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+.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
+************
+Common Tasks
+************
+This chapter describes fundamental procedures such as creating layers,
+adding new software packages, extending or customizing images, porting
+work to new hardware (adding a new machine), and so forth. You will find
+that the procedures documented here occur often in the development cycle
+using the Yocto Project.
+Understanding and Creating Layers
+=================================
+The OpenEmbedded build system supports organizing
+:term:`Metadata` into multiple layers.
+Layers allow you to isolate different types of customizations from each
+other. For introductory information on the Yocto Project Layer Model,
+see the
+":ref:`overview-manual/overview-manual-yp-intro:the yocto project layer model`"
+section in the Yocto Project Overview and Concepts Manual.
+Creating Your Own Layer
+-----------------------
+It is very easy to create your own layers to use with the OpenEmbedded
+build system. The Yocto Project ships with tools that speed up creating
+layers. This section describes the steps you perform by hand to create
+layers so that you can better understand them. For information about the
+layer-creation tools, see the
+":ref:`bsp-guide/bsp:creating a new bsp layer using the \`\`bitbake-layers\`\` script`"
+section in the Yocto Project Board Support Package (BSP) Developer's
+Guide and the ":ref:`dev-manual/common-tasks:creating a general layer using the \`\`bitbake-layers\`\` script`"
+section further down in this manual.
+Follow these general steps to create your layer without using tools:
+1. *Check Existing Layers:* Before creating a new layer, you should be
+   sure someone has not already created a layer containing the Metadata
+   you need. You can see the `OpenEmbedded Metadata
+   Index <https://layers.openembedded.org/layerindex/layers/>`__ for a
+   list of layers from the OpenEmbedded community that can be used in
+   the Yocto Project. You could find a layer that is identical or close
+   to what you need.
+2. *Create a Directory:* Create the directory for your layer. When you
+   create the layer, be sure to create the directory in an area not
+   associated with the Yocto Project :term:`Source Directory`
+   (e.g. the cloned ``poky`` repository).
+   While not strictly required, prepend the name of the directory with
+   the string "meta-". For example:
+   ::
+      meta-mylayer
+      meta-GUI_xyz
+      meta-mymachine
+   With rare exceptions, a layer's name follows this form:
+   ::
+      meta-root_name
+   Following this layer naming convention can save
+   you trouble later when tools, components, or variables "assume" your
+   layer name begins with "meta-". A notable example is in configuration
+   files as shown in the following step where layer names without the
+   "meta-" string are appended to several variables used in the
+   configuration.
+3. *Create a Layer Configuration File:* Inside your new layer folder,
+   you need to create a ``conf/layer.conf`` file. It is easiest to take
+   an existing layer configuration file and copy that to your layer's
+   ``conf`` directory and then modify the file as needed.
+   The ``meta-yocto-bsp/conf/layer.conf`` file in the Yocto Project
+   :yocto_git:`Source Repositories </poky/tree/meta-yocto-bsp/conf>`
+   demonstrates the required syntax. For your layer, you need to replace
+   "yoctobsp" with a unique identifier for your layer (e.g. "machinexyz"
+   for a layer named "meta-machinexyz"):
+   ::
+      # We have a conf and classes directory, add to BBPATH
+      BBPATH .= ":${LAYERDIR}"
+      # We have recipes-* directories, add to BBFILES
+      BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
+                  ${LAYERDIR}/recipes-*/*/*.bbappend"
+      BBFILE_COLLECTIONS += "yoctobsp"
+      BBFILE_PATTERN_yoctobsp = "^${LAYERDIR}/"
+      BBFILE_PRIORITY_yoctobsp = "5"
+      LAYERVERSION_yoctobsp = "4"
+      LAYERSERIES_COMPAT_yoctobsp = "dunfell"
+   Following is an explanation of the layer configuration file:
+   -  :term:`BBPATH`: Adds the layer's
+      root directory to BitBake's search path. Through the use of the
+      ``BBPATH`` variable, BitBake locates class files (``.bbclass``),
+      configuration files, and files that are included with ``include``
+      and ``require`` statements. For these cases, BitBake uses the
+      first file that matches the name found in ``BBPATH``. This is
+      similar to the way the ``PATH`` variable is used for binaries. It
+      is recommended, therefore, that you use unique class and
+      configuration filenames in your custom layer.
+   -  :term:`BBFILES`: Defines the
+      location for all recipes in the layer.
+   -  :term:`BBFILE_COLLECTIONS`:
+      Establishes the current layer through a unique identifier that is
+      used throughout the OpenEmbedded build system to refer to the
+      layer. In this example, the identifier "yoctobsp" is the
+      representation for the container layer named "meta-yocto-bsp".
+   -  :term:`BBFILE_PATTERN`:
+      Expands immediately during parsing to provide the directory of the
+      layer.
+   -  :term:`BBFILE_PRIORITY`:
+      Establishes a priority to use for recipes in the layer when the
+      OpenEmbedded build finds recipes of the same name in different
+      layers.
+   -  :term:`LAYERVERSION`:
+      Establishes a version number for the layer. You can use this
+      version number to specify this exact version of the layer as a
+      dependency when using the
+      :term:`LAYERDEPENDS`
+      variable.
+   -  :term:`LAYERDEPENDS`:
+      Lists all layers on which this layer depends (if any).
+   -  :term:`LAYERSERIES_COMPAT`:
+      Lists the :yocto_wiki:`Yocto Project </Releases>`
+      releases for which the current version is compatible. This
+      variable is a good way to indicate if your particular layer is
+      current.
+4. *Add Content:* Depending on the type of layer, add the content. If
+   the layer adds support for a machine, add the machine configuration
+   in a ``conf/machine/`` file within the layer. If the layer adds
+   distro policy, add the distro configuration in a ``conf/distro/``
+   file within the layer. If the layer introduces new recipes, put the
+   recipes you need in ``recipes-*`` subdirectories within the layer.
+   .. note::
+      For an explanation of layer hierarchy that is compliant with the
+      Yocto Project, see the ":ref:`bsp-guide/bsp:example filesystem layout`"
+      section in the Yocto Project Board Support Package (BSP) Developer's Guide.
+5. *Optionally Test for Compatibility:* If you want permission to use
+   the Yocto Project Compatibility logo with your layer or application
+   that uses your layer, perform the steps to apply for compatibility.
+   See the "`Making Sure Your Layer is Compatible With Yocto
+   Project <#making-sure-your-layer-is-compatible-with-yocto-project>`__"
+   section for more information.
+Following Best Practices When Creating Layers
+---------------------------------------------
+To create layers that are easier to maintain and that will not impact
+builds for other machines, you should consider the information in the
+following list:
+-  *Avoid "Overlaying" Entire Recipes from Other Layers in Your
+   Configuration:* In other words, do not copy an entire recipe into
+   your layer and then modify it. Rather, use an append file
+   (``.bbappend``) to override only those parts of the original recipe
+   you need to modify.
+-  *Avoid Duplicating Include Files:* Use append files (``.bbappend``)
+   for each recipe that uses an include file. Or, if you are introducing
+   a new recipe that requires the included file, use the path relative
+   to the original layer directory to refer to the file. For example,
+   use ``require recipes-core/``\ `package`\ ``/``\ `file`\ ``.inc`` instead
+   of ``require`` `file`\ ``.inc``. If you're finding you have to overlay
+   the include file, it could indicate a deficiency in the include file
+   in the layer to which it originally belongs. If this is the case, you
+   should try to address that deficiency instead of overlaying the
+   include file. For example, you could address this by getting the
+   maintainer of the include file to add a variable or variables to make
+   it easy to override the parts needing to be overridden.
+-  *Structure Your Layers:* Proper use of overrides within append files
+   and placement of machine-specific files within your layer can ensure
+   that a build is not using the wrong Metadata and negatively impacting
+   a build for a different machine. Following are some examples:
+   -  *Modify Variables to Support a Different Machine:* Suppose you
+      have a layer named ``meta-one`` that adds support for building
+      machine "one". To do so, you use an append file named
+      ``base-files.bbappend`` and create a dependency on "foo" by
+      altering the :term:`DEPENDS`
+      variable:
+      ::
+         DEPENDS = "foo"
+      The dependency is created during any
+      build that includes the layer ``meta-one``. However, you might not
+      want this dependency for all machines. For example, suppose you
+      are building for machine "two" but your ``bblayers.conf`` file has
+      the ``meta-one`` layer included. During the build, the
+      ``base-files`` for machine "two" will also have the dependency on
+      ``foo``.
+      To make sure your changes apply only when building machine "one",
+      use a machine override with the ``DEPENDS`` statement:
+      ::
+         DEPENDS_one = "foo"
+      You should follow the same strategy when using ``_append``
+      and ``_prepend`` operations:
+      ::
+         DEPENDS_append_one = " foo"
+         DEPENDS_prepend_one = "foo "
+      As an actual example, here's a
+      snippet from the generic kernel include file ``linux-yocto.inc``,
+      wherein the kernel compile and link options are adjusted in the
+      case of a subset of the supported architectures:
+      ::
+         DEPENDS_append_aarch64 = " libgcc"
+         KERNEL_CC_append_aarch64 = " ${TOOLCHAIN_OPTIONS}"
+         KERNEL_LD_append_aarch64 = " ${TOOLCHAIN_OPTIONS}"
+         DEPENDS_append_nios2 = " libgcc"
+         KERNEL_CC_append_nios2 = " ${TOOLCHAIN_OPTIONS}"
+         KERNEL_LD_append_nios2 = " ${TOOLCHAIN_OPTIONS}"
+         DEPENDS_append_arc = " libgcc"
+         KERNEL_CC_append_arc = " ${TOOLCHAIN_OPTIONS}"
+         KERNEL_LD_append_arc = " ${TOOLCHAIN_OPTIONS}"
+         KERNEL_FEATURES_append_qemuall=" features/debug/printk.scc"
+      .. note::
+         Avoiding "+=" and "=+" and using machine-specific ``_append``
+         and ``_prepend`` operations is recommended as well.
+   -  *Place Machine-Specific Files in Machine-Specific Locations:* When
+      you have a base recipe, such as ``base-files.bb``, that contains a
+      :term:`SRC_URI` statement to a
+      file, you can use an append file to cause the build to use your
+      own version of the file. For example, an append file in your layer
+      at ``meta-one/recipes-core/base-files/base-files.bbappend`` could
+      extend :term:`FILESPATH` using :term:`FILESEXTRAPATHS` as follows:
+      ::
+         FILESEXTRAPATHS_prepend := "${THISDIR}/${BPN}:"
+      The build for machine "one" will pick up your machine-specific file as
+      long as you have the file in
+      ``meta-one/recipes-core/base-files/base-files/``. However, if you
+      are building for a different machine and the ``bblayers.conf``
+      file includes the ``meta-one`` layer and the location of your
+      machine-specific file is the first location where that file is
+      found according to ``FILESPATH``, builds for all machines will
+      also use that machine-specific file.
+      You can make sure that a machine-specific file is used for a
+      particular machine by putting the file in a subdirectory specific
+      to the machine. For example, rather than placing the file in
+      ``meta-one/recipes-core/base-files/base-files/`` as shown above,
+      put it in ``meta-one/recipes-core/base-files/base-files/one/``.
+      Not only does this make sure the file is used only when building
+      for machine "one", but the build process locates the file more
+      quickly.
+      In summary, you need to place all files referenced from
+      ``SRC_URI`` in a machine-specific subdirectory within the layer in
+      order to restrict those files to machine-specific builds.
+-  *Perform Steps to Apply for Yocto Project Compatibility:* If you want
+   permission to use the Yocto Project Compatibility logo with your
+   layer or application that uses your layer, perform the steps to apply
+   for compatibility. See the "`Making Sure Your Layer is Compatible
+   With Yocto
+   Project <#making-sure-your-layer-is-compatible-with-yocto-project>`__"
+   section for more information.
+-  *Follow the Layer Naming Convention:* Store custom layers in a Git
+   repository that use the ``meta-layer_name`` format.
+-  *Group Your Layers Locally:* Clone your repository alongside other
+   cloned ``meta`` directories from the :term:`Source Directory`.
+Making Sure Your Layer is Compatible With Yocto Project
+-------------------------------------------------------
+When you create a layer used with the Yocto Project, it is advantageous
+to make sure that the layer interacts well with existing Yocto Project
+layers (i.e. the layer is compatible with the Yocto Project). Ensuring
+compatibility makes the layer easy to be consumed by others in the Yocto
+Project community and could allow you permission to use the Yocto
+Project Compatible Logo.
