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+******************************************
+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.
+
+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.
+
+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
+```SSTATE_MIRRORS`` <#var-SSTATE_MIRRORS>`__ and ``bblayers.conf``.
+
+.. _migration-1.3-sstate-mirrors:
+
+SSTATE_MIRRORS
+~~~~~~~~~~~~~~
+
+The shared state cache (sstate-cache), as pointed to by
+```SSTATE_DIR`` <#var-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
+```SSTATE_MIRRORS`` <#var-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:
+
+-  Python function whitespace
+
+-  ``proto=`` in ``SRC_URI``
+
+-  ``nativesdk``
+
+-  Task recipes
+
+-  ``IMAGE_FEATURES``
+
+-  Removed recipes
+
+.. _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 ```SRC_URI`` <#var-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 ```SDK_ARCH`` <#var-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
+```LIC_FILES_CHKSUM`` <#var-LIC_FILES_CHKSUM>`__, and so forth. See the
+"```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
+```IMAGE_FEATURES`` <#var-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
+`Metadata <#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 Project `Source
+Repositories <&YOCTO_DOCS_OM_URL;#source-repositories>`__.
+
+.. _1.3-linux-kernel-naming:
+
+Linux Kernel Naming
+-------------------
+
+The naming scheme for kernel output binaries has been changed to now
+include ```PE`` <#var-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
+
+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
+   ```RDEPENDS`` <#var-RDEPENDS>`__,
+   ```RRECOMMENDS`` <#var-RRECOMMENDS>`__,
+   ```RSUGGESTS`` <#var-RSUGGESTS>`__,
+   ```RPROVIDES`` <#var-RPROVIDES>`__,
+   ```RCONFLICTS`` <#var-RCONFLICTS>`__,
+   ```RREPLACES`` <#var-RREPLACES>`__, ```FILES`` <#var-FILES>`__,
+   ```ALLOW_EMPTY`` <#var-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
+   ```SRC_URI`` <#var-SRC_URI>`__, the build system now uses
+   ```FILESOVERRIDES`` <#var-FILESOVERRIDES>`__ instead of
+   ```OVERRIDES`` <#var-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 ```MACHINEOVERRIDES`` <#var-MACHINEOVERRIDES>`__ or
+   ```DISTROOVERRIDES`` <#var-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 `Source Directory <#source-directory>`__ at
+``meta/recipes-core/init-ifupdown``. For information on how to use
+append files, see the "`Using .bbappend
+Files <&YOCTO_DOCS_DEV_URL;#using-bbappend-files>`__" 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,
+   ```SANITY_TESTED_DISTROS`` <#var-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 ``${``\ ```PN`` <#var-PN>`__\ ``}``,
+   ``${``\ ```PF`` <#var-PF>`__\ ``}``,
+   ``${``\ ```P`` <#var-P>`__\ ``}``, and ``FILE_DIRNAME`` directories
+   have been dropped from the default value of the
+   ```FILESPATH`` <#var-FILESPATH>`__ variable, which is used as the
+   search path for finding files referred to in
+   ```SRC_URI`` <#var-SRC_URI>`__. If you have a recipe that relied upon
+   these directories, which would be unusual, then you will need to add
+   the appropriate paths within the recipe or, alternatively, rearrange
+   the files. The most common locations are still covered by ``${BP}``,
+   ``${BPN}``, and "files", which all remain in the default value of
+   ```FILESPATH`` <#var-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.
+
+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.
+
+-  ``${``\ ```P`` <#var-P>`__\ ``}`` and
+   ``${``\ ```PF`` <#var-PF>`__\ ``}`` are no longer added to
+   ```PROVIDES`` <#var-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 ```ERROR_QA`` <#var-ERROR_QA>`__ or
+   ```WARN_QA`` <#var-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 "```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 ```do_install`` <#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
+   "```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 ```SDK_NAME`` <#var-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
+   ```DEPLOY_DIR_IMAGE`` <#var-DEPLOY_DIR_IMAGE>`__ variable continues
+   to point to the directory containing images for the current
+   ```MACHINE`` <#var-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
+   `Build Directory <#build-directory>`__ rather than
+   ```TMPDIR`` <#var-TMPDIR>`__. Doing so makes it easier to delete
+   ``TMPDIR`` and preserve the build history. Additionally, data for
+   produced SDKs is now split by ```IMAGE_NAME`` <#var-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 ```SRCPV`` <#var-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
+```IMAGE_FEATURES`` <#var-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
+   ```IMAGE_INSTALL`` <#var-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,
+   ```COMPLEMENTARY_GLOB`` <#var-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 <http://permalink.gmane.org/gmane.comp.handhelds.openembedded/58530>`__.
