "linux" for ``glibc``-based systems and to "linux-musl" for
+      ``musl``. For ARM/EABI targets, there are also "linux-gnueabi" and
+      "linux-musleabi" values possible.
+
+   HOST_PREFIX
+      Specifies the prefix for the cross-compile toolchain. ``HOST_PREFIX``
+      is normally the same as :term:`TARGET_PREFIX`.
+
+   HOST_SYS
+      Specifies the system, including the architecture and the operating
+      system, for which the build is occurring in the context of the
+      current recipe.
+
+      The OpenEmbedded build system automatically sets this variable based
+      on :term:`HOST_ARCH`,
+      :term:`HOST_VENDOR`, and
+      :term:`HOST_OS` variables.
+
+      .. note::
+
+         You do not need to set the variable yourself.
+
+      Consider these two examples:
+
+      -  Given a native recipe on a 32-bit x86 machine running Linux, the
+         value is "i686-linux".
+
+      -  Given a recipe being built for a little-endian MIPS target running
+         Linux, the value might be "mipsel-linux".
+
+   HOSTTOOLS
+      A space-separated list (filter) of tools on the build host that
+      should be allowed to be called from within build tasks. Using this
+      filter helps reduce the possibility of host contamination. If a tool
+      specified in the value of ``HOSTTOOLS`` is not found on the build
+      host, the OpenEmbedded build system produces an error and the build
+      is not started.
+
+      For additional information, see
+      :term:`HOSTTOOLS_NONFATAL`.
+
+   HOSTTOOLS_NONFATAL
+      A space-separated list (filter) of tools on the build host that
+      should be allowed to be called from within build tasks. Using this
+      filter helps reduce the possibility of host contamination. Unlike
+      :term:`HOSTTOOLS`, the OpenEmbedded build system
+      does not produce an error if a tool specified in the value of
+      ``HOSTTOOLS_NONFATAL`` is not found on the build host. Thus, you can
+      use ``HOSTTOOLS_NONFATAL`` to filter optional host tools.
+
+   HOST_VENDOR
+      Specifies the name of the vendor. ``HOST_VENDOR`` is normally the
+      same as :term:`TARGET_VENDOR`.
+
+   ICECC_DISABLED
+      Disables or enables the ``icecc`` (Icecream) function. For more
+      information on this function and best practices for using this
+      variable, see the ":ref:`icecc.bbclass <ref-classes-icecc>`"
+      section.
+
+      Setting this variable to "1" in your ``local.conf`` disables the
+      function:
+      ::
+
+         ICECC_DISABLED ??= "1"
+
+      To enable the function, set the variable as follows:
+      ::
+
+         ICECC_DISABLED = ""
+
+   ICECC_ENV_EXEC
+      Points to the ``icecc-create-env`` script that you provide. This
+      variable is used by the :ref:`icecc <ref-classes-icecc>` class. You
+      set this variable in your ``local.conf`` file.
+
+      If you do not point to a script that you provide, the OpenEmbedded
+      build system uses the default script provided by the
+      ``icecc-create-env.bb`` recipe, which is a modified version and not
+      the one that comes with ``icecc``.
+
+   ICECC_PARALLEL_MAKE
+      Extra options passed to the ``make`` command during the
+      :ref:`ref-tasks-compile` task that specify parallel
+      compilation. This variable usually takes the form of "-j x", where x
+      represents the maximum number of parallel threads ``make`` can run.
+
+      .. note::
+
+         The options passed affect builds on all enabled machines on the
+         network, which are machines running the
+         iceccd
+         daemon.
+
+      If your enabled machines support multiple cores, coming up with the
+      maximum number of parallel threads that gives you the best
+      performance could take some experimentation since machine speed,
+      network lag, available memory, and existing machine loads can all
+      affect build time. Consequently, unlike the
+      :term:`PARALLEL_MAKE` variable, there is no
+      rule-of-thumb for setting ``ICECC_PARALLEL_MAKE`` to achieve optimal
+      performance.
+
+      If you do not set ``ICECC_PARALLEL_MAKE``, the build system does not
+      use it (i.e. the system does not detect and assign the number of
+      cores as is done with ``PARALLEL_MAKE``).
+
+   ICECC_PATH
+      The location of the ``icecc`` binary. You can set this variable in
+      your ``local.conf`` file. If your ``local.conf`` file does not define
+      this variable, the :ref:`icecc <ref-classes-icecc>` class attempts
+      to define it by locating ``icecc`` using ``which``.
+
+   ICECC_USER_CLASS_BL
+      Identifies user classes that you do not want the Icecream distributed
+      compile support to consider. This variable is used by the
+      :ref:`icecc <ref-classes-icecc>` class. You set this variable in
+      your ``local.conf`` file.
+
+      When you list classes using this variable, you are "blacklisting"
+      them from distributed compilation across remote hosts. Any classes
+      you list will be distributed and compiled locally.
+
+   ICECC_USER_PACKAGE_BL
+      Identifies user recipes that you do not want the Icecream distributed
+      compile support to consider. This variable is used by the
+      :ref:`icecc <ref-classes-icecc>` class. You set this variable in
+      your ``local.conf`` file.
+
+      When you list packages using this variable, you are "blacklisting"
+      them from distributed compilation across remote hosts. Any packages
+      you list will be distributed and compiled locally.
+
+   ICECC_USER_PACKAGE_WL
+      Identifies user recipes that use an empty
+      :term:`PARALLEL_MAKE` variable that you want to
+      force remote distributed compilation on using the Icecream
+      distributed compile support. This variable is used by the
+      :ref:`icecc <ref-classes-icecc>` class. You set this variable in
+      your ``local.conf`` file.
+
+   IMAGE_BASENAME
+      The base name of image output files. This variable defaults to the
+      recipe name (``${``\ :term:`PN`\ ``}``).
+
+   IMAGE_BOOT_FILES
+      A space-separated list of files installed into the boot partition
+      when preparing an image using the Wic tool with the
+      ``bootimg-partition`` or ``bootimg-efi`` source plugin. By default,
+      the files are
+      installed under the same name as the source files. To change the
+      installed name, separate it from the original name with a semi-colon
+      (;). Source files need to be located in
+      :term:`DEPLOY_DIR_IMAGE`. Here are two
+      examples:
+      ::
+
+         IMAGE_BOOT_FILES = "u-boot.img uImage;kernel"
+         IMAGE_BOOT_FILES = "u-boot.${UBOOT_SUFFIX} ${KERNEL_IMAGETYPE}"
+
+      Alternatively, source files can be picked up using a glob pattern. In
+      this case, the destination file must have the same name as the base
+      name of the source file path. To install files into a directory
+      within the target location, pass its name after a semi-colon (;).
+      Here are two examples:
+      ::
+
+         IMAGE_BOOT_FILES = "bcm2835-bootfiles/*"
+         IMAGE_BOOT_FILES = "bcm2835-bootfiles/*;boot/"
+
+      The first example
+      installs all files from ``${DEPLOY_DIR_IMAGE}/bcm2835-bootfiles``
+      into the root of the target partition. The second example installs
+      the same files into a ``boot`` directory within the target partition.
+
+      You can find information on how to use the Wic tool in the
+      ":ref:`dev-manual/dev-manual-common-tasks:creating partitioned images using wic`"
+      section of the Yocto Project Development Tasks Manual. Reference
+      material for Wic is located in the
+      ":doc:`../ref-manual/ref-kickstart`" chapter.
+
+   IMAGE_CLASSES
+      A list of classes that all images should inherit. You typically use
+      this variable to specify the list of classes that register the
+      different types of images the OpenEmbedded build system creates.
+
+      The default value for ``IMAGE_CLASSES`` is ``image_types``. You can
+      set this variable in your ``local.conf`` or in a distribution
+      configuration file.
+
+      For more information, see ``meta/classes/image_types.bbclass`` in the
+      :term:`Source Directory`.
+
+   IMAGE_CMD
+      Specifies the command to create the image file for a specific image
+      type, which corresponds to the value set set in
+      :term:`IMAGE_FSTYPES`, (e.g. ``ext3``,
+      ``btrfs``, and so forth). When setting this variable, you should use
+      an override for the associated type. Here is an example:
+      ::
+
+         IMAGE_CMD_jffs2 = "mkfs.jffs2 --root=${IMAGE_ROOTFS} \
+             --faketime --output=${DEPLOY_DIR_IMAGE}/${IMAGE_NAME}.rootfs.jffs2 \
+             ${EXTRA_IMAGECMD}"
+
+      You typically do not need to set this variable unless you are adding
+      support for a new image type. For more examples on how to set this
+      variable, see the :ref:`image_types <ref-classes-image_types>`
+      class file, which is ``meta/classes/image_types.bbclass``.
+
+   IMAGE_DEVICE_TABLES
+      Specifies one or more files that contain custom device tables that
+      are passed to the ``makedevs`` command as part of creating an image.
+      These files list basic device nodes that should be created under
+      ``/dev`` within the image. If ``IMAGE_DEVICE_TABLES`` is not set,
+      ``files/device_table-minimal.txt`` is used, which is located by
+      :term:`BBPATH`. For details on how you should write
+      device table files, see ``meta/files/device_table-minimal.txt`` as an
+      example.
+
+   IMAGE_FEATURES
+      The primary list of features to include in an image. Typically, you
+      configure this variable in an image recipe. Although you can use this
+      variable from your ``local.conf`` file, which is found in the
+      :term:`Build Directory`, best practices dictate that you do
+      not.
+
+      .. note::
+
+         To enable extra features from outside the image recipe, use the
+         EXTRA_IMAGE_FEATURES
+         variable.
+
+      For a list of image features that ships with the Yocto Project, see
+      the "`Image Features <#ref-features-image>`__" section.
+
+      For an example that shows how to customize your image by using this
+      variable, see the ":ref:`usingpoky-extend-customimage-imagefeatures`"
+      section in the Yocto Project Development Tasks Manual.
+
+   IMAGE_FSTYPES
+      Specifies the formats the OpenEmbedded build system uses during the
+      build when creating the root filesystem. For example, setting
+      ``IMAGE_FSTYPES`` as follows causes the build system to create root
+      filesystems using two formats: ``.ext3`` and ``.tar.bz2``:
+      ::
+
+         IMAGE_FSTYPES = "ext3 tar.bz2"
+
+      For the complete list of supported image formats from which you can
+      choose, see :term:`IMAGE_TYPES`.
+
+      .. note::
+
+         -  If an image recipe uses the "inherit image" line and you are
+            setting ``IMAGE_FSTYPES`` inside the recipe, you must set
+            ``IMAGE_FSTYPES`` prior to using the "inherit image" line.
+
+         -  Due to the way the OpenEmbedded build system processes this
+            variable, you cannot update its contents by using ``_append``
+            or ``_prepend``. You must use the ``+=`` operator to add one or
+            more options to the ``IMAGE_FSTYPES`` variable.
+
+   IMAGE_INSTALL
+      Used by recipes to specify the packages to install into an image
+      through the :ref:`image <ref-classes-image>` class. Use the
+      ``IMAGE_INSTALL`` variable with care to avoid ordering issues.
+
+      Image recipes set ``IMAGE_INSTALL`` to specify the packages to
+      install into an image through ``image.bbclass``. Additionally,
+      "helper" classes such as the
+      :ref:`core-image <ref-classes-core-image>` class exist that can
+      take lists used with ``IMAGE_FEATURES`` and turn them into
+      auto-generated entries in ``IMAGE_INSTALL`` in addition to its
+      default contents.
+
+      When you use this variable, it is best to use it as follows:
+      ::
+
+         IMAGE_INSTALL_append = " package-name"
+
+      Be sure to include the space
+      between the quotation character and the start of the package name or
+      names.
+
+      .. note::
+
+         -  When working with a
+            ```core-image-minimal-initramfs`` <#images-core-image-minimal-initramfs>`__
+            image, do not use the ``IMAGE_INSTALL`` variable to specify
+            packages for installation. Instead, use the
+            :term:`PACKAGE_INSTALL` variable, which
+            allows the initial RAM filesystem (initramfs) recipe to use a
+            fixed set of packages and not be affected by ``IMAGE_INSTALL``.
+            For information on creating an initramfs, see the
+            ":ref:`building-an-initramfs-image`"
+            section in the Yocto Project Development Tasks Manual.
+
+         -  Using ``IMAGE_INSTALL`` with the
+            :ref:`+= <bitbake:appending-and-prepending>`
+            BitBake operator within the ``/conf/local.conf`` file or from
+            within an image recipe is not recommended. Use of this operator
+            in these ways can cause ordering issues. Since
+            ``core-image.bbclass`` sets ``IMAGE_INSTALL`` to a default
+            value using the
+            :ref:`?= <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:setting a default value (?=)>`
+            operator, using a ``+=`` operation against ``IMAGE_INSTALL``
+            results in unexpected behavior when used within
+            ``conf/local.conf``. Furthermore, the same operation from
+            within an image recipe may or may not succeed depending on the
+            specific situation. In both these cases, the behavior is
+            contrary to how most users expect the ``+=`` operator to work.
+
+   IMAGE_LINGUAS
+      Specifies the list of locales to install into the image during the
+      root filesystem construction process. The OpenEmbedded build system
+      automatically splits locale files, which are used for localization,
+      into separate packages. Setting the ``IMAGE_LINGUAS`` variable
+      ensures that any locale packages that correspond to packages already
+      selected for installation into the image are also installed. Here is
+      an example:
+      ::
+
+         IMAGE_LINGUAS = "pt-br de-de"
+
+      In this example, the build system ensures any Brazilian Portuguese
+      and German locale files that correspond to packages in the image are
+      installed (i.e. ``*-locale-pt-br`` and ``*-locale-de-de`` as well as
+      ``*-locale-pt`` and ``*-locale-de``, since some software packages
+      only provide locale files by language and not by country-specific
+      language).
+
+      See the :term:`GLIBC_GENERATE_LOCALES`
+      variable for information on generating GLIBC locales.
+
+   IMAGE_MANIFEST
+      The manifest file for the image. This file lists all the installed
+      packages that make up the image. The file contains package
+      information on a line-per-package basis as follows:
+      ::
+
+          packagename packagearch version
+
+      The :ref:`image <ref-classes-image>` class defines the manifest
+      file as follows:
+      ::
+
+         IMAGE_MANIFEST ="${DEPLOY_DIR_IMAGE}/${IMAGE_NAME}.rootfs.manifest"
+
+      The location is
+      derived using the :term:`DEPLOY_DIR_IMAGE`
+      and :term:`IMAGE_NAME` variables. You can find
+      information on how the image is created in the ":ref:`image-generation-dev-environment`"
+      section in the Yocto Project Overview and Concepts Manual.
+
+   IMAGE_NAME
+      The name of the output image files minus the extension. This variable
+      is derived using the :term:`IMAGE_BASENAME`,
+      :term:`MACHINE`, and :term:`DATETIME`
+      variables:
+      ::
+
+         IMAGE_NAME = "${IMAGE_BASENAME}-${MACHINE}-${DATETIME}"
+
+   IMAGE_OVERHEAD_FACTOR
+      Defines a multiplier that the build system applies to the initial
+      image size for cases when the multiplier times the returned disk
+      usage value for the image is greater than the sum of
+      ``IMAGE_ROOTFS_SIZE`` and ``IMAGE_ROOTFS_EXTRA_SPACE``. The result of
+      the multiplier applied to the initial image size creates free disk
+      space in the image as overhead. By default, the build process uses a
+      multiplier of 1.3 for this variable. This default value results in
+      30% free disk space added to the image when this method is used to
+      determine the final generated image size. You should be aware that
+      post install scripts and the package management system uses disk
+      space inside this overhead area. Consequently, the multiplier does
+      not produce an image with all the theoretical free disk space. See
+      ``IMAGE_ROOTFS_SIZE`` for information on how the build system
+      determines the overall image size.
+
+      The default 30% free disk space typically gives the image enough room
+      to boot and allows for basic post installs while still leaving a
+      small amount of free disk space. If 30% free space is inadequate, you
+      can increase the default value. For example, the following setting
+      gives you 50% free space added to the image:
+      ::
+
+         IMAGE_OVERHEAD_FACTOR = "1.5"
+
+      Alternatively, you can ensure a specific amount of free disk space is
+      added to the image by using the ``IMAGE_ROOTFS_EXTRA_SPACE``
+      variable.
+
+   IMAGE_PKGTYPE
+      Defines the package type (i.e. DEB, RPM, IPK, or TAR) used by the
+      OpenEmbedded build system. The variable is defined appropriately by
+      the :ref:`package_deb <ref-classes-package_deb>`,
+      :ref:`package_rpm <ref-classes-package_rpm>`,
+      :ref:`package_ipk <ref-classes-package_ipk>`, or
+      :ref:`package_tar <ref-classes-package_tar>` class.
+
+      .. note::
+
+         The
+         package_tar
+         class is broken and is not supported. It is recommended that you
+         do not use it.
+
+      The :ref:`populate_sdk_* <ref-classes-populate-sdk-*>` and
+      :ref:`image <ref-classes-image>` classes use the ``IMAGE_PKGTYPE``
+      for packaging up images and SDKs.
+
+      You should not set the ``IMAGE_PKGTYPE`` manually. Rather, the
+      variable is set indirectly through the appropriate
+      :ref:`package_* <ref-classes-package>` class using the
+      :term:`PACKAGE_CLASSES` variable. The
+      OpenEmbedded build system uses the first package type (e.g. DEB, RPM,
+      or IPK) that appears with the variable
+
+      .. note::
+
+         Files using the
+         .tar
+         format are never used as a substitute packaging format for DEB,
+         RPM, and IPK formatted files for your image or SDK.
+
+   IMAGE_POSTPROCESS_COMMAND
+      Specifies a list of functions to call once the OpenEmbedded build
+      system creates the final image output files. You can specify
+      functions separated by semicolons:
+      ::
+
+         IMAGE_POSTPROCESS_COMMAND += "function; ... "
+
+      If you need to pass the root filesystem path to a command within the
+      function, you can use ``${IMAGE_ROOTFS}``, which points to the
+      directory that becomes the root filesystem image. See the
+      :term:`IMAGE_ROOTFS` variable for more
+      information.
+
+   IMAGE_PREPROCESS_COMMAND
+      Specifies a list of functions to call before the OpenEmbedded build
+      system creates the final image output files. You can specify
+      functions separated by semicolons:
+      ::
+
+         IMAGE_PREPROCESS_COMMAND += "function; ... "
+
+      If you need to pass the root filesystem path to a command within the
+      function, you can use ``${IMAGE_ROOTFS}``, which points to the
+      directory that becomes the root filesystem image. See the
+      :term:`IMAGE_ROOTFS` variable for more
+      information.
+
+   IMAGE_ROOTFS
+      The location of the root filesystem while it is under construction
+      (i.e. during the :ref:`ref-tasks-rootfs` task). This
+      variable is not configurable. Do not change it.
+
+   IMAGE_ROOTFS_ALIGNMENT
+      Specifies the alignment for the output image file in Kbytes. If the
+      size of the image is not a multiple of this value, then the size is
+      rounded up to the nearest multiple of the value. The default value is
+      "1". See :term:`IMAGE_ROOTFS_SIZE` for
+      additional information.
+
+   IMAGE_ROOTFS_EXTRA_SPACE
+      Defines additional free disk space created in the image in Kbytes. By
+      default, this variable is set to "0". This free disk space is added
+      to the image after the build system determines the image size as
+      described in ``IMAGE_ROOTFS_SIZE``.
+
+      This variable is particularly useful when you want to ensure that a
+      specific amount of free disk space is available on a device after an
+      image is installed and running. For example, to be sure 5 Gbytes of
+      free disk space is available, set the variable as follows:
+      ::
+
+         IMAGE_ROOTFS_EXTRA_SPACE = "5242880"
+
+      For example, the Yocto Project Build Appliance specifically requests
+      40 Gbytes of extra space with the line:
+      ::
+
+         IMAGE_ROOTFS_EXTRA_SPACE = "41943040"
+
+   IMAGE_ROOTFS_SIZE
+      Defines the size in Kbytes for the generated image. The OpenEmbedded
+      build system determines the final size for the generated image using
+      an algorithm that takes into account the initial disk space used for
+      the generated image, a requested size for the image, and requested
+      additional free disk space to be added to the image. Programatically,
+      the build system determines the final size of the generated image as
+      follows:
+      ::
+
+         if (image-du * overhead) < rootfs-size:
+             internal-rootfs-size = rootfs-size + xspace
+         else:
+             internal-rootfs-size = (image-du * overhead) + xspace
+         where:
+             image-du = Returned value of the du command on the image.
+             overhead = IMAGE_OVERHEAD_FACTOR
+             rootfs-size = IMAGE_ROOTFS_SIZE
+             internal-rootfs-size = Initial root filesystem size before any modifications.
+             xspace = IMAGE_ROOTFS_EXTRA_SPACE
+
+      See the :term:`IMAGE_OVERHEAD_FACTOR`
+      and :term:`IMAGE_ROOTFS_EXTRA_SPACE`
+      variables for related information.
+
+   IMAGE_TYPEDEP
+      Specifies a dependency from one image type on another. Here is an
+      example from the :ref:`image-live <ref-classes-image-live>` class:
+      ::
+
+         IMAGE_TYPEDEP_live = "ext3"
+
+      In the previous example, the variable ensures that when "live" is
+      listed with the :term:`IMAGE_FSTYPES` variable,
+      the OpenEmbedded build system produces an ``ext3`` image first since
+      one of the components of the live image is an ``ext3`` formatted
+      partition containing the root filesystem.
+
+   IMAGE_TYPES
+      Specifies the complete list of supported image types by default:
+
+      - btrfs
+      - container
+      - cpio
+      - cpio.gz
+      - cpio.lz4
+      - cpio.lzma
+      - cpio.xz
+      - cramfs
+      - ext2
+      - ext2.bz2
+      - ext2.gz
+      - ext2.lzma
+      - ext3
+      - ext3.gz
+      - ext4
+      - ext4.gz
+      - f2fs
+      - hddimg
+      - iso
+      - jffs2
+      - jffs2.sum
+      - multiubi
+      - squashfs
+      - squashfs-lz4
+      - squashfs-lzo
+      - squashfs-xz
+      - tar
+      - tar.bz2
+      - tar.gz
+      - tar.lz4
+      - tar.xz
+      - tar.zst
+      - ubi
+      - ubifs
+      - wic
+      - wic.bz2
+      - wic.gz
+      - wic.lzma
+
+      For more information about these types of images, see
+      ``meta/classes/image_types*.bbclass`` in the :term:`Source Directory`.
+
+   INC_PR
+      Helps define the recipe revision for recipes that share a common
+      ``include`` file. You can think of this variable as part of the
+      recipe revision as set from within an include file.
+
+      Suppose, for example, you have a set of recipes that are used across
+      several projects. And, within each of those recipes the revision (its
+      :term:`PR` value) is set accordingly. In this case, when
+      the revision of those recipes changes, the burden is on you to find
+      all those recipes and be sure that they get changed to reflect the
+      updated version of the recipe. In this scenario, it can get
+      complicated when recipes that are used in many places and provide
+      common functionality are upgraded to a new revision.
+
+      A more efficient way of dealing with this situation is to set the
+      ``INC_PR`` variable inside the ``include`` files that the recipes
+      share and then expand the ``INC_PR`` variable within the recipes to
+      help define the recipe revision.
+
+      The following provides an example that shows how to use the
+      ``INC_PR`` variable given a common ``include`` file that defines the
+      variable. Once the variable is defined in the ``include`` file, you
+      can use the variable to set the ``PR`` values in each recipe. You
+      will notice that when you set a recipe's ``PR`` you can provide more
+      granular revisioning by appending values to the ``INC_PR`` variable:
+      ::
+
+         recipes-graphics/xorg-font/xorg-font-common.inc:INC_PR = "r2"
+         recipes-graphics/xorg-font/encodings_1.0.4.bb:PR = "${INC_PR}.1"
+         recipes-graphics/xorg-font/font-util_1.3.0.bb:PR = "${INC_PR}.0"
+         recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
+
+      The
+      first line of the example establishes the baseline revision to be
+      used for all recipes that use the ``include`` file. The remaining
+      lines in the example are from individual recipes and show how the
+      ``PR`` value is set.
+
+   INCOMPATIBLE_LICENSE
+      Specifies a space-separated list of license names (as they would
+      appear in :term:`LICENSE`) that should be excluded
+      from the build. Recipes that provide no alternatives to listed
+      incompatible licenses are not built. Packages that are individually
+      licensed with the specified incompatible licenses will be deleted.
+
+      .. note::
+
+         This functionality is only regularly tested using the following
+         setting:
+         ::
+
+                 INCOMPATIBLE_LICENSE = "GPL-3.0 LGPL-3.0 AGPL-3.0"
+
+
+         Although you can use other settings, you might be required to
+         remove dependencies on or provide alternatives to components that
+         are required to produce a functional system image.
+
+      .. note::
+
+         It is possible to define a list of licenses that are allowed to be
+         used instead of the licenses that are excluded. To do this, define
+         a variable
+         COMPATIBLE_LICENSES
+         with the names of the licences that are allowed. Then define
+         INCOMPATIBLE_LICENSE
+         as:
+         ::
+
+                 INCOMPATIBLE_LICENSE = "${@' '.join(sorted(set(d.getVar('AVAILABLE_LICENSES').split()) - set(d.getVar('COMPATIBLE_LICENSES').split())))}"
+
+
+         This will result in
+         INCOMPATIBLE_LICENSE
+         containing the names of all licences from
+         AVAILABLE_LICENSES
+         except the ones specified in
+         COMPATIBLE_LICENSES
+         , thus only allowing the latter licences to be used.
+
+   INHERIT
+      Causes the named class or classes to be inherited globally. Anonymous
+      functions in the class or classes are not executed for the base
+      configuration and in each individual recipe. The OpenEmbedded build
+      system ignores changes to ``INHERIT`` in individual recipes.
+
+      For more information on ``INHERIT``, see the
+      :ref:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata:\`\`inherit\`\` configuration directive`"
+      section in the Bitbake User Manual.
+
+   INHERIT_DISTRO
+      Lists classes that will be inherited at the distribution level. It is
+      unlikely that you want to edit this variable.
+
+      The default value of the variable is set as follows in the
+      ``meta/conf/distro/defaultsetup.conf`` file:
+      ::
+
+         INHERIT_DISTRO ?= "debian devshell sstate license"
+
+   INHIBIT_DEFAULT_DEPS
+      Prevents the default dependencies, namely the C compiler and standard
+      C library (libc), from being added to :term:`DEPENDS`.
+      This variable is usually used within recipes that do not require any
+      compilation using the C compiler.
+
+      Set the variable to "1" to prevent the default dependencies from
+      being added.
+
+   INHIBIT_PACKAGE_DEBUG_SPLIT
+      Prevents the OpenEmbedded build system from splitting out debug
+      information during packaging. By default, the build system splits out
+      debugging information during the
+      :ref:`ref-tasks-package` task. For more information on
+      how debug information is split out, see the
+      :term:`PACKAGE_DEBUG_SPLIT_STYLE`
+      variable.
+
+      To prevent the build system from splitting out debug information
+      during packaging, set the ``INHIBIT_PACKAGE_DEBUG_SPLIT`` variable as
+      follows:
+      ::
+
+         INHIBIT_PACKAGE_DEBUG_SPLIT = "1"
+
+   INHIBIT_PACKAGE_STRIP
+      If set to "1", causes the build to not strip binaries in resulting
+      packages and prevents the ``-dbg`` package from containing the source
+      files.
+
+      By default, the OpenEmbedded build system strips binaries and puts
+      the debugging symbols into ``${``\ :term:`PN`\ ``}-dbg``.
+      Consequently, you should not set ``INHIBIT_PACKAGE_STRIP`` when you
+      plan to debug in general.
+
+   INHIBIT_SYSROOT_STRIP
+      If set to "1", causes the build to not strip binaries in the
+      resulting sysroot.
+
+      By default, the OpenEmbedded build system strips binaries in the
+      resulting sysroot. When you specifically set the
+      ``INHIBIT_SYSROOT_STRIP`` variable to "1" in your recipe, you inhibit
+      this stripping.
+
+      If you want to use this variable, include the
+      :ref:`staging <ref-classes-staging>` class. This class uses a
+      ``sys_strip()`` function to test for the variable and acts
+      accordingly.
+
+      .. note::
+
+         Use of the
+         INHIBIT_SYSROOT_STRIP
+         variable occurs in rare and special circumstances. For example,
+         suppose you are building bare-metal firmware by using an external
+         GCC toolchain. Furthermore, even if the toolchain's binaries are
+         strippable, other files exist that are needed for the build that
+         are not strippable.
+
+   INITRAMFS_FSTYPES
+      Defines the format for the output image of an initial RAM filesystem
+      (initramfs), which is used during boot. Supported formats are the
+      same as those supported by the
+      :term:`IMAGE_FSTYPES` variable.
+
+      The default value of this variable, which is set in the
+      ``meta/conf/bitbake.conf`` configuration file in the
+      :term:`Source Directory`, is "cpio.gz". The Linux kernel's
+      initramfs mechanism, as opposed to the initial RAM filesystem
+      `initrd <https://en.wikipedia.org/wiki/Initrd>`__ mechanism, expects
+      an optionally compressed cpio archive.
+
+   INITRAMFS_IMAGE
+      Specifies the :term:`PROVIDES` name of an image
+      recipe that is used to build an initial RAM filesystem (initramfs)
+      image. In other words, the ``INITRAMFS_IMAGE`` variable causes an
+      additional recipe to be built as a dependency to whatever root
+      filesystem recipe you might be using (e.g. ``core-image-sato``). The
+      initramfs image recipe you provide should set
+      :term:`IMAGE_FSTYPES` to
+      :term:`INITRAMFS_FSTYPES`.
+
+      An initramfs image provides a temporary root filesystem used for
+      early system initialization (e.g. loading of modules needed to locate
+      and mount the "real" root filesystem).
+
+      .. note::
+
+         See the
+         meta/recipes-core/images/core-image-minimal-initramfs.bb
+         recipe in the
+         Source Directory
+         for an example initramfs recipe. To select this sample recipe as
+         the one built to provide the initramfs image, set
+         INITRAMFS_IMAGE
+         to "core-image-minimal-initramfs".
+
+      You can also find more information by referencing the
+      ``meta-poky/conf/local.conf.sample.extended`` configuration file in
+      the Source Directory, the :ref:`image <ref-classes-image>` class,
+      and the :ref:`kernel <ref-classes-kernel>` class to see how to use
+      the ``INITRAMFS_IMAGE`` variable.
+
+      If ``INITRAMFS_IMAGE`` is empty, which is the default, then no
+      initramfs image is built.
+
+      For more information, you can also see the
+      :term:`INITRAMFS_IMAGE_BUNDLE`
+      variable, which allows the generated image to be bundled inside the
+      kernel image. Additionally, for information on creating an initramfs
+      image, see the ":ref:`building-an-initramfs-image`" section
+      in the Yocto Project Development Tasks Manual.
+
+   INITRAMFS_IMAGE_BUNDLE
+      Controls whether or not the image recipe specified by
+      :term:`INITRAMFS_IMAGE` is run through an
+      extra pass
+      (:ref:`ref-tasks-bundle_initramfs`) during
+      kernel compilation in order to build a single binary that contains
+      both the kernel image and the initial RAM filesystem (initramfs)
+      image. This makes use of the
+      :term:`CONFIG_INITRAMFS_SOURCE` kernel
+      feature.
+
+      .. note::
+
+         Using an extra compilation pass to bundle the initramfs avoids a
+         circular dependency between the kernel recipe and the initramfs
+         recipe should the initramfs include kernel modules. Should that be
+         the case, the initramfs recipe depends on the kernel for the
+         kernel modules, and the kernel depends on the initramfs recipe
+         since the initramfs is bundled inside the kernel image.
+
+      The combined binary is deposited into the ``tmp/deploy`` directory,
+      which is part of the :term:`Build Directory`.
+
+      Setting the variable to "1" in a configuration file causes the
+      OpenEmbedded build system to generate a kernel image with the
+      initramfs specified in ``INITRAMFS_IMAGE`` bundled within:
+      ::
+
+         INITRAMFS_IMAGE_BUNDLE = "1"
+
+      By default, the
+      :ref:`kernel <ref-classes-kernel>` class sets this variable to a
+      null string as follows:
+      ::
+
+         INITRAMFS_IMAGE_BUNDLE ?= ""
+
+      .. note::
+
+         You must set the
+         INITRAMFS_IMAGE_BUNDLE
+         variable in a configuration file. You cannot set the variable in a
+         recipe file.
+
+      See the
+      :yocto_git:`local.conf.sample.extended </cgit/cgit.cgi/poky/tree/meta-poky/conf/local.conf.sample.extended>`
+      file for additional information. Also, for information on creating an
+      initramfs, see the ":ref:`building-an-initramfs-image`" section
+      in the Yocto Project Development Tasks Manual.