+.. note::
+   Only Yocto Project member organizations are permitted to use the
+   Yocto Project Compatible Logo. The logo is not available for general
+   use. For information on how to become a Yocto Project member
+   organization, see the :yocto_home:`Yocto Project Website <>`.
+The Yocto Project Compatibility Program consists of a layer application
+process that requests permission to use the Yocto Project Compatibility
+Logo for your layer and application. The process consists of two parts:
+1. Successfully passing a script (``yocto-check-layer``) that when run
+   against your layer, tests it against constraints based on experiences
+   of how layers have worked in the real world and where pitfalls have
+   been found. Getting a "PASS" result from the script is required for
+   successful compatibility registration.
+2. Completion of an application acceptance form, which you can find at
+   https://www.yoctoproject.org/webform/yocto-project-compatible-registration.
+To be granted permission to use the logo, you need to satisfy the
+following:
+-  Be able to check the box indicating that you got a "PASS" when
+   running the script against your layer.
+-  Answer "Yes" to the questions on the form or have an acceptable
+   explanation for any questions answered "No".
+-  Be a Yocto Project Member Organization.
+The remainder of this section presents information on the registration
+form and on the ``yocto-check-layer`` script.
+Yocto Project Compatible Program Application
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Use the form to apply for your layer's approval. Upon successful
+application, you can use the Yocto Project Compatibility Logo with your
+layer and the application that uses your layer.
+To access the form, use this link:
+https://www.yoctoproject.org/webform/yocto-project-compatible-registration.
+Follow the instructions on the form to complete your application.
+The application consists of the following sections:
+-  *Contact Information:* Provide your contact information as the fields
+   require. Along with your information, provide the released versions
+   of the Yocto Project for which your layer is compatible.
+-  *Acceptance Criteria:* Provide "Yes" or "No" answers for each of the
+   items in the checklist. Space exists at the bottom of the form for
+   any explanations for items for which you answered "No".
+-  *Recommendations:* Provide answers for the questions regarding Linux
+   kernel use and build success.
+``yocto-check-layer`` Script
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The ``yocto-check-layer`` script provides you a way to assess how
+compatible your layer is with the Yocto Project. You should run this
+script prior to using the form to apply for compatibility as described
+in the previous section. You need to achieve a "PASS" result in order to
+have your application form successfully processed.
+The script divides tests into three areas: COMMON, BSP, and DISTRO. For
+example, given a distribution layer (DISTRO), the layer must pass both
+the COMMON and DISTRO related tests. Furthermore, if your layer is a BSP
+layer, the layer must pass the COMMON and BSP set of tests.
+To execute the script, enter the following commands from your build
+directory:
+::
+   $ source oe-init-build-env
+   $ yocto-check-layer your_layer_directory
+Be sure to provide the actual directory for your
+layer as part of the command.
+Entering the command causes the script to determine the type of layer
+and then to execute a set of specific tests against the layer. The
+following list overviews the test:
+-  ``common.test_readme``: Tests if a ``README`` file exists in the
+   layer and the file is not empty.
+-  ``common.test_parse``: Tests to make sure that BitBake can parse the
+   files without error (i.e. ``bitbake -p``).
+-  ``common.test_show_environment``: Tests that the global or per-recipe
+   environment is in order without errors (i.e. ``bitbake -e``).
+-  ``common.test_world``: Verifies that ``bitbake world`` works.
+-  ``common.test_signatures``: Tests to be sure that BSP and DISTRO
+   layers do not come with recipes that change signatures.
+-  ``common.test_layerseries_compat``: Verifies layer compatibility is
+   set properly.
+-  ``bsp.test_bsp_defines_machines``: Tests if a BSP layer has machine
+   configurations.
+-  ``bsp.test_bsp_no_set_machine``: Tests to ensure a BSP layer does not
+   set the machine when the layer is added.
+-  ``bsp.test_machine_world``: Verifies that ``bitbake world`` works
+   regardless of which machine is selected.
+-  ``bsp.test_machine_signatures``: Verifies that building for a
+   particular machine affects only the signature of tasks specific to
+   that machine.
+-  ``distro.test_distro_defines_distros``: Tests if a DISTRO layer has
+   distro configurations.
+-  ``distro.test_distro_no_set_distros``: Tests to ensure a DISTRO layer
+   does not set the distribution when the layer is added.
+Enabling Your Layer
+-------------------
+Before the OpenEmbedded build system can use your new layer, you need to
+enable it. To enable your layer, simply add your layer's path to the
+``BBLAYERS`` variable in your ``conf/bblayers.conf`` file, which is
+found in the :term:`Build Directory`.
+The following example shows how to enable a layer named
+``meta-mylayer``:
+::
+   # POKY_BBLAYERS_CONF_VERSION is increased each time build/conf/bblayers.conf
+   # changes incompatibly
+   POKY_BBLAYERS_CONF_VERSION = "2"
+   BBPATH = "${TOPDIR}"
+   BBFILES ?= ""
+   BBLAYERS ?= " \
+       /home/user/poky/meta \
+       /home/user/poky/meta-poky \
+       /home/user/poky/meta-yocto-bsp \
+       /home/user/poky/meta-mylayer \
+       "
+BitBake parses each ``conf/layer.conf`` file from the top down as
+specified in the ``BBLAYERS`` variable within the ``conf/bblayers.conf``
+file. During the processing of each ``conf/layer.conf`` file, BitBake
+adds the recipes, classes and configurations contained within the
+particular layer to the source directory.
+Using .bbappend Files in Your Layer
+-----------------------------------
+A recipe that appends Metadata to another recipe is called a BitBake
+append file. A BitBake append file uses the ``.bbappend`` file type
+suffix, while the corresponding recipe to which Metadata is being
+appended uses the ``.bb`` file type suffix.
+You can use a ``.bbappend`` file in your layer to make additions or
+changes to the content of another layer's recipe without having to copy
+the other layer's recipe into your layer. Your ``.bbappend`` file
+resides in your layer, while the main ``.bb`` recipe file to which you
+are appending Metadata resides in a different layer.
+Being able to append information to an existing recipe not only avoids
+duplication, but also automatically applies recipe changes from a
+different layer into your layer. If you were copying recipes, you would
+have to manually merge changes as they occur.
+When you create an append file, you must use the same root name as the
+corresponding recipe file. For example, the append file
+``someapp_3.1.bbappend`` must apply to ``someapp_3.1.bb``. This
+means the original recipe and append file names are version
+number-specific. If the corresponding recipe is renamed to update to a
+newer version, you must also rename and possibly update the
+corresponding ``.bbappend`` as well. During the build process, BitBake
+displays an error on starting if it detects a ``.bbappend`` file that
+does not have a corresponding recipe with a matching name. See the
+:term:`BB_DANGLINGAPPENDS_WARNONLY`
+variable for information on how to handle this error.
+As an example, consider the main formfactor recipe and a corresponding
+formfactor append file both from the :term:`Source Directory`.
+Here is the main
+formfactor recipe, which is named ``formfactor_0.0.bb`` and located in
+the "meta" layer at ``meta/recipes-bsp/formfactor``:
+::
+   SUMMARY = "Device formfactor information"
+   DESCRIPTION = "A formfactor configuration file provides information about the \
+   target hardware for which the image is being built and information that the \
+   build system cannot obtain from other sources such as the kernel."
+   SECTION = "base"
+   LICENSE = "MIT"
+   LIC_FILES_CHKSUM = "file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420"
+   PR = "r45"
+   SRC_URI = "file://config file://machconfig"
+   S = "${WORKDIR}"
+   PACKAGE_ARCH = "${MACHINE_ARCH}"
+   INHIBIT_DEFAULT_DEPS = "1"
+   do_install() {
+           # Install file only if it has contents
+           install -d ${D}${sysconfdir}/formfactor/
+           install -m 0644 ${S}/config ${D}${sysconfdir}/formfactor/
+           if [ -s "${S}/machconfig" ]; then
+                   install -m 0644 ${S}/machconfig ${D}${sysconfdir}/formfactor/
+           fi
+   }
+In the main recipe, note the :term:`SRC_URI`
+variable, which tells the OpenEmbedded build system where to find files
+during the build.
+Following is the append file, which is named ``formfactor_0.0.bbappend``
+and is from the Raspberry Pi BSP Layer named ``meta-raspberrypi``. The
+file is in the layer at ``recipes-bsp/formfactor``:
+::
+   FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"
+By default, the build system uses the
+:term:`FILESPATH` variable to
+locate files. This append file extends the locations by setting the
+:term:`FILESEXTRAPATHS`
+variable. Setting this variable in the ``.bbappend`` file is the most
+reliable and recommended method for adding directories to the search
+path used by the build system to find files.
+The statement in this example extends the directories to include
+``${``\ :term:`THISDIR`\ ``}/${``\ :term:`PN`\ ``}``,
+which resolves to a directory named ``formfactor`` in the same directory
+in which the append file resides (i.e.
+``meta-raspberrypi/recipes-bsp/formfactor``. This implies that you must
+have the supporting directory structure set up that will contain any
+files or patches you will be including from the layer.
+Using the immediate expansion assignment operator ``:=`` is important
+because of the reference to ``THISDIR``. The trailing colon character is
+important as it ensures that items in the list remain colon-separated.
+.. note::
+   BitBake automatically defines the ``THISDIR`` variable. You should
+   never set this variable yourself. Using "_prepend" as part of the
+   ``FILESEXTRAPATHS`` ensures your path will be searched prior to other
+   paths in the final list.
+   Also, not all append files add extra files. Many append files simply
+   exist to add build options (e.g. ``systemd``). For these cases, your
+   append file would not even use the ``FILESEXTRAPATHS`` statement.
+Prioritizing Your Layer
+-----------------------
+Each layer is assigned a priority value. Priority values control which
+layer takes precedence if there are recipe files with the same name in
+multiple layers. For these cases, the recipe file from the layer with a
+higher priority number takes precedence. Priority values also affect the
+order in which multiple ``.bbappend`` files for the same recipe are
+applied. You can either specify the priority manually, or allow the
+build system to calculate it based on the layer's dependencies.
+To specify the layer's priority manually, use the
+:term:`BBFILE_PRIORITY`
+variable and append the layer's root name:
+::
+   BBFILE_PRIORITY_mylayer = "1"
+.. note::
+   It is possible for a recipe with a lower version number
+   :term:`PV` in a layer that has a higher
+   priority to take precedence.
+   Also, the layer priority does not currently affect the precedence
+   order of ``.conf`` or ``.bbclass`` files. Future versions of BitBake
+   might address this.
+Managing Layers
+---------------
+You can use the BitBake layer management tool ``bitbake-layers`` to
+provide a view into the structure of recipes across a multi-layer
+project. Being able to generate output that reports on configured layers
+with their paths and priorities and on ``.bbappend`` files and their
+applicable recipes can help to reveal potential problems.
+For help on the BitBake layer management tool, use the following
+command:
+::
+   $ bitbake-layers --help
+   NOTE: Starting bitbake server...
+   usage: bitbake-layers [-d] [-q] [-F] [--color COLOR] [-h] <subcommand> ...
+   BitBake layers utility
+   optional arguments:
+     -d, --debug           Enable debug output
+     -q, --quiet           Print only errors
+     -F, --force           Force add without recipe parse verification
+     --color COLOR         Colorize output (where COLOR is auto, always, never)
+     -h, --help            show this help message and exit
+   subcommands:
+     <subcommand>
+       layerindex-fetch    Fetches a layer from a layer index along with its
+                           dependent layers, and adds them to conf/bblayers.conf.
+       layerindex-show-depends
+                           Find layer dependencies from layer index.
+       add-layer           Add one or more layers to bblayers.conf.
+       remove-layer        Remove one or more layers from bblayers.conf.
+       flatten             flatten layer configuration into a separate output
+                           directory.
+       show-layers         show current configured layers.
+       show-overlayed      list overlayed recipes (where the same recipe exists
+                           in another layer)
+       show-recipes        list available recipes, showing the layer they are
+                           provided by
+       show-appends        list bbappend files and recipe files they apply to
+       show-cross-depends  Show dependencies between recipes that cross layer
+                           boundaries.
+       create-layer        Create a basic layer
+   Use bitbake-layers <subcommand> --help to get help on a specific command
+The following list describes the available commands:
+-  ``help:`` Displays general help or help on a specified command.