+
+.. _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
+```ROOTFS_POSTPROCESS_COMMAND`` <#var-ROOTFS_POSTPROCESS_COMMAND>`__.
+This addition is now handled automatically when "package-management" is
+not in ```IMAGE_FEATURES`` <#var-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 ```do_rootfs`` <#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
+"```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
+```BUSYBOX_SPLIT_SUID`` <#var-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
+```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
+"`Performing Automated Runtime
+Testing <&YOCTO_DOCS_DEV_URL;#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 "`Maintaining Build
+Output
+Quality <&YOCTO_DOCS_DEV_URL;#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
+   ```RRECOMMENDS`` <#var-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
+   ```BAD_RECOMMENDATIONS`` <#var-BAD_RECOMMENDATIONS>`__ supports
+   pre-renamed package names.
+
+-  ``classes/rootfs_rpm``: Implement ``BAD_RECOMMENDATIONS`` for RPM.
+
+-  ``systemd``: Remove ``systemd_unitdir`` if ``systemd`` is not in
+   ```DISTRO_FEATURES`` <#var-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.
+
+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 ```archiver`` <#ref-classes-archiver>`__ class has been rewritten
+and its configuration has been simplified. For more details on the
+source archiver, see the "`Maintaining Open Source License Compliance
+During Your Product's
+Lifecycle <&YOCTO_DOCS_DEV_URL;#maintaining-open-source-license-compliance-during-your-products-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 `BitBake <#bitbake-term>`__.
+
+.. _migration-1.6-matching-branch-requirement-for-git-fetching:
+
+Matching Branch Requirement for Git Fetching
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When fetching source from a Git repository using
+```SRC_URI`` <#var-SRC_URI>`__, BitBake will now validate the
+```SRCREV`` <#var-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 ```do_populate_sdk`` <#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``
+~~~~~~~~~~
+
+```TMPDIR`` <#var-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 ```PR`` <#var-PR>`__ increments on changes,
+use the PR service instead. You can find out more about this service in
+the "`Working With a PR
+Service <&YOCTO_DOCS_DEV_URL;#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 ```IMAGE_TYPES`` <#var-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 ```COPY_LIC_MANIFEST`` <#var-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 ```COPY_LIC_DIRS`` <#var-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
+```FEATURE_PACKAGES`` <#var-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:
+`ROOTFS_PREPROCESS_COMMAND <#var-ROOTFS_PREPROCESS_COMMAND>`__
+`ROOTFS_POSTPROCESS_COMMAND <#var-ROOTFS_POSTPROCESS_COMMAND>`__
+`SDK_POSTPROCESS_COMMAND <#var-SDK_POSTPROCESS_COMMAND>`__
+`POPULATE_SDK_POST_TARGET_COMMAND <#var-POPULATE_SDK_POST_TARGET_COMMAND>`__
+`POPULATE_SDK_POST_HOST_COMMAND <#var-POPULATE_SDK_POST_HOST_COMMAND>`__
+`IMAGE_POSTPROCESS_COMMAND <#var-IMAGE_POSTPROCESS_COMMAND>`__
+`IMAGE_PREPROCESS_COMMAND <#var-IMAGE_PREPROCESS_COMMAND>`__
+`ROOTFS_POSTUNINSTALL_COMMAND <#var-ROOTFS_POSTUNINSTALL_COMMAND>`__
+`ROOTFS_POSTINSTALL_COMMAND <#var-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 "`Testing Packages with
+ptest <&YOCTO_DOCS_DEV_URL;#testing-packages-with-ptest>`__" section in
+the Yocto Project Development Tasks Manual. For information on the
+``ptest`` class, see the "```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 ```cmake`` <#ref-classes-cmake>`__ class. In
+future releases the ```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
+```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 `OE-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
+```LIC_FILES_CHKSUM`` <#var-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
+```CFLAGS`` <#var-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
+```IMAGE_FSTYPES`` <#var-IMAGE_FSTYPES>`__, must declare their
+dependencies on other image types (if any) using a new
+```IMAGE_TYPEDEP`` <#var-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 `Source
+Repositories <&YOCTO_GIT_URL;>`__ at
+http://git.yoctoproject.org/cgit/cgit.cgi/meta-yocto-bsp-old/.