+
+   INITRAMFS_LINK_NAME
+      The link name of the initial RAM filesystem image. This variable is
+      set in the ``meta/classes/kernel-artifact-names.bbclass`` file as
+      follows:
+      ::
+
+         INITRAMFS_LINK_NAME ?= "initramfs-${KERNEL_ARTIFACT_LINK_NAME}"
+
+      The value of the
+      ``KERNEL_ARTIFACT_LINK_NAME`` variable, which is set in the same
+      file, has the following value:
+      ::
+
+         KERNEL_ARTIFACT_LINK_NAME ?= "${MACHINE}"
+
+      See the :term:`MACHINE` variable for additional
+      information.
+
+   INITRAMFS_NAME
+      The base name of the initial RAM filesystem image. This variable is
+      set in the ``meta/classes/kernel-artifact-names.bbclass`` file as
+      follows:
+      ::
+
+         INITRAMFS_NAME ?= "initramfs-${KERNEL_ARTIFACT_NAME}"
+
+      The value of the :term:`KERNEL_ARTIFACT_NAME`
+      variable, which is set in the same file, has the following value:
+      ::
+
+         KERNEL_ARTIFACT_NAME ?= "${PKGE}-${PKGV}-${PKGR}-${MACHINE}${IMAGE_VERSION_SUFFIX}"
+
+   INITRD
+      Indicates list of filesystem images to concatenate and use as an
+      initial RAM disk (``initrd``).
+
+      The ``INITRD`` variable is an optional variable used with the
+      :ref:`image-live <ref-classes-image-live>` class.
+
+   INITRD_IMAGE
+      When building a "live" bootable image (i.e. when
+      :term:`IMAGE_FSTYPES` contains "live"),
+      ``INITRD_IMAGE`` specifies the image recipe that should be built to
+      provide the initial RAM disk image. The default value is
+      "core-image-minimal-initramfs".
+
+      See the :ref:`image-live <ref-classes-image-live>` class for more
+      information.
+
+   INITSCRIPT_NAME
+      The filename of the initialization script as installed to
+      ``${sysconfdir}/init.d``.
+
+      This variable is used in recipes when using ``update-rc.d.bbclass``.
+      The variable is mandatory.
+
+   INITSCRIPT_PACKAGES
+      A list of the packages that contain initscripts. If multiple packages
+      are specified, you need to append the package name to the other
+      ``INITSCRIPT_*`` as an override.
+
+      This variable is used in recipes when using ``update-rc.d.bbclass``.
+      The variable is optional and defaults to the :term:`PN`
+      variable.
+
+   INITSCRIPT_PARAMS
+      Specifies the options to pass to ``update-rc.d``. Here is an example:
+      ::
+
+         INITSCRIPT_PARAMS = "start 99 5 2 . stop 20 0 1 6 ."
+
+      In this example, the script has a runlevel of 99, starts the script
+      in initlevels 2 and 5, and stops the script in levels 0, 1 and 6.
+
+      The variable's default value is "defaults", which is set in the
+      :ref:`update-rc.d <ref-classes-update-rc.d>` class.
+
+      The value in ``INITSCRIPT_PARAMS`` is passed through to the
+      ``update-rc.d`` command. For more information on valid parameters,
+      please see the ``update-rc.d`` manual page at
+      https://manpages.debian.org/buster/init-system-helpers/update-rc.d.8.en.html
+
+   INSANE_SKIP
+      Specifies the QA checks to skip for a specific package within a
+      recipe. For example, to skip the check for symbolic link ``.so``
+      files in the main package of a recipe, add the following to the
+      recipe. The package name override must be used, which in this example
+      is ``${PN}``:
+      ::
+
+         INSANE_SKIP_${PN} += "dev-so"
+
+      See the ":ref:`insane.bbclass <ref-classes-insane>`" section for a
+      list of the valid QA checks you can specify using this variable.
+
+   INSTALL_TIMEZONE_FILE
+      By default, the ``tzdata`` recipe packages an ``/etc/timezone`` file.
+      Set the ``INSTALL_TIMEZONE_FILE`` variable to "0" at the
+      configuration level to disable this behavior.
+
+   IPK_FEED_URIS
+      When the IPK backend is in use and package management is enabled on
+      the target, you can use this variable to set up ``opkg`` in the
+      target image to point to package feeds on a nominated server. Once
+      the feed is established, you can perform installations or upgrades
+      using the package manager at runtime.
+
+   KARCH
+      Defines the kernel architecture used when assembling the
+      configuration. Architectures supported for this release are:
+
+      - powerpc
+      - i386
+      - x86_64
+      - arm
+      - qemu
+      - mips
+
+      You define the ``KARCH`` variable in the :ref:`kernel-dev/kernel-dev-advanced:bsp descriptions`.
+
+   KBRANCH
+      A regular expression used by the build process to explicitly identify
+      the kernel branch that is validated, patched, and configured during a
+      build. You must set this variable to ensure the exact kernel branch
+      you want is being used by the build process.
+
+      Values for this variable are set in the kernel's recipe file and the
+      kernel's append file. For example, if you are using the
+      ``linux-yocto_4.12`` kernel, the kernel recipe file is the
+      ``meta/recipes-kernel/linux/linux-yocto_4.12.bb`` file. ``KBRANCH``
+      is set as follows in that kernel recipe file:
+      ::
+
+         KBRANCH ?= "standard/base"
+
+      This variable is also used from the kernel's append file to identify
+      the kernel branch specific to a particular machine or target
+      hardware. Continuing with the previous kernel example, the kernel's
+      append file (i.e. ``linux-yocto_4.12.bbappend``) is located in the
+      BSP layer for a given machine. For example, the append file for the
+      Beaglebone, EdgeRouter, and generic versions of both 32 and 64-bit IA
+      machines (``meta-yocto-bsp``) is named
+      ``meta-yocto-bsp/recipes-kernel/linux/linux-yocto_4.12.bbappend``.
+      Here are the related statements from that append file:
+      ::
+
+         KBRANCH_genericx86 = "standard/base"
+         KBRANCH_genericx86-64 = "standard/base"
+         KBRANCH_edgerouter = "standard/edgerouter"
+         KBRANCH_beaglebone = "standard/beaglebone"
+
+      The ``KBRANCH`` statements
+      identify the kernel branch to use when building for each supported
+      BSP.
+
+   KBUILD_DEFCONFIG
+      When used with the :ref:`kernel-yocto <ref-classes-kernel-yocto>`
+      class, specifies an "in-tree" kernel configuration file for use
+      during a kernel build.
+
+      Typically, when using a ``defconfig`` to configure a kernel during a
+      build, you place the file in your layer in the same manner as you
+      would place patch files and configuration fragment files (i.e.
+      "out-of-tree"). However, if you want to use a ``defconfig`` file that
+      is part of the kernel tree (i.e. "in-tree"), you can use the
+      ``KBUILD_DEFCONFIG`` variable and append the
+      :term:`KMACHINE` variable to point to the
+      ``defconfig`` file.
+
+      To use the variable, set it in the append file for your kernel recipe
+      using the following form:
+      ::
+
+         KBUILD_DEFCONFIG_KMACHINE ?= defconfig_file
+
+      Here is an example from a "raspberrypi2" ``KMACHINE`` build that uses
+      a ``defconfig`` file named "bcm2709_defconfig":
+      ::
+
+         KBUILD_DEFCONFIG_raspberrypi2 = "bcm2709_defconfig"
+
+      As an alternative, you can use the following within your append file:
+      ::
+
+         KBUILD_DEFCONFIG_pn-linux-yocto ?= defconfig_file
+
+      For more
+      information on how to use the ``KBUILD_DEFCONFIG`` variable, see the
+      ":ref:`kernel-dev/kernel-dev-common:using an "in-tree" \`\`defconfig\`\` file`"
+      section in the Yocto Project Linux Kernel Development Manual.
+
+   KERNEL_ALT_IMAGETYPE
+      Specifies an alternate kernel image type for creation in addition to
+      the kernel image type specified using the
+      :term:`KERNEL_IMAGETYPE` variable.
+
+   KERNEL_ARTIFACT_NAME
+      Specifies the name of all of the build artifacts. You can change the
+      name of the artifacts by changing the ``KERNEL_ARTIFACT_NAME``
+      variable.
+
+      The value of ``KERNEL_ARTIFACT_NAME``, which is set in the
+      ``meta/classes/kernel-artifact-names.bbclass`` file, has the
+      following default value:
+      ::
+
+         KERNEL_ARTIFACT_NAME ?= "${PKGE}-${PKGV}-${PKGR}-${MACHINE}${IMAGE_VERSION_SUFFIX}"
+
+      See the :term:`PKGE`, :term:`PKGV`, :term:`PKGR`, and :term:`MACHINE`
+      variables for additional information.
+
+      .. note::
+
+         The IMAGE_VERSION_SUFFIX variable is set to DATETIME.
+
+   KERNEL_CLASSES
+      A list of classes defining kernel image types that the
+      :ref:`kernel <ref-classes-kernel>` class should inherit. You
+      typically append this variable to enable extended image types. An
+      example is the "kernel-fitimage", which enables fitImage support and
+      resides in ``meta/classes/kernel-fitimage.bbclass``. You can register
+      custom kernel image types with the ``kernel`` class using this
+      variable.
+
+   KERNEL_DEVICETREE
+      Specifies the name of the generated Linux kernel device tree (i.e.
+      the ``.dtb``) file.
+
+      .. note::
+
+         Legacy support exists for specifying the full path to the device
+         tree. However, providing just the .dtb file is preferred.
+
+      In order to use this variable, the
+      :ref:`kernel-devicetree <ref-classes-kernel-devicetree>` class must
+      be inherited.
+
+   KERNEL_DTB_LINK_NAME
+      The link name of the kernel device tree binary (DTB). This variable
+      is set in the ``meta/classes/kernel-artifact-names.bbclass`` file as
+      follows:
+      ::
+
+         KERNEL_DTB_LINK_NAME ?= "${KERNEL_ARTIFACT_LINK_NAME}"
+
+      The
+      value of the ``KERNEL_ARTIFACT_LINK_NAME`` variable, which is set in
+      the same file, has the following value:
+      ::
+
+         KERNEL_ARTIFACT_LINK_NAME ?= "${MACHINE}"
+
+      See the :term:`MACHINE` variable for additional
+      information.
+
+   KERNEL_DTB_NAME
+      The base name of the kernel device tree binary (DTB). This variable
+      is set in the ``meta/classes/kernel-artifact-names.bbclass`` file as
+      follows:
+      ::
+
+         KERNEL_DTB_NAME ?= "${KERNEL_ARTIFACT_NAME}"
+
+      The value of the :term:`KERNEL_ARTIFACT_NAME`
+      variable, which is set in the same file, has the following value:
+      ::
+
+         KERNEL_ARTIFACT_NAME ?= "${PKGE}-${PKGV}-${PKGR}-${MACHINE}${IMAGE_VERSION_SUFFIX}"
+
+   KERNEL_EXTRA_ARGS
+      Specifies additional ``make`` command-line arguments the OpenEmbedded
+      build system passes on when compiling the kernel.
+
+   KERNEL_FEATURES
+      Includes additional kernel metadata. In the OpenEmbedded build
+      system, the default Board Support Packages (BSPs)
+      :term:`Metadata` is provided through the
+      :term:`KMACHINE` and :term:`KBRANCH`
+      variables. You can use the ``KERNEL_FEATURES`` variable from within
+      the kernel recipe or kernel append file to further add metadata for
+      all BSPs or specific BSPs.
+
+      The metadata you add through this variable includes config fragments
+      and features descriptions, which usually includes patches as well as
+      config fragments. You typically override the ``KERNEL_FEATURES``
+      variable for a specific machine. In this way, you can provide
+      validated, but optional, sets of kernel configurations and features.
+
+      For example, the following example from the ``linux-yocto-rt_4.12``
+      kernel recipe adds "netfilter" and "taskstats" features to all BSPs
+      as well as "virtio" configurations to all QEMU machines. The last two
+      statements add specific configurations to targeted machine types:
+      ::
+
+         KERNEL_EXTRA_FEATURES ?= "features/netfilter/netfilter.scc features/taskstats/taskstats.scc"
+         KERNEL_FEATURES_append = "${KERNEL_EXTRA_FEATURES}"
+         KERNEL_FEATURES_append_qemuall = "cfg/virtio.scc"
+         KERNEL_FEATURES_append_qemux86 = " cfg/sound.scc cfg/paravirt_kvm.scc"
+         KERNEL_FEATURES_append_qemux86-64 = "cfg/sound.scc"
+
+   KERNEL_FIT_LINK_NAME
+      The link name of the kernel flattened image tree (FIT) image. This
+      variable is set in the ``meta/classes/kernel-artifact-names.bbclass``
+      file as follows:
+      ::
+
+         KERNEL_FIT_LINK_NAME ?= "${KERNEL_ARTIFACT_LINK_NAME}"
+
+      The value of the
+      ``KERNEL_ARTIFACT_LINK_NAME`` variable, which is set in the same
+      file, has the following value:
+      ::
+
+         KERNEL_ARTIFACT_LINK_NAME ?= "${MACHINE}"
+
+      See the :term:`MACHINE` variable for additional
+      information.
+
+   KERNEL_FIT_NAME
+      The base name of the kernel flattened image tree (FIT) image. This
+      variable is set in the ``meta/classes/kernel-artifact-names.bbclass``
+      file as follows:
+      ::
+
+         KERNEL_FIT_NAME ?= "${KERNEL_ARTIFACT_NAME}"
+
+      The value of the :term:`KERNEL_ARTIFACT_NAME`
+      variable, which is set in the same file, has the following value:
+      ::
+
+         KERNEL_ARTIFACT_NAME ?= "${PKGE}-${PKGV}-${PKGR}-${MACHINE}${IMAGE_VERSION_SUFFIX}"
+
+   KERNEL_IMAGE_LINK_NAME
+      The link name for the kernel image. This variable is set in the
+      ``meta/classes/kernel-artifact-names.bbclass`` file as follows:
+      ::
+
+         KERNEL_IMAGE_LINK_NAME ?= "${KERNEL_ARTIFACT_LINK_NAME}"
+
+      The value of
+      the ``KERNEL_ARTIFACT_LINK_NAME`` variable, which is set in the same
+      file, has the following value:
+      ::
+
+         KERNEL_ARTIFACT_LINK_NAME ?= "${MACHINE}"
+
+      See the :term:`MACHINE` variable for additional
+      information.
+
+   KERNEL_IMAGE_MAXSIZE
+      Specifies the maximum size of the kernel image file in kilobytes. If
+      ``KERNEL_IMAGE_MAXSIZE`` is set, the size of the kernel image file is
+      checked against the set value during the
+      :ref:`ref-tasks-sizecheck` task. The task fails if
+      the kernel image file is larger than the setting.
+
+      ``KERNEL_IMAGE_MAXSIZE`` is useful for target devices that have a
+      limited amount of space in which the kernel image must be stored.
+
+      By default, this variable is not set, which means the size of the
+      kernel image is not checked.
+
+   KERNEL_IMAGE_NAME
+      The base name of the kernel image. This variable is set in the
+      ``meta/classes/kernel-artifact-names.bbclass`` file as follows:
+      ::
+
+         KERNEL_IMAGE_NAME ?= "${KERNEL_ARTIFACT_NAME}"
+
+      The value of the
+      :term:`KERNEL_ARTIFACT_NAME` variable,
+      which is set in the same file, has the following value:
+      ::
+
+         KERNEL_ARTIFACT_NAME ?= "${PKGE}-${PKGV}-${PKGR}-${MACHINE}${IMAGE_VERSION_SUFFIX}"
+
+   KERNEL_IMAGETYPE
+      The type of kernel to build for a device, usually set by the machine
+      configuration files and defaults to "zImage". This variable is used
+      when building the kernel and is passed to ``make`` as the target to
+      build.
+
+      If you want to build an alternate kernel image type, use the
+      :term:`KERNEL_ALT_IMAGETYPE` variable.
+
+   KERNEL_MODULE_AUTOLOAD
+      Lists kernel modules that need to be auto-loaded during boot.
+
+      .. note::
+
+         This variable replaces the deprecated
+         module_autoload
+         variable.
+
+      You can use the ``KERNEL_MODULE_AUTOLOAD`` variable anywhere that it
+      can be recognized by the kernel recipe or by an out-of-tree kernel
+      module recipe (e.g. a machine configuration file, a distribution
+      configuration file, an append file for the recipe, or the recipe
+      itself).
+
+      Specify it as follows:
+      ::
+
+         KERNEL_MODULE_AUTOLOAD += "module_name1 module_name2 module_name3"
+
+      Including ``KERNEL_MODULE_AUTOLOAD`` causes the OpenEmbedded build
+      system to populate the ``/etc/modules-load.d/modname.conf`` file with
+      the list of modules to be auto-loaded on boot. The modules appear
+      one-per-line in the file. Here is an example of the most common use
+      case:
+      ::
+
+         KERNEL_MODULE_AUTOLOAD += "module_name"
+
+      For information on how to populate the ``modname.conf`` file with
+      ``modprobe.d`` syntax lines, see the :term:`KERNEL_MODULE_PROBECONF` variable.
+
+   KERNEL_MODULE_PROBECONF
+      Provides a list of modules for which the OpenEmbedded build system
+      expects to find ``module_conf_``\ modname values that specify
+      configuration for each of the modules. For information on how to
+      provide those module configurations, see the
+      :term:`module_conf_* <module_conf>` variable.
+
+   KERNEL_PATH
+      The location of the kernel sources. This variable is set to the value
+      of the :term:`STAGING_KERNEL_DIR` within
+      the :ref:`module <ref-classes-module>` class. For information on
+      how this variable is used, see the
+      ":ref:`kernel-dev/kernel-dev-common:incorporating out-of-tree modules`"
+      section in the Yocto Project Linux Kernel Development Manual.
+
+      To help maximize compatibility with out-of-tree drivers used to build
+      modules, the OpenEmbedded build system also recognizes and uses the
+      :term:`KERNEL_SRC` variable, which is identical to
+      the ``KERNEL_PATH`` variable. Both variables are common variables
+      used by external Makefiles to point to the kernel source directory.
+
+   KERNEL_SRC
+      The location of the kernel sources. This variable is set to the value
+      of the :term:`STAGING_KERNEL_DIR` within
+      the :ref:`module <ref-classes-module>` class. For information on
+      how this variable is used, see the
+      ":ref:`kernel-dev/kernel-dev-common:incorporating out-of-tree modules`"
+      section in the Yocto Project Linux Kernel Development Manual.
+
+      To help maximize compatibility with out-of-tree drivers used to build
+      modules, the OpenEmbedded build system also recognizes and uses the
+      :term:`KERNEL_PATH` variable, which is identical
+      to the ``KERNEL_SRC`` variable. Both variables are common variables
+      used by external Makefiles to point to the kernel source directory.
+
+   KERNEL_VERSION
+      Specifies the version of the kernel as extracted from ``version.h``
+      or ``utsrelease.h`` within the kernel sources. Effects of setting
+      this variable do not take affect until the kernel has been
+      configured. Consequently, attempting to refer to this variable in
+      contexts prior to configuration will not work.
+
+   KERNELDEPMODDEPEND
+      Specifies whether the data referenced through
+      :term:`PKGDATA_DIR` is needed or not. The
+      ``KERNELDEPMODDEPEND`` does not control whether or not that data
+      exists, but simply whether or not it is used. If you do not need to
+      use the data, set the ``KERNELDEPMODDEPEND`` variable in your
+      ``initramfs`` recipe. Setting the variable there when the data is not
+      needed avoids a potential dependency loop.
+
+   KFEATURE_DESCRIPTION
+      Provides a short description of a configuration fragment. You use
+      this variable in the ``.scc`` file that describes a configuration
+      fragment file. Here is the variable used in a file named ``smp.scc``
+      to describe SMP being enabled:
+      ::
+
+          define KFEATURE_DESCRIPTION "Enable SMP"
+
+   KMACHINE
+      The machine as known by the kernel. Sometimes the machine name used
+      by the kernel does not match the machine name used by the
+      OpenEmbedded build system. For example, the machine name that the
+      OpenEmbedded build system understands as ``core2-32-intel-common``
+      goes by a different name in the Linux Yocto kernel. The kernel
+      understands that machine as ``intel-core2-32``. For cases like these,
+      the ``KMACHINE`` variable maps the kernel machine name to the
+      OpenEmbedded build system machine name.
+
+      These mappings between different names occur in the Yocto Linux
+      Kernel's ``meta`` branch. As an example take a look in the
+      ``common/recipes-kernel/linux/linux-yocto_3.19.bbappend`` file:
+      ::
+
+         LINUX_VERSION_core2-32-intel-common = "3.19.0"
+         COMPATIBLE_MACHINE_core2-32-intel-common = "${MACHINE}"
+         SRCREV_meta_core2-32-intel-common = "8897ef68b30e7426bc1d39895e71fb155d694974"
+         SRCREV_machine_core2-32-intel-common = "43b9eced9ba8a57add36af07736344dcc383f711"
+         KMACHINE_core2-32-intel-common = "intel-core2-32"
+         KBRANCH_core2-32-intel-common = "standard/base"
+         KERNEL_FEATURES_append_core2-32-intel-common = "${KERNEL_FEATURES_INTEL_COMMON}"
+
+      The ``KMACHINE`` statement says
+      that the kernel understands the machine name as "intel-core2-32".
+      However, the OpenEmbedded build system understands the machine as
+      "core2-32-intel-common".
+
+   KTYPE
+      Defines the kernel type to be used in assembling the configuration.
+      The linux-yocto recipes define "standard", "tiny", and "preempt-rt"
+      kernel types. See the ":ref:`kernel-dev/kernel-dev-advanced:kernel types`"
+      section in the
+      Yocto Project Linux Kernel Development Manual for more information on
+      kernel types.
+
+      You define the ``KTYPE`` variable in the
+      :ref:`kernel-dev/kernel-dev-advanced:bsp descriptions`. The
+      value you use must match the value used for the
+      :term:`LINUX_KERNEL_TYPE` value used by the
+      kernel recipe.
+
+   LABELS
+      Provides a list of targets for automatic configuration.
+
+      See the :ref:`grub-efi <ref-classes-grub-efi>` class for more
+      information on how this variable is used.
+
+   LAYERDEPENDS
+      Lists the layers, separated by spaces, on which this recipe depends.
+      Optionally, you can specify a specific layer version for a dependency
+      by adding it to the end of the layer name. Here is an example:
+      ::
+
+         LAYERDEPENDS_mylayer = "anotherlayer (=3)"
+
+      In this previous example,
+      version 3 of "anotherlayer" is compared against
+      :term:`LAYERVERSION`\ ``_anotherlayer``.
+
+      An error is produced if any dependency is missing or the version
+      numbers (if specified) do not match exactly. This variable is used in
+      the ``conf/layer.conf`` file and must be suffixed with the name of
+      the specific layer (e.g. ``LAYERDEPENDS_mylayer``).
+
+   LAYERDIR
+      When used inside the ``layer.conf`` configuration file, this variable
+      provides the path of the current layer. This variable is not
+      available outside of ``layer.conf`` and references are expanded
+      immediately when parsing of the file completes.
+
+   LAYERRECOMMENDS
+      Lists the layers, separated by spaces, recommended for use with this
+      layer.
+
+      Optionally, you can specify a specific layer version for a
+      recommendation by adding the version to the end of the layer name.
+      Here is an example:
+      ::
+
+         LAYERRECOMMENDS_mylayer = "anotherlayer (=3)"
+
+      In this previous example, version 3 of "anotherlayer" is compared
+      against ``LAYERVERSION_anotherlayer``.
+
+      This variable is used in the ``conf/layer.conf`` file and must be
+      suffixed with the name of the specific layer (e.g.
+      ``LAYERRECOMMENDS_mylayer``).
+
+   LAYERSERIES_COMPAT
+      Lists the versions of the :term:`OpenEmbedded-Core (OE-Core)` for which
+      a layer is compatible. Using the ``LAYERSERIES_COMPAT`` variable
+      allows the layer maintainer to indicate which combinations of the
+      layer and OE-Core can be expected to work. The variable gives the
+      system a way to detect when a layer has not been tested with new
+      releases of OE-Core (e.g. the layer is not maintained).
+
+      To specify the OE-Core versions for which a layer is compatible, use
+      this variable in your layer's ``conf/layer.conf`` configuration file.
+      For the list, use the Yocto Project
+      :yocto_wiki:`Release Name </wiki/Releases>` (e.g.
+      DISTRO_NAME_NO_CAP). To specify multiple OE-Core versions for the
+      layer, use a space-separated list:
+      ::
+
+         LAYERSERIES_COMPAT_layer_root_name = "DISTRO_NAME_NO_CAP DISTRO_NAME_NO_CAP_MINUS_ONE"
+
+      .. note::
+
+         Setting
+         LAYERSERIES_COMPAT
+         is required by the Yocto Project Compatible version 2 standard.
+         The OpenEmbedded build system produces a warning if the variable
+         is not set for any given layer.
+
+      See the ":ref:`dev-manual/dev-manual-common-tasks:creating your own layer`"
+      section in the Yocto Project Development Tasks Manual.
+
+   LAYERVERSION
+      Optionally specifies the version of a layer as a single number. You
+      can use this within :term:`LAYERDEPENDS` for
+      another layer in order to depend on a specific version of the layer.
+      This variable is used in the ``conf/layer.conf`` file and must be
+      suffixed with the name of the specific layer (e.g.
+      ``LAYERVERSION_mylayer``).
+
+   LD
+      The minimal command and arguments used to run the linker.
+
+   LDFLAGS
+      Specifies the flags to pass to the linker. This variable is exported
+      to an environment variable and thus made visible to the software
+      being built during the compilation step.
+
+      Default initialization for ``LDFLAGS`` varies depending on what is
+      being built:
+
+      -  :term:`TARGET_LDFLAGS` when building for the
+         target
+
+      -  :term:`BUILD_LDFLAGS` when building for the
+         build host (i.e. ``-native``)
+
+      -  :term:`BUILDSDK_LDFLAGS` when building for
+         an SDK (i.e. ``nativesdk-``)
+
+   LEAD_SONAME
+      Specifies the lead (or primary) compiled library file (i.e. ``.so``)
+      that the :ref:`debian <ref-classes-debian>` class applies its
+      naming policy to given a recipe that packages multiple libraries.
+
+      This variable works in conjunction with the ``debian`` class.
+
+   LIC_FILES_CHKSUM
+      Checksums of the license text in the recipe source code.
+
+      This variable tracks changes in license text of the source code
+      files. If the license text is changed, it will trigger a build
+      failure, which gives the developer an opportunity to review any
+      license change.
+
+      This variable must be defined for all recipes (unless
+      :term:`LICENSE` is set to "CLOSED").
+
+      For more information, see the ":ref:`usingpoky-configuring-lic_files_chksum`"
+      section in the Yocto Project Development Tasks Manual.
+
+   LICENSE
+      The list of source licenses for the recipe. Follow these rules:
+
+      -  Do not use spaces within individual license names.
+
+      -  Separate license names using \| (pipe) when there is a choice
+         between licenses.
+
+      -  Separate license names using & (ampersand) when multiple licenses
+         exist that cover different parts of the source.
+
+      -  You can use spaces between license names.
+
+      -  For standard licenses, use the names of the files in
+         ``meta/files/common-licenses/`` or the
+         :term:`SPDXLICENSEMAP` flag names defined in
+         ``meta/conf/licenses.conf``.
+
+      Here are some examples:
+      ::
+
+         LICENSE = "LGPLv2.1 | GPLv3"
+         LICENSE = "MPL-1 & LGPLv2.1"
+         LICENSE = "GPLv2+"
+
+      The first example is from the
+      recipes for Qt, which the user may choose to distribute under either
+      the LGPL version 2.1 or GPL version 3. The second example is from
+      Cairo where two licenses cover different parts of the source code.
+      The final example is from ``sysstat``, which presents a single
+      license.
+
+      You can also specify licenses on a per-package basis to handle
+      situations where components of the output have different licenses.
+      For example, a piece of software whose code is licensed under GPLv2
+      but has accompanying documentation licensed under the GNU Free
+      Documentation License 1.2 could be specified as follows:
+      ::
+
+         LICENSE = "GFDL-1.2 & GPLv2"
+         LICENSE_${PN} = "GPLv2"
+         LICENSE_${PN}-doc = "GFDL-1.2"
+
+   LICENSE_CREATE_PACKAGE
+      Setting ``LICENSE_CREATE_PACKAGE`` to "1" causes the OpenEmbedded
+      build system to create an extra package (i.e.
+      ``${``\ :term:`PN`\ ``}-lic``) for each recipe and to add
+      those packages to the
+      :term:`RRECOMMENDS`\ ``_${PN}``.
+
+      The ``${PN}-lic`` package installs a directory in
+      ``/usr/share/licenses`` named ``${PN}``, which is the recipe's base
+      name, and installs files in that directory that contain license and
+      copyright information (i.e. copies of the appropriate license files
+      from ``meta/common-licenses`` that match the licenses specified in
+      the :term:`LICENSE` variable of the recipe metadata
+      and copies of files marked in
+      :term:`LIC_FILES_CHKSUM` as containing
+      license text).
+
+      For related information on providing license text, see the
+      :term:`COPY_LIC_DIRS` variable, the
+      :term:`COPY_LIC_MANIFEST` variable, and the
+      ":ref:`dev-manual/dev-manual-common-tasks:providing license text`"
+      section in the Yocto Project Development Tasks Manual.
+
+   LICENSE_FLAGS
+      Specifies additional flags for a recipe you must whitelist through
+      :term:`LICENSE_FLAGS_WHITELIST` in
+      order to allow the recipe to be built. When providing multiple flags,
+      separate them with spaces.
+
+      This value is independent of :term:`LICENSE` and is
+      typically used to mark recipes that might require additional licenses
+      in order to be used in a commercial product. For more information,
+      see the
+      ":ref:`dev-manual/dev-manual-common-tasks:enabling commercially licensed recipes`"
+      section in the Yocto Project Development Tasks Manual.
+
+   LICENSE_FLAGS_WHITELIST
+      Lists license flags that when specified in
+      :term:`LICENSE_FLAGS` within a recipe should not
+      prevent that recipe from being built. This practice is otherwise
+      known as "whitelisting" license flags. For more information, see the
+      ":ref:`dev-manual/dev-manual-common-tasks:enabling commercially licensed recipes`"
+      section in the Yocto Project Development Tasks Manual.
+
+   LICENSE_PATH
+      Path to additional licenses used during the build. By default, the
+      OpenEmbedded build system uses ``COMMON_LICENSE_DIR`` to define the
+      directory that holds common license text used during the build. The
+      ``LICENSE_PATH`` variable allows you to extend that location to other
+      areas that have additional licenses:
+      ::
+
+         LICENSE_PATH += "path-to-additional-common-licenses"
+
+   LINUX_KERNEL_TYPE
+      Defines the kernel type to be used in assembling the configuration.
+      The linux-yocto recipes define "standard", "tiny", and "preempt-rt"
+      kernel types. See the ":ref:`kernel-dev/kernel-dev-advanced:kernel types`"
+      section in the
+      Yocto Project Linux Kernel Development Manual for more information on
+      kernel types.
+
+      If you do not specify a ``LINUX_KERNEL_TYPE``, it defaults to
+      "standard". Together with :term:`KMACHINE`, the
+      ``LINUX_KERNEL_TYPE`` variable defines the search arguments used by
+      the kernel tools to find the appropriate description within the
+      kernel :term:`Metadata` with which to build out the sources
+      and configuration.
+
+   LINUX_VERSION
+      The Linux version from ``kernel.org`` on which the Linux kernel image
+      being built using the OpenEmbedded build system is based. You define
+      this variable in the kernel recipe. For example, the
+      ``linux-yocto-3.4.bb`` kernel recipe found in
+      ``meta/recipes-kernel/linux`` defines the variables as follows:
+      ::
+
+         LINUX_VERSION ?= "3.4.24"
+
+      The ``LINUX_VERSION`` variable is used to define :term:`PV`
+      for the recipe:
+      ::
+
+         PV = "${LINUX_VERSION}+git${SRCPV}"
+
+   LINUX_VERSION_EXTENSION
+      A string extension compiled into the version string of the Linux
+      kernel built with the OpenEmbedded build system. You define this
+      variable in the kernel recipe. For example, the linux-yocto kernel
+      recipes all define the variable as follows:
+      ::
+
+         LINUX_VERSION_EXTENSION ?= "-yocto-${LINUX_KERNEL_TYPE}"
+
+      Defining this variable essentially sets the Linux kernel
+      configuration item ``CONFIG_LOCALVERSION``, which is visible through
+      the ``uname`` command. Here is an example that shows the extension
+      assuming it was set as previously shown:
+      ::
+
+         $ uname -r
+         3.7.0-rc8-custom
+
+   LOG_DIR
+      Specifies the directory to which the OpenEmbedded build system writes
+      overall log files. The default directory is ``${TMPDIR}/log``.