+-  ``show-layers:`` Shows the current configured layers.
+-  ``show-overlayed:`` Lists overlayed recipes. A recipe is overlayed
+   when a recipe with the same name exists in another layer that has a
+   higher layer priority.
+-  ``show-recipes:`` Lists available recipes and the layers that
+   provide them.
+-  ``show-appends:`` Lists ``.bbappend`` files and the recipe files to
+   which they apply.
+-  ``show-cross-depends:`` Lists dependency relationships between
+   recipes that cross layer boundaries.
+-  ``add-layer:`` Adds a layer to ``bblayers.conf``.
+-  ``remove-layer:`` Removes a layer from ``bblayers.conf``
+-  ``flatten:`` Flattens the layer configuration into a separate
+   output directory. Flattening your layer configuration builds a
+   "flattened" directory that contains the contents of all layers, with
+   any overlayed recipes removed and any ``.bbappend`` files appended to
+   the corresponding recipes. You might have to perform some manual
+   cleanup of the flattened layer as follows:
+   -  Non-recipe files (such as patches) are overwritten. The flatten
+      command shows a warning for these files.
+   -  Anything beyond the normal layer setup has been added to the
+      ``layer.conf`` file. Only the lowest priority layer's
+      ``layer.conf`` is used.
+   -  Overridden and appended items from ``.bbappend`` files need to be
+      cleaned up. The contents of each ``.bbappend`` end up in the
+      flattened recipe. However, if there are appended or changed
+      variable values, you need to tidy these up yourself. Consider the
+      following example. Here, the ``bitbake-layers`` command adds the
+      line ``#### bbappended ...`` so that you know where the following
+      lines originate:
+      ::
+         ...
+         DESCRIPTION = "A useful utility"
+         ...
+         EXTRA_OECONF = "--enable-something"
+         ...
+         #### bbappended from meta-anotherlayer ####
+         DESCRIPTION = "Customized utility"
+         EXTRA_OECONF += "--enable-somethingelse"
+      Ideally, you would tidy up these utilities as follows:
+      ::
+         ...
+         DESCRIPTION = "Customized utility"
+         ...
+         EXTRA_OECONF = "--enable-something --enable-somethingelse"
+         ...
+-  ``layerindex-fetch``: Fetches a layer from a layer index, along
+   with its dependent layers, and adds the layers to the
+   ``conf/bblayers.conf`` file.
+-  ``layerindex-show-depends``: Finds layer dependencies from the
+   layer index.
+-  ``create-layer``: Creates a basic layer.
+Creating a General Layer Using the ``bitbake-layers`` Script
+------------------------------------------------------------
+The ``bitbake-layers`` script with the ``create-layer`` subcommand
+simplifies creating a new general layer.
+.. note::
+   -  For information on BSP layers, see the ":ref:`bsp-guide/bsp:bsp layers`"
+      section in the Yocto
+      Project Board Specific (BSP) Developer's Guide.
+   -  In order to use a layer with the OpenEmbedded build system, you
+      need to add the layer to your ``bblayers.conf`` configuration
+      file. See the ":ref:`dev-manual/common-tasks:adding a layer using the \`\`bitbake-layers\`\` script`"
+      section for more information.
+The default mode of the script's operation with this subcommand is to
+create a layer with the following:
+-  A layer priority of 6.
+-  A ``conf`` subdirectory that contains a ``layer.conf`` file.
+-  A ``recipes-example`` subdirectory that contains a further
+   subdirectory named ``example``, which contains an ``example.bb``
+   recipe file.
+-  A ``COPYING.MIT``, which is the license statement for the layer. The
+   script assumes you want to use the MIT license, which is typical for
+   most layers, for the contents of the layer itself.
+-  A ``README`` file, which is a file describing the contents of your
+   new layer.
+In its simplest form, you can use the following command form to create a
+layer. The command creates a layer whose name corresponds to
+"your_layer_name" in the current directory:
+::
+   $ bitbake-layers create-layer your_layer_name
+As an example, the following command creates a layer named ``meta-scottrif``
+in your home directory:
+::
+   $ cd /usr/home
+   $ bitbake-layers create-layer meta-scottrif
+   NOTE: Starting bitbake server...
+   Add your new layer with 'bitbake-layers add-layer meta-scottrif'
+If you want to set the priority of the layer to other than the default
+value of "6", you can either use the ``--priority`` option or you
+can edit the
+:term:`BBFILE_PRIORITY` value
+in the ``conf/layer.conf`` after the script creates it. Furthermore, if
+you want to give the example recipe file some name other than the
+default, you can use the ``--example-recipe-name`` option.
+The easiest way to see how the ``bitbake-layers create-layer`` command
+works is to experiment with the script. You can also read the usage
+information by entering the following:
+::
+   $ bitbake-layers create-layer --help
+   NOTE: Starting bitbake server...
+   usage: bitbake-layers create-layer [-h] [--priority PRIORITY]
+                                      [--example-recipe-name EXAMPLERECIPE]
+                                      layerdir
+   Create a basic layer
+   positional arguments:
+     layerdir              Layer directory to create
+   optional arguments:
+     -h, --help            show this help message and exit
+     --priority PRIORITY, -p PRIORITY
+                           Layer directory to create
+     --example-recipe-name EXAMPLERECIPE, -e EXAMPLERECIPE
+                           Filename of the example recipe
+Adding a Layer Using the ``bitbake-layers`` Script
+--------------------------------------------------
+Once you create your general layer, you must add it to your
+``bblayers.conf`` file. Adding the layer to this configuration file
+makes the OpenEmbedded build system aware of your layer so that it can
+search it for metadata.
+Add your layer by using the ``bitbake-layers add-layer`` command:
+::
+   $ bitbake-layers add-layer your_layer_name
+Here is an example that adds a
+layer named ``meta-scottrif`` to the configuration file. Following the
+command that adds the layer is another ``bitbake-layers`` command that
+shows the layers that are in your ``bblayers.conf`` file:
+::
+   $ bitbake-layers add-layer meta-scottrif
+   NOTE: Starting bitbake server...
+   Parsing recipes: 100% |##########################################################| Time: 0:00:49
+   Parsing of 1441 .bb files complete (0 cached, 1441 parsed). 2055 targets, 56 skipped, 0 masked, 0 errors.
+   $ bitbake-layers show-layers
+   NOTE: Starting bitbake server...
+   layer                 path                                      priority
+   ==========================================================================
+   meta                  /home/scottrif/poky/meta                  5
+   meta-poky             /home/scottrif/poky/meta-poky             5
+   meta-yocto-bsp        /home/scottrif/poky/meta-yocto-bsp        5
+   workspace             /home/scottrif/poky/build/workspace       99
+   meta-scottrif         /home/scottrif/poky/build/meta-scottrif   6
+Adding the layer to this file
+enables the build system to locate the layer during the build.
+.. note::
+   During a build, the OpenEmbedded build system looks in the layers
+   from the top of the list down to the bottom in that order.
+Customizing Images
+==================
+You can customize images to satisfy particular requirements. This
+section describes several methods and provides guidelines for each.
+Customizing Images Using ``local.conf``
+---------------------------------------
+Probably the easiest way to customize an image is to add a package by
+way of the ``local.conf`` configuration file. Because it is limited to
+local use, this method generally only allows you to add packages and is
+not as flexible as creating your own customized image. When you add
+packages using local variables this way, you need to realize that these
+variable changes are in effect for every build and consequently affect
+all images, which might not be what you require.
+To add a package to your image using the local configuration file, use
+the ``IMAGE_INSTALL`` variable with the ``_append`` operator:
+::
+   IMAGE_INSTALL_append = " strace"
+Use of the syntax is important -
+specifically, the space between the quote and the package name, which is
+``strace`` in this example. This space is required since the ``_append``
+operator does not add the space.
+Furthermore, you must use ``_append`` instead of the ``+=`` operator if
+you want to avoid ordering issues. The reason for this is because doing
+so unconditionally appends to the variable and avoids ordering problems
+due to the variable being set in image recipes and ``.bbclass`` files
+with operators like ``?=``. Using ``_append`` ensures the operation
+takes effect.
+As shown in its simplest use, ``IMAGE_INSTALL_append`` affects all
+images. It is possible to extend the syntax so that the variable applies
+to a specific image only. Here is an example:
+::
+   IMAGE_INSTALL_append_pn-core-image-minimal = " strace"
+This example adds ``strace`` to the ``core-image-minimal`` image only.
+You can add packages using a similar approach through the
+``CORE_IMAGE_EXTRA_INSTALL`` variable. If you use this variable, only
+``core-image-*`` images are affected.
+Customizing Images Using Custom ``IMAGE_FEATURES`` and ``EXTRA_IMAGE_FEATURES``
+-------------------------------------------------------------------------------
+Another method for customizing your image is to enable or disable
+high-level image features by using the
+:term:`IMAGE_FEATURES` and
+:term:`EXTRA_IMAGE_FEATURES`
+variables. Although the functions for both variables are nearly
+equivalent, best practices dictate using ``IMAGE_FEATURES`` from within
+a recipe and using ``EXTRA_IMAGE_FEATURES`` from within your
+``local.conf`` file, which is found in the
+:term:`Build Directory`.
+To understand how these features work, the best reference is
+``meta/classes/core-image.bbclass``. This class lists out the available
+``IMAGE_FEATURES`` of which most map to package groups while some, such
+as ``debug-tweaks`` and ``read-only-rootfs``, resolve as general
+configuration settings.
+In summary, the file looks at the contents of the ``IMAGE_FEATURES``
+variable and then maps or configures the feature accordingly. Based on
+this information, the build system automatically adds the appropriate
+packages or configurations to the
+:term:`IMAGE_INSTALL` variable.
+Effectively, you are enabling extra features by extending the class or
+creating a custom class for use with specialized image ``.bb`` files.
+Use the ``EXTRA_IMAGE_FEATURES`` variable from within your local
+configuration file. Using a separate area from which to enable features
+with this variable helps you avoid overwriting the features in the image
+recipe that are enabled with ``IMAGE_FEATURES``. The value of
+``EXTRA_IMAGE_FEATURES`` is added to ``IMAGE_FEATURES`` within
+``meta/conf/bitbake.conf``.
+To illustrate how you can use these variables to modify your image,
+consider an example that selects the SSH server. The Yocto Project ships
+with two SSH servers you can use with your images: Dropbear and OpenSSH.
+Dropbear is a minimal SSH server appropriate for resource-constrained
+environments, while OpenSSH is a well-known standard SSH server
+implementation. By default, the ``core-image-sato`` image is configured
+to use Dropbear. The ``core-image-full-cmdline`` and ``core-image-lsb``
+images both include OpenSSH. The ``core-image-minimal`` image does not
+contain an SSH server.
+You can customize your image and change these defaults. Edit the
+``IMAGE_FEATURES`` variable in your recipe or use the
+``EXTRA_IMAGE_FEATURES`` in your ``local.conf`` file so that it
+configures the image you are working with to include
+``ssh-server-dropbear`` or ``ssh-server-openssh``.
+.. note::
+   See the ":ref:`ref-manual/ref-features:image features`" section in the Yocto
+   Project Reference Manual for a complete list of image features that ship
+   with the Yocto Project.
+Customizing Images Using Custom .bb Files
+-----------------------------------------
+You can also customize an image by creating a custom recipe that defines
+additional software as part of the image. The following example shows
+the form for the two lines you need:
+::
+   IMAGE_INSTALL = "packagegroup-core-x11-base package1 package2"
+   inherit core-image
+Defining the software using a custom recipe gives you total control over
+the contents of the image. It is important to use the correct names of
+packages in the ``IMAGE_INSTALL`` variable. You must use the
+OpenEmbedded notation and not the Debian notation for the names (e.g.
+``glibc-dev`` instead of ``libc6-dev``).
+The other method for creating a custom image is to base it on an
+existing image. For example, if you want to create an image based on
+``core-image-sato`` but add the additional package ``strace`` to the
+image, copy the ``meta/recipes-sato/images/core-image-sato.bb`` to a new
+``.bb`` and add the following line to the end of the copy:
+::
+   IMAGE_INSTALL += "strace"
+Customizing Images Using Custom Package Groups
+----------------------------------------------
+For complex custom images, the best approach for customizing an image is
+to create a custom package group recipe that is used to build the image
+or images. A good example of a package group recipe is
+``meta/recipes-core/packagegroups/packagegroup-base.bb``.