+
+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
+```PACKAGECONFIG`` <#var-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 `Git <&YOCTO_DOCS_OM_URL;#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 ```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
+   (```B`` <#var-B>`__), which is separate from the source directory
+   (```S`` <#var-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 ```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 ```module_autoload_*`` <#var-module_autoload>`__ variable is now
+deprecated and a new
+```KERNEL_MODULE_AUTOLOAD`` <#var-KERNEL_MODULE_AUTOLOAD>`__ variable
+should be used instead. Also, ```module_conf_*`` <#var-module_conf>`__
+must now be used in conjunction with a new
+```KERNEL_MODULE_PROBECONF`` <#var-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
+   ```do_package_qa`` <#ref-tasks-package_qa>`__ task rather than being
+   part of the ```do_package`` <#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
+   ```do_populate_sysroot`` <#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 ```TMPDIR`` <#var-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 "`Maintaining Build Output
+   Quality <&YOCTO_DOCS_DEV_URL;#maintaining-build-output-quality>`__"
+   section in the Yocto Project Development Tasks Manual.
+
+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
+```DISTRO_FEATURES`` <#var-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
+```do_configure`` <#ref-tasks-configure>`__ and
+```do_install`` <#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
+```EXTRA_OECONF`` <#var-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 ```base`` <#ref-classes-base>`__,
+```autotools`` <#ref-classes-autotools>`__, and
+```cmake`` <#ref-classes-cmake>`__ classes to clean out generated files
+when the ```do_configure`` <#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
+```CLEANBROKEN`` <#var-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
+   ```FILES`` <#var-FILES>`__ values where ```D`` <#var-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}``.
+
+-  ```S`` <#var-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 ```do_unpack`` <#ref-tasks-unpack>`__ task
+   finishes, a warning will be shown.
+
+-  ```LICENSE`` <#var-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 ```PKGDATA_DIR`` <#var-PKGDATA_DIR>`__ from the
+   build environment.
+
+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 `OE-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 ```DISTRO_FEATURES`` <#var-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
+```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.
+   ```DESCRIPTION`` <#var-DESCRIPTION>`__,
+   ```SUMMARY`` <#var-SUMMARY>`__, ```LICENSE`` <#var-LICENSE>`__, and
+   ```SECTION`` <#var-SECTION>`__). Some package managers do not support
+   these characters.
+
+-  Added an "invalid-packageconfig" check for any options specified in
+   ```PACKAGECONFIG`` <#var-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`` ```IMAGE_FEATURES`` <#var-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 ```IMAGE_FSTYPES`` <#var-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``.
+
+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 ```OVERRIDES`` <#var-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
+----------------------------
+
+```EXTRA_OEMAKE`` <#var-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 ```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 ```do_configure`` <#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 ```do_rootfs`` <#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
+```image`` <#ref-classes-image>`__ class to the
+```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
+   ```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
+   ```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 "`Using the Toaster Web
+   Interface <&YOCTO_DOCS_TOAST_URL;#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 `standard
+SDK <&YOCTO_DOCS_SDK_URL;#sdk-using-the-standard-sdk>`__ and the
+`extensible SDK <&YOCTO_DOCS_SDK_URL;#sdk-extensible>`__. For
+information on these SDKs and how to build and use them, see the `Yocto
+Project Application Development and the Extensible Software Development
+Kit (eSDK) <&YOCTO_DOCS_SDK_URL;>`__ 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 ```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
+"`Enabling GObject Introspection
+Support <&YOCTO_DOCS_DEV_URL;#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
+   ```IMAGE_FEATURES`` <#var-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
+   ```devtool modify`` <&YOCTO_DOCS_SDK_URL;#sdk-devtool-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.