+
+      For the directory containing logs specific to each task, see the
+      :term:`T` variable.
+
+   MACHINE
+      Specifies the target device for which the image is built. You define
+      ``MACHINE`` in the ``local.conf`` file found in the
+      :term:`Build Directory`. By default, ``MACHINE`` is set to
+      "qemux86", which is an x86-based architecture machine to be emulated
+      using QEMU:
+      ::
+
+         MACHINE ?= "qemux86"
+
+      The variable corresponds to a machine configuration file of the same
+      name, through which machine-specific configurations are set. Thus,
+      when ``MACHINE`` is set to "qemux86" there exists the corresponding
+      ``qemux86.conf`` machine configuration file, which can be found in
+      the :term:`Source Directory` in
+      ``meta/conf/machine``.
+
+      The list of machines supported by the Yocto Project as shipped
+      include the following:
+      ::
+
+         MACHINE ?= "qemuarm"
+         MACHINE ?= "qemuarm64"
+         MACHINE ?= "qemumips"
+         MACHINE ?= "qemumips64"
+         MACHINE ?= "qemuppc"
+         MACHINE ?= "qemux86"
+         MACHINE ?= "qemux86-64"
+         MACHINE ?= "genericx86"
+         MACHINE ?= "genericx86-64"
+         MACHINE ?= "beaglebone"
+         MACHINE ?= "edgerouter"
+
+      The last five are Yocto Project reference hardware
+      boards, which are provided in the ``meta-yocto-bsp`` layer.
+
+      .. note::
+
+         Adding additional Board Support Package (BSP) layers to your
+         configuration adds new possible settings for
+         MACHINE
+         .
+
+   MACHINE_ARCH
+      Specifies the name of the machine-specific architecture. This
+      variable is set automatically from :term:`MACHINE` or
+      :term:`TUNE_PKGARCH`. You should not hand-edit
+      the ``MACHINE_ARCH`` variable.
+
+   MACHINE_ESSENTIAL_EXTRA_RDEPENDS
+      A list of required machine-specific packages to install as part of
+      the image being built. The build process depends on these packages
+      being present. Furthermore, because this is a "machine-essential"
+      variable, the list of packages are essential for the machine to boot.
+      The impact of this variable affects images based on
+      ``packagegroup-core-boot``, including the ``core-image-minimal``
+      image.
+
+      This variable is similar to the
+      ``MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS`` variable with the exception
+      that the image being built has a build dependency on the variable's
+      list of packages. In other words, the image will not build if a file
+      in this list is not found.
+
+      As an example, suppose the machine for which you are building
+      requires ``example-init`` to be run during boot to initialize the
+      hardware. In this case, you would use the following in the machine's
+      ``.conf`` configuration file:
+      ::
+
+         MACHINE_ESSENTIAL_EXTRA_RDEPENDS += "example-init"
+
+   MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS
+      A list of recommended machine-specific packages to install as part of
+      the image being built. The build process does not depend on these
+      packages being present. However, because this is a
+      "machine-essential" variable, the list of packages are essential for
+      the machine to boot. The impact of this variable affects images based
+      on ``packagegroup-core-boot``, including the ``core-image-minimal``
+      image.
+
+      This variable is similar to the ``MACHINE_ESSENTIAL_EXTRA_RDEPENDS``
+      variable with the exception that the image being built does not have
+      a build dependency on the variable's list of packages. In other
+      words, the image will still build if a package in this list is not
+      found. Typically, this variable is used to handle essential kernel
+      modules, whose functionality may be selected to be built into the
+      kernel rather than as a module, in which case a package will not be
+      produced.
+
+      Consider an example where you have a custom kernel where a specific
+      touchscreen driver is required for the machine to be usable. However,
+      the driver can be built as a module or into the kernel depending on
+      the kernel configuration. If the driver is built as a module, you
+      want it to be installed. But, when the driver is built into the
+      kernel, you still want the build to succeed. This variable sets up a
+      "recommends" relationship so that in the latter case, the build will
+      not fail due to the missing package. To accomplish this, assuming the
+      package for the module was called ``kernel-module-ab123``, you would
+      use the following in the machine's ``.conf`` configuration file:
+      ::
+
+         MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS += "kernel-module-ab123"
+
+      .. note::
+
+         In this example, the
+         kernel-module-ab123
+         recipe needs to explicitly set its
+         PACKAGES
+         variable to ensure that BitBake does not use the kernel recipe's
+         PACKAGES_DYNAMIC
+         variable to satisfy the dependency.
+
+      Some examples of these machine essentials are flash, screen,
+      keyboard, mouse, or touchscreen drivers (depending on the machine).
+
+   MACHINE_EXTRA_RDEPENDS
+      A list of machine-specific packages to install as part of the image
+      being built that are not essential for the machine to boot. However,
+      the build process for more fully-featured images depends on the
+      packages being present.
+
+      This variable affects all images based on ``packagegroup-base``,
+      which does not include the ``core-image-minimal`` or
+      ``core-image-full-cmdline`` images.
+
+      The variable is similar to the ``MACHINE_EXTRA_RRECOMMENDS`` variable
+      with the exception that the image being built has a build dependency
+      on the variable's list of packages. In other words, the image will
+      not build if a file in this list is not found.
+
+      An example is a machine that has WiFi capability but is not essential
+      for the machine to boot the image. However, if you are building a
+      more fully-featured image, you want to enable the WiFi. The package
+      containing the firmware for the WiFi hardware is always expected to
+      exist, so it is acceptable for the build process to depend upon
+      finding the package. In this case, assuming the package for the
+      firmware was called ``wifidriver-firmware``, you would use the
+      following in the ``.conf`` file for the machine:
+      ::
+
+         MACHINE_EXTRA_RDEPENDS += "wifidriver-firmware"
+
+   MACHINE_EXTRA_RRECOMMENDS
+      A list of machine-specific packages to install as part of the image
+      being built that are not essential for booting the machine. The image
+      being built has no build dependency on this list of packages.
+
+      This variable affects only images based on ``packagegroup-base``,
+      which does not include the ``core-image-minimal`` or
+      ``core-image-full-cmdline`` images.
+
+      This variable is similar to the ``MACHINE_EXTRA_RDEPENDS`` variable
+      with the exception that the image being built does not have a build
+      dependency on the variable's list of packages. In other words, the
+      image will build if a file in this list is not found.
+
+      An example is a machine that has WiFi capability but is not essential
+      For the machine to boot the image. However, if you are building a
+      more fully-featured image, you want to enable WiFi. In this case, the
+      package containing the WiFi kernel module will not be produced if the
+      WiFi driver is built into the kernel, in which case you still want
+      the build to succeed instead of failing as a result of the package
+      not being found. To accomplish this, assuming the package for the
+      module was called ``kernel-module-examplewifi``, you would use the
+      following in the ``.conf`` file for the machine:
+      ::
+
+         MACHINE_EXTRA_RRECOMMENDS += "kernel-module-examplewifi"
+
+   MACHINE_FEATURES
+      Specifies the list of hardware features the
+      :term:`MACHINE` is capable of supporting. For related
+      information on enabling features, see the
+      :term:`DISTRO_FEATURES`,
+      :term:`COMBINED_FEATURES`, and
+      :term:`IMAGE_FEATURES` variables.
+
+      For a list of hardware features supported by the Yocto Project as
+      shipped, see the "`Machine Features <#ref-features-machine>`__"
+      section.
+
+   MACHINE_FEATURES_BACKFILL
+      Features to be added to ``MACHINE_FEATURES`` if not also present in
+      ``MACHINE_FEATURES_BACKFILL_CONSIDERED``.
+
+      This variable is set in the ``meta/conf/bitbake.conf`` file. It is
+      not intended to be user-configurable. It is best to just reference
+      the variable to see which machine features are being backfilled for
+      all machine configurations. See the "`Feature
+      Backfilling <#ref-features-backfill>`__" section for more
+      information.
+
+   MACHINE_FEATURES_BACKFILL_CONSIDERED
+      Features from ``MACHINE_FEATURES_BACKFILL`` that should not be
+      backfilled (i.e. added to ``MACHINE_FEATURES``) during the build. See
+      the "`Feature Backfilling <#ref-features-backfill>`__" section for
+      more information.
+
+   MACHINEOVERRIDES
+      A colon-separated list of overrides that apply to the current
+      machine. By default, this list includes the value of
+      :term:`MACHINE`.
+
+      You can extend ``MACHINEOVERRIDES`` to add extra overrides that
+      should apply to a machine. For example, all machines emulated in QEMU
+      (e.g. ``qemuarm``, ``qemux86``, and so forth) include a file named
+      ``meta/conf/machine/include/qemu.inc`` that prepends the following
+      override to ``MACHINEOVERRIDES``:
+      ::
+
+         MACHINEOVERRIDES =. "qemuall:"
+
+      This
+      override allows variables to be overriden for all machines emulated
+      in QEMU, like in the following example from the ``connman-conf``
+      recipe:
+      ::
+
+         SRC_URI_append_qemuall = "file://wired.config \
+             file://wired-setup \
+             "
+
+      The underlying mechanism behind
+      ``MACHINEOVERRIDES`` is simply that it is included in the default
+      value of :term:`OVERRIDES`.
+
+   MAINTAINER
+      The email address of the distribution maintainer.
+
+   MIRRORS
+      Specifies additional paths from which the OpenEmbedded build system
+      gets source code. When the build system searches for source code, it
+      first tries the local download directory. If that location fails, the
+      build system tries locations defined by
+      :term:`PREMIRRORS`, the upstream source, and then
+      locations specified by ``MIRRORS`` in that order.
+
+      Assuming your distribution (:term:`DISTRO`) is "poky",
+      the default value for ``MIRRORS`` is defined in the
+      ``conf/distro/poky.conf`` file in the ``meta-poky`` Git repository.
+
+   MLPREFIX
+      Specifies a prefix has been added to :term:`PN` to create a
+      special version of a recipe or package (i.e. a Multilib version). The
+      variable is used in places where the prefix needs to be added to or
+      removed from a the name (e.g. the :term:`BPN` variable).
+      ``MLPREFIX`` gets set when a prefix has been added to ``PN``.
+
+      .. note::
+
+         The "ML" in
+         MLPREFIX
+         stands for "MultiLib". This representation is historical and comes
+         from a time when
+         nativesdk
+         was a suffix rather than a prefix on the recipe name. When
+         nativesdk
+         was turned into a prefix, it made sense to set
+         MLPREFIX
+         for it as well.
+
+      To help understand when ``MLPREFIX`` might be needed, consider when
+      :term:`BBCLASSEXTEND` is used to provide a
+      ``nativesdk`` version of a recipe in addition to the target version.
+      If that recipe declares build-time dependencies on tasks in other
+      recipes by using :term:`DEPENDS`, then a dependency on
+      "foo" will automatically get rewritten to a dependency on
+      "nativesdk-foo". However, dependencies like the following will not
+      get rewritten automatically:
+      ::
+
+         do_foo[depends] += "recipe:do_foo"
+
+      If you want such a dependency to also get transformed, you can do the
+      following:
+      ::
+
+         do_foo[depends] += "${MLPREFIX}recipe:do_foo"
+
+   module_autoload
+      This variable has been replaced by the ``KERNEL_MODULE_AUTOLOAD``
+      variable. You should replace all occurrences of ``module_autoload``
+      with additions to ``KERNEL_MODULE_AUTOLOAD``, for example:
+      ::
+
+         module_autoload_rfcomm = "rfcomm"
+
+      should now be replaced with:
+      ::
+
+         KERNEL_MODULE_AUTOLOAD += "rfcomm"
+
+      See the :term:`KERNEL_MODULE_AUTOLOAD` variable for more information.
+
+   module_conf
+      Specifies `modprobe.d <http://linux.die.net/man/5/modprobe.d>`_
+      syntax lines for inclusion in the ``/etc/modprobe.d/modname.conf``
+      file.
+
+      You can use this variable anywhere that it can be recognized by the
+      kernel recipe or out-of-tree kernel module recipe (e.g. a machine
+      configuration file, a distribution configuration file, an append file
+      for the recipe, or the recipe itself). If you use this variable, you
+      must also be sure to list the module name in the
+      :term:`KERNEL_MODULE_AUTOLOAD`
+      variable.
+
+      Here is the general syntax:
+      ::
+
+         module_conf_module_name = "modprobe.d-syntax"
+
+      You must use the kernel module name override.
+
+      Run ``man modprobe.d`` in the shell to find out more information on
+      the exact syntax you want to provide with ``module_conf``.
+
+      Including ``module_conf`` causes the OpenEmbedded build system to
+      populate the ``/etc/modprobe.d/modname.conf`` file with
+      ``modprobe.d`` syntax lines. Here is an example that adds the options
+      ``arg1`` and ``arg2`` to a module named ``mymodule``:
+      ::
+
+         module_conf_mymodule = "options mymodule arg1=val1 arg2=val2"
+
+      For information on how to specify kernel modules to auto-load on
+      boot, see the :term:`KERNEL_MODULE_AUTOLOAD` variable.
+
+   MODULE_TARBALL_DEPLOY
+      Controls creation of the ``modules-*.tgz`` file. Set this variable to
+      "0" to disable creation of this file, which contains all of the
+      kernel modules resulting from a kernel build.
+
+   MODULE_TARBALL_LINK_NAME
+      The link name of the kernel module tarball. This variable is set in
+      the ``meta/classes/kernel-artifact-names.bbclass`` file as follows:
+      ::
+
+         MODULE_TARBALL_LINK_NAME ?= "${KERNEL_ARTIFACT_LINK_NAME}"
+
+      The value
+      of the ``KERNEL_ARTIFACT_LINK_NAME`` variable, which is set in the
+      same file, has the following value:
+      ::
+
+         KERNEL_ARTIFACT_LINK_NAME ?= "${MACHINE}"
+
+      See the :term:`MACHINE` variable for additional information.
+
+   MODULE_TARBALL_NAME
+      The base name of the kernel module tarball. This variable is set in
+      the ``meta/classes/kernel-artifact-names.bbclass`` file as follows:
+      ::
+
+         MODULE_TARBALL_NAME ?= "${KERNEL_ARTIFACT_NAME}"
+
+      The value of the :term:`KERNEL_ARTIFACT_NAME` variable,
+      which is set in the same file, has the following value:
+      ::
+
+         KERNEL_ARTIFACT_NAME ?= "${PKGE}-${PKGV}-${PKGR}-${MACHINE}${IMAGE_VERSION_SUFFIX}"
+
+   MULTIMACH_TARGET_SYS
+      Uniquely identifies the type of the target system for which packages
+      are being built. This variable allows output for different types of
+      target systems to be put into different subdirectories of the same
+      output directory.
+
+      The default value of this variable is:
+      ::
+
+         ${PACKAGE_ARCH}${TARGET_VENDOR}-${TARGET_OS}
+
+      Some classes (e.g.
+      :ref:`cross-canadian <ref-classes-cross-canadian>`) modify the
+      ``MULTIMACH_TARGET_SYS`` value.
+
+      See the :term:`STAMP` variable for an example. See the
+      :term:`STAGING_DIR_TARGET` variable for more information.
+
+   NATIVELSBSTRING
+      A string identifying the host distribution. Strings consist of the
+      host distributor ID followed by the release, as reported by the
+      ``lsb_release`` tool or as read from ``/etc/lsb-release``. For
+      example, when running a build on Ubuntu 12.10, the value is
+      "Ubuntu-12.10". If this information is unable to be determined, the
+      value resolves to "Unknown".
+
+      This variable is used by default to isolate native shared state
+      packages for different distributions (e.g. to avoid problems with
+      ``glibc`` version incompatibilities). Additionally, the variable is
+      checked against
+      :term:`SANITY_TESTED_DISTROS` if that
+      variable is set.
+
+   NM
+      The minimal command and arguments to run ``nm``.
+
+   NO_GENERIC_LICENSE
+      Avoids QA errors when you use a non-common, non-CLOSED license in a
+      recipe. Packages exist, such as the linux-firmware package, with many
+      licenses that are not in any way common. Also, new licenses are added
+      occasionally to avoid introducing a lot of common license files,
+      which are only applicable to a specific package.
+      ``NO_GENERIC_LICENSE`` is used to allow copying a license that does
+      not exist in common licenses.
+
+      The following example shows how to add ``NO_GENERIC_LICENSE`` to a
+      recipe:
+      ::
+
+         NO_GENERIC_LICENSE[license_name] = "license_file_in_fetched_source"
+
+      The following is an example that
+      uses the ``LICENSE.Abilis.txt`` file as the license from the fetched
+      source:
+      ::
+
+         NO_GENERIC_LICENSE[Firmware-Abilis] = "LICENSE.Abilis.txt"
+
+   NO_RECOMMENDATIONS
+      Prevents installation of all "recommended-only" packages.
+      Recommended-only packages are packages installed only through the
+      :term:`RRECOMMENDS` variable). Setting the
+      ``NO_RECOMMENDATIONS`` variable to "1" turns this feature on: ::
+
+         NO_RECOMMENDATIONS = "1"
+
+      You can set this variable globally in your ``local.conf`` file or you
+      can attach it to a specific image recipe by using the recipe name
+      override: ::
+
+         NO_RECOMMENDATIONS_pn-target_image = "1"
+
+      It is important to realize that if you choose to not install packages
+      using this variable and some other packages are dependent on them
+      (i.e. listed in a recipe's :term:`RDEPENDS`
+      variable), the OpenEmbedded build system ignores your request and
+      will install the packages to avoid dependency errors.
+
+      .. note::
+
+         Some recommended packages might be required for certain system
+         functionality, such as kernel modules. It is up to you to add
+         packages with the IMAGE_INSTALL variable.
+
+      Support for this variable exists only when using the IPK and RPM
+      packaging backend. Support does not exist for DEB.
+
+      See the :term:`BAD_RECOMMENDATIONS` and
+      the :term:`PACKAGE_EXCLUDE` variables for
+      related information.
+
+   NOAUTOPACKAGEDEBUG
+      Disables auto package from splitting ``.debug`` files. If a recipe
+      requires ``FILES_${PN}-dbg`` to be set manually, the
+      ``NOAUTOPACKAGEDEBUG`` can be defined allowing you to define the
+      content of the debug package. For example:
+      ::
+
+         NOAUTOPACKAGEDEBUG = "1"
+         FILES_${PN}-dev = "${includedir}/${QT_DIR_NAME}/Qt/*"
+         FILES_${PN}-dbg = "/usr/src/debug/"
+         FILES_${QT_BASE_NAME}-demos-doc = "${docdir}/${QT_DIR_NAME}/qch/qt.qch"
+
+   OBJCOPY
+      The minimal command and arguments to run ``objcopy``.
+
+   OBJDUMP
+      The minimal command and arguments to run ``objdump``.
+
+   OE_BINCONFIG_EXTRA_MANGLE
+      When inheriting the :ref:`binconfig <ref-classes-binconfig>` class,
+      this variable specifies additional arguments passed to the "sed"
+      command. The sed command alters any paths in configuration scripts
+      that have been set up during compilation. Inheriting this class
+      results in all paths in these scripts being changed to point into the
+      ``sysroots/`` directory so that all builds that use the script will
+      use the correct directories for the cross compiling layout.
+
+      See the ``meta/classes/binconfig.bbclass`` in the
+      :term:`Source Directory` for details on how this class
+      applies these additional sed command arguments. For general
+      information on the ``binconfig`` class, see the
+      ":ref:`binconfig.bbclass <ref-classes-binconfig>`" section.
+
+   OE_IMPORTS
+      An internal variable used to tell the OpenEmbedded build system what
+      Python modules to import for every Python function run by the system.
+
+      .. note::
+
+         Do not set this variable. It is for internal use only.
+
+   OE_INIT_ENV_SCRIPT
+      The name of the build environment setup script for the purposes of
+      setting up the environment within the extensible SDK. The default
+      value is "oe-init-build-env".
+
+      If you use a custom script to set up your build environment, set the
+      ``OE_INIT_ENV_SCRIPT`` variable to its name.
+
+   OE_TERMINAL
+      Controls how the OpenEmbedded build system spawns interactive
+      terminals on the host development system (e.g. using the BitBake
+      command with the ``-c devshell`` command-line option). For more
+      information, see the ":ref:`platdev-appdev-devshell`" section in
+      the Yocto Project Development Tasks Manual.
+
+      You can use the following values for the ``OE_TERMINAL`` variable:
+
+      - auto
+      - gnome
+      - xfce
+      - rxvt
+      - screen
+      - konsole
+      - none
+
+   OEROOT
+      The directory from which the top-level build environment setup script
+      is sourced. The Yocto Project provides a top-level build environment
+      setup script: ````` <#structure-core-script>`__. When you run this
+      script, the ``OEROOT`` variable resolves to the directory that
+      contains the script.
+
+      For additional information on how this variable is used, see the
+      initialization script.
+
+   OLDEST_KERNEL
+      Declares the oldest version of the Linux kernel that the produced
+      binaries must support. This variable is passed into the build of the
+      Embedded GNU C Library (``glibc``).
+
+      The default for this variable comes from the
+      ``meta/conf/bitbake.conf`` configuration file. You can override this
+      default by setting the variable in a custom distribution
+      configuration file.
+
+   OVERRIDES
+      A colon-separated list of overrides that currently apply. Overrides
+      are a BitBake mechanism that allows variables to be selectively
+      overridden at the end of parsing. The set of overrides in
+      ``OVERRIDES`` represents the "state" during building, which includes
+      the current recipe being built, the machine for which it is being
+      built, and so forth.
+
+      As an example, if the string "an-override" appears as an element in
+      the colon-separated list in ``OVERRIDES``, then the following
+      assignment will override ``FOO`` with the value "overridden" at the
+      end of parsing:
+      ::
+
+         FOO_an-override = "overridden"
+
+      See the
+      ":ref:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata:conditional syntax (overrides)`"
+      section in the BitBake User Manual for more information on the
+      overrides mechanism.
+
+      The default value of ``OVERRIDES`` includes the values of the
+      :term:`CLASSOVERRIDE`,
+      :term:`MACHINEOVERRIDES`, and
+      :term:`DISTROOVERRIDES` variables. Another
+      important override included by default is ``pn-${PN}``. This override
+      allows variables to be set for a single recipe within configuration
+      (``.conf``) files. Here is an example:
+      ::
+
+         FOO_pn-myrecipe = "myrecipe-specific value"
+
+      .. note::
+
+         An easy way to see what overrides apply is to search for
+         OVERRIDES
+         in the output of the
+         bitbake -e
+         command. See the "
+         Viewing Variable Values
+         " section in the Yocto Project Development Tasks Manual for more
+         information.
+
+   P
+      The recipe name and version. ``P`` is comprised of the following:
+      ::
+
+         ${PN}-${PV}
+
+   PACKAGE_ADD_METADATA
+      This variable defines additional metdata to add to packages.
+
+      You may find you need to inject additional metadata into packages.
+      This variable allows you to do that by setting the injected data as
+      the value. Multiple fields can be added by splitting the content with
+      the literal separator "\n".
+
+      The suffixes '_IPK', '_DEB', or '_RPM' can be applied to the variable
+      to do package type specific settings. It can also be made package
+      specific by using the package name as a suffix.
+
+      You can find out more about applying this variable in the
+      ":ref:`dev-manual/dev-manual-common-tasks:adding custom metadata to packages`"
+      section in the Yocto Project Development Tasks Manual.
+
+   PACKAGE_ARCH
+      The architecture of the resulting package or packages.
+
+      By default, the value of this variable is set to
+      :term:`TUNE_PKGARCH` when building for the
+      target, :term:`BUILD_ARCH` when building for the
+      build host, and "${SDK_ARCH}-${SDKPKGSUFFIX}" when building for the
+      SDK.
+
+      .. note::
+
+         See
+         SDK_ARCH
+         for more information.
+
+      However, if your recipe's output packages are built specific to the
+      target machine rather than generally for the architecture of the
+      machine, you should set ``PACKAGE_ARCH`` to the value of
+      :term:`MACHINE_ARCH` in the recipe as follows:
+      ::
+
+         PACKAGE_ARCH = "${MACHINE_ARCH}"
+
+   PACKAGE_ARCHS
+      Specifies a list of architectures compatible with the target machine.
+      This variable is set automatically and should not normally be
+      hand-edited. Entries are separated using spaces and listed in order
+      of priority. The default value for ``PACKAGE_ARCHS`` is "all any
+      noarch ${PACKAGE_EXTRA_ARCHS} ${MACHINE_ARCH}".
+
+   PACKAGE_BEFORE_PN
+      Enables easily adding packages to ``PACKAGES`` before ``${PN}`` so
+      that those added packages can pick up files that would normally be
+      included in the default package.
+
+   PACKAGE_CLASSES
+      This variable, which is set in the ``local.conf`` configuration file
+      found in the ``conf`` folder of the
+      :term:`Build Directory`, specifies the package manager the
+      OpenEmbedded build system uses when packaging data.
+
+      You can provide one or more of the following arguments for the
+      variable: PACKAGE_CLASSES ?= "package_rpm package_deb package_ipk
+      package_tar"
+
+      .. note::
+
+         While it is a legal option, the
+         package_tar
+         class has limited functionality due to no support for package
+         dependencies by that backend. Therefore, it is recommended that
+         you do not use it.
+
+      The build system uses only the first argument in the list as the
+      package manager when creating your image or SDK. However, packages
+      will be created using any additional packaging classes you specify.
+      For example, if you use the following in your ``local.conf`` file:
+      ::
+
+         PACKAGE_CLASSES ?= "package_ipk"
+
+      The OpenEmbedded build system uses
+      the IPK package manager to create your image or SDK.
+
+      For information on packaging and build performance effects as a
+      result of the package manager in use, see the
+      ":ref:`package.bbclass <ref-classes-package>`" section.
+
+   PACKAGE_DEBUG_SPLIT_STYLE
+      Determines how to split up the binary and debug information when
+      creating ``*-dbg`` packages to be used with the GNU Project Debugger
+      (GDB).
+
+      With the ``PACKAGE_DEBUG_SPLIT_STYLE`` variable, you can control
+      where debug information, which can include or exclude source files,
+      is stored:
+
+      -  ".debug": Debug symbol files are placed next to the binary in a
+         ``.debug`` directory on the target. For example, if a binary is
+         installed into ``/bin``, the corresponding debug symbol files are
+         installed in ``/bin/.debug``. Source files are placed in
+         ``/usr/src/debug``.
+
+      -  "debug-file-directory": Debug symbol files are placed under
+         ``/usr/lib/debug`` on the target, and separated by the path from
+         where the binary is installed. For example, if a binary is
+         installed in ``/bin``, the corresponding debug symbols are
+         installed in ``/usr/lib/debug/bin``. Source files are placed in
+         ``/usr/src/debug``.
+
+      -  "debug-without-src": The same behavior as ".debug" previously
+         described with the exception that no source files are installed.
+
+      -  "debug-with-srcpkg": The same behavior as ".debug" previously
+         described with the exception that all source files are placed in a
+         separate ``*-src`` pkg. This is the default behavior.
+
+      You can find out more about debugging using GDB by reading the
+      ":ref:`platdev-gdb-remotedebug`" section
+      in the Yocto Project Development Tasks Manual.
+
+   PACKAGE_EXCLUDE_COMPLEMENTARY
+      Prevents specific packages from being installed when you are
+      installing complementary packages.
+
+      You might find that you want to prevent installing certain packages
+      when you are installing complementary packages. For example, if you
+      are using :term:`IMAGE_FEATURES` to install
+      ``dev-pkgs``, you might not want to install all packages from a
+      particular multilib. If you find yourself in this situation, you can
+      use the ``PACKAGE_EXCLUDE_COMPLEMENTARY`` variable to specify regular
+      expressions to match the packages you want to exclude.
+
+   PACKAGE_EXCLUDE
+      Lists packages that should not be installed into an image. For
+      example:
+      ::
+
+         PACKAGE_EXCLUDE = "package_name package_name package_name ..."
+
+      You can set this variable globally in your ``local.conf`` file or you
+      can attach it to a specific image recipe by using the recipe name
+      override:
+      ::
+
+         PACKAGE_EXCLUDE_pn-target_image = "package_name"
+
+      If you choose to not install a package using this variable and some
+      other package is dependent on it (i.e. listed in a recipe's
+      :term:`RDEPENDS` variable), the OpenEmbedded build
+      system generates a fatal installation error. Because the build system
+      halts the process with a fatal error, you can use the variable with
+      an iterative development process to remove specific components from a
+      system.
+
+      Support for this variable exists only when using the IPK and RPM
+      packaging backend. Support does not exist for DEB.
+
+      See the :term:`NO_RECOMMENDATIONS` and the
+      :term:`BAD_RECOMMENDATIONS` variables for
+      related information.
+
+   PACKAGE_EXTRA_ARCHS
+      Specifies the list of architectures compatible with the device CPU.
+      This variable is useful when you build for several different devices
+      that use miscellaneous processors such as XScale and ARM926-EJS.
+
+   PACKAGE_FEED_ARCHS
+      Optionally specifies the package architectures used as part of the
+      package feed URIs during the build. When used, the
+      ``PACKAGE_FEED_ARCHS`` variable is appended to the final package feed
+      URI, which is constructed using the
+      :term:`PACKAGE_FEED_URIS` and
+      :term:`PACKAGE_FEED_BASE_PATHS`
+      variables.
+
+      .. note::
+
+         You can use the
+         PACKAGE_FEEDS_ARCHS
+         variable to whitelist specific package architectures. If you do
+         not need to whitelist specific architectures, which is a common
+         case, you can omit this variable. Omitting the variable results in
+         all available architectures for the current machine being included
+         into remote package feeds.
+
+      Consider the following example where the ``PACKAGE_FEED_URIS``,
+      ``PACKAGE_FEED_BASE_PATHS``, and ``PACKAGE_FEED_ARCHS`` variables are
+      defined in your ``local.conf`` file:
+      ::
+
+         PACKAGE_FEED_URIS = "https://example.com/packagerepos/release \
+                              https://example.com/packagerepos/updates"
+         PACKAGE_FEED_BASE_PATHS = "rpm rpm-dev"
+         PACKAGE_FEED_ARCHS = "all core2-64"
+
+      Given these settings, the resulting package feeds are as follows:
+      ::
+
+         https://example.com/packagerepos/release/rpm/all
+         https://example.com/packagerepos/release/rpm/core2-64
+         https://example.com/packagerepos/release/rpm-dev/all
+         https://example.com/packagerepos/release/rpm-dev/core2-64
+         https://example.com/packagerepos/updates/rpm/all
+         https://example.com/packagerepos/updates/rpm/core2-64
+         https://example.com/packagerepos/updates/rpm-dev/all
+         https://example.com/packagerepos/updates/rpm-dev/core2-64
+
+   PACKAGE_FEED_BASE_PATHS
+      Specifies the base path used when constructing package feed URIs. The
+      ``PACKAGE_FEED_BASE_PATHS`` variable makes up the middle portion of a
+      package feed URI used by the OpenEmbedded build system. The base path
+      lies between the :term:`PACKAGE_FEED_URIS`
+      and :term:`PACKAGE_FEED_ARCHS` variables.
+
+      Consider the following example where the ``PACKAGE_FEED_URIS``,
+      ``PACKAGE_FEED_BASE_PATHS``, and ``PACKAGE_FEED_ARCHS`` variables are
+      defined in your ``local.conf`` file:
+      ::
+
+         PACKAGE_FEED_URIS = "https://example.com/packagerepos/release \
+                              https://example.com/packagerepos/updates"
+         PACKAGE_FEED_BASE_PATHS = "rpm rpm-dev"
+         PACKAGE_FEED_ARCHS = "all core2-64"
+
+      Given these settings, the resulting package feeds are as follows:
+      ::
+
+         https://example.com/packagerepos/release/rpm/all
+         https://example.com/packagerepos/release/rpm/core2-64
+         https://example.com/packagerepos/release/rpm-dev/all
+         https://example.com/packagerepos/release/rpm-dev/core2-64
+         https://example.com/packagerepos/updates/rpm/all
+         https://example.com/packagerepos/updates/rpm/core2-64
+         https://example.com/packagerepos/updates/rpm-dev/all
+         https://example.com/packagerepos/updates/rpm-dev/core2-64
+
+   PACKAGE_FEED_URIS
+      Specifies the front portion of the package feed URI used by the
+      OpenEmbedded build system. Each final package feed URI is comprised
+      of ``PACKAGE_FEED_URIS``,
+      :term:`PACKAGE_FEED_BASE_PATHS`, and
+      :term:`PACKAGE_FEED_ARCHS` variables.