+If you examine that recipe, you see that the ``PACKAGES`` variable lists
+the package group packages to produce. The ``inherit packagegroup``
+statement sets appropriate default values and automatically adds
+``-dev``, ``-dbg``, and ``-ptest`` complementary packages for each
+package specified in the ``PACKAGES`` statement.
+.. note::
+   The ``inherit packagegroup`` line should be located near the top of the
+   recipe, certainly before the ``PACKAGES`` statement.
+For each package you specify in ``PACKAGES``, you can use ``RDEPENDS``
+and ``RRECOMMENDS`` entries to provide a list of packages the parent
+task package should contain. You can see examples of these further down
+in the ``packagegroup-base.bb`` recipe.
+Here is a short, fabricated example showing the same basic pieces for a
+hypothetical packagegroup defined in ``packagegroup-custom.bb``, where
+the variable ``PN`` is the standard way to abbreviate the reference to
+the full packagegroup name ``packagegroup-custom``:
+::
+   DESCRIPTION = "My Custom Package Groups"
+   inherit packagegroup
+   PACKAGES = "\
+       ${PN}-apps \
+       ${PN}-tools \
+       "
+   RDEPENDS_${PN}-apps = "\
+       dropbear \
+       portmap \
+       psplash"
+   RDEPENDS_${PN}-tools = "\
+       oprofile \
+       oprofileui-server \
+       lttng-tools"
+   RRECOMMENDS_${PN}-tools = "\
+       kernel-module-oprofile"
+In the previous example, two package group packages are created with
+their dependencies and their recommended package dependencies listed:
+``packagegroup-custom-apps``, and ``packagegroup-custom-tools``. To
+build an image using these package group packages, you need to add
+``packagegroup-custom-apps`` and/or ``packagegroup-custom-tools`` to
+``IMAGE_INSTALL``. For other forms of image dependencies see the other
+areas of this section.
+Customizing an Image Hostname
+-----------------------------
+By default, the configured hostname (i.e. ``/etc/hostname``) in an image
+is the same as the machine name. For example, if
+:term:`MACHINE` equals "qemux86", the
+configured hostname written to ``/etc/hostname`` is "qemux86".
+You can customize this name by altering the value of the "hostname"
+variable in the ``base-files`` recipe using either an append file or a
+configuration file. Use the following in an append file:
+::
+   hostname = "myhostname"
+Use the following in a configuration file:
+::
+   hostname_pn-base-files = "myhostname"
+Changing the default value of the variable "hostname" can be useful in
+certain situations. For example, suppose you need to do extensive
+testing on an image and you would like to easily identify the image
+under test from existing images with typical default hostnames. In this
+situation, you could change the default hostname to "testme", which
+results in all the images using the name "testme". Once testing is
+complete and you do not need to rebuild the image for test any longer,
+you can easily reset the default hostname.
+Another point of interest is that if you unset the variable, the image
+will have no default hostname in the filesystem. Here is an example that
+unsets the variable in a configuration file:
+::
+  hostname_pn-base-files = ""
+Having no default hostname in the filesystem is suitable for
+environments that use dynamic hostnames such as virtual machines.
+Writing a New Recipe
+====================
+Recipes (``.bb`` files) are fundamental components in the Yocto Project
+environment. Each software component built by the OpenEmbedded build
+system requires a recipe to define the component. This section describes
+how to create, write, and test a new recipe.
+.. note::
+   For information on variables that are useful for recipes and for
+   information about recipe naming issues, see the
+   ":ref:`ref-manual/ref-varlocality:recipes`" section of the Yocto Project
+   Reference Manual.
+Overview
+--------
+The following figure shows the basic process for creating a new recipe.
+The remainder of the section provides details for the steps.
+.. image:: figures/recipe-workflow.png
+   :align: center
+Locate or Automatically Create a Base Recipe
+--------------------------------------------
+You can always write a recipe from scratch. However, three choices exist
+that can help you quickly get a start on a new recipe:
+-  ``devtool add``: A command that assists in creating a recipe and an
+   environment conducive to development.
+-  ``recipetool create``: A command provided by the Yocto Project that
+   automates creation of a base recipe based on the source files.
+-  *Existing Recipes:* Location and modification of an existing recipe
+   that is similar in function to the recipe you need.
+.. note::
+   For information on recipe syntax, see the
+   ":ref:`dev-manual/common-tasks:recipe syntax`" section.
+Creating the Base Recipe Using ``devtool add``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The ``devtool add`` command uses the same logic for auto-creating the
+recipe as ``recipetool create``, which is listed below. Additionally,
+however, ``devtool add`` sets up an environment that makes it easy for
+you to patch the source and to make changes to the recipe as is often
+necessary when adding a recipe to build a new piece of software to be
+included in a build.
+You can find a complete description of the ``devtool add`` command in
+the ":ref:`sdk-manual/sdk-extensible:a closer look at \`\`devtool add\`\``" section
+in the Yocto Project Application Development and the Extensible Software
+Development Kit (eSDK) manual.
+Creating the Base Recipe Using ``recipetool create``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+``recipetool create`` automates creation of a base recipe given a set of
+source code files. As long as you can extract or point to the source
+files, the tool will construct a recipe and automatically configure all
+pre-build information into the recipe. For example, suppose you have an
+application that builds using Autotools. Creating the base recipe using
+``recipetool`` results in a recipe that has the pre-build dependencies,
+license requirements, and checksums configured.
+To run the tool, you just need to be in your
+:term:`Build Directory` and have sourced the
+build environment setup script (i.e.
+:ref:`structure-core-script`).
+To get help on the tool, use the following command:
+::
+   $ recipetool -h
+   NOTE: Starting bitbake server...
+   usage: recipetool [-d] [-q] [--color COLOR] [-h] <subcommand> ...
+   OpenEmbedded recipe tool
+   options:
+     -d, --debug     Enable debug output
+     -q, --quiet     Print only errors
+     --color COLOR   Colorize output (where COLOR is auto, always, never)
+     -h, --help      show this help message and exit
+   subcommands:
+     create          Create a new recipe
+     newappend       Create a bbappend for the specified target in the specified
+                       layer
+     setvar          Set a variable within a recipe
+     appendfile      Create/update a bbappend to replace a target file
+     appendsrcfiles  Create/update a bbappend to add or replace source files
+     appendsrcfile   Create/update a bbappend to add or replace a source file
+   Use recipetool <subcommand> --help to get help on a specific command
+Running ``recipetool create -o OUTFILE`` creates the base recipe and
+locates it properly in the layer that contains your source files.
+Following are some syntax examples:
+ - Use this syntax to generate a recipe based on source. Once generated,
+   the recipe resides in the existing source code layer:
+   ::
+      recipetool create -o OUTFILE source
+ - Use this syntax to generate a recipe using code that
+   you extract from source. The extracted code is placed in its own layer
+   defined by ``EXTERNALSRC``.
+   ::
+      recipetool create -o OUTFILE -x EXTERNALSRC source
+ - Use this syntax to generate a recipe based on source. The options
+   direct ``recipetool`` to generate debugging information. Once generated,
+   the recipe resides in the existing source code layer:
+   ::
+      recipetool create -d -o OUTFILE source
+Locating and Using a Similar Recipe
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Before writing a recipe from scratch, it is often useful to discover
+whether someone else has already written one that meets (or comes close
+to meeting) your needs. The Yocto Project and OpenEmbedded communities
+maintain many recipes that might be candidates for what you are doing.
+You can find a good central index of these recipes in the `OpenEmbedded
+Layer Index <https://layers.openembedded.org>`__.
+Working from an existing recipe or a skeleton recipe is the best way to
+get started. Here are some points on both methods:
+-  *Locate and modify a recipe that is close to what you want to do:*
+   This method works when you are familiar with the current recipe
+   space. The method does not work so well for those new to the Yocto
+   Project or writing recipes.
+   Some risks associated with this method are using a recipe that has
+   areas totally unrelated to what you are trying to accomplish with
+   your recipe, not recognizing areas of the recipe that you might have
+   to add from scratch, and so forth. All these risks stem from
+   unfamiliarity with the existing recipe space.
+-  *Use and modify the following skeleton recipe:* If for some reason
+   you do not want to use ``recipetool`` and you cannot find an existing
+   recipe that is close to meeting your needs, you can use the following
+   structure to provide the fundamental areas of a new recipe.
+   ::
+      DESCRIPTION = ""
+      HOMEPAGE = ""
+      LICENSE = ""
+      SECTION = ""
+      DEPENDS = ""
+      LIC_FILES_CHKSUM = ""
+      SRC_URI = ""
+Storing and Naming the Recipe
+-----------------------------
+Once you have your base recipe, you should put it in your own layer and
+name it appropriately. Locating it correctly ensures that the
+OpenEmbedded build system can find it when you use BitBake to process
+the recipe.
+-  *Storing Your Recipe:* The OpenEmbedded build system locates your
+   recipe through the layer's ``conf/layer.conf`` file and the
+   :term:`BBFILES` variable. This
+   variable sets up a path from which the build system can locate
+   recipes. Here is the typical use:
+   ::
+      BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
+                  ${LAYERDIR}/recipes-*/*/*.bbappend"
+   Consequently, you need to be sure you locate your new recipe inside
+   your layer such that it can be found.
+   You can find more information on how layers are structured in the
+   "`Understanding and Creating
+   Layers <#understanding-and-creating-layers>`__" section.
+-  *Naming Your Recipe:* When you name your recipe, you need to follow
+   this naming convention:
+   ::
+      basename_version.bb
+   Use lower-cased characters and do not include the reserved suffixes
+   ``-native``, ``-cross``, ``-initial``, or ``-dev`` casually (i.e. do not use
+   them as part of your recipe name unless the string applies). Here are some
+   examples:
+   .. code-block:: none
+      cups_1.7.0.bb
+      gawk_4.0.2.bb
+      irssi_0.8.16-rc1.bb
+Running a Build on the Recipe
+-----------------------------
+Creating a new recipe is usually an iterative process that requires
+using BitBake to process the recipe multiple times in order to
+progressively discover and add information to the recipe file.
+Assuming you have sourced the build environment setup script (i.e.
+:ref:`structure-core-script`) and you are in
+the :term:`Build Directory`, use
+BitBake to process your recipe. All you need to provide is the
+``basename`` of the recipe as described in the previous section:
+::
+   $ bitbake basename
+During the build, the OpenEmbedded build system creates a temporary work
+directory for each recipe
+(``${``\ :term:`WORKDIR`\ ``}``)
+where it keeps extracted source files, log files, intermediate
+compilation and packaging files, and so forth.
+The path to the per-recipe temporary work directory depends on the
+context in which it is being built. The quickest way to find this path
+is to have BitBake return it by running the following:
+::
+   $ bitbake -e basename | grep ^WORKDIR=
+As an example, assume a Source Directory
+top-level folder named ``poky``, a default Build Directory at
+``poky/build``, and a ``qemux86-poky-linux`` machine target system.
+Furthermore, suppose your recipe is named ``foo_1.3.0.bb``. In this
+case, the work directory the build system uses to build the package
+would be as follows:
+::
+   poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0
+Inside this directory you can find sub-directories such as ``image``,
+``packages-split``, and ``temp``. After the build, you can examine these
+to determine how well the build went.
+.. note::
+   You can find log files for each task in the recipe's ``temp``
+   directory (e.g. ``poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0/temp``).
+   Log files are named ``log.taskname`` (e.g. ``log.do_configure``,
+   ``log.do_fetch``, and ``log.do_compile``).
+You can find more information about the build process in
+":doc:`/overview-manual/overview-manual-development-environment`"
+chapter of the Yocto Project Overview and Concepts Manual.
+Fetching Code
+-------------
+The first thing your recipe must do is specify how to fetch the source
+files. Fetching is controlled mainly through the
+:term:`SRC_URI` variable. Your recipe
+must have a ``SRC_URI`` variable that points to where the source is
+located. For a graphical representation of source locations, see the
+":ref:`overview-manual/overview-manual-concepts:sources`" section in
+the Yocto Project Overview and Concepts Manual.
+The :ref:`ref-tasks-fetch` task uses
+the prefix of each entry in the ``SRC_URI`` variable value to determine
+which :ref:`fetcher <bitbake:bitbake-user-manual/bitbake-user-manual-fetching:fetchers>` to use to get your
+source files. It is the ``SRC_URI`` variable that triggers the fetcher.
+The :ref:`ref-tasks-patch` task uses
+the variable after source is fetched to apply patches. The OpenEmbedded
+build system uses
+:term:`FILESOVERRIDES` for
+scanning directory locations for local files in ``SRC_URI``.