+
+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 ```SYSROOT_DIRS`` <#var-SYSROOT_DIRS>`__,
+```SYSROOT_DIRS_NATIVE`` <#var-SYSROOT_DIRS_NATIVE>`__, and
+```SYSROOT_DIRS_BLACKLIST`` <#var-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 `OE-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:
+
+``${B}`` No Longer Default Working Directory for Tasks
+------------------------------------------------------
+
+``${``\ ```B`` <#var-B>`__\ ``}`` is no longer the default working
+directory for tasks. Consequently, any custom tasks you define now need
+to either have the
+``[``\ ```dirs`` <&YOCTO_DOCS_BB_URL;#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
+`OE-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 ```IMAGE_CLASSES`` <#var-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 ```LDFLAGS`` <#var-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 += "${LDFLAGS}"
+
+.. _migration-2.2-kernel-image-base-name-no-longer-uses-kernel-imagetype:
+
+``KERNEL_IMAGE_BASE_NAME`` no Longer Uses ``KERNEL_IMAGETYPE``
+--------------------------------------------------------------
+
+The ``KERNEL_IMAGE_BASE_NAME`` variable no longer uses the
+```KERNEL_IMAGETYPE`` <#var-KERNEL_IMAGETYPE>`__ variable to create the
+image's base name. Because the OpenEmbedded build system can now build
+multiple kernel image types, this part of the kernel image base name as
+been removed leaving only the following: KERNEL_IMAGE_BASE_NAME ?=
+"${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 ```SRCREV`` <#var-SRCREV>`__ for
+   specifying the source revision to use, be it
+   ``${``\ ```AUTOREV`` <#var-AUTOREV>`__\ ``}``, changelist number,
+   p4date, or label, in preference to separate
+   ```SRC_URI`` <#var-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 ```DEPENDS`` <#var-DEPENDS>`__ and
+   ```SECTION`` <#var-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
+   ```SRCREV`` <#var-SRCREV>`__ by default when fetching from a Git
+   repository. You can override this in either case to use
+   ``${``\ ```AUTOREV`` <#var-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``.
+
+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 ```PACKAGE_WRITE_DEPS`` <#var-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
+   ```do_rootfs`` <#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
+   ```DISTRO_FEATURES`` <#var-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
+   ```SYSROOT_PREPROCESS_FUNCS`` <#var-SYSROOT_PREPROCESS_FUNCS>`__.
+
+   For an example, see the ``pixbufcache`` class in ``meta/classes/`` in
+   the Yocto Project `Source
+   Repositories <&YOCTO_DOCS_OM_URL;#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
+   ```STAGING_DIR_NATIVE`` <#var-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 ```HOSTTOOLS`` <#var-HOSTTOOLS>`__ and
+```HOSTTOOLS_NONFATAL`` <#var-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 ```DEPENDS`` <#var-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 ```TMPDIR`` <#var-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
+   ```MIRRORS`` <#var-MIRRORS>`__, ```PREMIRRORS`` <#var-PREMIRRORS>`__,
+   and ```SSTATE_MIRRORS`` <#var-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 ```do_fetch`` <#ref-tasks-fetch>`__ task.
+
+   See the "`Subversion (SVN) Fetcher
+   (svn://) <&YOCTO_DOCS_BB_URL;#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 ```INCOMPATIBLE_LICENSE`` <#var-INCOMPATIBLE_LICENSE>`__ to
+exclude GPLv3 or set ```PREFERRED_VERSION`` <#var-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 ```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 `OE-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
+   ```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`` ```DISTRO_FEATURES`` <#var-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 ```DISTRO_VERSION`` <#var-DISTRO_VERSION>`__ value contains
+   the value of the ```DATE`` <#var-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
+   ```ROOTFS_POSTPROCESS_COMMAND`` <#var-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 ```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
+   ```COPYLEFT_LICENSE_INCLUDE`` <#var-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
+   ```INHERIT_DISTRO`` <#var-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 ```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
+   ```DISTRO_FEATURES_NATIVE`` <#var-DISTRO_FEATURES_NATIVE>`__ added to
+   an intersection of ``DISTRO_FEATURES`` and
+   ```DISTRO_FEATURES_FILTER_NATIVE`` <#var-DISTRO_FEATURES_FILTER_NATIVE>`__.