+
+      Consider the following example where the ``PACKAGE_FEED_URIS``,
+      ``PACKAGE_FEED_BASE_PATHS``, and ``PACKAGE_FEED_ARCHS`` variables are
+      defined in your ``local.conf`` file:
+      ::
+
+         PACKAGE_FEED_URIS = "https://example.com/packagerepos/release \
+                              https://example.com/packagerepos/updates"
+         PACKAGE_FEED_BASE_PATHS = "rpm rpm-dev"
+         PACKAGE_FEED_ARCHS = "all core2-64"
+
+      Given these settings, the resulting package feeds are as follows:
+      ::
+
+         https://example.com/packagerepos/release/rpm/all
+         https://example.com/packagerepos/release/rpm/core2-64
+         https://example.com/packagerepos/release/rpm-dev/all
+         https://example.com/packagerepos/release/rpm-dev/core2-64
+         https://example.com/packagerepos/updates/rpm/all
+         https://example.com/packagerepos/updates/rpm/core2-64
+         https://example.com/packagerepos/updates/rpm-dev/all
+         https://example.com/packagerepos/updates/rpm-dev/core2-64
+
+   PACKAGE_INSTALL
+      The final list of packages passed to the package manager for
+      installation into the image.
+
+      Because the package manager controls actual installation of all
+      packages, the list of packages passed using ``PACKAGE_INSTALL`` is
+      not the final list of packages that are actually installed. This
+      variable is internal to the image construction code. Consequently, in
+      general, you should use the
+      :term:`IMAGE_INSTALL` variable to specify
+      packages for installation. The exception to this is when working with
+      the
+      ```core-image-minimal-initramfs`` <#images-core-image-minimal-initramfs>`__
+      image. When working with an initial RAM filesystem (initramfs) image,
+      use the ``PACKAGE_INSTALL`` variable. For information on creating an
+      initramfs, see the ":ref:`building-an-initramfs-image`" section
+      in the Yocto Project Development Tasks Manual.
+
+   PACKAGE_INSTALL_ATTEMPTONLY
+      Specifies a list of packages the OpenEmbedded build system attempts
+      to install when creating an image. If a listed package fails to
+      install, the build system does not generate an error. This variable
+      is generally not user-defined.
+
+   PACKAGE_PREPROCESS_FUNCS
+      Specifies a list of functions run to pre-process the
+      :term:`PKGD` directory prior to splitting the files out
+      to individual packages.
+
+   PACKAGE_WRITE_DEPS
+      Specifies a list of dependencies for post-installation and
+      pre-installation scripts on native/cross tools. If your
+      post-installation or pre-installation script can execute at rootfs
+      creation time rather than on the target but depends on a native tool
+      in order to execute, you need to list the tools in
+      ``PACKAGE_WRITE_DEPS``.
+
+      For information on running post-installation scripts, see the
+      ":ref:`dev-manual/dev-manual-common-tasks:post-installation scripts`"
+      section in the Yocto Project Development Tasks Manual.
+
+   PACKAGECONFIG
+      This variable provides a means of enabling or disabling features of a
+      recipe on a per-recipe basis. ``PACKAGECONFIG`` blocks are defined in
+      recipes when you specify features and then arguments that define
+      feature behaviors. Here is the basic block structure (broken over
+      multiple lines for readability):
+      ::
+
+         PACKAGECONFIG ??= "f1 f2 f3 ..."
+         PACKAGECONFIG[f1] = "\
+             --with-f1, \
+             --without-f1, \
+             build-deps-for-f1, \
+             runtime-deps-for-f1, \
+             runtime-recommends-for-f1, \
+             packageconfig-conflicts-for-f1"
+         PACKAGECONFIG[f2] = "\
+              ... and so on and so on ...
+
+      The ``PACKAGECONFIG`` variable itself specifies a space-separated
+      list of the features to enable. Following the features, you can
+      determine the behavior of each feature by providing up to six
+      order-dependent arguments, which are separated by commas. You can
+      omit any argument you like but must retain the separating commas. The
+      order is important and specifies the following:
+
+      1. Extra arguments that should be added to the configure script
+         argument list (:term:`EXTRA_OECONF` or
+         :term:`PACKAGECONFIG_CONFARGS`) if
+         the feature is enabled.
+
+      2. Extra arguments that should be added to ``EXTRA_OECONF`` or
+         ``PACKAGECONFIG_CONFARGS`` if the feature is disabled.
+
+      3. Additional build dependencies (:term:`DEPENDS`)
+         that should be added if the feature is enabled.
+
+      4. Additional runtime dependencies (:term:`RDEPENDS`)
+         that should be added if the feature is enabled.
+
+      5. Additional runtime recommendations
+         (:term:`RRECOMMENDS`) that should be added if
+         the feature is enabled.
+
+      6. Any conflicting (that is, mutually exclusive) ``PACKAGECONFIG``
+         settings for this feature.
+
+      Consider the following ``PACKAGECONFIG`` block taken from the
+      ``librsvg`` recipe. In this example the feature is ``gtk``, which has
+      three arguments that determine the feature's behavior.
+      ::
+
+         PACKAGECONFIG[gtk] = "--with-gtk3,--without-gtk3,gtk+3"
+
+      The
+      ``--with-gtk3`` and ``gtk+3`` arguments apply only if the feature is
+      enabled. In this case, ``--with-gtk3`` is added to the configure
+      script argument list and ``gtk+3`` is added to ``DEPENDS``. On the
+      other hand, if the feature is disabled say through a ``.bbappend``
+      file in another layer, then the second argument ``--without-gtk3`` is
+      added to the configure script instead.
+
+      The basic ``PACKAGECONFIG`` structure previously described holds true
+      regardless of whether you are creating a block or changing a block.
+      When creating a block, use the structure inside your recipe.
+
+      If you want to change an existing ``PACKAGECONFIG`` block, you can do
+      so one of two ways:
+
+      -  *Append file:* Create an append file named
+         recipename\ ``.bbappend`` in your layer and override the value of
+         ``PACKAGECONFIG``. You can either completely override the
+         variable:
+         ::
+
+            PACKAGECONFIG = "f4 f5"
+
+         Or, you can just append the variable:
+         ::
+
+            PACKAGECONFIG_append = " f4"
+
+      -  *Configuration file:* This method is identical to changing the
+         block through an append file except you edit your ``local.conf``
+         or ``mydistro.conf`` file. As with append files previously
+         described, you can either completely override the variable:
+         PACKAGECONFIG_pn-recipename = "f4 f5" Or, you can just amend the
+         variable:
+         ::
+
+            PACKAGECONFIG_append_pn-recipename = " f4"
+
+   PACKAGECONFIG_CONFARGS
+      A space-separated list of configuration options generated from the
+      :term:`PACKAGECONFIG` setting.
+
+      Classes such as :ref:`autotools <ref-classes-autotools>` and
+      :ref:`cmake <ref-classes-cmake>` use ``PACKAGECONFIG_CONFARGS`` to
+      pass ``PACKAGECONFIG`` options to ``configure`` and ``cmake``,
+      respectively. If you are using ``PACKAGECONFIG`` but not a class that
+      handles the ``do_configure`` task, then you need to use
+      ``PACKAGECONFIG_CONFARGS`` appropriately.
+
+   PACKAGEGROUP_DISABLE_COMPLEMENTARY
+      For recipes inheriting the
+      :ref:`packagegroup <ref-classes-packagegroup>` class, setting
+      ``PACKAGEGROUP_DISABLE_COMPLEMENTARY`` to "1" specifies that the
+      normal complementary packages (i.e. ``-dev``, ``-dbg``, and so forth)
+      should not be automatically created by the ``packagegroup`` recipe,
+      which is the default behavior.
+
+   PACKAGES
+      The list of packages the recipe creates. The default value is the
+      following:
+      ::
+
+         ${PN}-dbg ${PN}-staticdev ${PN}-dev ${PN}-doc ${PN}-locale ${PACKAGE_BEFORE_PN} ${PN}
+
+      During packaging, the :ref:`ref-tasks-package` task
+      goes through ``PACKAGES`` and uses the :term:`FILES`
+      variable corresponding to each package to assign files to the
+      package. If a file matches the ``FILES`` variable for more than one
+      package in ``PACKAGES``, it will be assigned to the earliest
+      (leftmost) package.
+
+      Packages in the variable's list that are empty (i.e. where none of
+      the patterns in ``FILES_``\ pkg match any files installed by the
+      :ref:`ref-tasks-install` task) are not generated,
+      unless generation is forced through the
+      :term:`ALLOW_EMPTY` variable.
+
+   PACKAGES_DYNAMIC
+      A promise that your recipe satisfies runtime dependencies for
+      optional modules that are found in other recipes.
+      ``PACKAGES_DYNAMIC`` does not actually satisfy the dependencies, it
+      only states that they should be satisfied. For example, if a hard,
+      runtime dependency (:term:`RDEPENDS`) of another
+      package is satisfied at build time through the ``PACKAGES_DYNAMIC``
+      variable, but a package with the module name is never actually
+      produced, then the other package will be broken. Thus, if you attempt
+      to include that package in an image, you will get a dependency
+      failure from the packaging system during the
+      :ref:`ref-tasks-rootfs` task.
+
+      Typically, if there is a chance that such a situation can occur and
+      the package that is not created is valid without the dependency being
+      satisfied, then you should use :term:`RRECOMMENDS`
+      (a soft runtime dependency) instead of ``RDEPENDS``.
+
+      For an example of how to use the ``PACKAGES_DYNAMIC`` variable when
+      you are splitting packages, see the
+      ":ref:`dev-manual/dev-manual-common-tasks:handling optional module packaging`"
+      section in the Yocto Project Development Tasks Manual.
+
+   PACKAGESPLITFUNCS
+      Specifies a list of functions run to perform additional splitting of
+      files into individual packages. Recipes can either prepend to this
+      variable or prepend to the ``populate_packages`` function in order to
+      perform additional package splitting. In either case, the function
+      should set :term:`PACKAGES`,
+      :term:`FILES`, :term:`RDEPENDS` and
+      other packaging variables appropriately in order to perform the
+      desired splitting.
+
+   PARALLEL_MAKE
+      Extra options passed to the ``make`` command during the
+      :ref:`ref-tasks-compile` task in order to specify
+      parallel compilation on the local build host. This variable is
+      usually in the form "-j x", where x represents the maximum number of
+      parallel threads ``make`` can run.
+
+      .. note::
+
+         In order for
+         PARALLEL_MAKE
+         to be effective,
+         make
+         must be called with
+         ${
+         EXTRA_OEMAKE
+         }
+         . An easy way to ensure this is to use the
+         oe_runmake
+         function.
+
+      By default, the OpenEmbedded build system automatically sets this
+      variable to be equal to the number of cores the build system uses.
+
+      .. note::
+
+         If the software being built experiences dependency issues during
+         the
+         do_compile
+         task that result in race conditions, you can clear the
+         PARALLEL_MAKE
+         variable within the recipe as a workaround. For information on
+         addressing race conditions, see the "
+         Debugging Parallel Make Races
+         " section in the Yocto Project Development Tasks Manual.
+
+      For single socket systems (i.e. one CPU), you should not have to
+      override this variable to gain optimal parallelism during builds.
+      However, if you have very large systems that employ multiple physical
+      CPUs, you might want to make sure the ``PARALLEL_MAKE`` variable is
+      not set higher than "-j 20".
+
+      For more information on speeding up builds, see the
+      ":ref:`dev-manual/dev-manual-common-tasks:speeding up a build`"
+      section in the Yocto Project Development Tasks Manual.
+
+   PARALLEL_MAKEINST
+      Extra options passed to the ``make install`` command during the
+      :ref:`ref-tasks-install` task in order to specify
+      parallel installation. This variable defaults to the value of
+      :term:`PARALLEL_MAKE`.
+
+      .. note::
+
+         In order for ``PARALLEL_MAKEINST`` to be effective, ``make`` must
+         be called with
+         ``${``\ :term:`EXTRA_OEMAKE`\ ``}``. An easy
+         way to ensure this is to use the ``oe_runmake`` function.
+
+         If the software being built experiences dependency issues during
+         the ``do_install`` task that result in race conditions, you can
+         clear the ``PARALLEL_MAKEINST`` variable within the recipe as a
+         workaround. For information on addressing race conditions, see the
+         ":ref:`dev-manual/dev-manual-common-tasks:debugging parallel make races`"
+         section in the Yocto Project Development Tasks Manual.
+
+   PATCHRESOLVE
+      Determines the action to take when a patch fails. You can set this
+      variable to one of two values: "noop" and "user".
+
+      The default value of "noop" causes the build to simply fail when the
+      OpenEmbedded build system cannot successfully apply a patch. Setting
+      the value to "user" causes the build system to launch a shell and
+      places you in the right location so that you can manually resolve the
+      conflicts.
+
+      Set this variable in your ``local.conf`` file.
+
+   PATCHTOOL
+      Specifies the utility used to apply patches for a recipe during the
+      :ref:`ref-tasks-patch` task. You can specify one of
+      three utilities: "patch", "quilt", or "git". The default utility used
+      is "quilt" except for the quilt-native recipe itself. Because the
+      quilt tool is not available at the time quilt-native is being
+      patched, it uses "patch".
+
+      If you wish to use an alternative patching tool, set the variable in
+      the recipe using one of the following:
+      ::
+
+         PATCHTOOL = "patch"
+         PATCHTOOL = "quilt"
+         PATCHTOOL = "git"
+
+   PE
+      The epoch of the recipe. By default, this variable is unset. The
+      variable is used to make upgrades possible when the versioning scheme
+      changes in some backwards incompatible way.
+
+      ``PE`` is the default value of the :term:`PKGE` variable.
+
+   PF
+      Specifies the recipe or package name and includes all version and
+      revision numbers (i.e. ``glibc-2.13-r20+svnr15508/`` and
+      ``bash-4.2-r1/``). This variable is comprised of the following:
+      ${:term:`PN`}-${:term:`EXTENDPE`}${:term:`PV`}-${:term:`PR`}
+
+   PIXBUF_PACKAGES
+      When inheriting the :ref:`pixbufcache <ref-classes-pixbufcache>`
+      class, this variable identifies packages that contain the pixbuf
+      loaders used with ``gdk-pixbuf``. By default, the ``pixbufcache``
+      class assumes that the loaders are in the recipe's main package (i.e.
+      ``${``\ :term:`PN`\ ``}``). Use this variable if the
+      loaders you need are in a package other than that main package.
+
+   PKG
+      The name of the resulting package created by the OpenEmbedded build
+      system.
+
+      .. note::
+
+         When using the
+         PKG
+         variable, you must use a package name override.
+
+      For example, when the :ref:`debian <ref-classes-debian>` class
+      renames the output package, it does so by setting
+      ``PKG_packagename``.
+
+   PKG_CONFIG_PATH
+      The path to ``pkg-config`` files for the current build context.
+      ``pkg-config`` reads this variable from the environment.
+
+   PKGD
+      Points to the destination directory for files to be packaged before
+      they are split into individual packages. This directory defaults to
+      the following:
+      ::
+
+         ${WORKDIR}/package
+
+      Do not change this default.
+
+   PKGDATA_DIR
+      Points to a shared, global-state directory that holds data generated
+      during the packaging process. During the packaging process, the
+      :ref:`ref-tasks-packagedata` task packages data
+      for each recipe and installs it into this temporary, shared area.
+      This directory defaults to the following, which you should not
+      change:
+      ::
+
+         ${STAGING_DIR_HOST}/pkgdata
+
+      For examples of how this data is used, see the
+      ":ref:`overview-manual/overview-manual-concepts:automatically added runtime dependencies`"
+      section in the Yocto Project Overview and Concepts Manual and the
+      ":ref:`dev-manual/dev-manual-common-tasks:viewing package information with \`\`oe-pkgdata-util\`\``"
+      section in the Yocto Project Development Tasks Manual. For more
+      information on the shared, global-state directory, see
+      :term:`STAGING_DIR_HOST`.
+
+   PKGDEST
+      Points to the parent directory for files to be packaged after they
+      have been split into individual packages. This directory defaults to
+      the following:
+      ::
+
+         ${WORKDIR}/packages-split
+
+      Under this directory, the build system creates directories for each
+      package specified in :term:`PACKAGES`. Do not change
+      this default.
+
+   PKGDESTWORK
+      Points to a temporary work area where the
+      :ref:`ref-tasks-package` task saves package metadata.
+      The ``PKGDESTWORK`` location defaults to the following:
+      ::
+
+         ${WORKDIR}/pkgdata
+
+      Do not change this default.
+
+      The :ref:`ref-tasks-packagedata` task copies the
+      package metadata from ``PKGDESTWORK`` to
+      :term:`PKGDATA_DIR` to make it available globally.
+
+   PKGE
+      The epoch of the package(s) built by the recipe. By default, ``PKGE``
+      is set to :term:`PE`.
+
+   PKGR
+      The revision of the package(s) built by the recipe. By default,
+      ``PKGR`` is set to :term:`PR`.
+
+   PKGV
+      The version of the package(s) built by the recipe. By default,
+      ``PKGV`` is set to :term:`PV`.
+
+   PN
+      This variable can have two separate functions depending on the
+      context: a recipe name or a resulting package name.
+
+      ``PN`` refers to a recipe name in the context of a file used by the
+      OpenEmbedded build system as input to create a package. The name is
+      normally extracted from the recipe file name. For example, if the
+      recipe is named ``expat_2.0.1.bb``, then the default value of ``PN``
+      will be "expat".
+
+      The variable refers to a package name in the context of a file
+      created or produced by the OpenEmbedded build system.
+
+      If applicable, the ``PN`` variable also contains any special suffix
+      or prefix. For example, using ``bash`` to build packages for the
+      native machine, ``PN`` is ``bash-native``. Using ``bash`` to build
+      packages for the target and for Multilib, ``PN`` would be ``bash``
+      and ``lib64-bash``, respectively.
+
+   PNBLACKLIST
+      Lists recipes you do not want the OpenEmbedded build system to build.
+      This variable works in conjunction with the
+      :ref:`blacklist <ref-classes-blacklist>` class, which is inherited
+      globally.
+
+      To prevent a recipe from being built, use the ``PNBLACKLIST``
+      variable in your ``local.conf`` file. Here is an example that
+      prevents ``myrecipe`` from being built:
+      ::
+
+         PNBLACKLIST[myrecipe] = "Not supported by our organization."
+
+   POPULATE_SDK_POST_HOST_COMMAND
+      Specifies a list of functions to call once the OpenEmbedded build
+      system has created the host part of the SDK. You can specify
+      functions separated by semicolons:
+      ::
+
+          POPULATE_SDK_POST_HOST_COMMAND += "function; ... "
+
+      If you need to pass the SDK path to a command within a function, you
+      can use ``${SDK_DIR}``, which points to the parent directory used by
+      the OpenEmbedded build system when creating SDK output. See the
+      :term:`SDK_DIR` variable for more information.
+
+   POPULATE_SDK_POST_TARGET_COMMAND
+      Specifies a list of functions to call once the OpenEmbedded build
+      system has created the target part of the SDK. You can specify
+      functions separated by semicolons:
+      ::
+
+         POPULATE_SDK_POST_TARGET_COMMAND += "function; ... "
+
+      If you need to pass the SDK path to a command within a function, you
+      can use ``${SDK_DIR}``, which points to the parent directory used by
+      the OpenEmbedded build system when creating SDK output. See the
+      :term:`SDK_DIR` variable for more information.
+
+   PR
+      The revision of the recipe. The default value for this variable is
+      "r0". Subsequent revisions of the recipe conventionally have the
+      values "r1", "r2", and so forth. When :term:`PV` increases,
+      ``PR`` is conventionally reset to "r0".
+
+      .. note::
+
+         The OpenEmbedded build system does not need the aid of
+         PR
+         to know when to rebuild a recipe. The build system uses the task
+         input checksums
+         along with the
+         stamp
+         and
+         shared state cache
+         mechanisms.
+
+      The ``PR`` variable primarily becomes significant when a package
+      manager dynamically installs packages on an already built image. In
+      this case, ``PR``, which is the default value of
+      :term:`PKGR`, helps the package manager distinguish which
+      package is the most recent one in cases where many packages have the
+      same ``PV`` (i.e. ``PKGV``). A component having many packages with
+      the same ``PV`` usually means that the packages all install the same
+      upstream version, but with later (``PR``) version packages including
+      packaging fixes.
+
+      .. note::
+
+         PR
+         does not need to be increased for changes that do not change the
+         package contents or metadata.
+
+      Because manually managing ``PR`` can be cumbersome and error-prone,
+      an automated solution exists. See the
+      ":ref:`dev-manual/dev-manual-common-tasks:working with a pr service`" section
+      in the Yocto Project Development Tasks Manual for more information.
+
+   PREFERRED_PROVIDER
+      If multiple recipes provide the same item, this variable determines
+      which recipe is preferred and thus provides the item (i.e. the
+      preferred provider). You should always suffix this variable with the
+      name of the provided item. And, you should define the variable using
+      the preferred recipe's name (:term:`PN`). Here is a common
+      example:
+      ::
+
+         PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
+
+      In the previous example, multiple recipes are providing "virtual/kernel".
+      The ``PREFERRED_PROVIDER`` variable is set with the name (``PN``) of
+      the recipe you prefer to provide "virtual/kernel".
+
+      Following are more examples:
+      ::
+
+         PREFERRED_PROVIDER_virtual/xserver = "xserver-xf86"
+         PREFERRED_PROVIDER_virtual/libgl ?= "mesa"
+
+      For more
+      information, see the ":ref:`metadata-virtual-providers`"
+      section in the Yocto Project Development Tasks Manual.
+
+      .. note::
+
+         If you use a
+         virtual/\*
+         item with
+         PREFERRED_PROVIDER
+         , then any recipe that
+         PROVIDES
+         that item but is not selected (defined) by
+         PREFERRED_PROVIDER
+         is prevented from building, which is usually desirable since this
+         mechanism is designed to select between mutually exclusive
+         alternative providers.
+
+   PREFERRED_VERSION
+      If multiple versions of recipes exist, this variable determines which
+      version is given preference. You must always suffix the variable with
+      the :term:`PN` you want to select, and you should set the
+      :term:`PV` accordingly for precedence.
+
+      The ``PREFERRED_VERSION`` variable supports limited wildcard use
+      through the "``%``" character. You can use the character to match any
+      number of characters, which can be useful when specifying versions
+      that contain long revision numbers that potentially change. Here are
+      two examples:
+      ::
+
+         PREFERRED_VERSION_python = "3.4.0"
+         PREFERRED_VERSION_linux-yocto = "5.0%"
+
+      .. note::
+
+         The use of the "%" character is limited in that it only works at the end of the
+         string. You cannot use the wildcard character in any other
+         location of the string.
+
+      The specified version is matched against :term:`PV`, which
+      does not necessarily match the version part of the recipe's filename.
+      For example, consider two recipes ``foo_1.2.bb`` and ``foo_git.bb``
+      where ``foo_git.bb`` contains the following assignment:
+      ::
+
+         PV = "1.1+git${SRCPV}"
+
+      In this case, the correct way to select
+      ``foo_git.bb`` is by using an assignment such as the following:
+      ::
+
+         PREFERRED_VERSION_foo = "1.1+git%"
+
+      Compare that previous example
+      against the following incorrect example, which does not work:
+      ::
+
+         PREFERRED_VERSION_foo = "git"
+
+      Sometimes the ``PREFERRED_VERSION`` variable can be set by
+      configuration files in a way that is hard to change. You can use
+      :term:`OVERRIDES` to set a machine-specific
+      override. Here is an example:
+      ::
+
+         PREFERRED_VERSION_linux-yocto_qemux86 = "5.0%"
+
+      Although not recommended, worst case, you can also use the
+      "forcevariable" override, which is the strongest override possible.
+      Here is an example:
+      ::
+
+         PREFERRED_VERSION_linux-yocto_forcevariable = "5.0%"
+
+      .. note::
+
+         The \_forcevariable override is not handled specially. This override
+         only works because the default value of OVERRIDES includes "forcevariable".
+
+   PREMIRRORS
+      Specifies additional paths from which the OpenEmbedded build system
+      gets source code. When the build system searches for source code, it
+      first tries the local download directory. If that location fails, the
+      build system tries locations defined by ``PREMIRRORS``, the upstream
+      source, and then locations specified by
+      :term:`MIRRORS` in that order.
+
+      Assuming your distribution (:term:`DISTRO`) is "poky",
+      the default value for ``PREMIRRORS`` is defined in the
+      ``conf/distro/poky.conf`` file in the ``meta-poky`` Git repository.
+
+      Typically, you could add a specific server for the build system to
+      attempt before any others by adding something like the following to
+      the ``local.conf`` configuration file in the
+      :term:`Build Directory`:
+      ::
+
+         PREMIRRORS_prepend = "\
+             git://.*/.* http://www.yoctoproject.org/sources/ \n \
+             ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
+             http://.*/.* http://www.yoctoproject.org/sources/ \n \
+             https://.*/.* http://www.yoctoproject.org/sources/ \n"
+
+      These changes cause the
+      build system to intercept Git, FTP, HTTP, and HTTPS requests and
+      direct them to the ``http://`` sources mirror. You can use
+      ``file://`` URLs to point to local directories or network shares as
+      well.
+
+   PRIORITY
+      Indicates the importance of a package.
+
+      ``PRIORITY`` is considered to be part of the distribution policy
+      because the importance of any given recipe depends on the purpose for
+      which the distribution is being produced. Thus, ``PRIORITY`` is not
+      normally set within recipes.
+
+      You can set ``PRIORITY`` to "required", "standard", "extra", and
+      "optional", which is the default.
+
+   PRIVATE_LIBS
+      Specifies libraries installed within a recipe that should be ignored
+      by the OpenEmbedded build system's shared library resolver. This
+      variable is typically used when software being built by a recipe has
+      its own private versions of a library normally provided by another
+      recipe. In this case, you would not want the package containing the
+      private libraries to be set as a dependency on other unrelated
+      packages that should instead depend on the package providing the
+      standard version of the library.
+
+      Libraries specified in this variable should be specified by their
+      file name. For example, from the Firefox recipe in meta-browser:
+      ::
+
+         PRIVATE_LIBS = "libmozjs.so \
+                         libxpcom.so \
+                         libnspr4.so \
+                         libxul.so \
+                         libmozalloc.so \
+                         libplc4.so \
+                         libplds4.so"
+
+      For more information, see the
+      ":ref:`overview-manual/overview-manual-concepts:automatically added runtime dependencies`"
+      section in the Yocto Project Overview and Concepts Manual.
+
+   PROVIDES
+      A list of aliases by which a particular recipe can be known. By
+      default, a recipe's own ``PN`` is implicitly already in its
+      ``PROVIDES`` list and therefore does not need to mention that it
+      provides itself. If a recipe uses ``PROVIDES``, the additional
+      aliases are synonyms for the recipe and can be useful for satisfying
+      dependencies of other recipes during the build as specified by
+      ``DEPENDS``.
+
+      Consider the following example ``PROVIDES`` statement from the recipe
+      file ``eudev_3.2.9.bb``:
+      ::
+
+         PROVIDES = "udev"
+
+      The ``PROVIDES`` statement
+      results in the "eudev" recipe also being available as simply "udev".
+
+      .. note::
+
+         Given that a recipe's own recipe name is already implicitly in its
+         own
+         PROVIDES
+         list, it is unnecessary to add aliases with the "+=" operator;
+         using a simple assignment will be sufficient. In other words,
+         while you could write:
+         ::
+
+                 PROVIDES += "udev"
+
+
+         in the above, the "+=" is overkill and unnecessary.
+
+      In addition to providing recipes under alternate names, the
+      ``PROVIDES`` mechanism is also used to implement virtual targets. A
+      virtual target is a name that corresponds to some particular
+      functionality (e.g. a Linux kernel). Recipes that provide the
+      functionality in question list the virtual target in ``PROVIDES``.
+      Recipes that depend on the functionality in question can include the
+      virtual target in ``DEPENDS`` to leave the choice of provider open.
+
+      Conventionally, virtual targets have names on the form
+      "virtual/function" (e.g. "virtual/kernel"). The slash is simply part
+      of the name and has no syntactical significance.
+
+      The :term:`PREFERRED_PROVIDER` variable is
+      used to select which particular recipe provides a virtual target.
+
+      .. note::
+
+         A corresponding mechanism for virtual runtime dependencies
+         (packages) exists. However, the mechanism does not depend on any
+         special functionality beyond ordinary variable assignments. For
+         example, ``VIRTUAL-RUNTIME_dev_manager`` refers to the package of
+         the component that manages the ``/dev`` directory.
+
+         Setting the "preferred provider" for runtime dependencies is as
+         simple as using the following assignment in a configuration file:
+         ::
+
+                 VIRTUAL-RUNTIME_dev_manager = "udev"
+
+
+   PRSERV_HOST
+      The network based :term:`PR` service host and port.
+
+      The ``conf/local.conf.sample.extended`` configuration file in the
+      :term:`Source Directory` shows how the
+      ``PRSERV_HOST`` variable is set:
+      ::
+
+         PRSERV_HOST = "localhost:0"
+
+      You must
+      set the variable if you want to automatically start a local :ref:`PR
+      service <dev-manual/dev-manual-common-tasks:working with a pr service>`. You can
+      set ``PRSERV_HOST`` to other values to use a remote PR service.
+
+   PTEST_ENABLED
+      Specifies whether or not :ref:`Package
+      Test <dev-manual/dev-manual-common-tasks:testing packages with ptest>` (ptest)
+      functionality is enabled when building a recipe. You should not set
+      this variable directly. Enabling and disabling building Package Tests
+      at build time should be done by adding "ptest" to (or removing it
+      from) :term:`DISTRO_FEATURES`.
+
+   PV
+      The version of the recipe. The version is normally extracted from the
+      recipe filename. For example, if the recipe is named
+      ``expat_2.0.1.bb``, then the default value of ``PV`` will be "2.0.1".
+      ``PV`` is generally not overridden within a recipe unless it is
+      building an unstable (i.e. development) version from a source code
+      repository (e.g. Git or Subversion).
+
+      ``PV`` is the default value of the :term:`PKGV` variable.
+
+   PYTHON_ABI
+      When used by recipes that inherit the
+      :ref:`distutils3 <ref-classes-distutils3>`,
+      :ref:`setuptools3 <ref-classes-setuptools3>`,
+      :ref:`distutils <ref-classes-distutils>`, or
+      :ref:`setuptools <ref-classes-setuptools>` classes, denotes the
+      Application Binary Interface (ABI) currently in use for Python. By
+      default, the ABI is "m". You do not have to set this variable as the
+      OpenEmbedded build system sets it for you.
+
+      The OpenEmbedded build system uses the ABI to construct directory
+      names used when installing the Python headers and libraries in
+      sysroot (e.g. ``.../python3.3m/...``).
+
+      Recipes that inherit the ``distutils`` class during cross-builds also
+      use this variable to locate the headers and libraries of the
+      appropriate Python that the extension is targeting.
+
+   PYTHON_PN
+      When used by recipes that inherit the
+      `distutils3 <ref-classes-distutils3>`,
+      :ref:`setuptools3 <ref-classes-setuptools3>`,
+      :ref:`distutils <ref-classes-distutils>`, or
+      :ref:`setuptools <ref-classes-setuptools>` classes, specifies the
+      major Python version being built. For Python 3.x, ``PYTHON_PN`` would
+      be "python3". You do not have to set this variable as the
+      OpenEmbedded build system automatically sets it for you.
+
+      The variable allows recipes to use common infrastructure such as the
+      following:
+      ::
+
+         DEPENDS += "${PYTHON_PN}-native"
+
+      In the previous example,
+      the version of the dependency is ``PYTHON_PN``.
+
+   RANLIB
+      The minimal command and arguments to run ``ranlib``.
+
+   RCONFLICTS
+      The list of packages that conflict with packages. Note that packages
+      will not be installed if conflicting packages are not first removed.
+
+      Like all package-controlling variables, you must always use them in
+      conjunction with a package name override. Here is an example:
+      ::
+
+         RCONFLICTS_${PN} = "another_conflicting_package_name"
+
+      BitBake, which the OpenEmbedded build system uses, supports
+      specifying versioned dependencies. Although the syntax varies
+      depending on the packaging format, BitBake hides these differences
+      from you. Here is the general syntax to specify versions with the
+      ``RCONFLICTS`` variable:
+      ::
+
+         RCONFLICTS_${PN} = "package (operator version)"
+
+      For ``operator``, you can specify the following: = < > <=
+      >= For example, the following sets up a dependency on version 1.2 or
+      greater of the package ``foo``:
+      ::
+
+         RCONFLICTS_${PN} = "foo (>= 1.2)"
+
+   RDEPENDS
+      Lists runtime dependencies of a package. These dependencies are other
+      packages that must be installed in order for the package to function
+      correctly. As an example, the following assignment declares that the
+      package ``foo`` needs the packages ``bar`` and ``baz`` to be
+      installed:
+      ::
+
+         RDEPENDS_foo = "bar baz"
+
+      The most common types of package
+      runtime dependencies are automatically detected and added. Therefore,
+      most recipes do not need to set ``RDEPENDS``. For more information,
+      see the
+      ":ref:`overview-manual/overview-manual-concepts:automatically added runtime dependencies`"
+      section in the Yocto Project Overview and Concepts Manual.