+The ``SRC_URI`` variable in your recipe must define each unique location
+for your source files. It is good practice to not hard-code version
+numbers in a URL used in ``SRC_URI``. Rather than hard-code these
+values, use ``${``\ :term:`PV`\ ``}``,
+which causes the fetch process to use the version specified in the
+recipe filename. Specifying the version in this manner means that
+upgrading the recipe to a future version is as simple as renaming the
+recipe to match the new version.
+Here is a simple example from the
+``meta/recipes-devtools/strace/strace_5.5.bb`` recipe where the source
+comes from a single tarball. Notice the use of the
+:term:`PV` variable:
+::
+   SRC_URI = "https://strace.io/files/${PV}/strace-${PV}.tar.xz \
+Files mentioned in ``SRC_URI`` whose names end in a typical archive
+extension (e.g. ``.tar``, ``.tar.gz``, ``.tar.bz2``, ``.zip``, and so
+forth), are automatically extracted during the
+:ref:`ref-tasks-unpack` task. For
+another example that specifies these types of files, see the
+"`Autotooled Package <#new-recipe-autotooled-package>`__" section.
+Another way of specifying source is from an SCM. For Git repositories,
+you must specify :term:`SRCREV` and
+you should specify :term:`PV` to include
+the revision with :term:`SRCPV`. Here
+is an example from the recipe
+``meta/recipes-kernel/blktrace/blktrace_git.bb``:
+::
+   SRCREV = "d6918c8832793b4205ed3bfede78c2f915c23385"
+   PR = "r6"
+   PV = "1.0.5+git${SRCPV}"
+   SRC_URI = "git://git.kernel.dk/blktrace.git \
+              file://ldflags.patch"
+If your ``SRC_URI`` statement includes URLs pointing to individual files
+fetched from a remote server other than a version control system,
+BitBake attempts to verify the files against checksums defined in your
+recipe to ensure they have not been tampered with or otherwise modified
+since the recipe was written. Two checksums are used:
+``SRC_URI[md5sum]`` and ``SRC_URI[sha256sum]``.
+If your ``SRC_URI`` variable points to more than a single URL (excluding
+SCM URLs), you need to provide the ``md5`` and ``sha256`` checksums for
+each URL. For these cases, you provide a name for each URL as part of
+the ``SRC_URI`` and then reference that name in the subsequent checksum
+statements. Here is an example combining lines from the files
+``git.inc`` and ``git_2.24.1.bb``:
+::
+   SRC_URI = "${KERNELORG_MIRROR}/software/scm/git/git-${PV}.tar.gz;name=tarball \
+              ${KERNELORG_MIRROR}/software/scm/git/git-manpages-${PV}.tar.gz;name=manpages"
+   SRC_URI[tarball.md5sum] = "166bde96adbbc11c8843d4f8f4f9811b"
+   SRC_URI[tarball.sha256sum] = "ad5334956301c86841eb1e5b1bb20884a6bad89a10a6762c958220c7cf64da02"
+   SRC_URI[manpages.md5sum] = "31c2272a8979022497ba3d4202df145d"
+   SRC_URI[manpages.sha256sum] = "9a7ae3a093bea39770eb96ca3e5b40bff7af0b9f6123f089d7821d0e5b8e1230"
+Proper values for ``md5`` and ``sha256`` checksums might be available
+with other signatures on the download page for the upstream source (e.g.
+``md5``, ``sha1``, ``sha256``, ``GPG``, and so forth). Because the
+OpenEmbedded build system only deals with ``sha256sum`` and ``md5sum``,
+you should verify all the signatures you find by hand.
+If no ``SRC_URI`` checksums are specified when you attempt to build the
+recipe, or you provide an incorrect checksum, the build will produce an
+error for each missing or incorrect checksum. As part of the error
+message, the build system provides the checksum string corresponding to
+the fetched file. Once you have the correct checksums, you can copy and
+paste them into your recipe and then run the build again to continue.
+.. note::
+   As mentioned, if the upstream source provides signatures for
+   verifying the downloaded source code, you should verify those
+   manually before setting the checksum values in the recipe and
+   continuing with the build.
+This final example is a bit more complicated and is from the
+``meta/recipes-sato/rxvt-unicode/rxvt-unicode_9.20.bb`` recipe. The
+example's ``SRC_URI`` statement identifies multiple files as the source
+files for the recipe: a tarball, a patch file, a desktop file, and an
+icon.
+::
+   SRC_URI = "http://dist.schmorp.de/rxvt-unicode/Attic/rxvt-unicode-${PV}.tar.bz2 \
+              file://xwc.patch \
+              file://rxvt.desktop \
+              file://rxvt.png"
+When you specify local files using the ``file://`` URI protocol, the
+build system fetches files from the local machine. The path is relative
+to the :term:`FILESPATH` variable
+and searches specific directories in a certain order:
+``${``\ :term:`BP`\ ``}``,
+``${``\ :term:`BPN`\ ``}``, and
+``files``. The directories are assumed to be subdirectories of the
+directory in which the recipe or append file resides. For another
+example that specifies these types of files, see the "`Single .c File
+Package (Hello
+World!) <#new-recipe-single-c-file-package-hello-world>`__" section.
+The previous example also specifies a patch file. Patch files are files
+whose names usually end in ``.patch`` or ``.diff`` but can end with
+compressed suffixes such as ``diff.gz`` and ``patch.bz2``, for example.
+The build system automatically applies patches as described in the
+"`Patching Code <#new-recipe-patching-code>`__" section.
+Unpacking Code
+--------------
+During the build, the
+:ref:`ref-tasks-unpack` task unpacks
+the source with ``${``\ :term:`S`\ ``}``
+pointing to where it is unpacked.
+If you are fetching your source files from an upstream source archived
+tarball and the tarball's internal structure matches the common
+convention of a top-level subdirectory named
+``${``\ :term:`BPN`\ ``}-${``\ :term:`PV`\ ``}``,
+then you do not need to set ``S``. However, if ``SRC_URI`` specifies to
+fetch source from an archive that does not use this convention, or from
+an SCM like Git or Subversion, your recipe needs to define ``S``.
+If processing your recipe using BitBake successfully unpacks the source
+files, you need to be sure that the directory pointed to by ``${S}``
+matches the structure of the source.
+Patching Code
+-------------
+Sometimes it is necessary to patch code after it has been fetched. Any
+files mentioned in ``SRC_URI`` whose names end in ``.patch`` or
+``.diff`` or compressed versions of these suffixes (e.g. ``diff.gz`` are
+treated as patches. The
+:ref:`ref-tasks-patch` task
+automatically applies these patches.
+The build system should be able to apply patches with the "-p1" option
+(i.e. one directory level in the path will be stripped off). If your
+patch needs to have more directory levels stripped off, specify the
+number of levels using the "striplevel" option in the ``SRC_URI`` entry
+for the patch. Alternatively, if your patch needs to be applied in a
+specific subdirectory that is not specified in the patch file, use the
+"patchdir" option in the entry.
+As with all local files referenced in
+:term:`SRC_URI` using ``file://``,
+you should place patch files in a directory next to the recipe either
+named the same as the base name of the recipe
+(:term:`BP` and
+:term:`BPN`) or "files".
+Licensing
+---------
+Your recipe needs to have both the
+:term:`LICENSE` and
+:term:`LIC_FILES_CHKSUM`
+variables:
+-  ``LICENSE``: This variable specifies the license for the software.
+   If you do not know the license under which the software you are
+   building is distributed, you should go to the source code and look
+   for that information. Typical files containing this information
+   include ``COPYING``, ``LICENSE``, and ``README`` files. You could
+   also find the information near the top of a source file. For example,
+   given a piece of software licensed under the GNU General Public
+   License version 2, you would set ``LICENSE`` as follows:
+   ::
+      LICENSE = "GPLv2"
+   The licenses you specify within ``LICENSE`` can have any name as long
+   as you do not use spaces, since spaces are used as separators between
+   license names. For standard licenses, use the names of the files in
+   ``meta/files/common-licenses/`` or the ``SPDXLICENSEMAP`` flag names
+   defined in ``meta/conf/licenses.conf``.
+-  ``LIC_FILES_CHKSUM``: The OpenEmbedded build system uses this
+   variable to make sure the license text has not changed. If it has,
+   the build produces an error and it affords you the chance to figure
+   it out and correct the problem.
+   You need to specify all applicable licensing files for the software.
+   At the end of the configuration step, the build process will compare
+   the checksums of the files to be sure the text has not changed. Any
+   differences result in an error with the message containing the
+   current checksum. For more explanation and examples of how to set the
+   ``LIC_FILES_CHKSUM`` variable, see the
+   ":ref:`dev-manual/common-tasks:tracking license changes`" section.
+   To determine the correct checksum string, you can list the
+   appropriate files in the ``LIC_FILES_CHKSUM`` variable with incorrect
+   md5 strings, attempt to build the software, and then note the
+   resulting error messages that will report the correct md5 strings.
+   See the "`Fetching Code <#new-recipe-fetching-code>`__" section for
+   additional information.
+   Here is an example that assumes the software has a ``COPYING`` file:
+   ::
+      LIC_FILES_CHKSUM = "file://COPYING;md5=xxx"
+   When you try to build the
+   software, the build system will produce an error and give you the
+   correct string that you can substitute into the recipe file for a
+   subsequent build.
+Dependencies
+------------
+Most software packages have a short list of other packages that they
+require, which are called dependencies. These dependencies fall into two
+main categories: build-time dependencies, which are required when the
+software is built; and runtime dependencies, which are required to be
+installed on the target in order for the software to run.
+Within a recipe, you specify build-time dependencies using the
+:term:`DEPENDS` variable. Although
+nuances exist, items specified in ``DEPENDS`` should be names of other
+recipes. It is important that you specify all build-time dependencies
+explicitly.
+Another consideration is that configure scripts might automatically
+check for optional dependencies and enable corresponding functionality
+if those dependencies are found. If you wish to make a recipe that is
+more generally useful (e.g. publish the recipe in a layer for others to
+use), instead of hard-disabling the functionality, you can use the
+:term:`PACKAGECONFIG` variable to allow functionality and the
+corresponding dependencies to be enabled and disabled easily by other
+users of the recipe.
+Similar to build-time dependencies, you specify runtime dependencies
+through a variable -
+:term:`RDEPENDS`, which is
+package-specific. All variables that are package-specific need to have
+the name of the package added to the end as an override. Since the main
+package for a recipe has the same name as the recipe, and the recipe's
+name can be found through the
+``${``\ :term:`PN`\ ``}`` variable, then
+you specify the dependencies for the main package by setting
+``RDEPENDS_${PN}``. If the package were named ``${PN}-tools``, then you
+would set ``RDEPENDS_${PN}-tools``, and so forth.
+Some runtime dependencies will be set automatically at packaging time.
+These dependencies include any shared library dependencies (i.e. if a
+package "example" contains "libexample" and another package "mypackage"
+contains a binary that links to "libexample" then the OpenEmbedded build
+system will automatically add a runtime dependency to "mypackage" on
+"example"). See the
+":ref:`overview-manual/overview-manual-concepts:automatically added runtime dependencies`"
+section in the Yocto Project Overview and Concepts Manual for further
+details.
+Configuring the Recipe
+----------------------
+Most software provides some means of setting build-time configuration
+options before compilation. Typically, setting these options is
+accomplished by running a configure script with options, or by modifying
+a build configuration file.
+.. note::
+   As of Yocto Project Release 1.7, some of the core recipes that
+   package binary configuration scripts now disable the scripts due to
+   the scripts previously requiring error-prone path substitution. The
+   OpenEmbedded build system uses ``pkg-config`` now, which is much more
+   robust. You can find a list of the ``*-config`` scripts that are disabled
+   in the ":ref:`migration-1.7-binary-configuration-scripts-disabled`" section
+   in the Yocto Project Reference Manual.
+A major part of build-time configuration is about checking for
+build-time dependencies and possibly enabling optional functionality as
+a result. You need to specify any build-time dependencies for the
+software you are building in your recipe's
+:term:`DEPENDS` value, in terms of
+other recipes that satisfy those dependencies. You can often find
+build-time or runtime dependencies described in the software's
+documentation.
+The following list provides configuration items of note based on how
+your software is built:
+-  *Autotools:* If your source files have a ``configure.ac`` file, then
+   your software is built using Autotools. If this is the case, you just
+   need to worry about modifying the configuration.