+
+   For nativesdk recipes, the corresponding variables are
+   ```DISTRO_FEATURES_NATIVESDK`` <#var-DISTRO_FEATURES_NATIVESDK>`__
+   and
+   ```DISTRO_FEATURES_FILTER_NATIVESDK`` <#var-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 ```FILESPATH`` <#var-FILESPATH>`__ instead.
+
+-  The ``MULTIMACH_HOST_SYS`` variable has been removed as it is no
+   longer needed with recipe-specific sysroots.
+
+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
+```BB_SERVER_TIMEOUT`` <#var-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
+      ```DISTRO_FEATURES`` <#var-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.
+      ```RDEPENDS`` <#var-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.
+      ```RRECOMMENDS`` <#var-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
+   ```BAD_RECOMMENDATIONS`` <#var-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
+```kernel-devicetree`` <#ref-classes-kernel-devicetree>`__ class.
+Functionality is automatically enabled for any recipe that inherits the
+```kernel`` <#ref-classes-kernel>`__ class and sets the
+```KERNEL_DEVICETREE`` <#var-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 ``${COREBASE}/LICENSE`` within
+   ```LIC_FILES_CHKSUM`` <#var-LIC_FILES_CHKSUM>`__ you receive a
+   warning because this file is a description of the license for
+   OE-Core. Use ``${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 ```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
+   ```BUILDHISTORY_COMMIT`` <#var-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 ```IMAGE_FSTYPES`` <#var-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
+   "`Events <&YOCTO_DOCS_BB_URL;#events>`__" section in the BitBake User
+   Manual.
+
+-  By default, the ``security_flags.inc`` file sets a
+   ```GCCPIE`` <#var-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 ```PREFERRED_VERSION`` <#var-PREFERRED_VERSION>`__
+   variable. This preference is set is due to the remaining
+   compatibility issues with other software. The
+   ```PROVIDES`` <#var-PROVIDES>`__ variable in the openssl 1.0 recipe
+   now includes "openssl10" as a marker that can be used in
+   ```DEPENDS`` <#var-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.
+
+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 "`BSP Kernel Recipe
+   Example <&YOCTO_DOCS_BSP_URL;#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
+```DEPENDS`` <&YOCTO_DOCS_REF_URL;#var-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 ```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 "`Post-Installation
+   Scripts <&YOCTO_DOCS_DEV_URL;#new-recipe-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.
+
+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 ```GCCVERSION`` <#var-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
+```distutils`` <#ref-classes-distutils>`__ and
+```distutils3`` <#ref-classes-distutils3>`__ classes to fetch code
+during the ```do_configure`` <#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 ```DEPENDS`` <#var-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. ```IMAGE_NAME`` <#var-IMAGE_NAME>`__) use a new
+   ``IMAGE_VERSION_SUFFIX`` variable instead of
+   ```DATETIME`` <#var-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 `KERNEL_IMAGE_NAME <#var-KERNEL_IMAGE_NAME>`__
+   KERNEL_IMAGE_SYMLINK_NAME
+   `KERNEL_IMAGE_LINK_NAME <#var-KERNEL_IMAGE_LINK_NAME>`__
+   MODULE_TARBALL_BASE_NAME
+   `MODULE_TARBALL_NAME <#var-MODULE_TARBALL_NAME>`__
+   MODULE_TARBALL_SYMLINK_NAME
+   `MODULE_TARBALL_LINK_NAME <#var-MODULE_TARBALL_LINK_NAME>`__
+   INITRAMFS_BASE_NAME `INITRAMFS_NAME <#var-INITRAMFS_NAME>`__
+
+-  The ``MODULE_IMAGE_BASE_NAME`` variable has been removed. The module
+   tarball name is now controlled directly with the
+   ```MODULE_TARBALL_NAME`` <#var-MODULE_TARBALL_NAME>`__ variable.
+
+-  The ```KERNEL_DTB_NAME`` <#var-KERNEL_DTB_NAME>`__ and
+   ```KERNEL_DTB_LINK_NAME`` <#var-KERNEL_DTB_LINK_NAME>`__ variables
+   have been introduced to control kernel Device Tree Binary (DTB)
+   artifact names instead of mangling ``KERNEL_IMAGE_*`` variables.