+
+      The practical effect of the above ``RDEPENDS`` assignment is that
+      ``bar`` and ``baz`` will be declared as dependencies inside the
+      package ``foo`` when it is written out by one of the
+      ```do_package_write_*`` <#ref-tasks-package_write_deb>`__ tasks.
+      Exactly how this is done depends on which package format is used,
+      which is determined by
+      :term:`PACKAGE_CLASSES`. When the
+      corresponding package manager installs the package, it will know to
+      also install the packages on which it depends.
+
+      To ensure that the packages ``bar`` and ``baz`` get built, the
+      previous ``RDEPENDS`` assignment also causes a task dependency to be
+      added. This dependency is from the recipe's
+      :ref:`ref-tasks-build` (not to be confused with
+      :ref:`ref-tasks-compile`) task to the
+      ``do_package_write_*`` task of the recipes that build ``bar`` and
+      ``baz``.
+
+      The names of the packages you list within ``RDEPENDS`` must be the
+      names of other packages - they cannot be recipe names. Although
+      package names and recipe names usually match, the important point
+      here is that you are providing package names within the ``RDEPENDS``
+      variable. For an example of the default list of packages created from
+      a recipe, see the :term:`PACKAGES` variable.
+
+      Because the ``RDEPENDS`` variable applies to packages being built,
+      you should always use the variable in a form with an attached package
+      name (remember that a single recipe can build multiple packages). For
+      example, suppose you are building a development package that depends
+      on the ``perl`` package. In this case, you would use the following
+      ``RDEPENDS`` statement:
+      ::
+
+         RDEPENDS_${PN}-dev += "perl"
+
+      In the example,
+      the development package depends on the ``perl`` package. Thus, the
+      ``RDEPENDS`` variable has the ``${PN}-dev`` package name as part of
+      the variable.
+
+      .. note::
+
+         RDEPENDS_${PN}-dev
+         includes
+         ${
+         PN
+         }
+         by default. This default is set in the BitBake configuration file
+         (
+         meta/conf/bitbake.conf
+         ). Be careful not to accidentally remove
+         ${PN}
+         when modifying
+         RDEPENDS_${PN}-dev
+         . Use the "+=" operator rather than the "=" operator.
+
+      The package names you use with ``RDEPENDS`` must appear as they would
+      in the ``PACKAGES`` variable. The :term:`PKG` variable
+      allows a different name to be used for the final package (e.g. the
+      :ref:`debian <ref-classes-debian>` class uses this to rename
+      packages), but this final package name cannot be used with
+      ``RDEPENDS``, which makes sense as ``RDEPENDS`` is meant to be
+      independent of the package format used.
+
+      BitBake, which the OpenEmbedded build system uses, supports
+      specifying versioned dependencies. Although the syntax varies
+      depending on the packaging format, BitBake hides these differences
+      from you. Here is the general syntax to specify versions with the
+      ``RDEPENDS`` variable:
+      ::
+
+         RDEPENDS_${PN} = "package (operator version)"
+
+      For operator, you can specify the following: = < > <= >= For version,
+      provide the version number.
+
+      .. note::
+
+         You can use
+         EXTENDPKGV
+         to provide a full package version specification.
+
+      For example, the following sets up a dependency on version 1.2 or
+      greater of the package ``foo``:
+      ::
+
+         RDEPENDS_${PN} = "foo (>= 1.2)"
+
+      For information on build-time dependencies, see the
+      :term:`DEPENDS` variable. You can also see the
+      ":ref:`Tasks <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:tasks>`" and
+      ":ref:`Dependencies <bitbake:bitbake-user-manual/bitbake-user-manual-execution:dependencies>`" sections in the
+      BitBake User Manual for additional information on tasks and
+      dependencies.
+
+   REQUIRED_DISTRO_FEATURES
+      When inheriting the
+      :ref:`distro_features_check <ref-classes-distro_features_check>`
+      class, this variable identifies distribution features that must exist
+      in the current configuration in order for the OpenEmbedded build
+      system to build the recipe. In other words, if the
+      ``REQUIRED_DISTRO_FEATURES`` variable lists a feature that does not
+      appear in ``DISTRO_FEATURES`` within the current configuration, an
+      error occurs and the build stops.
+
+   RM_WORK_EXCLUDE
+      With ``rm_work`` enabled, this variable specifies a list of recipes
+      whose work directories should not be removed. See the
+      ":ref:`rm_work.bbclass <ref-classes-rm-work>`" section for more
+      details.
+
+   ROOT_HOME
+      Defines the root home directory. By default, this directory is set as
+      follows in the BitBake configuration file:
+      ::
+
+         ROOT_HOME ??= "/home/root"
+
+      .. note::
+
+         This default value is likely used because some embedded solutions
+         prefer to have a read-only root filesystem and prefer to keep
+         writeable data in one place.
+
+      You can override the default by setting the variable in any layer or
+      in the ``local.conf`` file. Because the default is set using a "weak"
+      assignment (i.e. "??="), you can use either of the following forms to
+      define your override:
+      ::
+
+         ROOT_HOME = "/root"
+         ROOT_HOME ?= "/root"
+
+      These
+      override examples use ``/root``, which is probably the most commonly
+      used override.
+
+   ROOTFS
+      Indicates a filesystem image to include as the root filesystem.
+
+      The ``ROOTFS`` variable is an optional variable used with the
+      :ref:`image-live <ref-classes-image-live>` class.
+
+   ROOTFS_POSTINSTALL_COMMAND
+      Specifies a list of functions to call after the OpenEmbedded build
+      system has installed packages. You can specify functions separated by
+      semicolons:
+      ::
+
+         ROOTFS_POSTINSTALL_COMMAND += "function; ... "
+
+      If you need to pass the root filesystem path to a command within a
+      function, you can use ``${IMAGE_ROOTFS}``, which points to the
+      directory that becomes the root filesystem image. See the
+      :term:`IMAGE_ROOTFS` variable for more
+      information.
+
+   ROOTFS_POSTPROCESS_COMMAND
+      Specifies a list of functions to call once the OpenEmbedded build
+      system has created the root filesystem. You can specify functions
+      separated by semicolons:
+      ::
+
+         ROOTFS_POSTPROCESS_COMMAND += "function; ... "
+
+      If you need to pass the root filesystem path to a command within a
+      function, you can use ``${IMAGE_ROOTFS}``, which points to the
+      directory that becomes the root filesystem image. See the
+      :term:`IMAGE_ROOTFS` variable for more
+      information.
+
+   ROOTFS_POSTUNINSTALL_COMMAND
+      Specifies a list of functions to call after the OpenEmbedded build
+      system has removed unnecessary packages. When runtime package
+      management is disabled in the image, several packages are removed
+      including ``base-passwd``, ``shadow``, and ``update-alternatives``.
+      You can specify functions separated by semicolons:
+      ::
+
+         ROOTFS_POSTUNINSTALL_COMMAND += "function; ... "
+
+      If you need to pass the root filesystem path to a command within a
+      function, you can use ``${IMAGE_ROOTFS}``, which points to the
+      directory that becomes the root filesystem image. See the
+      :term:`IMAGE_ROOTFS` variable for more
+      information.
+
+   ROOTFS_PREPROCESS_COMMAND
+      Specifies a list of functions to call before the OpenEmbedded build
+      system has created the root filesystem. You can specify functions
+      separated by semicolons:
+      ::
+
+         ROOTFS_PREPROCESS_COMMAND += "function; ... "
+
+      If you need to pass the root filesystem path to a command within a
+      function, you can use ``${IMAGE_ROOTFS}``, which points to the
+      directory that becomes the root filesystem image. See the
+      :term:`IMAGE_ROOTFS` variable for more
+      information.
+
+   RPROVIDES
+      A list of package name aliases that a package also provides. These
+      aliases are useful for satisfying runtime dependencies of other
+      packages both during the build and on the target (as specified by
+      ``RDEPENDS``).
+
+      .. note::
+
+         A package's own name is implicitly already in its
+         RPROVIDES
+         list.
+
+      As with all package-controlling variables, you must always use the
+      variable in conjunction with a package name override. Here is an
+      example:
+      ::
+
+         RPROVIDES_${PN} = "widget-abi-2"
+
+   RRECOMMENDS
+      A list of packages that extends the usability of a package being
+      built. The package being built does not depend on this list of
+      packages in order to successfully build, but rather uses them for
+      extended usability. To specify runtime dependencies for packages, see
+      the ``RDEPENDS`` variable.
+
+      The package manager will automatically install the ``RRECOMMENDS``
+      list of packages when installing the built package. However, you can
+      prevent listed packages from being installed by using the
+      :term:`BAD_RECOMMENDATIONS`,
+      :term:`NO_RECOMMENDATIONS`, and
+      :term:`PACKAGE_EXCLUDE` variables.
+
+      Packages specified in ``RRECOMMENDS`` need not actually be produced.
+      However, a recipe must exist that provides each package, either
+      through the :term:`PACKAGES` or
+      :term:`PACKAGES_DYNAMIC` variables or the
+      :term:`RPROVIDES` variable, or an error will occur
+      during the build. If such a recipe does exist and the package is not
+      produced, the build continues without error.
+
+      Because the ``RRECOMMENDS`` variable applies to packages being built,
+      you should always attach an override to the variable to specify the
+      particular package whose usability is being extended. For example,
+      suppose you are building a development package that is extended to
+      support wireless functionality. In this case, you would use the
+      following:
+      ::
+
+         RRECOMMENDS_${PN}-dev += "wireless_package_name"
+
+      In the
+      example, the package name (``${PN}-dev``) must appear as it would in
+      the ``PACKAGES`` namespace before any renaming of the output package
+      by classes such as ``debian.bbclass``.
+
+      BitBake, which the OpenEmbedded build system uses, supports
+      specifying versioned recommends. Although the syntax varies depending
+      on the packaging format, BitBake hides these differences from you.
+      Here is the general syntax to specify versions with the
+      ``RRECOMMENDS`` variable:
+      ::
+
+         RRECOMMENDS_${PN} = "package (operator version)"
+
+      For ``operator``, you can specify the following:
+
+      - =
+      - <
+      - >
+      - <=
+      - >=
+
+      For example, the following sets up a recommend on version 1.2 or
+      greater of the package ``foo``:
+      ::
+
+         RRECOMMENDS_${PN} = "foo (>= 1.2)"
+
+   RREPLACES
+      A list of packages replaced by a package. The package manager uses
+      this variable to determine which package should be installed to
+      replace other package(s) during an upgrade. In order to also have the
+      other package(s) removed at the same time, you must add the name of
+      the other package to the ``RCONFLICTS`` variable.
+
+      As with all package-controlling variables, you must use this variable
+      in conjunction with a package name override. Here is an example:
+      ::
+
+         RREPLACES_${PN} = "other_package_being_replaced"
+
+      BitBake, which the OpenEmbedded build system uses, supports
+      specifying versioned replacements. Although the syntax varies
+      depending on the packaging format, BitBake hides these differences
+      from you. Here is the general syntax to specify versions with the
+      ``RREPLACES`` variable:
+      ::
+
+         RREPLACES_${PN} = "package (operator version)"
+
+      For ``operator``, you can specify the following:
+
+      - =
+      - <
+      - >
+      - <=
+      - >=
+
+      For example, the following sets up a replacement using version 1.2
+      or greater of the package ``foo``:
+      ::
+
+          RREPLACES_${PN} = "foo (>= 1.2)"
+
+   RSUGGESTS
+      A list of additional packages that you can suggest for installation
+      by the package manager at the time a package is installed. Not all
+      package managers support this functionality.
+
+      As with all package-controlling variables, you must always use this
+      variable in conjunction with a package name override. Here is an
+      example:
+      ::
+
+         RSUGGESTS_${PN} = "useful_package another_package"
+
+   S
+      The location in the :term:`Build Directory` where
+      unpacked recipe source code resides. By default, this directory is
+      ``${``\ :term:`WORKDIR`\ ``}/${``\ :term:`BPN`\ ``}-${``\ :term:`PV`\ ``}``,
+      where ``${BPN}`` is the base recipe name and ``${PV}`` is the recipe
+      version. If the source tarball extracts the code to a directory named
+      anything other than ``${BPN}-${PV}``, or if the source code is
+      fetched from an SCM such as Git or Subversion, then you must set
+      ``S`` in the recipe so that the OpenEmbedded build system knows where
+      to find the unpacked source.
+
+      As an example, assume a :term:`Source Directory`
+      top-level folder named ``poky`` and a default Build Directory at
+      ``poky/build``. In this case, the work directory the build system
+      uses to keep the unpacked recipe for ``db`` is the following:
+      ::
+
+         poky/build/tmp/work/qemux86-poky-linux/db/5.1.19-r3/db-5.1.19
+
+      The unpacked source code resides in the ``db-5.1.19`` folder.
+
+      This next example assumes a Git repository. By default, Git
+      repositories are cloned to ``${WORKDIR}/git`` during
+      :ref:`ref-tasks-fetch`. Since this path is different
+      from the default value of ``S``, you must set it specifically so the
+      source can be located:
+      ::
+
+         SRC_URI = "git://path/to/repo.git"
+         S = "${WORKDIR}/git"
+
+   SANITY_REQUIRED_UTILITIES
+      Specifies a list of command-line utilities that should be checked for
+      during the initial sanity checking process when running BitBake. If
+      any of the utilities are not installed on the build host, then
+      BitBake immediately exits with an error.
+
+   SANITY_TESTED_DISTROS
+      A list of the host distribution identifiers that the build system has
+      been tested against. Identifiers consist of the host distributor ID
+      followed by the release, as reported by the ``lsb_release`` tool or
+      as read from ``/etc/lsb-release``. Separate the list items with
+      explicit newline characters (``\n``). If ``SANITY_TESTED_DISTROS`` is
+      not empty and the current value of
+      :term:`NATIVELSBSTRING` does not appear in the
+      list, then the build system reports a warning that indicates the
+      current host distribution has not been tested as a build host.
+
+   SDK_ARCH
+      The target architecture for the SDK. Typically, you do not directly
+      set this variable. Instead, use :term:`SDKMACHINE`.
+
+   SDK_DEPLOY
+      The directory set up and used by the
+      :ref:`populate_sdk_base <ref-classes-populate-sdk>` class to which
+      the SDK is deployed. The ``populate_sdk_base`` class defines
+      ``SDK_DEPLOY`` as follows:
+      ::
+
+         SDK_DEPLOY = "${TMPDIR}/deploy/sdk"
+
+   SDK_DIR
+      The parent directory used by the OpenEmbedded build system when
+      creating SDK output. The
+      :ref:`populate_sdk_base <ref-classes-populate-sdk-*>` class defines
+      the variable as follows:
+      ::
+
+         SDK_DIR = "${WORKDIR}/sdk"
+
+      .. note::
+
+         The
+         SDK_DIR
+         directory is a temporary directory as it is part of
+         WORKDIR
+         . The final output directory is
+         SDK_DEPLOY
+         .
+
+   SDK_EXT_TYPE
+      Controls whether or not shared state artifacts are copied into the
+      extensible SDK. The default value of "full" copies all of the
+      required shared state artifacts into the extensible SDK. The value
+      "minimal" leaves these artifacts out of the SDK.
+
+      .. note::
+
+         If you set the variable to "minimal", you need to ensure
+         SSTATE_MIRRORS
+         is set in the SDK's configuration to enable the artifacts to be
+         fetched as needed.
+
+   SDK_HOST_MANIFEST
+      The manifest file for the host part of the SDK. This file lists all
+      the installed packages that make up the host part of the SDK. The
+      file contains package information on a line-per-package basis as
+      follows:
+      ::
+
+         packagename packagearch version
+
+      The :ref:`populate_sdk_base <ref-classes-populate-sdk-*>` class
+      defines the manifest file as follows:
+      ::
+
+         SDK_HOST_MANIFEST = "${SDK_DEPLOY}/${TOOLCHAIN_OUTPUTNAME}.host.manifest"
+
+      The location is derived using the :term:`SDK_DEPLOY` and
+      :term:`TOOLCHAIN_OUTPUTNAME` variables.
+
+   SDK_INCLUDE_PKGDATA
+      When set to "1", specifies to include the packagedata for all recipes
+      in the "world" target in the extensible SDK. Including this data
+      allows the ``devtool search`` command to find these recipes in search
+      results, as well as allows the ``devtool add`` command to map
+      dependencies more effectively.
+
+      .. note::
+
+         Enabling the
+         SDK_INCLUDE_PKGDATA
+         variable significantly increases build time because all of world
+         needs to be built. Enabling the variable also slightly increases
+         the size of the extensible SDK.
+
+   SDK_INCLUDE_TOOLCHAIN
+      When set to "1", specifies to include the toolchain in the extensible
+      SDK. Including the toolchain is useful particularly when
+      :term:`SDK_EXT_TYPE` is set to "minimal" to keep
+      the SDK reasonably small but you still want to provide a usable
+      toolchain. For example, suppose you want to use the toolchain from an
+      IDE or from other tools and you do not want to perform additional
+      steps to install the toolchain.
+
+      The ``SDK_INCLUDE_TOOLCHAIN`` variable defaults to "0" if
+      ``SDK_EXT_TYPE`` is set to "minimal", and defaults to "1" if
+      ``SDK_EXT_TYPE`` is set to "full".
+
+   SDK_INHERIT_BLACKLIST
+      A list of classes to remove from the :term:`INHERIT`
+      value globally within the extensible SDK configuration. The
+      :ref:`populate-sdk-ext <ref-classes-populate-sdk-*>` class sets the
+      default value:
+      ::
+
+         SDK_INHERIT_BLACKLIST ?= "buildhistory icecc"
+
+      Some classes are not generally applicable within the extensible SDK
+      context. You can use this variable to disable those classes.
+
+      For additional information on how to customize the extensible SDK's
+      configuration, see the
+      ":ref:`sdk-manual/sdk-appendix-customizing:configuring the extensible sdk`"
+      section in the Yocto Project Application Development and the
+      Extensible Software Development Kit (eSDK) manual.
+
+   SDK_LOCAL_CONF_BLACKLIST
+      A list of variables not allowed through from the OpenEmbedded build
+      system configuration into the extensible SDK configuration. Usually,
+      these are variables that are specific to the machine on which the
+      build system is running and thus would be potentially problematic
+      within the extensible SDK.
+
+      By default, ``SDK_LOCAL_CONF_BLACKLIST`` is set in the
+      :ref:`populate-sdk-ext <ref-classes-populate-sdk-*>` class and
+      excludes the following variables:
+
+      - :term:`CONF_VERSION`
+      - :term:`BB_NUMBER_THREADS`
+      - :term:`bitbake:BB_NUMBER_PARSE_THREADS`
+      - :term:`PARALLEL_MAKE`
+      - :term:`PRSERV_HOST`
+      - :term:`SSTATE_MIRRORS` :term:`DL_DIR`
+      - :term:`SSTATE_DIR` :term:`TMPDIR`
+      - :term:`BB_SERVER_TIMEOUT`
+
+      For additional information on how to customize the extensible SDK's
+      configuration, see the
+      ":ref:`sdk-manual/sdk-appendix-customizing:configuring the extensible sdk`"
+      section in the Yocto Project Application Development and the
+      Extensible Software Development Kit (eSDK) manual.
+
+   SDK_LOCAL_CONF_WHITELIST
+      A list of variables allowed through from the OpenEmbedded build
+      system configuration into the extensible SDK configuration. By
+      default, the list of variables is empty and is set in the
+      :ref:`populate-sdk-ext <ref-classes-populate-sdk-*>` class.
+
+      This list overrides the variables specified using the
+      :term:`SDK_LOCAL_CONF_BLACKLIST`
+      variable as well as any variables identified by automatic
+      blacklisting due to the "/" character being found at the start of the
+      value, which is usually indicative of being a path and thus might not
+      be valid on the system where the SDK is installed.
+
+      For additional information on how to customize the extensible SDK's
+      configuration, see the
+      ":ref:`sdk-manual/sdk-appendix-customizing:configuring the extensible sdk`"
+      section in the Yocto Project Application Development and the
+      Extensible Software Development Kit (eSDK) manual.
+
+   SDK_NAME
+      The base name for SDK output files. The name is derived from the
+      :term:`DISTRO`, :term:`TCLIBC`,
+      :term:`SDK_ARCH`,
+      :term:`IMAGE_BASENAME`, and
+      :term:`TUNE_PKGARCH` variables:
+      ::
+
+         SDK_NAME = "${DISTRO}-${TCLIBC}-${SDK_ARCH}-${IMAGE_BASENAME}-${TUNE_PKGARCH}"
+
+   SDK_OS
+      Specifies the operating system for which the SDK will be built. The
+      default value is the value of :term:`BUILD_OS`.
+
+   SDK_OUTPUT
+      The location used by the OpenEmbedded build system when creating SDK
+      output. The :ref:`populate_sdk_base <ref-classes-populate-sdk-*>`
+      class defines the variable as follows:
+      ::
+
+         SDK_DIR = "${WORKDIR}/sdk"
+         SDK_OUTPUT = "${SDK_DIR}/image"
+         SDK_DEPLOY = "${DEPLOY_DIR}/sdk"
+
+      .. note::
+
+         The SDK_OUTPUT directory is a temporary directory as it is part of
+         WORKDIR by way of SDK_DIR. The final output directory is
+         SDK_DEPLOY.
+
+   SDK_PACKAGE_ARCHS
+      Specifies a list of architectures compatible with the SDK machine.
+      This variable is set automatically and should not normally be
+      hand-edited. Entries are separated using spaces and listed in order
+      of priority. The default value for ``SDK_PACKAGE_ARCHS`` is "all any
+      noarch ${SDK_ARCH}-${SDKPKGSUFFIX}".
+
+   SDK_POSTPROCESS_COMMAND
+      Specifies a list of functions to call once the OpenEmbedded build
+      system creates the SDK. You can specify functions separated by
+      semicolons: SDK_POSTPROCESS_COMMAND += "function; ... "
+
+      If you need to pass an SDK path to a command within a function, you
+      can use ``${SDK_DIR}``, which points to the parent directory used by
+      the OpenEmbedded build system when creating SDK output. See the
+      :term:`SDK_DIR` variable for more information.
+
+   SDK_PREFIX
+      The toolchain binary prefix used for ``nativesdk`` recipes. The
+      OpenEmbedded build system uses the ``SDK_PREFIX`` value to set the
+      :term:`TARGET_PREFIX` when building
+      ``nativesdk`` recipes. The default value is "${SDK_SYS}-".
+
+   SDK_RECRDEP_TASKS
+      A list of shared state tasks added to the extensible SDK. By default,
+      the following tasks are added:
+
+      - do_populate_lic
+      - do_package_qa
+      - do_populate_sysroot
+      - do_deploy
+
+      Despite the default value of "" for the
+      ``SDK_RECRDEP_TASKS`` variable, the above four tasks are always added
+      to the SDK. To specify tasks beyond these four, you need to use the
+      ``SDK_RECRDEP_TASKS`` variable (e.g. you are defining additional
+      tasks that are needed in order to build
+      :term:`SDK_TARGETS`).
+
+   SDK_SYS
+      Specifies the system, including the architecture and the operating
+      system, for which the SDK will be built.
+
+      The OpenEmbedded build system automatically sets this variable based
+      on :term:`SDK_ARCH`,
+      :term:`SDK_VENDOR`, and
+      :term:`SDK_OS`. You do not need to set the ``SDK_SYS``
+      variable yourself.
+
+   SDK_TARGET_MANIFEST
+      The manifest file for the target part of the SDK. This file lists all
+      the installed packages that make up the target part of the SDK. The
+      file contains package information on a line-per-package basis as
+      follows:
+      ::
+
+         packagename packagearch version
+
+      The :ref:`populate_sdk_base <ref-classes-populate-sdk-*>` class
+      defines the manifest file as follows:
+      ::
+
+         SDK_TARGET_MANIFEST = "${SDK_DEPLOY}/${TOOLCHAIN_OUTPUTNAME}.target.manifest"
+
+      The location is derived using the :term:`SDK_DEPLOY` and
+      :term:`TOOLCHAIN_OUTPUTNAME` variables.
+
+   SDK_TARGETS
+      A list of targets to install from shared state as part of the
+      standard or extensible SDK installation. The default value is "${PN}"
+      (i.e. the image from which the SDK is built).
+
+      The ``SDK_TARGETS`` variable is an internal variable and typically
+      would not be changed.
+
+   SDK_TITLE
+      The title to be printed when running the SDK installer. By default,
+      this title is based on the :term:`DISTRO_NAME` or
+      :term:`DISTRO` variable and is set in the
+      :ref:`populate_sdk_base <ref-classes-populate-sdk-*>` class as
+      follows:
+      ::
+
+         SDK_TITLE ??= "${@d.getVar('DISTRO_NAME') or d.getVar('DISTRO')} SDK"
+
+      For the default distribution "poky",
+      ``SDK_TITLE`` is set to "Poky (Yocto Project Reference Distro)".
+
+      For information on how to change this default title, see the
+      ":ref:`sdk-manual/sdk-appendix-customizing:changing the extensible sdk installer title`"
+      section in the Yocto Project Application Development and the
+      Extensible Software Development Kit (eSDK) manual.
+
+   SDK_UPDATE_URL
+      An optional URL for an update server for the extensible SDK. If set,
+      the value is used as the default update server when running
+      ``devtool sdk-update`` within the extensible SDK.
+
+   SDK_VENDOR
+      Specifies the name of the SDK vendor.
+
+   SDK_VERSION
+      Specifies the version of the SDK. The distribution configuration file
+      (e.g. ``/meta-poky/conf/distro/poky.conf``) defines the
+      ``SDK_VERSION`` as follows:
+      ::
+
+         SDK_VERSION = "${@d.getVar('DISTRO_VERSION').replace('snapshot-${DATE}','snapshot')}"
+
+      For additional information, see the
+      :term:`DISTRO_VERSION` and
+      :term:`DATE` variables.
+
+   SDKEXTPATH
+      The default installation directory for the Extensible SDK. By
+      default, this directory is based on the :term:`DISTRO`
+      variable and is set in the
+      :ref:`populate_sdk_base <ref-classes-populate-sdk-*>` class as
+      follows:
+      ::
+
+         SDKEXTPATH ??= "~/${@d.getVar('DISTRO')}_sdk"
+
+      For the
+      default distribution "poky", the ``SDKEXTPATH`` is set to "poky_sdk".
+
+      For information on how to change this default directory, see the
+      ":ref:`sdk-manual/sdk-appendix-customizing:changing the default sdk installation directory`"
+      section in the Yocto Project Application Development and the
+      Extensible Software Development Kit (eSDK) manual.
+
+   SDKIMAGE_FEATURES
+      Equivalent to ``IMAGE_FEATURES``. However, this variable applies to
+      the SDK generated from an image using the following command:
+      ::
+
+         $ bitbake -c populate_sdk imagename
+
+   SDKMACHINE
+      The machine for which the SDK is built. In other words, the SDK is
+      built such that it runs on the target you specify with the
+      ``SDKMACHINE`` value. The value points to a corresponding ``.conf``
+      file under ``conf/machine-sdk/``.
+
+      You can use "i686" and "x86_64" as possible values for this variable.
+      The variable defaults to "i686" and is set in the local.conf file in
+      the Build Directory.
+      ::
+
+         SDKMACHINE ?= "i686"
+
+      .. note::
+
+         You cannot set the
+         SDKMACHINE
+         variable in your distribution configuration file. If you do, the
+         configuration will not take affect.
+
+   SDKPATH
+      Defines the path offered to the user for installation of the SDK that
+      is generated by the OpenEmbedded build system. The path appears as
+      the default location for installing the SDK when you run the SDK's
+      installation script. You can override the offered path when you run
+      the script.
+
+   SDKTARGETSYSROOT
+      The full path to the sysroot used for cross-compilation within an SDK
+      as it will be when installed into the default
+      :term:`SDKPATH`.
+
+   SECTION
+      The section in which packages should be categorized. Package
+      management utilities can make use of this variable.
+
+   SELECTED_OPTIMIZATION
+      Specifies the optimization flags passed to the C compiler when
+      building for the target. The flags are passed through the default
+      value of the :term:`TARGET_CFLAGS` variable.
+
+      The ``SELECTED_OPTIMIZATION`` variable takes the value of
+      ``FULL_OPTIMIZATION`` unless ``DEBUG_BUILD`` = "1". If that is the
+      case, the value of ``DEBUG_OPTIMIZATION`` is used.
+
+   SERIAL_CONSOLE
+      Defines a serial console (TTY) to enable using
+      `getty <https://en.wikipedia.org/wiki/Getty_(Unix)>`__. Provide a
+      value that specifies the baud rate followed by the TTY device name
+      separated by a space. You cannot specify more than one TTY device:
+      ::
+
+         SERIAL_CONSOLE = "115200 ttyS0"
+
+      .. note::
+
+         The
+         SERIAL_CONSOLE
+         variable is deprecated. Please use the
+         SERIAL_CONSOLES
+         variable.
+
+   SERIAL_CONSOLES
+      Defines a serial console (TTY) to enable using
+      `getty <https://en.wikipedia.org/wiki/Getty_(Unix)>`__. Provide a
+      value that specifies the baud rate followed by the TTY device name
+      separated by a semicolon. Use spaces to separate multiple devices:
+      ::
+
+         SERIAL_CONSOLES = "115200;ttyS0 115200;ttyS1"
+
+   SERIAL_CONSOLES_CHECK
+      Specifies serial consoles, which must be listed in
+      :term:`SERIAL_CONSOLES`, to check against
+      ``/proc/console`` before enabling them using getty. This variable
+      allows aliasing in the format: <device>:<alias>. If a device was
+      listed as "sclp_line0" in ``/dev/`` and "ttyS0" was listed in
+      ``/proc/console``, you would do the following: ::
+
+         SERIAL_CONSOLES_CHECK = "slcp_line0:ttyS0"
+
+      This variable is currently only supported with SysVinit (i.e. not
+      with systemd).
+
+   SIGGEN_EXCLUDE_SAFE_RECIPE_DEPS
+      A list of recipe dependencies that should not be used to determine
+      signatures of tasks from one recipe when they depend on tasks from
+      another recipe. For example: ::
+
+         SIGGEN_EXCLUDE_SAFE_RECIPE_DEPS += "intone->mplayer2"
+
+      In the previous example, ``intone`` depends on ``mplayer2``.
+
+      You can use the special token ``"*"`` on the left-hand side of the
+      dependency to match all recipes except the one on the right-hand
+      side. Here is an example: ::
+
+         SIGGEN_EXCLUDE_SAFE_RECIPE_DEPS += "*->quilt-native"
+
+      In the previous example, all recipes except ``quilt-native`` ignore
+      task signatures from the ``quilt-native`` recipe when determining
+      their task signatures.
+
+      Use of this variable is one mechanism to remove dependencies that
+      affect task signatures and thus force rebuilds when a recipe changes.
+
+      .. note::
+
+         If you add an inappropriate dependency for a recipe relationship,
+         the software might break during runtime if the interface of the
+         second recipe was changed after the first recipe had been built.
+
+   SIGGEN_EXCLUDERECIPES_ABISAFE
+      A list of recipes that are completely stable and will never change.
+      The ABI for the recipes in the list are presented by output from the
+      tasks run to build the recipe. Use of this variable is one way to
+      remove dependencies from one recipe on another that affect task
+      signatures and thus force rebuilds when the recipe changes.
+
+      .. note::
+
+         If you add an inappropriate variable to this list, the software
+         might break at runtime if the interface of the recipe was changed
+         after the other had been built.
+
+   SITEINFO_BITS
+      Specifies the number of bits for the target system CPU. The value
+      should be either "32" or "64".
+
+   SITEINFO_ENDIANNESS
+      Specifies the endian byte order of the target system. The value
+      should be either "le" for little-endian or "be" for big-endian.
+
+   SKIP_FILEDEPS
+      Enables removal of all files from the "Provides" section of an RPM
+      package. Removal of these files is required for packages containing
+      prebuilt binaries and libraries such as ``libstdc++`` and ``glibc``.
+
+      To enable file removal, set the variable to "1" in your
+      ``conf/local.conf`` configuration file in your:
+      :term:`Build Directory`.
+      ::
+
+         SKIP_FILEDEPS = "1"
+
+   SOC_FAMILY
+      Groups together machines based upon the same family of SOC (System On
+      Chip). You typically set this variable in a common ``.inc`` file that
+      you include in the configuration files of all the machines.
+
+      .. note::
+
+         You must include
+         conf/machine/include/soc-family.inc
+         for this variable to appear in
+         MACHINEOVERRIDES
+         .
+
+   SOLIBS
+      Defines the suffix for shared libraries used on the target platform.
+      By default, this suffix is ".so.*" for all Linux-based systems and is
+      defined in the ``meta/conf/bitbake.conf`` configuration file.