+   When using Autotools, your recipe needs to inherit the
+   :ref:`autotools <ref-classes-autotools>` class
+   and your recipe does not have to contain a
+   :ref:`ref-tasks-configure` task.
+   However, you might still want to make some adjustments. For example,
+   you can set
+   :term:`EXTRA_OECONF` or
+   :term:`PACKAGECONFIG_CONFARGS`
+   to pass any needed configure options that are specific to the recipe.
+-  *CMake:* If your source files have a ``CMakeLists.txt`` file, then
+   your software is built using CMake. If this is the case, you just
+   need to worry about modifying the configuration.
+   When you use CMake, your recipe needs to inherit the
+   :ref:`cmake <ref-classes-cmake>` class and your
+   recipe does not have to contain a
+   :ref:`ref-tasks-configure` task.
+   You can make some adjustments by setting
+   :term:`EXTRA_OECMAKE` to
+   pass any needed configure options that are specific to the recipe.
+   .. note::
+      If you need to install one or more custom CMake toolchain files
+      that are supplied by the application you are building, install the
+      files to ``${D}${datadir}/cmake/Modules`` during ``do_install``.
+-  *Other:* If your source files do not have a ``configure.ac`` or
+   ``CMakeLists.txt`` file, then your software is built using some
+   method other than Autotools or CMake. If this is the case, you
+   normally need to provide a
+   :ref:`ref-tasks-configure` task
+   in your recipe unless, of course, there is nothing to configure.
+   Even if your software is not being built by Autotools or CMake, you
+   still might not need to deal with any configuration issues. You need
+   to determine if configuration is even a required step. You might need
+   to modify a Makefile or some configuration file used for the build to
+   specify necessary build options. Or, perhaps you might need to run a
+   provided, custom configure script with the appropriate options.
+   For the case involving a custom configure script, you would run
+   ``./configure --help`` and look for the options you need to set.
+Once configuration succeeds, it is always good practice to look at the
+``log.do_configure`` file to ensure that the appropriate options have
+been enabled and no additional build-time dependencies need to be added
+to ``DEPENDS``. For example, if the configure script reports that it
+found something not mentioned in ``DEPENDS``, or that it did not find
+something that it needed for some desired optional functionality, then
+you would need to add those to ``DEPENDS``. Looking at the log might
+also reveal items being checked for, enabled, or both that you do not
+want, or items not being found that are in ``DEPENDS``, in which case
+you would need to look at passing extra options to the configure script
+as needed. For reference information on configure options specific to
+the software you are building, you can consult the output of the
+``./configure --help`` command within ``${S}`` or consult the software's
+upstream documentation.
+Using Headers to Interface with Devices
+---------------------------------------
+If your recipe builds an application that needs to communicate with some
+device or needs an API into a custom kernel, you will need to provide
+appropriate header files. Under no circumstances should you ever modify
+the existing
+``meta/recipes-kernel/linux-libc-headers/linux-libc-headers.inc`` file.
+These headers are used to build ``libc`` and must not be compromised
+with custom or machine-specific header information. If you customize
+``libc`` through modified headers all other applications that use
+``libc`` thus become affected.
+.. note::
+   Never copy and customize the ``libc`` header file (i.e.
+   ``meta/recipes-kernel/linux-libc-headers/linux-libc-headers.inc``).
+The correct way to interface to a device or custom kernel is to use a
+separate package that provides the additional headers for the driver or
+other unique interfaces. When doing so, your application also becomes
+responsible for creating a dependency on that specific provider.
+Consider the following:
+-  Never modify ``linux-libc-headers.inc``. Consider that file to be
+   part of the ``libc`` system, and not something you use to access the
+   kernel directly. You should access ``libc`` through specific ``libc``
+   calls.
+-  Applications that must talk directly to devices should either provide
+   necessary headers themselves, or establish a dependency on a special
+   headers package that is specific to that driver.
+For example, suppose you want to modify an existing header that adds I/O
+control or network support. If the modifications are used by a small
+number programs, providing a unique version of a header is easy and has
+little impact. When doing so, bear in mind the guidelines in the
+previous list.
+.. note::
+   If for some reason your changes need to modify the behavior of the ``libc``,
+   and subsequently all other applications on the system, use a ``.bbappend``
+   to modify the ``linux-kernel-headers.inc`` file. However, take care to not
+   make the changes machine specific.
+Consider a case where your kernel is older and you need an older
+``libc`` ABI. The headers installed by your recipe should still be a
+standard mainline kernel, not your own custom one.
+When you use custom kernel headers you need to get them from
+:term:`STAGING_KERNEL_DIR`,
+which is the directory with kernel headers that are required to build
+out-of-tree modules. Your recipe will also need the following:
+::
+   do_configure[depends] += "virtual/kernel:do_shared_workdir"
+Compilation
+-----------
+During a build, the ``do_compile`` task happens after source is fetched,
+unpacked, and configured. If the recipe passes through ``do_compile``
+successfully, nothing needs to be done.
+However, if the compile step fails, you need to diagnose the failure.
+Here are some common issues that cause failures.
+.. note::
+   For cases where improper paths are detected for configuration files
+   or for when libraries/headers cannot be found, be sure you are using
+   the more robust ``pkg-config``. See the note in section
+   ":ref:`dev-manual/common-tasks:Configuring the Recipe`" for additional information.
+-  *Parallel build failures:* These failures manifest themselves as
+   intermittent errors, or errors reporting that a file or directory
+   that should be created by some other part of the build process could
+   not be found. This type of failure can occur even if, upon
+   inspection, the file or directory does exist after the build has
+   failed, because that part of the build process happened in the wrong
+   order.
+   To fix the problem, you need to either satisfy the missing dependency
+   in the Makefile or whatever script produced the Makefile, or (as a
+   workaround) set :term:`PARALLEL_MAKE` to an empty string:
+   ::
+      PARALLEL_MAKE = ""
+   For information on parallel Makefile issues, see the "`Debugging
+   Parallel Make Races <#debugging-parallel-make-races>`__" section.
+-  *Improper host path usage:* This failure applies to recipes building
+   for the target or ``nativesdk`` only. The failure occurs when the
+   compilation process uses improper headers, libraries, or other files
+   from the host system when cross-compiling for the target.
+   To fix the problem, examine the ``log.do_compile`` file to identify
+   the host paths being used (e.g. ``/usr/include``, ``/usr/lib``, and
+   so forth) and then either add configure options, apply a patch, or do
+   both.
+-  *Failure to find required libraries/headers:* If a build-time
+   dependency is missing because it has not been declared in
+   :term:`DEPENDS`, or because the
+   dependency exists but the path used by the build process to find the
+   file is incorrect and the configure step did not detect it, the
+   compilation process could fail. For either of these failures, the
+   compilation process notes that files could not be found. In these
+   cases, you need to go back and add additional options to the
+   configure script as well as possibly add additional build-time
+   dependencies to ``DEPENDS``.
+   Occasionally, it is necessary to apply a patch to the source to
+   ensure the correct paths are used. If you need to specify paths to
+   find files staged into the sysroot from other recipes, use the
+   variables that the OpenEmbedded build system provides (e.g.
+   ``STAGING_BINDIR``, ``STAGING_INCDIR``, ``STAGING_DATADIR``, and so
+   forth).
+Installing
+----------
+During ``do_install``, the task copies the built files along with their
+hierarchy to locations that would mirror their locations on the target
+device. The installation process copies files from the
+``${``\ :term:`S`\ ``}``,
+``${``\ :term:`B`\ ``}``, and
+``${``\ :term:`WORKDIR`\ ``}``
+directories to the ``${``\ :term:`D`\ ``}``
+directory to create the structure as it should appear on the target
+system.
+How your software is built affects what you must do to be sure your
+software is installed correctly. The following list describes what you
+must do for installation depending on the type of build system used by
+the software being built:
+-  *Autotools and CMake:* If the software your recipe is building uses
+   Autotools or CMake, the OpenEmbedded build system understands how to
+   install the software. Consequently, you do not have to have a
+   ``do_install`` task as part of your recipe. You just need to make
+   sure the install portion of the build completes with no issues.
+   However, if you wish to install additional files not already being
+   installed by ``make install``, you should do this using a
+   ``do_install_append`` function using the install command as described
+   in the "Manual" bulleted item later in this list.
+-  *Other (using* ``make install``\ *)*: You need to define a ``do_install``
+   function in your recipe. The function should call
+   ``oe_runmake install`` and will likely need to pass in the
+   destination directory as well. How you pass that path is dependent on
+   how the ``Makefile`` being run is written (e.g. ``DESTDIR=${D}``,
+   ``PREFIX=${D}``, ``INSTALLROOT=${D}``, and so forth).
+   For an example recipe using ``make install``, see the
+   "`Makefile-Based Package <#new-recipe-makefile-based-package>`__"
+   section.
+-  *Manual:* You need to define a ``do_install`` function in your
+   recipe. The function must first use ``install -d`` to create the
+   directories under
+   ``${``\ :term:`D`\ ``}``. Once the
+   directories exist, your function can use ``install`` to manually
+   install the built software into the directories.
+   You can find more information on ``install`` at
+   https://www.gnu.org/software/coreutils/manual/html_node/install-invocation.html.
+For the scenarios that do not use Autotools or CMake, you need to track
+the installation and diagnose and fix any issues until everything
+installs correctly. You need to look in the default location of
+``${D}``, which is ``${WORKDIR}/image``, to be sure your files have been
+installed correctly.
+.. note::
+   -  During the installation process, you might need to modify some of
+      the installed files to suit the target layout. For example, you
+      might need to replace hard-coded paths in an initscript with
+      values of variables provided by the build system, such as
+      replacing ``/usr/bin/`` with ``${bindir}``. If you do perform such
+      modifications during ``do_install``, be sure to modify the
+      destination file after copying rather than before copying.
+      Modifying after copying ensures that the build system can
+      re-execute ``do_install`` if needed.
+   -  ``oe_runmake install``, which can be run directly or can be run
+      indirectly by the
+      :ref:`autotools <ref-classes-autotools>` and
+      :ref:`cmake <ref-classes-cmake>` classes,
+      runs ``make install`` in parallel. Sometimes, a Makefile can have
+      missing dependencies between targets that can result in race
+      conditions. If you experience intermittent failures during
+      ``do_install``, you might be able to work around them by disabling
+      parallel Makefile installs by adding the following to the recipe:
+      ::
+         PARALLEL_MAKEINST = ""
+      See :term:`PARALLEL_MAKEINST` for additional information.
+   -  If you need to install one or more custom CMake toolchain files
+      that are supplied by the application you are building, install the
+      files to ``${D}${datadir}/cmake/Modules`` during
+      :ref:`ref-tasks-install`.
+Enabling System Services
+------------------------
+If you want to install a service, which is a process that usually starts
+on boot and runs in the background, then you must include some
+additional definitions in your recipe.
+If you are adding services and the service initialization script or the
+service file itself is not installed, you must provide for that
+installation in your recipe using a ``do_install_append`` function. If
+your recipe already has a ``do_install`` function, update the function
+near its end rather than adding an additional ``do_install_append``
+function.
+When you create the installation for your services, you need to
+accomplish what is normally done by ``make install``. In other words,
+make sure your installation arranges the output similar to how it is
+arranged on the target system.
+The OpenEmbedded build system provides support for starting services two
+different ways:
+-  *SysVinit:* SysVinit is a system and service manager that manages the
+   init system used to control the very basic functions of your system.
+   The init program is the first program started by the Linux kernel
+   when the system boots. Init then controls the startup, running and
+   shutdown of all other programs.
+   To enable a service using SysVinit, your recipe needs to inherit the
+   :ref:`update-rc.d <ref-classes-update-rc.d>`
+   class. The class helps facilitate safely installing the package on
+   the target.
+   You will need to set the
+   :term:`INITSCRIPT_PACKAGES`,
+   :term:`INITSCRIPT_NAME`,
+   and
+   :term:`INITSCRIPT_PARAMS`
+   variables within your recipe.
+-  *systemd:* System Management Daemon (systemd) was designed to replace
+   SysVinit and to provide enhanced management of services. For more
+   information on systemd, see the systemd homepage at
+   https://freedesktop.org/wiki/Software/systemd/.
+   To enable a service using systemd, your recipe needs to inherit the
+   :ref:`systemd <ref-classes-systemd>` class. See
+   the ``systemd.bbclass`` file located in your :term:`Source Directory`
+   section for
+   more information.