+
+-  The ```KERNEL_FIT_NAME`` <#var-KERNEL_FIT_NAME>`__ and
+   ```KERNEL_FIT_LINK_NAME`` <#var-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 ```MODULE_TARBALL_NAME`` <#var-MODULE_TARBALL_NAME>`__ and
+   ```MODULE_TARBALL_LINK_NAME`` <#var-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 ```INITRAMFS_LINK_NAME`` <#var-INITRAMFS_LINK_NAME>`__
+   variable so that the symlink can be controlled similarly to other
+   artifact types.
+
+-  ```INITRAMFS_NAME`` <#var-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 ```SERIAL_CONSOLE`` <#var-SERIAL_CONSOLE>`__ variable has been
+functionally replaced by the
+```SERIAL_CONSOLES`` <#var-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 ```OVERRIDES`` <#var-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-${BUILD_OS}``, which is typically ``build-linux``, override
+   has been removed because building on a host operating system other
+   than a recent version of Linux is neither supported nor recommended.
+   Dropping the override avoids giving the impression that other host
+   operating systems might be supported.
+
+-  The "_remove" operator now preserves whitespace. Consequently, when
+   specifying list items to remove, be aware that leading and trailing
+   whitespace resulting from the removal is retained.
+
+   See the "`Removal (Override Style
+   Syntax) <&YOCTO_DOCS_BB_URL;#removing-override-style-syntax>`__"
+   section in the BitBake User Manual for a detailed example.
+
+.. _migration-2.6-systemd-configuration-now-split-out-to-system-conf:
+
+``systemd`` Configuration is Now Split Into ``systemd-conf``
+------------------------------------------------------------
+
+The configuration for the ``systemd`` recipe has been moved into a
+``system-conf`` recipe. Moving this configuration to a separate recipe
+avoids the ``systemd`` recipe from becoming machine-specific for cases
+where machine-specific configurations need to be applied (e.g. for
+``qemu*`` machines).
+
+Currently, the new recipe packages the following files:
+${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
+   ```TESTIMAGE_AUTO`` <#var-TESTIMAGE_AUTO>`__ variable.
+
+-  *Inheriting the ``testimage`` and ``testsdk`` Classes:* Best
+   practices now dictate that you use the
+   ```IMAGE_CLASSES`` <#var-IMAGE_CLASSES>`__ variable rather than the
+   ```INHERIT`` <#var-INHERIT>`__ variable when you inherit the
+   ```testimage`` <#ref-classes-testimage*>`__ and
+   ```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 `Build Directory <#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 ```do_rootfs`` <#ref-tasks-rootfs>`__ task.
+
+For more information on post-installation behavior, see the
+"`Post-Installation
+Scripts <&YOCTO_DOCS_DEV_URL;#new-recipe-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
+```MACHINE`` <#var-MACHINE>`__ has support for user-mode emulation in
+QEMU (i.e. "qemu-usermode" is in
+```MACHINE_FEATURES`` <#var-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
+```PACKAGECONFIG`` <#var-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 ```IMAGE_FSTYPES`` <#var-IMAGE_FSTYPES>`__ variable.
+
+-  The ``scripts/contrib/mkefidisk.sh`` has been removed in favor of
+   Wic.
+
+-  ``kernel-modules`` has been removed from
+   ```RRECOMMENDS`` <#var-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
+   ```TARGET_LDFLAGS`` <#var-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.
+
+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
+   ```BBFILE_COLLECTIONS`` <#var-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
+```LICENSE`` <#var-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
+   ```IMAGE_FEATURES`` <#var-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 ```SDKIMAGE_FEATURES`` <#var-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 ```RRECOMMENDS`` <#var-RRECOMMENDS>`__ and
+   ```RDEPENDS`` <#var-RDEPENDS>`__ variables. As a result, existing
+   images should not see any changes assuming
+   ```NO_RECOMMENDATIONS`` <#var-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
+   ```PACKAGE_PREPROCESS_FUNCS`` <#var-PACKAGE_PREPROCESS_FUNCS>`__
+
+-  ``base/pixbufcache``: Obsolete ``sstatecompletions`` code has been
+   removed.