+
+      You will see this variable referenced in the default values of
+      ``FILES_${PN}``.
+
+   SOLIBSDEV
+      Defines the suffix for the development symbolic link (symlink) for
+      shared libraries on the target platform. By default, this suffix is
+      ".so" for Linux-based systems and is defined in the
+      ``meta/conf/bitbake.conf`` configuration file.
+
+      You will see this variable referenced in the default values of
+      ``FILES_${PN}-dev``.
+
+   SOURCE_MIRROR_FETCH
+      When you are fetching files to create a mirror of sources (i.e.
+      creating a source mirror), setting ``SOURCE_MIRROR_FETCH`` to "1" in
+      your ``local.conf`` configuration file ensures the source for all
+      recipes are fetched regardless of whether or not a recipe is
+      compatible with the configuration. A recipe is considered
+      incompatible with the currently configured machine when either or
+      both the :term:`COMPATIBLE_MACHINE`
+      variable and :term:`COMPATIBLE_HOST` variables
+      specify compatibility with a machine other than that of the current
+      machine or host.
+
+      .. note::
+
+         Do not set the
+         SOURCE_MIRROR_FETCH
+         variable unless you are creating a source mirror. In other words,
+         do not set the variable during a normal build.
+
+   SOURCE_MIRROR_URL
+      Defines your own :term:`PREMIRRORS` from which to
+      first fetch source before attempting to fetch from the upstream
+      specified in :term:`SRC_URI`.
+
+      To use this variable, you must globally inherit the
+      :ref:`own-mirrors <ref-classes-own-mirrors>` class and then provide
+      the URL to your mirrors. Here is the general syntax:
+      ::
+
+         INHERIT += "own-mirrors"
+         SOURCE_MIRROR_URL = "http://example.com/my_source_mirror"
+
+      .. note::
+
+         You can specify only a single URL in
+         SOURCE_MIRROR_URL
+         .
+
+   SPDXLICENSEMAP
+      Maps commonly used license names to their SPDX counterparts found in
+      ``meta/files/common-licenses/``. For the default ``SPDXLICENSEMAP``
+      mappings, see the ``meta/conf/licenses.conf`` file.
+
+      For additional information, see the :term:`LICENSE`
+      variable.
+
+   SPECIAL_PKGSUFFIX
+      A list of prefixes for :term:`PN` used by the OpenEmbedded
+      build system to create variants of recipes or packages. The list
+      specifies the prefixes to strip off during certain circumstances such
+      as the generation of the :term:`BPN` variable.
+
+   SPL_BINARY
+      The file type for the Secondary Program Loader (SPL). Some devices
+      use an SPL from which to boot (e.g. the BeagleBone development
+      board). For such cases, you can declare the file type of the SPL
+      binary in the ``u-boot.inc`` include file, which is used in the
+      U-Boot recipe.
+
+      The SPL file type is set to "null" by default in the ``u-boot.inc``
+      file as follows:
+      ::
+
+         # Some versions of u-boot build an SPL (Second Program Loader) image that
+         # should be packaged along with the u-boot binary as well as placed in the
+         # deploy directory. For those versions they can set the following variables
+         # to allow packaging the SPL.
+         SPL_BINARY ?= ""
+         SPL_BINARYNAME ?= "${@os.path.basename(d.getVar("SPL_BINARY"))}"
+         SPL_IMAGE ?= "${SPL_BINARYNAME}-${MACHINE}-${PV}-${PR}"
+         SPL_SYMLINK ?= "${SPL_BINARYNAME}-${MACHINE}"
+
+      The ``SPL_BINARY`` variable helps form
+      various ``SPL_*`` variables used by the OpenEmbedded build system.
+
+      See the BeagleBone machine configuration example in the
+      ":ref:`dev-manual/dev-manual-common-tasks:adding a layer using the \`\`bitbake-layers\`\` script`"
+      section in the Yocto Project Board Support Package Developer's Guide
+      for additional information.
+
+   SRC_URI
+      The list of source files - local or remote. This variable tells the
+      OpenEmbedded build system which bits to pull in for the build and how
+      to pull them in. For example, if the recipe or append file only needs
+      to fetch a tarball from the Internet, the recipe or append file uses
+      a single ``SRC_URI`` entry. On the other hand, if the recipe or
+      append file needs to fetch a tarball, apply two patches, and include
+      a custom file, the recipe or append file would include four instances
+      of the variable.
+
+      The following list explains the available URI protocols. URI
+      protocols are highly dependent on particular BitBake Fetcher
+      submodules. Depending on the fetcher BitBake uses, various URL
+      parameters are employed. For specifics on the supported Fetchers, see
+      the ":ref:`Fetchers <bitbake:bb-fetchers>`" section in the
+      BitBake User Manual.
+
+      -  ``file://`` - Fetches files, which are usually files shipped
+         with the :term:`Metadata`, from the local machine (e.g.
+         :ref:`patch <patching-dev-environment>` files).
+         The path is relative to the :term:`FILESPATH`
+         variable. Thus, the build system searches, in order, from the
+         following directories, which are assumed to be a subdirectories of
+         the directory in which the recipe file (``.bb``) or append file
+         (``.bbappend``) resides:
+
+         -  ``${BPN}`` - The base recipe name without any special suffix
+            or version numbers.
+
+         -  ``${BP}`` - ``${BPN}-${PV}``. The base recipe name and
+            version but without any special package name suffix.
+
+         -  *files -* Files within a directory, which is named ``files``
+            and is also alongside the recipe or append file.
+
+         .. note::
+
+            If you want the build system to pick up files specified through
+            a
+            SRC_URI
+            statement from your append file, you need to be sure to extend
+            the
+            FILESPATH
+            variable by also using the
+            FILESEXTRAPATHS
+            variable from within your append file.
+
+      -  ``bzr://`` - Fetches files from a Bazaar revision control
+         repository.
+
+      -  ``git://`` - Fetches files from a Git revision control
+         repository.
+
+      -  ``osc://`` - Fetches files from an OSC (OpenSUSE Build service)
+         revision control repository.
+
+      -  ``repo://`` - Fetches files from a repo (Git) repository.
+
+      -  ``ccrc://`` - Fetches files from a ClearCase repository.
+
+      -  ``http://`` - Fetches files from the Internet using ``http``.
+
+      -  ``https://`` - Fetches files from the Internet using ``https``.
+
+      -  ``ftp://`` - Fetches files from the Internet using ``ftp``.
+
+      -  ``cvs://`` - Fetches files from a CVS revision control
+         repository.
+
+      -  ``hg://`` - Fetches files from a Mercurial (``hg``) revision
+         control repository.
+
+      -  ``p4://`` - Fetches files from a Perforce (``p4``) revision
+         control repository.
+
+      -  ``ssh://`` - Fetches files from a secure shell.
+
+      -  ``svn://`` - Fetches files from a Subversion (``svn``) revision
+         control repository.
+
+      -  ``npm://`` - Fetches JavaScript modules from a registry.
+
+      Standard and recipe-specific options for ``SRC_URI`` exist. Here are
+      standard options:
+
+      -  ``apply`` - Whether to apply the patch or not. The default
+         action is to apply the patch.
+
+      -  ``striplevel`` - Which striplevel to use when applying the
+         patch. The default level is 1.
+
+      -  ``patchdir`` - Specifies the directory in which the patch should
+         be applied. The default is ``${``\ :term:`S`\ ``}``.
+
+      Here are options specific to recipes building code from a revision
+      control system:
+
+      -  ``mindate`` - Apply the patch only if
+         :term:`SRCDATE` is equal to or greater than
+         ``mindate``.
+
+      -  ``maxdate`` - Apply the patch only if ``SRCDATE`` is not later
+         than ``maxdate``.
+
+      -  ``minrev`` - Apply the patch only if ``SRCREV`` is equal to or
+         greater than ``minrev``.
+
+      -  ``maxrev`` - Apply the patch only if ``SRCREV`` is not later
+         than ``maxrev``.
+
+      -  ``rev`` - Apply the patch only if ``SRCREV`` is equal to
+         ``rev``.
+
+      -  ``notrev`` - Apply the patch only if ``SRCREV`` is not equal to
+         ``rev``.
+
+      Here are some additional options worth mentioning:
+
+      -  ``unpack`` - Controls whether or not to unpack the file if it is
+         an archive. The default action is to unpack the file.
+
+      -  ``destsuffix`` - Places the file (or extracts its contents) into
+         the specified subdirectory of :term:`WORKDIR` when
+         the Git fetcher is used.
+
+      -  ``subdir`` - Places the file (or extracts its contents) into the
+         specified subdirectory of ``WORKDIR`` when the local (``file://``)
+         fetcher is used.
+
+      -  ``localdir`` - Places the file (or extracts its contents) into
+         the specified subdirectory of ``WORKDIR`` when the CVS fetcher is
+         used.
+
+      -  ``subpath`` - Limits the checkout to a specific subpath of the
+         tree when using the Git fetcher is used.
+
+      -  ``name`` - Specifies a name to be used for association with
+         ``SRC_URI`` checksums when you have more than one file specified
+         in ``SRC_URI``.
+
+      -  ``downloadfilename`` - Specifies the filename used when storing
+         the downloaded file.
+
+   SRC_URI_OVERRIDES_PACKAGE_ARCH
+      By default, the OpenEmbedded build system automatically detects
+      whether ``SRC_URI`` contains files that are machine-specific. If so,
+      the build system automatically changes ``PACKAGE_ARCH``. Setting this
+      variable to "0" disables this behavior.
+
+   SRCDATE
+      The date of the source code used to build the package. This variable
+      applies only if the source was fetched from a Source Code Manager
+      (SCM).
+
+   SRCPV
+      Returns the version string of the current package. This string is
+      used to help define the value of :term:`PV`.
+
+      The ``SRCPV`` variable is defined in the ``meta/conf/bitbake.conf``
+      configuration file in the :term:`Source Directory` as
+      follows:
+      ::
+
+         SRCPV = "${@bb.fetch2.get_srcrev(d)}"
+
+      Recipes that need to define ``PV`` do so with the help of the
+      ``SRCPV``. For example, the ``ofono`` recipe (``ofono_git.bb``)
+      located in ``meta/recipes-connectivity`` in the Source Directory
+      defines ``PV`` as follows:
+      ::
+
+         PV = "0.12-git${SRCPV}"
+
+   SRCREV
+      The revision of the source code used to build the package. This
+      variable applies to Subversion, Git, Mercurial, and Bazaar only. Note
+      that if you want to build a fixed revision and you want to avoid
+      performing a query on the remote repository every time BitBake parses
+      your recipe, you should specify a ``SRCREV`` that is a full revision
+      identifier and not just a tag.
+
+      .. note::
+
+         For information on limitations when inheriting the latest revision
+         of software using
+         SRCREV
+         , see the
+         AUTOREV
+         variable description and the "
+         Automatically Incrementing a Binary Package Revision Number
+         " section, which is in the Yocto Project Development Tasks Manual.
+
+   SSTATE_DIR
+      The directory for the shared state cache.
+
+   SSTATE_MIRROR_ALLOW_NETWORK
+      If set to "1", allows fetches from mirrors that are specified in
+      :term:`SSTATE_MIRRORS` to work even when
+      fetching from the network is disabled by setting ``BB_NO_NETWORK`` to
+      "1". Using the ``SSTATE_MIRROR_ALLOW_NETWORK`` variable is useful if
+      you have set ``SSTATE_MIRRORS`` to point to an internal server for
+      your shared state cache, but you want to disable any other fetching
+      from the network.
+
+   SSTATE_MIRRORS
+      Configures the OpenEmbedded build system to search other mirror
+      locations for prebuilt cache data objects before building out the
+      data. This variable works like fetcher :term:`MIRRORS`
+      and :term:`PREMIRRORS` and points to the cache
+      locations to check for the shared state (sstate) objects.
+
+      You can specify a filesystem directory or a remote URL such as HTTP
+      or FTP. The locations you specify need to contain the shared state
+      cache (sstate-cache) results from previous builds. The sstate-cache
+      you point to can also be from builds on other machines.
+
+      When pointing to sstate build artifacts on another machine that uses
+      a different GCC version for native builds, you must configure
+      ``SSTATE_MIRRORS`` with a regular expression that maps local search
+      paths to server paths. The paths need to take into account
+      :term:`NATIVELSBSTRING` set by the
+      :ref:`uninative <ref-classes-uninative>` class. For example, the
+      following maps the local search path ``universal-4.9`` to the
+      server-provided path server_url_sstate_path:
+      ::
+
+         SSTATE_MIRRORS ?= "file://universal-4.9/(.*) http://server_url_sstate_path/universal-4.8/\1 \n"
+
+      If a mirror uses the same structure as
+      :term:`SSTATE_DIR`, you need to add "PATH" at the
+      end as shown in the examples below. The build system substitutes the
+      correct path within the directory structure.
+      ::
+
+         SSTATE_MIRRORS ?= "\
+             file://.* http://someserver.tld/share/sstate/PATH;downloadfilename=PATH \n \
+             file://.* file:///some-local-dir/sstate/PATH"
+
+   SSTATE_SCAN_FILES
+      Controls the list of files the OpenEmbedded build system scans for
+      hardcoded installation paths. The variable uses a space-separated
+      list of filenames (not paths) with standard wildcard characters
+      allowed.
+
+      During a build, the OpenEmbedded build system creates a shared state
+      (sstate) object during the first stage of preparing the sysroots.
+      That object is scanned for hardcoded paths for original installation
+      locations. The list of files that are scanned for paths is controlled
+      by the ``SSTATE_SCAN_FILES`` variable. Typically, recipes add files
+      they want to be scanned to the value of ``SSTATE_SCAN_FILES`` rather
+      than the variable being comprehensively set. The
+      :ref:`sstate <ref-classes-sstate>` class specifies the default list
+      of files.
+
+      For details on the process, see the
+      :ref:`staging <ref-classes-staging>` class.
+
+   STAGING_BASE_LIBDIR_NATIVE
+      Specifies the path to the ``/lib`` subdirectory of the sysroot
+      directory for the build host.
+
+   STAGING_BASELIBDIR
+      Specifies the path to the ``/lib`` subdirectory of the sysroot
+      directory for the target for which the current recipe is being built
+      (:term:`STAGING_DIR_HOST`).
+
+   STAGING_BINDIR
+      Specifies the path to the ``/usr/bin`` subdirectory of the sysroot
+      directory for the target for which the current recipe is being built
+      (:term:`STAGING_DIR_HOST`).
+
+   STAGING_BINDIR_CROSS
+      Specifies the path to the directory containing binary configuration
+      scripts. These scripts provide configuration information for other
+      software that wants to make use of libraries or include files
+      provided by the software associated with the script.
+
+      .. note::
+
+         This style of build configuration has been largely replaced by
+         pkg-config
+         . Consequently, if
+         pkg-config
+         is supported by the library to which you are linking, it is
+         recommended you use
+         pkg-config
+         instead of a provided configuration script.
+
+   STAGING_BINDIR_NATIVE
+      Specifies the path to the ``/usr/bin`` subdirectory of the sysroot
+      directory for the build host.
+
+   STAGING_DATADIR
+      Specifies the path to the ``/usr/share`` subdirectory of the sysroot
+      directory for the target for which the current recipe is being built
+      (:term:`STAGING_DIR_HOST`).
+
+   STAGING_DATADIR_NATIVE
+      Specifies the path to the ``/usr/share`` subdirectory of the sysroot
+      directory for the build host.
+
+   STAGING_DIR
+      Helps construct the ``recipe-sysroots`` directory, which is used
+      during packaging.
+
+      For information on how staging for recipe-specific sysroots occurs,
+      see the :ref:`ref-tasks-populate_sysroot`
+      task, the ":ref:`sdk-manual/sdk-extensible:sharing files between recipes`"
+      section in the Yocto Project Development Tasks Manual, the
+      ":ref:`configuration-compilation-and-staging-dev-environment`"
+      section in the Yocto Project Overview and Concepts Manual, and the
+      :term:`SYSROOT_DIRS` variable.
+
+      .. note::
+
+         Recipes should never write files directly under the
+         STAGING_DIR
+         directory because the OpenEmbedded build system manages the
+         directory automatically. Instead, files should be installed to
+         ${
+         D
+         }
+         within your recipe's
+         do_install
+         task and then the OpenEmbedded build system will stage a subset of
+         those files into the sysroot.
+
+   STAGING_DIR_HOST
+      Specifies the path to the sysroot directory for the system on which
+      the component is built to run (the system that hosts the component).
+      For most recipes, this sysroot is the one in which that recipe's
+      :ref:`ref-tasks-populate_sysroot` task copies
+      files. Exceptions include ``-native`` recipes, where the
+      ``do_populate_sysroot`` task instead uses
+      :term:`STAGING_DIR_NATIVE`. Depending on
+      the type of recipe and the build target, ``STAGING_DIR_HOST`` can
+      have the following values:
+
+      -  For recipes building for the target machine, the value is
+         "${:term:`STAGING_DIR`}/${:term:`MACHINE`}".
+
+      -  For native recipes building for the build host, the value is empty
+         given the assumption that when building for the build host, the
+         build host's own directories should be used.
+
+         .. note::
+
+            ``-native`` recipes are not installed into host paths like such
+            as ``/usr``. Rather, these recipes are installed into
+            ``STAGING_DIR_NATIVE``. When compiling ``-native`` recipes,
+            standard build environment variables such as
+            :term:`CPPFLAGS` and
+            :term:`CFLAGS` are set up so that both host paths
+            and ``STAGING_DIR_NATIVE`` are searched for libraries and
+            headers using, for example, GCC's ``-isystem`` option.
+
+            Thus, the emphasis is that the ``STAGING_DIR*`` variables
+            should be viewed as input variables by tasks such as
+            :ref:`ref-tasks-configure`,
+            :ref:`ref-tasks-compile`, and
+            :ref:`ref-tasks-install`. Having the real system
+            root correspond to ``STAGING_DIR_HOST`` makes conceptual sense
+            for ``-native`` recipes, as they make use of host headers and
+            libraries.
+
+   STAGING_DIR_NATIVE
+      Specifies the path to the sysroot directory used when building
+      components that run on the build host itself.
+
+   STAGING_DIR_TARGET
+      Specifies the path to the sysroot used for the system for which the
+      component generates code. For components that do not generate code,
+      which is the majority, ``STAGING_DIR_TARGET`` is set to match
+      :term:`STAGING_DIR_HOST`.
+
+      Some recipes build binaries that can run on the target system but
+      those binaries in turn generate code for another different system
+      (e.g. cross-canadian recipes). Using terminology from GNU, the
+      primary system is referred to as the "HOST" and the secondary, or
+      different, system is referred to as the "TARGET". Thus, the binaries
+      run on the "HOST" system and generate binaries for the "TARGET"
+      system. The ``STAGING_DIR_HOST`` variable points to the sysroot used
+      for the "HOST" system, while ``STAGING_DIR_TARGET`` points to the
+      sysroot used for the "TARGET" system.
+
+   STAGING_ETCDIR_NATIVE
+      Specifies the path to the ``/etc`` subdirectory of the sysroot
+      directory for the build host.
+
+   STAGING_EXECPREFIXDIR
+      Specifies the path to the ``/usr`` subdirectory of the sysroot
+      directory for the target for which the current recipe is being built
+      (:term:`STAGING_DIR_HOST`).
+
+   STAGING_INCDIR
+      Specifies the path to the ``/usr/include`` subdirectory of the
+      sysroot directory for the target for which the current recipe being
+      built (:term:`STAGING_DIR_HOST`).
+
+   STAGING_INCDIR_NATIVE
+      Specifies the path to the ``/usr/include`` subdirectory of the
+      sysroot directory for the build host.
+
+   STAGING_KERNEL_BUILDDIR
+      Points to the directory containing the kernel build artifacts.
+      Recipes building software that needs to access kernel build artifacts
+      (e.g. ``systemtap-uprobes``) can look in the directory specified with
+      the ``STAGING_KERNEL_BUILDDIR`` variable to find these artifacts
+      after the kernel has been built.
+
+   STAGING_KERNEL_DIR
+      The directory with kernel headers that are required to build
+      out-of-tree modules.
+
+   STAGING_LIBDIR
+      Specifies the path to the ``/usr/lib`` subdirectory of the sysroot
+      directory for the target for which the current recipe is being built
+      (:term:`STAGING_DIR_HOST`).
+
+   STAGING_LIBDIR_NATIVE
+      Specifies the path to the ``/usr/lib`` subdirectory of the sysroot
+      directory for the build host.
+
+   STAMP
+      Specifies the base path used to create recipe stamp files. The path
+      to an actual stamp file is constructed by evaluating this string and
+      then appending additional information. Currently, the default
+      assignment for ``STAMP`` as set in the ``meta/conf/bitbake.conf``
+      file is:
+      ::
+
+         STAMP = "${STAMPS_DIR}/${MULTIMACH_TARGET_SYS}/${PN}/${EXTENDPE}${PV}-${PR}"
+
+      For information on how BitBake uses stamp files to determine if a
+      task should be rerun, see the
+      ":ref:`overview-manual/overview-manual-concepts:stamp files and the rerunning of tasks`"
+      section in the Yocto Project Overview and Concepts Manual.
+
+      See :term:`STAMPS_DIR`,
+      :term:`MULTIMACH_TARGET_SYS`,
+      :term:`PN`, :term:`EXTENDPE`,
+      :term:`PV`, and :term:`PR` for related variable
+      information.
+
+   STAMPS_DIR
+      Specifies the base directory in which the OpenEmbedded build system
+      places stamps. The default directory is ``${TMPDIR}/stamps``.
+
+   STRIP
+      The minimal command and arguments to run ``strip``, which is used to
+      strip symbols.
+
+   SUMMARY
+      The short (72 characters or less) summary of the binary package for
+      packaging systems such as ``opkg``, ``rpm``, or ``dpkg``. By default,
+      ``SUMMARY`` is used to define the
+      :term:`DESCRIPTION` variable if ``DESCRIPTION`` is
+      not set in the recipe.
+
+   SVNDIR
+      The directory in which files checked out of a Subversion system are
+      stored.
+
+   SYSLINUX_DEFAULT_CONSOLE
+      Specifies the kernel boot default console. If you want to use a
+      console other than the default, set this variable in your recipe as
+      follows where "X" is the console number you want to use:
+      ::
+
+         SYSLINUX_DEFAULT_CONSOLE = "console=ttyX"
+
+      The :ref:`syslinux <ref-classes-syslinux>` class initially sets
+      this variable to null but then checks for a value later.
+
+   SYSLINUX_OPTS
+      Lists additional options to add to the syslinux file. You need to set
+      this variable in your recipe. If you want to list multiple options,
+      separate the options with a semicolon character (``;``).
+
+      The :ref:`syslinux <ref-classes-syslinux>` class uses this variable
+      to create a set of options.
+
+   SYSLINUX_SERIAL
+      Specifies the alternate serial port or turns it off. To turn off
+      serial, set this variable to an empty string in your recipe. The
+      variable's default value is set in the
+      :ref:`syslinux <ref-classes-syslinux>` class as follows:
+      ::
+
+         SYSLINUX_SERIAL ?= "0 115200"
+
+      The class checks for and uses the variable as needed.
+
+   SYSLINUX_SPLASH
+      An ``.LSS`` file used as the background for the VGA boot menu when
+      you use the boot menu. You need to set this variable in your recipe.
+
+      The :ref:`syslinux <ref-classes-syslinux>` class checks for this
+      variable and if found, the OpenEmbedded build system installs the
+      splash screen.
+
+   SYSLINUX_SERIAL_TTY
+      Specifies the alternate console=tty... kernel boot argument. The
+      variable's default value is set in the
+      :ref:`syslinux <ref-classes-syslinux>` class as follows:
+      ::
+
+         SYSLINUX_SERIAL_TTY ?= "console=ttyS0,115200"
+
+      The class checks for and uses the variable as needed.
+
+   SYSROOT_DESTDIR
+      Points to the temporary directory under the work directory (default
+      "``${``\ :term:`WORKDIR`\ ``}/sysroot-destdir``")
+      where the files populated into the sysroot are assembled during the
+      :ref:`ref-tasks-populate_sysroot` task.
+
+   SYSROOT_DIRS
+      Directories that are staged into the sysroot by the
+      :ref:`ref-tasks-populate_sysroot` task. By
+      default, the following directories are staged:
+      ::
+
+         SYSROOT_DIRS = " \
+             ${includedir} \
+             ${libdir} \
+             ${base_libdir} \
+             ${nonarch_base_libdir} \
+             ${datadir} \
+             "
+
+   SYSROOT_DIRS_BLACKLIST
+      Directories that are not staged into the sysroot by the
+      :ref:`ref-tasks-populate_sysroot` task. You
+      can use this variable to exclude certain subdirectories of
+      directories listed in :term:`SYSROOT_DIRS` from
+      staging. By default, the following directories are not staged:
+      ::
+
+         SYSROOT_DIRS_BLACKLIST = " \
+             ${mandir} \
+             ${docdir} \
+             ${infodir} \
+             ${datadir}/locale \
+             ${datadir}/applications \
+             ${datadir}/fonts \
+             ${datadir}/pixmaps \
+             "
+
+   SYSROOT_DIRS_NATIVE
+      Extra directories staged into the sysroot by the
+      :ref:`ref-tasks-populate_sysroot` task for
+      ``-native`` recipes, in addition to those specified in
+      :term:`SYSROOT_DIRS`. By default, the following
+      extra directories are staged:
+      ::
+
+         SYSROOT_DIRS_NATIVE = " \
+             ${bindir} \
+             ${sbindir} \
+             ${base_bindir} \
+             ${base_sbindir} \
+             ${libexecdir} \
+             ${sysconfdir} \
+             ${localstatedir} \
+             "
+
+      .. note::
+
+         Programs built by
+         -native
+         recipes run directly from the sysroot (
+         STAGING_DIR_NATIVE
+         ), which is why additional directories containing program
+         executables and supporting files need to be staged.
+
+   SYSROOT_PREPROCESS_FUNCS
+      A list of functions to execute after files are staged into the
+      sysroot. These functions are usually used to apply additional
+      processing on the staged files, or to stage additional files.
+
+   SYSTEMD_AUTO_ENABLE
+      When inheriting the :ref:`systemd <ref-classes-systemd>` class,
+      this variable specifies whether the specified service in
+      :term:`SYSTEMD_SERVICE` should start
+      automatically or not. By default, the service is enabled to
+      automatically start at boot time. The default setting is in the
+      :ref:`systemd <ref-classes-systemd>` class as follows:
+      ::
+
+         SYSTEMD_AUTO_ENABLE ??= "enable"
+
+      You can disable the service by setting the variable to "disable".
+
+   SYSTEMD_BOOT_CFG
+      When :term:`EFI_PROVIDER` is set to
+      "systemd-boot", the ``SYSTEMD_BOOT_CFG`` variable specifies the
+      configuration file that should be used. By default, the
+      :ref:`systemd-boot <ref-classes-systemd-boot>` class sets the
+      ``SYSTEMD_BOOT_CFG`` as follows:
+      ::
+
+         SYSTEMD_BOOT_CFG ?= "${:term:`S`}/loader.conf"
+
+      For information on Systemd-boot, see the `Systemd-boot
+      documentation <http://www.freedesktop.org/wiki/Software/systemd/systemd-boot/>`__.
+
+   SYSTEMD_BOOT_ENTRIES
+      When :term:`EFI_PROVIDER` is set to
+      "systemd-boot", the ``SYSTEMD_BOOT_ENTRIES`` variable specifies a
+      list of entry files (``*.conf``) to install that contain one boot
+      entry per file. By default, the
+      :ref:`systemd-boot <ref-classes-systemd-boot>` class sets the
+      ``SYSTEMD_BOOT_ENTRIES`` as follows:
+      ::
+
+          SYSTEMD_BOOT_ENTRIES ?= ""
+
+      For information on Systemd-boot, see the `Systemd-boot
+      documentation <http://www.freedesktop.org/wiki/Software/systemd/systemd-boot/>`__.
+
+   SYSTEMD_BOOT_TIMEOUT
+      When :term:`EFI_PROVIDER` is set to
+      "systemd-boot", the ``SYSTEMD_BOOT_TIMEOUT`` variable specifies the
+      boot menu timeout in seconds. By default, the
+      :ref:`systemd-boot <ref-classes-systemd-boot>` class sets the
+      ``SYSTEMD_BOOT_TIMEOUT`` as follows:
+      ::
+
+         SYSTEMD_BOOT_TIMEOUT ?= "10"
+
+      For information on Systemd-boot, see the `Systemd-boot
+      documentation <http://www.freedesktop.org/wiki/Software/systemd/systemd-boot/>`__.
+
+   SYSTEMD_PACKAGES
+      When inheriting the :ref:`systemd <ref-classes-systemd>` class,
+      this variable locates the systemd unit files when they are not found
+      in the main recipe's package. By default, the ``SYSTEMD_PACKAGES``
+      variable is set such that the systemd unit files are assumed to
+      reside in the recipes main package:
+      ::
+
+         SYSTEMD_PACKAGES ?= "${PN}"
+
+      If these unit files are not in this recipe's main package, you need
+      to use ``SYSTEMD_PACKAGES`` to list the package or packages in which
+      the build system can find the systemd unit files.
+
+   SYSTEMD_SERVICE
+      When inheriting the :ref:`systemd <ref-classes-systemd>` class,
+      this variable specifies the systemd service name for a package.
+
+      When you specify this file in your recipe, use a package name
+      override to indicate the package to which the value applies. Here is
+      an example from the connman recipe:
+      ::
+
+         SYSTEMD_SERVICE_${PN} = "connman.service"
+
+   SYSVINIT_ENABLED_GETTYS
+      When using
+      :ref:`SysVinit <dev-manual/dev-manual-common-tasks:enabling system services>`,
+      specifies a space-separated list of the virtual terminals that should
+      run a `getty <http://en.wikipedia.org/wiki/Getty_%28Unix%29>`__
+      (allowing login), assuming :term:`USE_VT` is not set to
+      "0".
+
+      The default value for ``SYSVINIT_ENABLED_GETTYS`` is "1" (i.e. only
+      run a getty on the first virtual terminal).
+
+   T
+      This variable points to a directory were BitBake places temporary
+      files, which consist mostly of task logs and scripts, when building a
+      particular recipe. The variable is typically set as follows:
+      ::
+
+         T = "${WORKDIR}/temp"
+
+      The :term:`WORKDIR` is the directory into which
+      BitBake unpacks and builds the recipe. The default ``bitbake.conf``
+      file sets this variable.
+
+      The ``T`` variable is not to be confused with the
+      :term:`TMPDIR` variable, which points to the root of
+      the directory tree where BitBake places the output of an entire
+      build.
+
+   TARGET_ARCH
+      The target machine's architecture. The OpenEmbedded build system
+      supports many architectures. Here is an example list of architectures
+      supported. This list is by no means complete as the architecture is
+      configurable:
+
+      - arm
+      - i586
+      - x86_64
+      - powerpc
+      - powerpc64
+      - mips
+      - mipsel
+
+      For additional information on machine architectures, see the
+      :term:`TUNE_ARCH` variable.
+
+   TARGET_AS_ARCH
+      Specifies architecture-specific assembler flags for the target
+      system. ``TARGET_AS_ARCH`` is initialized from
+      :term:`TUNE_ASARGS` by default in the BitBake
+      configuration file (``meta/conf/bitbake.conf``):
+      ::
+
+         TARGET_AS_ARCH = "${TUNE_ASARGS}"
+
+   TARGET_CC_ARCH
+      Specifies architecture-specific C compiler flags for the target
+      system. ``TARGET_CC_ARCH`` is initialized from
+      :term:`TUNE_CCARGS` by default.
+
+      .. note::
+
+         It is a common workaround to append
+         LDFLAGS
+         to
+         TARGET_CC_ARCH
+         in recipes that build software for the target that would not
+         otherwise respect the exported
+         LDFLAGS
+         variable.
+
+   TARGET_CC_KERNEL_ARCH
+      This is a specific kernel compiler flag for a CPU or Application
+      Binary Interface (ABI) tune. The flag is used rarely and only for
+      cases where a userspace :term:`TUNE_CCARGS` is not
+      compatible with the kernel compilation. The ``TARGET_CC_KERNEL_ARCH``
+      variable allows the kernel (and associated modules) to use a
+      different configuration. See the
+      ``meta/conf/machine/include/arm/feature-arm-thumb.inc`` file in the
+      :term:`Source Directory` for an example.
+
+   TARGET_CFLAGS
+      Specifies the flags to pass to the C compiler when building for the
+      target. When building in the target context,
+      :term:`CFLAGS` is set to the value of this variable by
+      default.
+
+      Additionally, the SDK's environment setup script sets the ``CFLAGS``
+      variable in the environment to the ``TARGET_CFLAGS`` value so that
+      executables built using the SDK also have the flags applied.