+Packaging
+---------
+Successful packaging is a combination of automated processes performed
+by the OpenEmbedded build system and some specific steps you need to
+take. The following list describes the process:
+-  *Splitting Files*: The ``do_package`` task splits the files produced
+   by the recipe into logical components. Even software that produces a
+   single binary might still have debug symbols, documentation, and
+   other logical components that should be split out. The ``do_package``
+   task ensures that files are split up and packaged correctly.
+-  *Running QA Checks*: The
+   :ref:`insane <ref-classes-insane>` class adds a
+   step to the package generation process so that output quality
+   assurance checks are generated by the OpenEmbedded build system. This
+   step performs a range of checks to be sure the build's output is free
+   of common problems that show up during runtime. For information on
+   these checks, see the
+   :ref:`insane <ref-classes-insane>` class and
+   the ":ref:`ref-manual/ref-qa-checks:qa error and warning messages`"
+   chapter in the Yocto Project Reference Manual.
+-  *Hand-Checking Your Packages*: After you build your software, you
+   need to be sure your packages are correct. Examine the
+   ``${``\ :term:`WORKDIR`\ ``}/packages-split``
+   directory and make sure files are where you expect them to be. If you
+   discover problems, you can set
+   :term:`PACKAGES`,
+   :term:`FILES`,
+   ``do_install(_append)``, and so forth as needed.
+-  *Splitting an Application into Multiple Packages*: If you need to
+   split an application into several packages, see the "`Splitting an
+   Application into Multiple
+   Packages <#splitting-an-application-into-multiple-packages>`__"
+   section for an example.
+-  *Installing a Post-Installation Script*: For an example showing how
+   to install a post-installation script, see the "`Post-Installation
+   Scripts <#new-recipe-post-installation-scripts>`__" section.
+-  *Marking Package Architecture*: Depending on what your recipe is
+   building and how it is configured, it might be important to mark the
+   packages produced as being specific to a particular machine, or to
+   mark them as not being specific to a particular machine or
+   architecture at all.
+   By default, packages apply to any machine with the same architecture
+   as the target machine. When a recipe produces packages that are
+   machine-specific (e.g. the
+   :term:`MACHINE` value is passed
+   into the configure script or a patch is applied only for a particular
+   machine), you should mark them as such by adding the following to the
+   recipe:
+   ::
+      PACKAGE_ARCH = "${MACHINE_ARCH}"
+   On the other hand, if the recipe produces packages that do not
+   contain anything specific to the target machine or architecture at
+   all (e.g. recipes that simply package script files or configuration
+   files), you should use the
+   :ref:`allarch <ref-classes-allarch>` class to
+   do this for you by adding this to your recipe:
+   ::
+      inherit allarch
+   Ensuring that the package architecture is correct is not critical
+   while you are doing the first few builds of your recipe. However, it
+   is important in order to ensure that your recipe rebuilds (or does
+   not rebuild) appropriately in response to changes in configuration,
+   and to ensure that you get the appropriate packages installed on the
+   target machine, particularly if you run separate builds for more than
+   one target machine.
+Sharing Files Between Recipes
+-----------------------------
+Recipes often need to use files provided by other recipes on the build
+host. For example, an application linking to a common library needs
+access to the library itself and its associated headers. The way this
+access is accomplished is by populating a sysroot with files. Each
+recipe has two sysroots in its work directory, one for target files
+(``recipe-sysroot``) and one for files that are native to the build host
+(``recipe-sysroot-native``).
+.. note::
+   You could find the term "staging" used within the Yocto project
+   regarding files populating sysroots (e.g. the :term:`STAGING_DIR`
+   variable).
+Recipes should never populate the sysroot directly (i.e. write files
+into sysroot). Instead, files should be installed into standard
+locations during the
+:ref:`ref-tasks-install` task within
+the ``${``\ :term:`D`\ ``}`` directory. The
+reason for this limitation is that almost all files that populate the
+sysroot are cataloged in manifests in order to ensure the files can be
+removed later when a recipe is either modified or removed. Thus, the
+sysroot is able to remain free from stale files.
+A subset of the files installed by the
+:ref:`ref-tasks-install` task are
+used by the
+:ref:`ref-tasks-populate_sysroot`
+task as defined by the the
+:term:`SYSROOT_DIRS` variable to
+automatically populate the sysroot. It is possible to modify the list of
+directories that populate the sysroot. The following example shows how
+you could add the ``/opt`` directory to the list of directories within a
+recipe:
+::
+   SYSROOT_DIRS += "/opt"
+For a more complete description of the
+:ref:`ref-tasks-populate_sysroot`
+task and its associated functions, see the
+:ref:`staging <ref-classes-staging>` class.
+Using Virtual Providers
+-----------------------
+Prior to a build, if you know that several different recipes provide the
+same functionality, you can use a virtual provider (i.e. ``virtual/*``)
+as a placeholder for the actual provider. The actual provider is
+determined at build-time.
+A common scenario where a virtual provider is used would be for the
+kernel recipe. Suppose you have three kernel recipes whose
+:term:`PN` values map to ``kernel-big``,
+``kernel-mid``, and ``kernel-small``. Furthermore, each of these recipes
+in some way uses a :term:`PROVIDES`
+statement that essentially identifies itself as being able to provide
+``virtual/kernel``. Here is one way through the
+:ref:`kernel <ref-classes-kernel>` class:
+::
+   PROVIDES += "${@ "virtual/kernel" if (d.getVar("KERNEL_PACKAGE_NAME") == "kernel") else "" }"
+Any recipe that inherits the ``kernel`` class is
+going to utilize a ``PROVIDES`` statement that identifies that recipe as
+being able to provide the ``virtual/kernel`` item.
+Now comes the time to actually build an image and you need a kernel
+recipe, but which one? You can configure your build to call out the
+kernel recipe you want by using the :term:`PREFERRED_PROVIDER` variable. As
+an example, consider the :yocto_git:`x86-base.inc
+</poky/tree/meta/conf/machine/include/x86-base.inc>` include file, which is a
+machine (i.e. :term:`MACHINE`) configuration file. This include file is the
+reason all x86-based machines use the ``linux-yocto`` kernel. Here are the
+relevant lines from the include file:
+::
+   PREFERRED_PROVIDER_virtual/kernel ??= "linux-yocto"
+   PREFERRED_VERSION_linux-yocto ??= "4.15%"
+When you use a virtual provider, you do not have to "hard code" a recipe
+name as a build dependency. You can use the
+:term:`DEPENDS` variable to state the
+build is dependent on ``virtual/kernel`` for example:
+::
+   DEPENDS = "virtual/kernel"
+During the build, the OpenEmbedded build system picks
+the correct recipe needed for the ``virtual/kernel`` dependency based on
+the ``PREFERRED_PROVIDER`` variable. If you want to use the small kernel
+mentioned at the beginning of this section, configure your build as
+follows:
+::
+   PREFERRED_PROVIDER_virtual/kernel ??= "kernel-small"
+.. note::
+   Any recipe that ``PROVIDES`` a ``virtual/*`` item that is ultimately not
+   selected through ``PREFERRED_PROVIDER`` does not get built. Preventing these
+   recipes from building is usually the desired behavior since this mechanism's
+   purpose is to select between mutually exclusive alternative providers.
+The following lists specific examples of virtual providers:
+-  ``virtual/kernel``: Provides the name of the kernel recipe to use
+   when building a kernel image.
+-  ``virtual/bootloader``: Provides the name of the bootloader to use
+   when building an image.
+-  ``virtual/libgbm``: Provides ``gbm.pc``.
+-  ``virtual/egl``: Provides ``egl.pc`` and possibly ``wayland-egl.pc``.
+-  ``virtual/libgl``: Provides ``gl.pc`` (i.e. libGL).
+-  ``virtual/libgles1``: Provides ``glesv1_cm.pc`` (i.e. libGLESv1_CM).
+-  ``virtual/libgles2``: Provides ``glesv2.pc`` (i.e. libGLESv2).
+.. note::
+   Virtual providers only apply to build time dependencies specified with
+   :term:`PROVIDES` and :term:`DEPENDS`. They do not apply to runtime
+   dependencies specified with :term:`RPROVIDES` and :term:`RDEPENDS`.
+Properly Versioning Pre-Release Recipes
+---------------------------------------
+Sometimes the name of a recipe can lead to versioning problems when the
+recipe is upgraded to a final release. For example, consider the
+``irssi_0.8.16-rc1.bb`` recipe file in the list of example recipes in
+the "`Storing and Naming the
+Recipe <#new-recipe-storing-and-naming-the-recipe>`__" section. This
+recipe is at a release candidate stage (i.e. "rc1"). When the recipe is
+released, the recipe filename becomes ``irssi_0.8.16.bb``. The version
+change from ``0.8.16-rc1`` to ``0.8.16`` is seen as a decrease by the
+build system and package managers, so the resulting packages will not
+correctly trigger an upgrade.
+In order to ensure the versions compare properly, the recommended
+convention is to set :term:`PV` within the
+recipe to "previous_version+current_version". You can use an additional
+variable so that you can use the current version elsewhere. Here is an
+example:
+::
+   REALPV = "0.8.16-rc1"
+   PV = "0.8.15+${REALPV}"
+Post-Installation Scripts
+-------------------------
+Post-installation scripts run immediately after installing a package on
+the target or during image creation when a package is included in an
+image. To add a post-installation script to a package, add a
+``pkg_postinst_``\ `PACKAGENAME`\ ``()`` function to the recipe file
+(``.bb``) and replace `PACKAGENAME` with the name of the package you want
+to attach to the ``postinst`` script. To apply the post-installation
+script to the main package for the recipe, which is usually what is
+required, specify
+``${``\ :term:`PN`\ ``}`` in place of
+PACKAGENAME.
+A post-installation function has the following structure:
+::
+   pkg_postinst_PACKAGENAME() {
+       # Commands to carry out
+   }
+The script defined in the post-installation function is called when the
+root filesystem is created. If the script succeeds, the package is
+marked as installed.
+.. note::
+   Any RPM post-installation script that runs on the target should
+   return a 0 exit code. RPM does not allow non-zero exit codes for
+   these scripts, and the RPM package manager will cause the package to
+   fail installation on the target.
+Sometimes it is necessary for the execution of a post-installation
+script to be delayed until the first boot. For example, the script might
+need to be executed on the device itself. To delay script execution
+until boot time, you must explicitly mark post installs to defer to the
+target. You can use ``pkg_postinst_ontarget()`` or call
+``postinst_intercept delay_to_first_boot`` from ``pkg_postinst()``. Any
+failure of a ``pkg_postinst()`` script (including exit 1) triggers an
+error during the
+:ref:`ref-tasks-rootfs` task.
+If you have recipes that use ``pkg_postinst`` function and they require
+the use of non-standard native tools that have dependencies during
+rootfs construction, you need to use the
+:term:`PACKAGE_WRITE_DEPS`
+variable in your recipe to list these tools. If you do not use this
+variable, the tools might be missing and execution of the
+post-installation script is deferred until first boot. Deferring the
+script to first boot is undesirable and for read-only rootfs impossible.
+.. note::
+   Equivalent support for pre-install, pre-uninstall, and post-uninstall
+   scripts exist by way of ``pkg_preinst``, ``pkg_prerm``, and ``pkg_postrm``,
+   respectively. These scrips work in exactly the same way as does
+   ``pkg_postinst`` with the exception that they run at different times. Also,
+   because of when they run, they are not applicable to being run at image
+   creation time like ``pkg_postinst``.
+Testing
+-------
+The final step for completing your recipe is to be sure that the
+software you built runs correctly. To accomplish runtime testing, add
+the build's output packages to your image and test them on the target.
+For information on how to customize your image by adding specific
+packages, see the "`Customizing
+Images <#usingpoky-extend-customimage>`__" section.
+Examples
+--------
+To help summarize how to write a recipe, this section provides some
+examples given various scenarios:
+-  Recipes that use local files
+-  Using an Autotooled package
+-  Using a Makefile-based package
+-  Splitting an application into multiple packages
+-  Adding binaries to an image
+Single .c File Package (Hello World!)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Building an application from a single file that is stored locally (e.g.
+under ``files``) requires a recipe that has the file listed in the
+``SRC_URI`` variable. Additionally, you need to manually write the
+``do_compile`` and ``do_install`` tasks. The ``S`` variable defines the
+directory containing the source code, which is set to
+:term:`WORKDIR` in this case - the
+directory BitBake uses for the build.