+
+-  ```native`` <#ref-classes-native>`__ class:
+   ```RDEPENDS`` <#var-RDEPENDS>`__ handling has been enabled.
+
+-  ``inetutils``: This recipe has rsh disabled.
+
+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
+   ```BB_SETSCENE_VERIFY_FUNCTION2`` <&YOCTO_DOCS_BB_URL;#var-bb-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
+   ```BB_HASHCHECK_FUNCTION`` <&YOCTO_DOCS_BB_URL;#var-bb-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.
+
+-  ```SRC_URI`` <#var-SRC_URI>`__ is now checked for usage of two
+   problematic items:
+
+   -  "${PN}" prefix/suffix use - Warnings always appear if ${PN} is
+      used. You must fix the issue regardless of whether multiconfig or
+      anything else that would cause prefixing/suffixing to happen.
+
+   -  Github archive tarballs - these are not guaranteed to be stable.
+      Consequently, it is likely that the tarballs will be refreshed and
+      thus the SRC_URI checksums will fail to apply. It is recommended
+      that you fetch either an official release tarball or a specific
+      revision from the actual Git repository instead.
+
+   Either one of these items now trigger a warning by default. If you
+   wish to disable this check, remove ``src-uri-bad`` from
+   ```WARN_QA`` <#var-WARN_QA>`__.
+
+-  The ``file-rdeps`` runtime dependency check no longer expands
+   ```RDEPENDS`` <#var-RDEPENDS>`__ recursively as there is no mechanism
+   to ensure they can be fully computed, and thus races sometimes result
+   in errors either showing up or not. Thus, you might now see errors
+   for missing runtime dependencies that were previously satisfied
+   recursively. Here is an example: package A contains a shell script
+   starting with ``#!/bin/bash`` but has no dependency on bash. However,
+   package A depends on package B, which does depend on bash. You need
+   to add the missing dependency or dependencies to resolve the warning.
+
+-  Setting ``DEPENDS_${PN}`` anywhere (i.e. typically in a recipe) now
+   triggers an error. The error is triggered because
+   ```DEPENDS`` <#var-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
+   ```KERNEL_DEVICETREE`` <#var-KERNEL_DEVICETREE>`__ in any kernel
+   recipe and only produced a warning. Remove any ``include`` or
+   ``require`` statements pointing to this file.
+
+-  ```TARGET_CFLAGS`` <#var-TARGET_CFLAGS>`__,
+   ```TARGET_CPPFLAGS`` <#var-TARGET_CPPFLAGS>`__,
+   ```TARGET_CXXFLAGS`` <#var-TARGET_CXXFLAGS>`__, and
+   ```TARGET_LDFLAGS`` <#var-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
+   ```NATIVELSBSTRING`` <#var-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
+   ```SANITY_TESTED_DISTROS`` <#var-SANITY_TESTED_DISTROS>`__.
+
+-  In the ``base-files`` recipe, writing the hostname into
+   ``/etc/hosts`` and ``/etc/hostname`` is now done within the main
+   ```do_install`` <#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.
+
+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
+```DISTRO_FEATURES`` <#var-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 ```SRC_URI`` <#var-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
+```SRC_URI`` <#var-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 ```RRECOMMENDS`` <#var-RRECOMMENDS>`__ of the main
+   ``glibc`` package if ``ldconfig`` is present in
+   ```DISTRO_FEATURES`` <#var-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 ``${datadir}/mime/packages``
+   but does not inherit the ``mime`` class
+
+.. _migration-3.1-x86-live-wic:
+
+``wic`` image type now used instead of ``live`` by default for x86
+------------------------------------------------------------------
+
+``conf/machine/include/x86-base.inc`` (inherited by most x86 machine
+configurations) now specifies ``wic`` instead of ``live`` by default in
+```IMAGE_FSTYPES`` <#var-IMAGE_FSTYPES>`__. The ``live`` image type will
+likely be removed in a future release so it is recommended that you use
+``wic`` instead.
+
+.. _migration-3.1-misc:
+
+Miscellaneous changes
+---------------------
+
+-  The undocumented ``SRC_DISTRIBUTE_LICENSES`` variable has now been
+   removed in favour of a new ``AVAILABLE_LICENSES`` variable which is
+   dynamically set based upon license files found in
+   ``${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.