+
+   TARGET_CPPFLAGS
+      Specifies the flags to pass to the C pre-processor (i.e. to both the
+      C and the C++ compilers) when building for the target. When building
+      in the target context, :term:`CPPFLAGS` is set to the
+      value of this variable by default.
+
+      Additionally, the SDK's environment setup script sets the
+      ``CPPFLAGS`` variable in the environment to the ``TARGET_CPPFLAGS``
+      value so that executables built using the SDK also have the flags
+      applied.
+
+   TARGET_CXXFLAGS
+      Specifies the flags to pass to the C++ compiler when building for the
+      target. When building in the target context,
+      :term:`CXXFLAGS` is set to the value of this variable
+      by default.
+
+      Additionally, the SDK's environment setup script sets the
+      ``CXXFLAGS`` variable in the environment to the ``TARGET_CXXFLAGS``
+      value so that executables built using the SDK also have the flags
+      applied.
+
+   TARGET_FPU
+      Specifies the method for handling FPU code. For FPU-less targets,
+      which include most ARM CPUs, the variable must be set to "soft". If
+      not, the kernel emulation gets used, which results in a performance
+      penalty.
+
+   TARGET_LD_ARCH
+      Specifies architecture-specific linker flags for the target system.
+      ``TARGET_LD_ARCH`` is initialized from
+      :term:`TUNE_LDARGS` by default in the BitBake
+      configuration file (``meta/conf/bitbake.conf``):
+      ::
+
+         TARGET_LD_ARCH = "${TUNE_LDARGS}"
+
+   TARGET_LDFLAGS
+      Specifies the flags to pass to the linker when building for the
+      target. When building in the target context,
+      :term:`LDFLAGS` is set to the value of this variable
+      by default.
+
+      Additionally, the SDK's environment setup script sets the
+      :term:`LDFLAGS` variable in the environment to the
+      ``TARGET_LDFLAGS`` value so that executables built using the SDK also
+      have the flags applied.
+
+   TARGET_OS
+      Specifies the target's operating system. The variable can be set to
+      "linux" for glibc-based systems (GNU C Library) and to "linux-musl"
+      for musl libc. For ARM/EABI targets, "linux-gnueabi" and
+      "linux-musleabi" possible values exist.
+
+   TARGET_PREFIX
+      Specifies the prefix used for the toolchain binary target tools.
+
+      Depending on the type of recipe and the build target,
+      ``TARGET_PREFIX`` is set as follows:
+
+      -  For recipes building for the target machine, the value is
+         "${:term:`TARGET_SYS`}-".
+
+      -  For native recipes, the build system sets the variable to the
+         value of ``BUILD_PREFIX``.
+
+      -  For native SDK recipes (``nativesdk``), the build system sets the
+         variable to the value of ``SDK_PREFIX``.
+
+   TARGET_SYS
+      Specifies the system, including the architecture and the operating
+      system, for which the build is occurring in the context of the
+      current recipe.
+
+      The OpenEmbedded build system automatically sets this variable based
+      on :term:`TARGET_ARCH`,
+      :term:`TARGET_VENDOR`, and
+      :term:`TARGET_OS` variables.
+
+      .. note::
+
+         You do not need to set the TARGET_SYS variable yourself.
+
+      Consider these two examples:
+
+      -  Given a native recipe on a 32-bit, x86 machine running Linux, the
+         value is "i686-linux".
+
+      -  Given a recipe being built for a little-endian, MIPS target
+         running Linux, the value might be "mipsel-linux".
+
+   TARGET_VENDOR
+      Specifies the name of the target vendor.
+
+   TCLIBC
+      Specifies the GNU standard C library (``libc``) variant to use during
+      the build process. This variable replaces ``POKYLIBC``, which is no
+      longer supported.
+
+      You can select "glibc", "musl", "newlib", or "baremetal"
+
+   TCLIBCAPPEND
+      Specifies a suffix to be appended onto the
+      :term:`TMPDIR` value. The suffix identifies the
+      ``libc`` variant for building. When you are building for multiple
+      variants with the same :term:`Build Directory`, this
+      mechanism ensures that output for different ``libc`` variants is kept
+      separate to avoid potential conflicts.
+
+      In the ``defaultsetup.conf`` file, the default value of
+      ``TCLIBCAPPEND`` is "-${TCLIBC}". However, distros such as poky,
+      which normally only support one ``libc`` variant, set
+      ``TCLIBCAPPEND`` to "" in their distro configuration file resulting
+      in no suffix being applied.
+
+   TCMODE
+      Specifies the toolchain selector. ``TCMODE`` controls the
+      characteristics of the generated packages and images by telling the
+      OpenEmbedded build system which toolchain profile to use. By default,
+      the OpenEmbedded build system builds its own internal toolchain. The
+      variable's default value is "default", which uses that internal
+      toolchain.
+
+      .. note::
+
+         If
+         TCMODE
+         is set to a value other than "default", then it is your
+         responsibility to ensure that the toolchain is compatible with the
+         default toolchain. Using older or newer versions of these
+         components might cause build problems. See the Release Notes for
+         the Yocto Project release for the specific components with which
+         the toolchain must be compatible. To access the Release Notes, go
+         to the
+         Downloads
+         page on the Yocto Project website and click on the "RELEASE
+         INFORMATION" link for the appropriate release.
+
+      The ``TCMODE`` variable is similar to :term:`TCLIBC`,
+      which controls the variant of the GNU standard C library (``libc``)
+      used during the build process: ``glibc`` or ``musl``.
+
+      With additional layers, it is possible to use a pre-compiled external
+      toolchain. One example is the Sourcery G++ Toolchain. The support for
+      this toolchain resides in the separate Mentor Graphics
+      ``meta-sourcery`` layer at
+      http://github.com/MentorEmbedded/meta-sourcery/.
+
+      The layer's ``README`` file contains information on how to use the
+      Sourcery G++ Toolchain as an external toolchain. In summary, you must
+      be sure to add the layer to your ``bblayers.conf`` file in front of
+      the ``meta`` layer and then set the ``EXTERNAL_TOOLCHAIN`` variable
+      in your ``local.conf`` file to the location in which you installed
+      the toolchain.
+
+      The fundamentals used for this example apply to any external
+      toolchain. You can use ``meta-sourcery`` as a template for adding
+      support for other external toolchains.
+
+   TEST_EXPORT_DIR
+      The location the OpenEmbedded build system uses to export tests when
+      the :term:`TEST_EXPORT_ONLY` variable is set
+      to "1".
+
+      The ``TEST_EXPORT_DIR`` variable defaults to
+      ``"${TMPDIR}/testimage/${PN}"``.
+
+   TEST_EXPORT_ONLY
+      Specifies to export the tests only. Set this variable to "1" if you
+      do not want to run the tests but you want them to be exported in a
+      manner that you to run them outside of the build system.
+
+   TEST_LOG_DIR
+      Holds the SSH log and the boot log for QEMU machines. The
+      ``TEST_LOG_DIR`` variable defaults to ``"${WORKDIR}/testimage"``.
+
+      .. note::
+
+         Actual test results reside in the task log (
+         log.do_testimage
+         ), which is in the
+         ${WORKDIR}/temp/
+         directory.
+
+   TEST_POWERCONTROL_CMD
+      For automated hardware testing, specifies the command to use to
+      control the power of the target machine under test. Typically, this
+      command would point to a script that performs the appropriate action
+      (e.g. interacting with a web-enabled power strip). The specified
+      command should expect to receive as the last argument "off", "on" or
+      "cycle" specifying to power off, on, or cycle (power off and then
+      power on) the device, respectively.
+
+   TEST_POWERCONTROL_EXTRA_ARGS
+      For automated hardware testing, specifies additional arguments to
+      pass through to the command specified in
+      :term:`TEST_POWERCONTROL_CMD`. Setting
+      ``TEST_POWERCONTROL_EXTRA_ARGS`` is optional. You can use it if you
+      wish, for example, to separate the machine-specific and
+      non-machine-specific parts of the arguments.
+
+   TEST_QEMUBOOT_TIMEOUT
+      The time in seconds allowed for an image to boot before automated
+      runtime tests begin to run against an image. The default timeout
+      period to allow the boot process to reach the login prompt is 500
+      seconds. You can specify a different value in the ``local.conf``
+      file.
+
+      For more information on testing images, see the
+      ":ref:`dev-manual/dev-manual-common-tasks:performing automated runtime testing`"
+      section in the Yocto Project Development Tasks Manual.
+
+   TEST_SERIALCONTROL_CMD
+      For automated hardware testing, specifies the command to use to
+      connect to the serial console of the target machine under test. This
+      command simply needs to connect to the serial console and forward
+      that connection to standard input and output as any normal terminal
+      program does.
+
+      For example, to use the Picocom terminal program on serial device
+      ``/dev/ttyUSB0`` at 115200bps, you would set the variable as follows:
+      ::
+
+         TEST_SERIALCONTROL_CMD = "picocom /dev/ttyUSB0 -b 115200"
+
+   TEST_SERIALCONTROL_EXTRA_ARGS
+      For automated hardware testing, specifies additional arguments to
+      pass through to the command specified in
+      :term:`TEST_SERIALCONTROL_CMD`. Setting
+      ``TEST_SERIALCONTROL_EXTRA_ARGS`` is optional. You can use it if you
+      wish, for example, to separate the machine-specific and
+      non-machine-specific parts of the command.
+
+   TEST_SERVER_IP
+      The IP address of the build machine (host machine). This IP address
+      is usually automatically detected. However, if detection fails, this
+      variable needs to be set to the IP address of the build machine (i.e.
+      where the build is taking place).
+
+      .. note::
+
+         The
+         TEST_SERVER_IP
+         variable is only used for a small number of tests such as the
+         "dnf" test suite, which needs to download packages from
+         WORKDIR/oe-rootfs-repo
+         .
+
+   TEST_TARGET
+      Specifies the target controller to use when running tests against a
+      test image. The default controller to use is "qemu":
+      ::
+
+         TEST_TARGET = "qemu"
+
+      A target controller is a class that defines how an image gets
+      deployed on a target and how a target is started. A layer can extend
+      the controllers by adding a module in the layer's
+      ``/lib/oeqa/controllers`` directory and by inheriting the
+      ``BaseTarget`` class, which is an abstract class that cannot be used
+      as a value of ``TEST_TARGET``.
+
+      You can provide the following arguments with ``TEST_TARGET``:
+
+      -  *"qemu":* Boots a QEMU image and runs the tests. See the
+         ":ref:`qemu-image-enabling-tests`" section
+         in the Yocto Project Development Tasks Manual for more
+         information.
+
+      -  *"simpleremote":* Runs the tests on target hardware that is
+         already up and running. The hardware can be on the network or it
+         can be a device running an image on QEMU. You must also set
+         :term:`TEST_TARGET_IP` when you use
+         "simpleremote".
+
+         .. note::
+
+            This argument is defined in
+            meta/lib/oeqa/controllers/simpleremote.py
+            .
+
+      For information on running tests on hardware, see the
+      ":ref:`hardware-image-enabling-tests`"
+      section in the Yocto Project Development Tasks Manual.
+
+   TEST_TARGET_IP
+      The IP address of your hardware under test. The ``TEST_TARGET_IP``
+      variable has no effect when :term:`TEST_TARGET` is
+      set to "qemu".
+
+      When you specify the IP address, you can also include a port. Here is
+      an example:
+      ::
+
+         TEST_TARGET_IP = "192.168.1.4:2201"
+
+      Specifying a port is
+      useful when SSH is started on a non-standard port or in cases when
+      your hardware under test is behind a firewall or network that is not
+      directly accessible from your host and you need to do port address
+      translation.
+
+   TEST_SUITES
+      An ordered list of tests (modules) to run against an image when
+      performing automated runtime testing.
+
+      The OpenEmbedded build system provides a core set of tests that can
+      be used against images.
+
+      .. note::
+
+         Currently, there is only support for running these tests under
+         QEMU.
+
+      Tests include ``ping``, ``ssh``, ``df`` among others. You can add
+      your own tests to the list of tests by appending ``TEST_SUITES`` as
+      follows:
+      ::
+
+         TEST_SUITES_append = " mytest"
+
+      Alternatively, you can
+      provide the "auto" option to have all applicable tests run against
+      the image.
+      ::
+
+         TEST_SUITES_append = " auto"
+
+      Using this option causes the
+      build system to automatically run tests that are applicable to the
+      image. Tests that are not applicable are skipped.
+
+      The order in which tests are run is important. Tests that depend on
+      another test must appear later in the list than the test on which
+      they depend. For example, if you append the list of tests with two
+      tests (``test_A`` and ``test_B``) where ``test_B`` is dependent on
+      ``test_A``, then you must order the tests as follows:
+      ::
+
+         TEST_SUITES = "test_A test_B"
+
+      For more information on testing images, see the
+      ":ref:`dev-manual/dev-manual-common-tasks:performing automated runtime testing`"
+      section in the Yocto Project Development Tasks Manual.
+
+   TESTIMAGE_AUTO
+      Automatically runs the series of automated tests for images when an
+      image is successfully built. Setting ``TESTIMAGE_AUTO`` to "1" causes
+      any image that successfully builds to automatically boot under QEMU.
+      Using the variable also adds in dependencies so that any SDK for
+      which testing is requested is automatically built first.
+
+      These tests are written in Python making use of the ``unittest``
+      module, and the majority of them run commands on the target system
+      over ``ssh``. You can set this variable to "1" in your ``local.conf``
+      file in the :term:`Build Directory` to have the
+      OpenEmbedded build system automatically run these tests after an
+      image successfully builds:
+
+         TESTIMAGE_AUTO = "1"
+
+      For more information
+      on enabling, running, and writing these tests, see the
+      ":ref:`dev-manual/dev-manual-common-tasks:performing automated runtime testing`"
+      section in the Yocto Project Development Tasks Manual and the
+      ":ref:`testimage*.bbclass <ref-classes-testimage*>`" section.
+
+   THISDIR
+      The directory in which the file BitBake is currently parsing is
+      located. Do not manually set this variable.
+
+   TIME
+      The time the build was started. Times appear using the hour, minute,
+      and second (HMS) format (e.g. "140159" for one minute and fifty-nine
+      seconds past 1400 hours).
+
+   TMPDIR
+      This variable is the base directory the OpenEmbedded build system
+      uses for all build output and intermediate files (other than the
+      shared state cache). By default, the ``TMPDIR`` variable points to
+      ``tmp`` within the :term:`Build Directory`.
+
+      If you want to establish this directory in a location other than the
+      default, you can uncomment and edit the following statement in the
+      ``conf/local.conf`` file in the :term:`Source Directory`:
+      ::
+
+         #TMPDIR = "${TOPDIR}/tmp"
+
+      An example use for this scenario is to set ``TMPDIR`` to a local disk,
+      which does not use NFS, while having the Build Directory use NFS.
+
+      The filesystem used by ``TMPDIR`` must have standard filesystem
+      semantics (i.e. mixed-case files are unique, POSIX file locking, and
+      persistent inodes). Due to various issues with NFS and bugs in some
+      implementations, NFS does not meet this minimum requirement.
+      Consequently, ``TMPDIR`` cannot be on NFS.
+
+   TOOLCHAIN_HOST_TASK
+      This variable lists packages the OpenEmbedded build system uses when
+      building an SDK, which contains a cross-development environment. The
+      packages specified by this variable are part of the toolchain set
+      that runs on the :term:`SDKMACHINE`, and each
+      package should usually have the prefix ``nativesdk-``. For example,
+      consider the following command when building an SDK:
+      ::
+
+         $ bitbake -c populate_sdk imagename
+
+      In this case, a default list of packages is
+      set in this variable, but you can add additional packages to the
+      list. See the
+      ":ref:`sdk-manual/sdk-appendix-customizing-standard:adding individual packages to the standard sdk`" section
+      in the Yocto Project Application Development and the Extensible
+      Software Development Kit (eSDK) manual for more information.
+
+      For background information on cross-development toolchains in the
+      Yocto Project development environment, see the
+      ":ref:`sdk-manual/sdk-intro:the cross-development toolchain`"
+      section in the Yocto Project Overview and Concepts Manual. For
+      information on setting up a cross-development environment, see the
+      :doc:`../sdk-manual/sdk-manual` manual.
+
+   TOOLCHAIN_OUTPUTNAME
+      This variable defines the name used for the toolchain output. The
+      :ref:`populate_sdk_base <ref-classes-populate-sdk-*>` class sets
+      the ``TOOLCHAIN_OUTPUTNAME`` variable as follows:
+      ::
+
+         TOOLCHAIN_OUTPUTNAME ?= "${SDK_NAME}-toolchain-${SDK_VERSION}"
+
+      See
+      the :term:`SDK_NAME` and
+      :term:`SDK_VERSION` variables for additional
+      information.
+
+   TOOLCHAIN_TARGET_TASK
+      This variable lists packages the OpenEmbedded build system uses when
+      it creates the target part of an SDK (i.e. the part built for the
+      target hardware), which includes libraries and headers. Use this
+      variable to add individual packages to the part of the SDK that runs
+      on the target. See the
+      ":ref:`sdk-manual/sdk-appendix-customizing-standard:adding individual packages to the standard sdk`" section
+      in the Yocto Project Application Development and the Extensible
+      Software Development Kit (eSDK) manual for more information.
+
+      For background information on cross-development toolchains in the
+      Yocto Project development environment, see the
+      ":ref:`sdk-manual/sdk-intro:the cross-development toolchain`"
+      section in the Yocto Project Overview and Concepts Manual. For
+      information on setting up a cross-development environment, see the
+      :doc:`../sdk-manual/sdk-manual` manual.
+
+   TOPDIR
+      The top-level :term:`Build Directory`. BitBake
+      automatically sets this variable when you initialize your build
+      environment using ````` <#structure-core-script>`__.
+
+   TRANSLATED_TARGET_ARCH
+      A sanitized version of :term:`TARGET_ARCH`. This
+      variable is used where the architecture is needed in a value where
+      underscores are not allowed, for example within package filenames. In
+      this case, dash characters replace any underscore characters used in
+      ``TARGET_ARCH``.
+
+      Do not edit this variable.
+
+   TUNE_ARCH
+      The GNU canonical architecture for a specific architecture (i.e.
+      ``arm``, ``armeb``, ``mips``, ``mips64``, and so forth). BitBake uses
+      this value to setup configuration.
+
+      ``TUNE_ARCH`` definitions are specific to a given architecture. The
+      definitions can be a single static definition, or can be dynamically
+      adjusted. You can see details for a given CPU family by looking at
+      the architecture's ``README`` file. For example, the
+      ``meta/conf/machine/include/mips/README`` file in the
+      :term:`Source Directory` provides information for
+      ``TUNE_ARCH`` specific to the ``mips`` architecture.
+
+      ``TUNE_ARCH`` is tied closely to
+      :term:`TARGET_ARCH`, which defines the target
+      machine's architecture. The BitBake configuration file
+      (``meta/conf/bitbake.conf``) sets ``TARGET_ARCH`` as follows:
+      ::
+
+         TARGET_ARCH = "${TUNE_ARCH}"
+
+      The following list, which is by no means complete since architectures
+      are configurable, shows supported machine architectures:
+
+      - arm
+      - i586
+      - x86_64
+      - powerpc
+      - powerpc64
+      - mips
+      - mipsel
+
+   TUNE_ASARGS
+      Specifies architecture-specific assembler flags for the target
+      system. The set of flags is based on the selected tune features.
+      ``TUNE_ASARGS`` is set using the tune include files, which are
+      typically under ``meta/conf/machine/include/`` and are influenced
+      through :term:`TUNE_FEATURES`. For example, the
+      ``meta/conf/machine/include/x86/arch-x86.inc`` file defines the flags
+      for the x86 architecture as follows:
+      ::
+
+         TUNE_ASARGS += "${@bb.utils.contains("TUNE_FEATURES", "mx32", "-x32", "", d)}"
+
+      .. note::
+
+         Board Support Packages (BSPs) select the tune. The selected tune,
+         in turn, affects the tune variables themselves (i.e. the tune can
+         supply its own set of flags).
+
+   TUNE_CCARGS
+      Specifies architecture-specific C compiler flags for the target
+      system. The set of flags is based on the selected tune features.
+      ``TUNE_CCARGS`` is set using the tune include files, which are
+      typically under ``meta/conf/machine/include/`` and are influenced
+      through :term:`TUNE_FEATURES`.
+
+      .. note::
+
+         Board Support Packages (BSPs) select the tune. The selected tune,
+         in turn, affects the tune variables themselves (i.e. the tune can
+         supply its own set of flags).
+
+   TUNE_LDARGS
+      Specifies architecture-specific linker flags for the target system.
+      The set of flags is based on the selected tune features.
+      ``TUNE_LDARGS`` is set using the tune include files, which are
+      typically under ``meta/conf/machine/include/`` and are influenced
+      through :term:`TUNE_FEATURES`. For example, the
+      ``meta/conf/machine/include/x86/arch-x86.inc`` file defines the flags
+      for the x86 architecture as follows:
+      ::
+
+         TUNE_LDARGS += "${@bb.utils.contains("TUNE_FEATURES", "mx32", "-m elf32_x86_64", "", d)}"
+
+      .. note::
+
+         Board Support Packages (BSPs) select the tune. The selected tune,
+         in turn, affects the tune variables themselves (i.e. the tune can
+         supply its own set of flags).
+
+   TUNE_FEATURES
+      Features used to "tune" a compiler for optimal use given a specific
+      processor. The features are defined within the tune files and allow
+      arguments (i.e. ``TUNE_*ARGS``) to be dynamically generated based on
+      the features.
+
+      The OpenEmbedded build system verifies the features to be sure they
+      are not conflicting and that they are supported.
+
+      The BitBake configuration file (``meta/conf/bitbake.conf``) defines
+      ``TUNE_FEATURES`` as follows:
+      ::
+
+         TUNE_FEATURES ??= "${TUNE_FEATURES_tune-${DEFAULTTUNE}}"
+
+      See the :term:`DEFAULTTUNE` variable for more information.
+
+   TUNE_PKGARCH
+      The package architecture understood by the packaging system to define
+      the architecture, ABI, and tuning of output packages. The specific
+      tune is defined using the "_tune" override as follows:
+      ::
+
+         TUNE_PKGARCH_tune-tune = "tune"
+
+      These tune-specific package architectures are defined in the machine
+      include files. Here is an example of the "core2-32" tuning as used in
+      the ``meta/conf/machine/include/tune-core2.inc`` file:
+      ::
+
+         TUNE_PKGARCH_tune-core2-32 = "core2-32"
+
+   TUNEABI
+      An underlying Application Binary Interface (ABI) used by a particular
+      tuning in a given toolchain layer. Providers that use prebuilt
+      libraries can use the ``TUNEABI``,
+      :term:`TUNEABI_OVERRIDE`, and
+      :term:`TUNEABI_WHITELIST` variables to check
+      compatibility of tunings against their selection of libraries.
+
+      If ``TUNEABI`` is undefined, then every tuning is allowed. See the
+      :ref:`sanity <ref-classes-sanity>` class to see how the variable is
+      used.
+
+   TUNEABI_OVERRIDE
+      If set, the OpenEmbedded system ignores the
+      :term:`TUNEABI_WHITELIST` variable.
+      Providers that use prebuilt libraries can use the
+      ``TUNEABI_OVERRIDE``, ``TUNEABI_WHITELIST``, and
+      :term:`TUNEABI` variables to check compatibility of a
+      tuning against their selection of libraries.
+
+      See the :ref:`sanity <ref-classes-sanity>` class to see how the
+      variable is used.
+
+   TUNEABI_WHITELIST
+      A whitelist of permissible :term:`TUNEABI` values. If
+      ``TUNEABI_WHITELIST`` is not set, all tunes are allowed. Providers
+      that use prebuilt libraries can use the ``TUNEABI_WHITELIST``,
+      :term:`TUNEABI_OVERRIDE`, and ``TUNEABI``
+      variables to check compatibility of a tuning against their selection
+      of libraries.
+
+      See the :ref:`sanity <ref-classes-sanity>` class to see how the
+      variable is used.
+
+   TUNECONFLICTS[feature]
+      Specifies CPU or Application Binary Interface (ABI) tuning features
+      that conflict with feature.
+
+      Known tuning conflicts are specified in the machine include files in
+      the :term:`Source Directory`. Here is an example from
+      the ``meta/conf/machine/include/mips/arch-mips.inc`` include file
+      that lists the "o32" and "n64" features as conflicting with the "n32"
+      feature:
+      ::
+
+         TUNECONFLICTS[n32] = "o32 n64"
+
+   TUNEVALID[feature]
+      Specifies a valid CPU or Application Binary Interface (ABI) tuning
+      feature. The specified feature is stored as a flag. Valid features
+      are specified in the machine include files (e.g.
+      ``meta/conf/machine/include/arm/arch-arm.inc``). Here is an example
+      from that file:
+      ::
+
+         TUNEVALID[bigendian] = "Enable big-endian mode."
+
+      See the machine include files in the :term:`Source Directory`
+      for these features.
+
+   UBOOT_CONFIG
+      Configures the :term:`UBOOT_MACHINE` and can
+      also define :term:`IMAGE_FSTYPES` for individual
+      cases.
+
+      Following is an example from the ``meta-fsl-arm`` layer. ::
+
+         UBOOT_CONFIG ??= "sd"
+         UBOOT_CONFIG[sd] = "mx6qsabreauto_config,sdcard"
+         UBOOT_CONFIG[eimnor] = "mx6qsabreauto_eimnor_config"
+         UBOOT_CONFIG[nand] = "mx6qsabreauto_nand_config,ubifs"
+         UBOOT_CONFIG[spinor] = "mx6qsabreauto_spinor_config"
+
+      In this example, "sd" is selected as the configuration of the possible four for the
+      ``UBOOT_MACHINE``. The "sd" configuration defines
+      "mx6qsabreauto_config" as the value for ``UBOOT_MACHINE``, while the
+      "sdcard" specifies the ``IMAGE_FSTYPES`` to use for the U-boot image.
+
+      For more information on how the ``UBOOT_CONFIG`` is handled, see the
+      :ref:`uboot-config <ref-classes-uboot-config>`
+      class.
+
+   UBOOT_DTB_LOADADDRESS
+      Specifies the load address for the dtb image used by U-boot. During FIT
+      image creation, the ``UBOOT_DTB_LOADADDRESS`` variable is used in
+      :ref:`kernel-fitimage <ref-classes-kernel-fitimage>` class to specify
+      the load address to be used in
+      creating the dtb sections of Image Tree Source for the FIT image.
+
+   UBOOT_DTBO_LOADADDRESS
+      Specifies the load address for the dtbo image used by U-boot.  During FIT
+      image creation, the ``UBOOT_DTBO_LOADADDRESS`` variable is used in
+      :ref:`kernel-fitimage <ref-classes-kernel-fitimage>` class to specify the load address to be used in
+      creating the dtbo sections of Image Tree Source for the FIT image.
+
+   UBOOT_ENTRYPOINT
+      Specifies the entry point for the U-Boot image. During U-Boot image
+      creation, the ``UBOOT_ENTRYPOINT`` variable is passed as a
+      command-line parameter to the ``uboot-mkimage`` utility.
+
+   UBOOT_LOADADDRESS
+      Specifies the load address for the U-Boot image. During U-Boot image
+      creation, the ``UBOOT_LOADADDRESS`` variable is passed as a
+      command-line parameter to the ``uboot-mkimage`` utility.
+
+   UBOOT_LOCALVERSION
+      Appends a string to the name of the local version of the U-Boot
+      image. For example, assuming the version of the U-Boot image built
+      was "2013.10", the full version string reported by U-Boot would be
+      "2013.10-yocto" given the following statement:
+      ::
+
+         UBOOT_LOCALVERSION = "-yocto"
+
+   UBOOT_MACHINE
+      Specifies the value passed on the ``make`` command line when building
+      a U-Boot image. The value indicates the target platform
+      configuration. You typically set this variable from the machine
+      configuration file (i.e. ``conf/machine/machine_name.conf``).
+
+      Please see the "Selection of Processor Architecture and Board Type"
+      section in the U-Boot README for valid values for this variable.
+
+   UBOOT_MAKE_TARGET
+      Specifies the target called in the ``Makefile``. The default target
+      is "all".
+
+   UBOOT_MKIMAGE_DTCOPTS
+      Options for the device tree compiler passed to mkimage '-D'
+      feature while creating FIT image in :ref:`kernel-fitimage <ref-classes-kernel-fitimage>` class.
+
+   UBOOT_RD_LOADADDRESS
+      Specifies the load address for the RAM disk image.
+      During FIT image creation, the
+      ``UBOOT_RD_LOADADDRESS`` variable is used
+      in :ref:`kernel-fitimage <ref-classes-kernel-fitimage>` class to specify the
+      load address to be used in creating the Image Tree Source for
+      the FIT image.
+
+   UBOOT_RD_ENTRYPOINT
+      Specifies the entrypoint for the RAM disk image.
+      During FIT image creation, the
+      ``UBOOT_RD_ENTRYPOINT`` variable is used
+      in :ref:`kernel-fitimage <ref-classes-kernel-fitimage>` class to specify the
+      entrypoint to be used in creating the Image Tree Source for
+      the FIT image.
+
+   UBOOT_SIGN_ENABLE
+      Enable signing of FIT image. The default value is "0".
+
+   UBOOT_SIGN_KEYDIR
+      Location of the directory containing the RSA key and
+      certificate used for signing FIT image.
+
+   UBOOT_SIGN_KEYNAME
+      The name of keys used for signing U-boot FIT image stored in
+      :term:`UBOOT_SIGN_KEYDIR` directory. For e.g. dev.key key and dev.crt
+      certificate stored in :term:`UBOOT_SIGN_KEYDIR` directory will have
+      :term:`UBOOT_SIGN_KEYNAME` set to "dev".
+
+   UBOOT_SUFFIX
+      Points to the generated U-Boot extension. For example, ``u-boot.sb``
+      has a ``.sb`` extension.
+
+      The default U-Boot extension is ``.bin``
+
+   UBOOT_TARGET
+      Specifies the target used for building U-Boot. The target is passed
+      directly as part of the "make" command (e.g. SPL and AIS). If you do
+      not specifically set this variable, the OpenEmbedded build process
+      passes and uses "all" for the target during the U-Boot building
+      process.
+
+   UNKNOWN_CONFIGURE_WHITELIST
+      Specifies a list of options that, if reported by the configure script
+      as being invalid, should not generate a warning during the
+      :ref:`ref-tasks-configure` task. Normally, invalid
+      configure options are simply not passed to the configure script (e.g.
+      should be removed from :term:`EXTRA_OECONF` or
+      :term:`PACKAGECONFIG_CONFARGS`).
+      However, common options, for example, exist that are passed to all
+      configure scripts at a class level that might not be valid for some
+      configure scripts. It follows that no benefit exists in seeing a
+      warning about these options. For these cases, the options are added
+      to ``UNKNOWN_CONFIGURE_WHITELIST``.
+
+      The configure arguments check that uses
+      ``UNKNOWN_CONFIGURE_WHITELIST`` is part of the
+      :ref:`insane <ref-classes-insane>` class and is only enabled if the
+      recipe inherits the :ref:`autotools <ref-classes-autotools>` class.
+
+   UPDATERCPN
+      For recipes inheriting the
+      :ref:`update-rc.d <ref-classes-update-rc.d>` class, ``UPDATERCPN``
+      specifies the package that contains the initscript that is enabled.
+
+      The default value is "${PN}". Given that almost all recipes that
+      install initscripts package them in the main package for the recipe,
+      you rarely need to set this variable in individual recipes.
+
+   UPSTREAM_CHECK_GITTAGREGEX
+      You can perform a per-recipe check for what the latest upstream
+      source code version is by calling ``bitbake -c checkpkg`` recipe. If
+      the recipe source code is provided from Git repositories, the
+      OpenEmbedded build system determines the latest upstream version by
+      picking the latest tag from the list of all repository tags.
+
+      You can use the ``UPSTREAM_CHECK_GITTAGREGEX`` variable to provide a
+      regular expression to filter only the relevant tags should the
+      default filter not work correctly.
+      ::
+
+         UPSTREAM_CHECK_GITTAGREGEX = "git_tag_regex"
+
+   UPSTREAM_CHECK_REGEX
+      Use the ``UPSTREAM_CHECK_REGEX`` variable to specify a different
+      regular expression instead of the default one when the package
+      checking system is parsing the page found using
+      :term:`UPSTREAM_CHECK_URI`.
+      ::
+
+         UPSTREAM_CHECK_REGEX = "package_regex"
+
+   UPSTREAM_CHECK_URI
+      You can perform a per-recipe check for what the latest upstream
+      source code version is by calling ``bitbake -c checkpkg`` recipe. If
+      the source code is provided from tarballs, the latest version is
+      determined by fetching the directory listing where the tarball is and
+      attempting to find a later tarball. When this approach does not work,
+      you can use ``UPSTREAM_CHECK_URI`` to provide a different URI that
+      contains the link to the latest tarball.
+      ::
+
+         UPSTREAM_CHECK_URI = "recipe_url"
+
+   USE_DEVFS
+      Determines if ``devtmpfs`` is used for ``/dev`` population. The
+      default value used for ``USE_DEVFS`` is "1" when no value is
+      specifically set. Typically, you would set ``USE_DEVFS`` to "0" for a
+      statically populated ``/dev`` directory.
+
+      See the ":ref:`selecting-dev-manager`" section in
+      the Yocto Project Development Tasks Manual for information on how to
+      use this variable.
+
+   USE_VT
+      When using
+      :ref:`SysVinit <new-recipe-enabling-system-services>`,
+      determines whether or not to run a
+      `getty <http://en.wikipedia.org/wiki/Getty_%28Unix%29>`__ on any
+      virtual terminals in order to enable logging in through those
+      terminals.
+
+      The default value used for ``USE_VT`` is "1" when no default value is
+      specifically set. Typically, you would set ``USE_VT`` to "0" in the
+      machine configuration file for machines that do not have a graphical
+      display attached and therefore do not need virtual terminal
+      functionality.
+
+   USER_CLASSES
+      A list of classes to globally inherit. These classes are used by the
+      OpenEmbedded build system to enable extra features (e.g.
+      ``buildstats``, ``image-mklibs``, and so forth).
+
+      The default list is set in your ``local.conf`` file:
+      ::
+
+         USER_CLASSES ?= "buildstats image-mklibs image-prelink"
+
+      For more information, see
+      ``meta-poky/conf/local.conf.sample`` in the :term:`Source Directory`.
+
+   USERADD_ERROR_DYNAMIC
+      If set to ``error``, forces the OpenEmbedded build system to produce
+      an error if the user identification (``uid``) and group
+      identification (``gid``) values are not defined in any of the files
+      listed in :term:`USERADD_UID_TABLES` and
+      :term:`USERADD_GID_TABLES`. If set to
+      ``warn``, a warning will be issued instead.
+
+      The default behavior for the build system is to dynamically apply
+      ``uid`` and ``gid`` values. Consequently, the
+      ``USERADD_ERROR_DYNAMIC`` variable is by default not set. If you plan
+      on using statically assigned ``gid`` and ``uid`` values, you should
+      set the ``USERADD_ERROR_DYNAMIC`` variable in your ``local.conf``
+      file as follows:
+      ::
+
+         USERADD_ERROR_DYNAMIC = "error"
+
+      Overriding the
+      default behavior implies you are going to also take steps to set
+      static ``uid`` and ``gid`` values through use of the
+      :term:`USERADDEXTENSION`,
+      :term:`USERADD_UID_TABLES`, and
+      :term:`USERADD_GID_TABLES` variables.
+
+      .. note::
+
+         There is a difference in behavior between setting
+         USERADD_ERROR_DYNAMIC
+         to
+         error
+         and setting it to
+         warn
+         . When it is set to
+         warn
+         , the build system will report a warning for every undefined
+         uid
+         and
+         gid
+         in any recipe. But when it is set to
+         error
+         , it will only report errors for recipes that are actually built.
+         This saves you from having to add static IDs for recipes that you
+         know will never be built.
+
+   USERADD_GID_TABLES
+      Specifies a password file to use for obtaining static group
+      identification (``gid``) values when the OpenEmbedded build system
+      adds a group to the system during package installation.
+
+      When applying static group identification (``gid``) values, the
+      OpenEmbedded build system looks in :term:`BBPATH` for a
+      ``files/group`` file and then applies those ``uid`` values. Set the
+      variable as follows in your ``local.conf`` file:
+      ::
+
+
+         USERADD_GID_TABLES = "files/group"
+
+      .. note::
+
+         Setting the
+         USERADDEXTENSION
+         variable to "useradd-staticids" causes the build system to use
+         static
+         gid
+         values.
+
+   USERADD_PACKAGES
+      When inheriting the :ref:`useradd <ref-classes-useradd>` class,
+      this variable specifies the individual packages within the recipe
+      that require users and/or groups to be added.
+
+      You must set this variable if the recipe inherits the class. For
+      example, the following enables adding a user for the main package in
+      a recipe:
+      ::
+
+         USERADD_PACKAGES = "${PN}"
+
+      .. note::
+
+         It follows that if you are going to use the
+         USERADD_PACKAGES
+         variable, you need to set one or more of the
+         USERADD_PARAM
+         ,
+         GROUPADD_PARAM
+         , or
+         GROUPMEMS_PARAM
+         variables.
+
+   USERADD_PARAM
+      When inheriting the :ref:`useradd <ref-classes-useradd>` class,
+      this variable specifies for a package what parameters should pass to
+      the ``useradd`` command if you add a user to the system when the
+      package is installed.
+
+      Here is an example from the ``dbus`` recipe:
+      ::
+
+         USERADD_PARAM_${PN} = "--system --home ${localstatedir}/lib/dbus \
+                                --no-create-home --shell /bin/false \
+                                --user-group messagebus"
+
+      For information on the
+      standard Linux shell command ``useradd``, see
+      http://linux.die.net/man/8/useradd.
+
+   USERADD_UID_TABLES
+      Specifies a password file to use for obtaining static user
+      identification (``uid``) values when the OpenEmbedded build system
+      adds a user to the system during package installation.
+
+      When applying static user identification (``uid``) values, the
+      OpenEmbedded build system looks in :term:`BBPATH` for a
+      ``files/passwd`` file and then applies those ``uid`` values. Set the
+      variable as follows in your ``local.conf`` file:
+      ::
+
+         USERADD_UID_TABLES = "files/passwd"
+
+      .. note::
+
+         Setting the
+         USERADDEXTENSION
+         variable to "useradd-staticids" causes the build system to use
+         static
+         uid
+         values.
+
+   USERADDEXTENSION
+      When set to "useradd-staticids", causes the OpenEmbedded build system
+      to base all user and group additions on a static ``passwd`` and
+      ``group`` files found in :term:`BBPATH`.
+
+      To use static user identification (``uid``) and group identification
+      (``gid``) values, set the variable as follows in your ``local.conf``
+      file: USERADDEXTENSION = "useradd-staticids"
+
+      .. note::
+
+         Setting this variable to use static
+         uid
+         and
+         gid
+         values causes the OpenEmbedded build system to employ the
+         useradd-staticids
+         class.
+
+      If you use static ``uid`` and ``gid`` information, you must also
+      specify the ``files/passwd`` and ``files/group`` files by setting the
+      :term:`USERADD_UID_TABLES` and
+      :term:`USERADD_GID_TABLES` variables.
+      Additionally, you should also set the
+      :term:`USERADD_ERROR_DYNAMIC` variable.
+
+   VOLATILE_LOG_DIR
+      Specifies the persistence of the target's ``/var/log`` directory,
+      which is used to house postinstall target log files.
+
+      By default, ``VOLATILE_LOG_DIR`` is set to "yes", which means the
+      file is not persistent. You can override this setting by setting the
+      variable to "no" to make the log directory persistent.
+
+   WARN_QA
+      Specifies the quality assurance checks whose failures are reported as
+      warnings by the OpenEmbedded build system. You set this variable in
+      your distribution configuration file. For a list of the checks you
+      can control with this variable, see the
+      ":ref:`insane.bbclass <ref-classes-insane>`" section.
+
+   WKS_FILE_DEPENDS
+      When placed in the recipe that builds your image, this variable lists
+      build-time dependencies. The ``WKS_FILE_DEPENDS`` variable is only
+      applicable when Wic images are active (i.e. when
+      :term:`IMAGE_FSTYPES` contains entries related
+      to Wic). If your recipe does not create Wic images, the variable has
+      no effect.
+
+      The ``WKS_FILE_DEPENDS`` variable is similar to the
+      :term:`DEPENDS` variable. When you use the variable in
+      your recipe that builds the Wic image, dependencies you list in the
+      ``WIC_FILE_DEPENDS`` variable are added to the ``DEPENDS`` variable.
+
+      With the ``WKS_FILE_DEPENDS`` variable, you have the possibility to
+      specify a list of additional dependencies (e.g. native tools,
+      bootloaders, and so forth), that are required to build Wic images.
+      Following is an example:
+      ::
+
+         WKS_FILE_DEPENDS = "some-native-tool"
+
+      In the
+      previous example, some-native-tool would be replaced with an actual
+      native tool on which the build would depend.
+
+   WKS_FILE
+      Specifies the location of the Wic kickstart file that is used by the
+      OpenEmbedded build system to create a partitioned image
+      (image\ ``.wic``). For information on how to create a partitioned
+      image, see the
+      ":ref:`dev-manual/dev-manual-common-tasks:creating partitioned images using wic`"
+      section in the Yocto Project Development Tasks Manual. For details on
+      the kickstart file format, see the ":doc:`../ref-manual/ref-kickstart`" Chapter.
+
+   WORKDIR
+      The pathname of the work directory in which the OpenEmbedded build
+      system builds a recipe. This directory is located within the
+      :term:`TMPDIR` directory structure and is specific to
+      the recipe being built and the system for which it is being built.
+
+      The ``WORKDIR`` directory is defined as follows:
+      ::
+
+         ${TMPDIR}/work/${MULTIMACH_TARGET_SYS}/${PN}/${EXTENDPE}${PV}-${PR}
+
+      The actual directory depends on several things:
+
+      -  TMPDIR
+         : The top-level build output directory
+      -  MULTIMACH_TARGET_SYS
+         : The target system identifier
+      -  PN
+         : The recipe name
+      -  EXTENDPE
+         : The epoch - (if
+         PE
+         is not specified, which is usually the case for most recipes, then
+         EXTENDPE
+         is blank)
+      -  PV
+         : The recipe version
+      -  PR
+         : The recipe revision
+
+      As an example, assume a Source Directory top-level folder name
+      ``poky``, a default Build Directory at ``poky/build``, and a
+      ``qemux86-poky-linux`` machine target system. Furthermore, suppose
+      your recipe is named ``foo_1.3.0-r0.bb``. In this case, the work
+      directory the build system uses to build the package would be as
+      follows:
+      ::
+
+         poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0
+
+   XSERVER
+      Specifies the packages that should be installed to provide an X
+      server and drivers for the current machine, assuming your image
+      directly includes ``packagegroup-core-x11-xserver`` or, perhaps
+      indirectly, includes "x11-base" in
+      :term:`IMAGE_FEATURES`.
+
+      The default value of ``XSERVER``, if not specified in the machine
+      configuration, is "xserver-xorg xf86-video-fbdev xf86-input-evdev".
+   
diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml
index 364cd09eb8..a5064807e5 100644
--- a/documentation/ref-manual/ref-variables.xml
+++ b/documentation/ref-manual/ref-variables.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <!-- Dummy chapter -->
 <chapter id='ref-variables-glos'>
@@ -4990,6 +4991,30 @@
             </glossdef>
         </glossentry>
 
+        <glossentry id='var-FIT_HASH_ALG'><glossterm>FIT_HASH_ALG</glossterm>
+            <info>
+               FIT_HASH_ALG[doc] = "Specifies the hash algorithm used in creating the FIT Image."
+            </info>
+            <glossdef>
+                <para role="glossdeffirst">
+                    Specifies the hash algorithm used in creating the FIT Image.
+                    For e.g. sha256.
+                </para>
+            </glossdef>
+        </glossentry>
+
+        <glossentry id='var-FIT_SIGN_ALG'><glossterm>FIT_SIGN_ALG</glossterm>
+            <info>
+               FIT_SIGN_ALG[doc] = "Specifies the signature algorithm used in creating the FIT Image."
+            </info>
+            <glossdef>
+                <para role="glossdeffirst">
+                    Specifies the signature algorithm used in creating the FIT Image.
+                    For e.g. rsa2048.
+                </para>
+            </glossdef>
+        </glossentry>
+
         <glossentry id='var-FONT_EXTRA_RDEPENDS'><glossterm>FONT_EXTRA_RDEPENDS</glossterm>
             <info>
                 FONT_EXTRA_RDEPENDS[doc] = "When a recipe inherits the fontcache class, this variable specifies runtime dependencies for font packages. This variable defaults to 'fontconfig-utils'."
@@ -5702,7 +5727,7 @@
                 <para role="glossdeffirst">
                     A space-separated list of files installed into the
                     boot partition when preparing an image using the Wic tool
-                    with the <filename>bootimg-partition</filename> source
+                    with the <filename>bootimg-partition</filename> or <filename>bootimg-efi</filename> source
                     plugin.
                     By default, the files are installed under the same name as
                     the source files.
@@ -9539,6 +9564,40 @@
             </glossdef>
         </glossentry>
 
+        <glossentry id='var-PACKAGE_ADD_METADATA'><glossterm>PACKAGE_ADD_METADATA</glossterm>
+            <info>
+                PACKAGE_ADD_METADATA[doc] = "This variable defines additional metadata to add to packages."
+            </info>
+            <glossdef>
+                <para role="glossdeffirst">
+<!--                <para role="glossdeffirst"><imagedata fileref="figures/define-generic.png" /> -->
+                    This variable defines additional metdata to add to packages.
+                </para>
+
+                <para>
+                    You may find you need to inject additional metadata into
+                    packages. This variable allows you to do that by setting
+                    the injected data as the value. Multiple fields can be
+                    added by splitting the content with the literal separator
+                    "\n".
+                </para>
+
+                <para>
+                    The suffixes '_IPK', '_DEB', or '_RPM' can be applied to
+                    the variable to do package type specific settings. It can
+                    also be made package specific by using the package name as
+                    a suffix.
+                </para>
+
+                <para>
+                    You can find out more about applying this variable in
+                    the
+                    "<ulink url='&YOCTO_DOCS_DEV_URL;#adding-custom-metadata-to-packages'>Adding custom metadata to packages</ulink>"
+                    section in the Yocto Project Development Tasks Manual.
+                </para>
+            </glossdef>
+        </glossentry>
+
         <glossentry id='var-PACKAGE_ARCH'><glossterm>PACKAGE_ARCH</glossterm>
             <info>
                 PACKAGE_ARCH[doc] = "The architecture of the resulting package or packages."
@@ -15925,6 +15984,38 @@
             </glossdef>
         </glossentry>
 
+        <glossentry id='var-UBOOT_DTB_LOADADDRESS'><glossterm>UBOOT_DTB_LOADADDRESS</glossterm>
+            <info>
+               UBOOT_DTB_LOADADDRESS[doc] = "Specifies the load address for the dtb."
+            </info>
+            <glossdef>
+                <para role="glossdeffirst">
+                    Specifies the load address for the dtb image used by U-boot.
+                    During FIT image creation, the
+                    <filename>UBOOT_DTB_LOADADDRESS</filename> variable is used
+                    in <filename>kernel-fitimage</filename> class to specify the
+                    load address to be used in creating the dtb sections of
+                    Image Tree Source for the FIT image.
+                </para>
+            </glossdef>
+        </glossentry>
+
+        <glossentry id='var-UBOOT_DTBO_LOADADDRESS'><glossterm>UBOOT_DTBO_LOADADDRESS</glossterm>
+            <info>
+               UBOOT_DTBO_LOADADDRESS[doc] = "Specifies the load address for the dtbo."
+            </info>
+            <glossdef>
+                <para role="glossdeffirst">
+                    Specifies the load address for the dtbo image used by U-boot.
+                    During FIT image creation, the
+                    <filename>UBOOT_DTBO_LOADADDRESS</filename> variable is used
+                    in <filename>kernel-fitimage</filename> class to specify the
+                    load address to be used in creating the dtbo sections of
+                    Image Tree Source for the FIT image.
+                </para>
+            </glossdef>
+        </glossentry>
+
         <glossentry id='var-UBOOT_ENTRYPOINT'><glossterm>UBOOT_ENTRYPOINT</glossterm>
             <info>
                UBOOT_ENTRYPOINT[doc] = "Specifies the entry point for the U-Boot image."
@@ -16010,6 +16101,51 @@
             </glossdef>
         </glossentry>
 
+        <glossentry id='var-UBOOT_MKIMAGE_DTCOPTS'><glossterm>UBOOT_MKIMAGE_DTCOPTS</glossterm>
+            <info>
+               UBOOT_MKIMAGE_DTCOPTS[doc] = "Options for the device tree compiler passed to mkimage '-D' feature."
+            </info>
+            <glossdef>
+                <para role="glossdeffirst">
+                    Options for the device tree compiler passed to mkimage '-D'
+                    feature while creating FIT image in
+                    <filename>kernel-fitimage</filename> class.
+                </para>
+            </glossdef>
+        </glossentry>
+
+        <glossentry id='var-UBOOT_RD_LOADADDRESS'><glossterm>UBOOT_RD_LOADADDRESS</glossterm>
+            <info>
+               UBOOT_RD_LOADADDRESS[doc] = "Specifies the load address for the ramdisk image."
+            </info>
+            <glossdef>
+                <para role="glossdeffirst">
+                    Specifies the load address for the RAM disk image.
+                    During FIT image creation, the
+                    <filename>UBOOT_RD_LOADADDRESS</filename> variable is used
+                    in <filename>kernel-fitimage</filename> class to specify the
+                    load address to be used in creating the Image Tree Source for
+                    the FIT image.
+                </para>
+            </glossdef>
+        </glossentry>
+
+        <glossentry id='var-UBOOT_RD_ENTRYPOINT'><glossterm>UBOOT_RD_ENTRYPOINT</glossterm>
+            <info>
+               UBOOT_RD_ENTRYPOINT[doc] = "Specifies the entrypoint for the ramdisk image."
+            </info>
+            <glossdef>
+                <para role="glossdeffirst">
+                    Specifies the entrypoint for the RAM disk image.
+                    During FIT image creation, the
+                    <filename>UBOOT_RD_ENTRYPOINT</filename> variable is used
+                    in <filename>kernel-fitimage</filename> class to specify the
+                    entrypoint to be used in creating the Image Tree Source for
+                    the FIT image.
+                </para>
+            </glossdef>
+        </glossentry>
+
         <glossentry id='var-UBOOT_SUFFIX'><glossterm>UBOOT_SUFFIX</glossterm>
             <info>
                UBOOT_SUFFIX[doc] = "Points to the generated U-Boot extension."
@@ -16028,6 +16164,47 @@
             </glossdef>
         </glossentry>
 
+        <glossentry id='var-UBOOT_SIGN_ENABLE'><glossterm>UBOOT_SIGN_ENABLE</glossterm>
+            <info>
+               UBOOT_SIGN_KEYDIR[doc] = "Enable signing of FIT image."
+            </info>
+            <glossdef>
+                <para role="glossdeffirst">
+                    Enable signing of FIT image. The default value is "0".
+                </para>
+            </glossdef>
+        </glossentry>
+
+        <glossentry id='var-UBOOT_SIGN_KEYDIR'><glossterm>UBOOT_SIGN_KEYDIR</glossterm>
+            <info>
+               UBOOT_SIGN_KEYDIR[doc] = "Location of the directory containing the RSA key and certificate used for signing FIT image."
+            </info>
+            <glossdef>
+                <para role="glossdeffirst">
+                    Location of the directory containing the RSA key and
+                    certificate used for signing FIT image.
+                </para>
+            </glossdef>
+        </glossentry>
+
+        <glossentry id='var-UBOOT_SIGN_KEYNAME'><glossterm>UBOOT_SIGN_KEYNAME</glossterm>
+            <info>
+               UBOOT_SIGN_KEYNAME[doc] = "The name of keys used for signing U-boot FIT image"
+            </info>
+            <glossdef>
+                <para role="glossdeffirst">
+                    The name of keys used for signing U-boot FIT image stored in
+                    <filename><link linkend='var-UBOOT_SIGN_KEYDIR'>UBOOT_SIGN_KEYDIR</link></filename>
+                    directory. For e.g. dev.key key and dev.crt certificate
+                    stored in
+                    <filename><link linkend='var-UBOOT_SIGN_KEYDIR'>UBOOT_SIGN_KEYDIR</link></filename>
+                    directory will have
+                    <filename><link linkend='var-UBOOT_SIGN_KEYNAME'>UBOOT_SIGN_KEYNAME</link></filename>
+                    set to "dev".
+                </para>
+            </glossdef>
+        </glossentry>
+
         <glossentry id='var-UBOOT_TARGET'><glossterm>UBOOT_TARGET</glossterm>
             <info>
                UBOOT_TARGET[doc] = "Specifies the target used for building U-Boot."
diff --git a/documentation/ref-manual/ref-varlocality.rst b/documentation/ref-manual/ref-varlocality.rst
new file mode 100644
index 0000000000..a95504b571
--- /dev/null
+++ b/documentation/ref-manual/ref-varlocality.rst
@@ -0,0 +1,166 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+****************
+Variable Context
+****************
+
+While you can use most variables in almost any context such as
+``.conf``, ``.bbclass``, ``.inc``, and ``.bb`` files, some variables are
+often associated with a particular locality or context. This chapter
+describes some common associations.
+
+.. _ref-varlocality-configuration:
+
+Configuration
+=============
+
+The following subsections provide lists of variables whose context is
+configuration: distribution, machine, and local.
+
+.. _ref-varlocality-config-distro:
+
+Distribution (Distro)
+---------------------
+
+This section lists variables whose configuration context is the
+distribution, or distro.
+
+-  :term:`DISTRO`
+
+-  :term:`DISTRO_NAME`
+
+-  :term:`DISTRO_VERSION`
+
+-  :term:`MAINTAINER`
+
+-  :term:`PACKAGE_CLASSES`
+
+-  :term:`TARGET_OS`
+
+-  :term:`TARGET_FPU`
+
+-  :term:`TCMODE`
+
+-  :term:`TCLIBC`
+
+.. _ref-varlocality-config-machine:
+
+Machine
+-------
+
+This section lists variables whose configuration context is the machine.
+
+-  :term:`TARGET_ARCH`
+
+-  :term:`SERIAL_CONSOLES`
+
+-  :term:`PACKAGE_EXTRA_ARCHS`
+
+-  :term:`IMAGE_FSTYPES`
+
+-  :term:`MACHINE_FEATURES`
+
+-  :term:`MACHINE_EXTRA_RDEPENDS`
+
+-  :term:`MACHINE_EXTRA_RRECOMMENDS`
+
+-  :term:`MACHINE_ESSENTIAL_EXTRA_RDEPENDS`
+
+-  :term:`MACHINE_ESSENTIAL_EXTRA_RRECOMMENDS`
+
+.. _ref-varlocality-config-local:
+
+Local
+-----
+
+This section lists variables whose configuration context is the local
+configuration through the ``local.conf`` file.
+
+-  :term:`DISTRO`
+
+-  :term:`MACHINE`
+
+-  :term:`DL_DIR`
+
+-  :term:`BBFILES`
+
+-  :term:`EXTRA_IMAGE_FEATURES`
+
+-  :term:`PACKAGE_CLASSES`
+
+-  :term:`BB_NUMBER_THREADS`
+
+-  :term:`BBINCLUDELOGS`
+
+-  :term:`ENABLE_BINARY_LOCALE_GENERATION`
+
+.. _ref-varlocality-recipes:
+
+Recipes
+=======
+
+The following subsections provide lists of variables whose context is
+recipes: required, dependencies, path, and extra build information.
+
+.. _ref-varlocality-recipe-required:
+
+Required
+--------
+
+This section lists variables that are required for recipes.
+
+-  :term:`LICENSE`
+
+-  :term:`LIC_FILES_CHKSUM`
+
+-  :term:`SRC_URI` - used in recipes that fetch local or remote files.
+
+.. _ref-varlocality-recipe-dependencies:
+
+Dependencies
+------------
+
+This section lists variables that define recipe dependencies.
+
+-  :term:`DEPENDS`
+
+-  :term:`RDEPENDS`
+
+-  :term:`RRECOMMENDS`
+
+-  :term:`RCONFLICTS`
+
+-  :term:`RREPLACES`
+
+.. _ref-varlocality-recipe-paths:
+
+Paths
+-----
+
+This section lists variables that define recipe paths.
+
+-  :term:`WORKDIR`
+
+-  :term:`S`
+
+-  :term:`FILES`
+
+.. _ref-varlocality-recipe-build:
+
+Extra Build Information
+-----------------------
+
+This section lists variables that define extra build information for
+recipes.
+
+-  :term:`DEFAULT_PREFERENCE`
+
+-  :term:`EXTRA_OECMAKE`
+
+-  :term:`EXTRA_OECONF`
+
+-  :term:`EXTRA_OEMAKE`
+
+-  :term:`PACKAGECONFIG_CONFARGS`
+
+-  :term:`PACKAGES`
diff --git a/documentation/ref-manual/ref-varlocality.xml b/documentation/ref-manual/ref-varlocality.xml
index 54524d5b60..a2436fb310 100644
--- a/documentation/ref-manual/ref-varlocality.xml
+++ b/documentation/ref-manual/ref-varlocality.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-varlocality'>
     <title>Variable Context</title>
diff --git a/documentation/ref-manual/resources.rst b/documentation/ref-manual/resources.rst
new file mode 100644
index 0000000000..2b82b79102
--- /dev/null
+++ b/documentation/ref-manual/resources.rst
@@ -0,0 +1,197 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+****************************************
+Contributions and Additional Information
+****************************************
+
+.. _resources-intro:
+
+Introduction
+============
+
+The Yocto Project team is happy for people to experiment with the Yocto
+Project. A number of places exist to find help if you run into
+difficulties or find bugs. This presents information about contributing
+and participating in the Yocto Project.
+
+.. _resources-contributions:
+
+Contributions
+=============
+
+The Yocto Project gladly accepts contributions. You can submit changes
+to the project either by creating and sending pull requests, or by
+submitting patches through email. For information on how to do both as
+well as information on how to identify the maintainer for each area of
+code, see the ":ref:`how-to-submit-a-change`" section in the
+Yocto Project Development Tasks Manual.
+
+.. _resources-bugtracker:
+
+Yocto Project Bugzilla
+======================
+
+The Yocto Project uses its own implementation of
+:yocto_bugs:`Bugzilla <>` to track defects (bugs).
+Implementations of Bugzilla work well for group development because they
+track bugs and code changes, can be used to communicate changes and
+problems with developers, can be used to submit and review patches, and
+can be used to manage quality assurance.
+
+Sometimes it is helpful to submit, investigate, or track a bug against
+the Yocto Project itself (e.g. when discovering an issue with some
+component of the build system that acts contrary to the documentation or
+your expectations).
+
+A general procedure and guidelines exist for when you use Bugzilla to
+submit a bug. For information on how to use Bugzilla to submit a bug
+against the Yocto Project, see the following:
+
+-  The ":ref:`dev-manual/dev-manual-common-tasks:submitting a defect against the yocto project`"
+   section in the Yocto Project Development Tasks Manual.
+
+-  The Yocto Project :yocto_wiki:`Bugzilla wiki page </wiki/Bugzilla_Configuration_and_Bug_Tracking>`
+
+For information on Bugzilla in general, see http://www.bugzilla.org/about/.
+
+.. _resources-mailinglist:
+
+Mailing lists
+=============
+
+A number of mailing lists maintained by the Yocto Project exist as well
+as related OpenEmbedded mailing lists for discussion, patch submission
+and announcements. To subscribe to one of the following mailing lists,
+click on the appropriate URL in the following list and follow the
+instructions:
+
+-  https://lists.yoctoproject.org/g/yocto - General Yocto Project
+   discussion mailing list.
+
+-  https://lists.openembedded.org/g/openembedded-core - Discussion mailing
+   list about OpenEmbedded-Core (the core metadata).
+
+-  https://lists.openembedded.org/g/openembedded-devel - Discussion
+   mailing list about OpenEmbedded.
+
+-  https://lists.openembedded.org/g/bitbake-devel - Discussion mailing
+   list about the :term:`BitBake` build tool.
+
+-  https://lists.yoctoproject.org/g/poky - Discussion mailing list
+   about `Poky <#poky>`__.
+
+-  https://lists.yoctoproject.org/g/yocto-announce - Mailing list to
+   receive official Yocto Project release and milestone announcements.
+
+For more Yocto Project-related mailing lists, see the
+Yocto Project Website
+.
+.. _resources-irc:
+
+Internet Relay Chat (IRC)
+=========================
+
+Two IRC channels on freenode are available for the Yocto Project and
+Poky discussions:
+
+-  ``#yocto``
+
+-  ``#poky``
+
+.. _resources-links-and-related-documentation:
+
+Links and Related Documentation
+===============================
+
+Here is a list of resources you might find helpful:
+
+-  :yocto_home:`The Yocto Project Website <>`\ *:* The home site
+   for the Yocto Project.
+
+-  :yocto_wiki:`The Yocto Project Main Wiki Page </wiki/Main_Page>`\ *:* The main wiki page for
+   the Yocto Project. This page contains information about project
+   planning, release engineering, QA & automation, a reference site map,
+   and other resources related to the Yocto Project.
+
+-  `OpenEmbedded <http://www.openembedded.org/>`__\ *:* The build system used by the
+   Yocto Project. This project is the upstream, generic, embedded
+   distribution from which the Yocto Project derives its build system
+   (Poky) and to which it contributes.
+
+-  `BitBake <http://www.openembedded.org/wiki/BitBake>`__\ *:* The tool
+   used to process metadata.
+
+-  :doc:`BitBake User Manual <bitbake:index>`\ *:* A comprehensive
+   guide to the BitBake tool. If you want information on BitBake, see
+   this manual.
+
+-  :doc:`../brief-yoctoprojectqs/brief-yoctoprojectqs` *:* This
+   short document lets you experience building an image using the Yocto
+   Project without having to understand any concepts or details.
+
+-  :doc:`../overview-manual/overview-manual` *:* This manual provides overview
+   and conceptual information about the Yocto Project.
+
+-  :doc:`../dev-manual/dev-manual` *:* This manual is a "how-to" guide
+   that presents procedures useful to both application and system
+   developers who use the Yocto Project.
+
+-  :doc:`../sdk-manual/sdk-manual` *manual :* This
+   guide provides information that lets you get going with the standard
+   or extensible SDK. An SDK, with its cross-development toolchains,
+   allows you to develop projects inside or outside of the Yocto Project
+   environment.
+
+-  :doc:`../bsp-guide/bsp` *:* This guide defines the structure
+   for BSP components. Having a commonly understood structure encourages
+   standardization.
+
+-  :doc:`../kernel-dev/kernel-dev` *:* This manual describes
+   how to work with Linux Yocto kernels as well as provides a bit of
+   conceptual information on the construction of the Yocto Linux kernel
+   tree.
+
+-  :doc:`../ref-manual/ref-manual` *:* This
+   manual provides reference material such as variable, task, and class
+   descriptions.
+
+-  `Yocto Project Mega-Manual <https://docs.yoctoproject.org/singleindex.html>`__\ *:* This manual
+   is simply a single HTML file comprised of the bulk of the Yocto
+   Project manuals. The Mega-Manual primarily exists as a vehicle by
+   which you can easily search for phrases and terms used in the Yocto
+   Project documentation set.
+
+-  :doc:`../profile-manual/profile-manual` *:* This manual presents a set of
+   common and generally useful tracing and profiling schemes along with
+   their applications (as appropriate) to each tool.
+
+-  :doc:`../toaster-manual/toaster-manual` *:* This manual
+   introduces and describes how to set up and use Toaster. Toaster is an
+   Application Programming Interface (API) and web-based interface to
+   the :term:`OpenEmbedded Build System`, which uses
+   BitBake, that reports build information.
+
+-  :yocto_wiki:`FAQ </wiki/FAQ>`\ *:* A list of commonly asked
+   questions and their answers.
+
+-  *Release Notes:* Features, updates and known issues for the current
+   release of the Yocto Project. To access the Release Notes, go to the
+   :yocto_home:`Downloads </software-overview/downloads>` page on
+   the Yocto Project website and click on the "RELEASE INFORMATION" link
+   for the appropriate release.
+
+-  `Bugzilla <https://bugzilla.yoctoproject.org>`__\ *:* The bug tracking application
+   the Yocto Project uses. If you find problems with the Yocto Project,
+   you should report them using this application.
+
+-  :yocto_wiki:`Bugzilla Configuration and Bug Tracking Wiki Page </wiki/Bugzilla_Configuration_and_Bug_Tracking>`\ *:*
+   Information on how to get set up and use the Yocto Project
+   implementation of Bugzilla for logging and tracking Yocto Project
+   defects.
+
+-  *Internet Relay Chat (IRC):* Two IRC channels on freenode are
+   available for Yocto Project and Poky discussions: ``#yocto`` and
+   ``#poky``, respectively.
+
+-  `Quick EMUlator (QEMU) <http://wiki.qemu.org/Index.html>`__\ *:* An
+   open-source machine emulator and virtualizer.
diff --git a/documentation/ref-manual/resources.xml b/documentation/ref-manual/resources.xml
index afe8e288de..4899b2e599 100644
--- a/documentation/ref-manual/resources.xml
+++ b/documentation/ref-manual/resources.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='resources'>
 <title>Contributions and Additional Information</title>