+::
+   SUMMARY = "Simple helloworld application"
+   SECTION = "examples"
+   LICENSE = "MIT"
+   LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"
+   SRC_URI = "file://helloworld.c"
+   S = "${WORKDIR}"
+   do_compile() {
+       ${CC} helloworld.c -o helloworld
+   }
+   do_install() {
+       install -d ${D}${bindir}
+       install -m 0755 helloworld ${D}${bindir}
+   }
+By default, the ``helloworld``, ``helloworld-dbg``, and
+``helloworld-dev`` packages are built. For information on how to
+customize the packaging process, see the "`Splitting an Application into
+Multiple Packages <#splitting-an-application-into-multiple-packages>`__"
+section.
+Autotooled Package
+~~~~~~~~~~~~~~~~~~
+Applications that use Autotools such as ``autoconf`` and ``automake``
+require a recipe that has a source archive listed in ``SRC_URI`` and
+also inherit the
+:ref:`autotools <ref-classes-autotools>` class,
+which contains the definitions of all the steps needed to build an
+Autotool-based application. The result of the build is automatically
+packaged. And, if the application uses NLS for localization, packages
+with local information are generated (one package per language).
+Following is one example: (``hello_2.3.bb``)
+::
+   SUMMARY = "GNU Helloworld application"
+   SECTION = "examples"
+   LICENSE = "GPLv2+"
+   LIC_FILES_CHKSUM = "file://COPYING;md5=751419260aa954499f7abaabaa882bbe"
+   SRC_URI = "${GNU_MIRROR}/hello/hello-${PV}.tar.gz"
+   inherit autotools gettext
+The variable ``LIC_FILES_CHKSUM`` is used to track source license
+changes as described in the
+":ref:`dev-manual/common-tasks:tracking license changes`" section in
+the Yocto Project Overview and Concepts Manual. You can quickly create
+Autotool-based recipes in a manner similar to the previous example.
+Makefile-Based Package
+~~~~~~~~~~~~~~~~~~~~~~
+Applications that use GNU ``make`` also require a recipe that has the
+source archive listed in ``SRC_URI``. You do not need to add a
+``do_compile`` step since by default BitBake starts the ``make`` command
+to compile the application. If you need additional ``make`` options, you
+should store them in the
+:term:`EXTRA_OEMAKE` or
+:term:`PACKAGECONFIG_CONFARGS`
+variables. BitBake passes these options into the GNU ``make``
+invocation. Note that a ``do_install`` task is still required.
+Otherwise, BitBake runs an empty ``do_install`` task by default.
+Some applications might require extra parameters to be passed to the
+compiler. For example, the application might need an additional header
+path. You can accomplish this by adding to the ``CFLAGS`` variable. The
+following example shows this:
+::
+   CFLAGS_prepend = "-I ${S}/include "
+In the following example, ``mtd-utils`` is a makefile-based package:
+::
+   SUMMARY = "Tools for managing memory technology devices"
+   SECTION = "base"
+   DEPENDS = "zlib lzo e2fsprogs util-linux"
+   HOMEPAGE = "http://www.linux-mtd.infradead.org/"
+   LICENSE = "GPLv2+"
+   LIC_FILES_CHKSUM = "file://COPYING;md5=0636e73ff0215e8d672dc4c32c317bb3 \
+       file://include/common.h;beginline=1;endline=17;md5=ba05b07912a44ea2bf81ce409380049c"
+   # Use the latest version at 26 Oct, 2013
+   SRCREV = "9f107132a6a073cce37434ca9cda6917dd8d866b"
+   SRC_URI = "git://git.infradead.org/mtd-utils.git \
+       file://add-exclusion-to-mkfs-jffs2-git-2.patch \
+       "
+   PV = "1.5.1+git${SRCPV}"
+   S = "${WORKDIR}/git"
+   EXTRA_OEMAKE = "'CC=${CC}' 'RANLIB=${RANLIB}' 'AR=${AR}' 'CFLAGS=${CFLAGS} -I${S}/include -DWITHOUT_XATTR' 'BUILDDIR=${S}'"
+   do_install () {
+       oe_runmake install DESTDIR=${D} SBINDIR=${sbindir} MANDIR=${mandir} INCLUDEDIR=${includedir}
+   }
+   PACKAGES =+ "mtd-utils-jffs2 mtd-utils-ubifs mtd-utils-misc"
+   FILES_mtd-utils-jffs2 = "${sbindir}/mkfs.jffs2 ${sbindir}/jffs2dump ${sbindir}/jffs2reader ${sbindir}/sumtool"
+   FILES_mtd-utils-ubifs = "${sbindir}/mkfs.ubifs ${sbindir}/ubi*"
+   FILES_mtd-utils-misc = "${sbindir}/nftl* ${sbindir}/ftl* ${sbindir}/rfd* ${sbindir}/doc* ${sbindir}/serve_image ${sbindir}/recv_image"
+   PARALLEL_MAKE = ""
+   BBCLASSEXTEND = "native"
+Splitting an Application into Multiple Packages
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+You can use the variables ``PACKAGES`` and ``FILES`` to split an
+application into multiple packages.
+Following is an example that uses the ``libxpm`` recipe. By default,
+this recipe generates a single package that contains the library along
+with a few binaries. You can modify the recipe to split the binaries
+into separate packages:
+::
+   require xorg-lib-common.inc
+   SUMMARY = "Xpm: X Pixmap extension library"
+   LICENSE = "BSD"
+   LIC_FILES_CHKSUM = "file://COPYING;md5=51f4270b012ecd4ab1a164f5f4ed6cf7"
+   DEPENDS += "libxext libsm libxt"
+   PE = "1"
+   XORG_PN = "libXpm"
+   PACKAGES =+ "sxpm cxpm"
+   FILES_cxpm = "${bindir}/cxpm"
+   FILES_sxpm = "${bindir}/sxpm"
+In the previous example, we want to ship the ``sxpm`` and ``cxpm``
+binaries in separate packages. Since ``bindir`` would be packaged into
+the main ``PN`` package by default, we prepend the ``PACKAGES`` variable
+so additional package names are added to the start of list. This results
+in the extra ``FILES_*`` variables then containing information that
+define which files and directories go into which packages. Files
+included by earlier packages are skipped by latter packages. Thus, the
+main ``PN`` package does not include the above listed files.
+Packaging Externally Produced Binaries
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Sometimes, you need to add pre-compiled binaries to an image. For
+example, suppose that binaries for proprietary code exist, which are
+created by a particular division of a company. Your part of the company
+needs to use those binaries as part of an image that you are building
+using the OpenEmbedded build system. Since you only have the binaries
+and not the source code, you cannot use a typical recipe that expects to
+fetch the source specified in
+:term:`SRC_URI` and then compile it.
+One method is to package the binaries and then install them as part of
+the image. Generally, it is not a good idea to package binaries since,
+among other things, it can hinder the ability to reproduce builds and
+could lead to compatibility problems with ABI in the future. However,
+sometimes you have no choice.
+The easiest solution is to create a recipe that uses the
+:ref:`bin_package <ref-classes-bin-package>` class
+and to be sure that you are using default locations for build artifacts.
+In most cases, the ``bin_package`` class handles "skipping" the
+configure and compile steps as well as sets things up to grab packages
+from the appropriate area. In particular, this class sets ``noexec`` on
+both the :ref:`ref-tasks-configure`
+and :ref:`ref-tasks-compile` tasks,
+sets ``FILES_${PN}`` to "/" so that it picks up all files, and sets up a
+:ref:`ref-tasks-install` task, which
+effectively copies all files from ``${S}`` to ``${D}``. The
+``bin_package`` class works well when the files extracted into ``${S}``
+are already laid out in the way they should be laid out on the target.
+For more information on these variables, see the
+:term:`FILES`,
+:term:`PN`,
+:term:`S`, and
+:term:`D` variables in the Yocto Project
+Reference Manual's variable glossary.
+.. note::
+   -  Using :term:`DEPENDS` is a good
+      idea even for components distributed in binary form, and is often
+      necessary for shared libraries. For a shared library, listing the
+      library dependencies in ``DEPENDS`` makes sure that the libraries
+      are available in the staging sysroot when other recipes link
+      against the library, which might be necessary for successful
+      linking.
+   -  Using ``DEPENDS`` also allows runtime dependencies between
+      packages to be added automatically. See the
+      ":ref:`overview-manual/overview-manual-concepts:automatically added runtime dependencies`"
+      section in the Yocto Project Overview and Concepts Manual for more
+      information.
+If you cannot use the ``bin_package`` class, you need to be sure you are
+doing the following:
+-  Create a recipe where the
+   :ref:`ref-tasks-configure` and
+   :ref:`ref-tasks-compile` tasks do
+   nothing: It is usually sufficient to just not define these tasks in
+   the recipe, because the default implementations do nothing unless a
+   Makefile is found in
+   ``${``\ :term:`S`\ ``}``.
+   If ``${S}`` might contain a Makefile, or if you inherit some class
+   that replaces ``do_configure`` and ``do_compile`` with custom
+   versions, then you can use the
+   ``[``\ :ref:`noexec <bitbake-user-manual/bitbake-user-manual-metadata:variable flags>`\ ``]``
+   flag to turn the tasks into no-ops, as follows:
+   ::
+      do_configure[noexec] = "1"
+      do_compile[noexec] = "1"
+   Unlike
+   :ref:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata:deleting a task`,
+   using the flag preserves the dependency chain from the
+   :ref:`ref-tasks-fetch`,
+   :ref:`ref-tasks-unpack`, and
+   :ref:`ref-tasks-patch` tasks to the
+   :ref:`ref-tasks-install` task.
+-  Make sure your ``do_install`` task installs the binaries
+   appropriately.
+-  Ensure that you set up :term:`FILES`
+   (usually
+   ``FILES_${``\ :term:`PN`\ ``}``) to
+   point to the files you have installed, which of course depends on
+   where you have installed them and whether those files are in
+   different locations than the defaults.
+.. note::
+  If image prelinking is enabled (e.g. "image-prelink" is in :term:`USER_CLASSES`
+  which it is by default), prelink will change the binaries in the generated images
+  and this often catches people out. Remove that class to ensure binaries are
+  preserved exactly if that is necessary.
+Following Recipe Style Guidelines
+---------------------------------
+When writing recipes, it is good to conform to existing style
+guidelines. The :oe_home:`OpenEmbedded Styleguide </wiki/Styleguide>` wiki page
+provides rough guidelines for preferred recipe style.
+It is common for existing recipes to deviate a bit from this style.
+However, aiming for at least a consistent style is a good idea. Some
+practices, such as omitting spaces around ``=`` operators in assignments
+or ordering recipe components in an erratic way, are widely seen as poor
+style.
+Recipe Syntax
+-------------
+Understanding recipe file syntax is important for writing recipes. The
+following list overviews the basic items that make up a BitBake recipe
+file. For more complete BitBake syntax descriptions, see the
+":doc:`bitbake-user-manual/bitbake-user-manual-metadata`"
+chapter of the BitBake User Manual.
+-  *Variable Assignments and Manipulations:* Variable assignments allow
+   a value to be assigned to a variable. The assignment can be static
+   text or might include the contents of other variables. In addition to
+   the assignment, appending and prepending operations are also
+   supported.
+   The following example shows some of the ways you can use variables in
+   recipes:
+   ::
+      S = "${WORKDIR}/postfix-${PV}"
+      CFLAGS += "-DNO_ASM"
+      SRC_URI_append = " file://fixup.patch"
+-  *Functions:* Functions provide a series of actions to be performed.
+   You usually use functions to override the default implementation of a
+   task function or to complement a default function (i.e. append or
+   prepend to an existing function). Standard functions use ``sh`` shell
+   syntax, although access to OpenEmbedded variables and internal
+   methods are also available.
+   The following is an example function from the ``sed`` recipe:
+   ::
+      do_install () {
+          autotools_do_install
+          install -d ${D}${base_bindir}
+          mv ${D}${bindir}/sed ${D}${base_bindir}/sed
+          rmdir ${D}${bindir}/
+      }
+   It is
+   also possible to implement new functions that are called between
+   existing tasks as long as the new functions are not replacing or
+   complementing the default functions. You can implement functions in
+   Python instead of shell. Both of these options are not seen in the
+   majority of recipes.
+-  *Keywords:* BitBake recipes use only a few keywords. You use keywords
+   to include common functions (``inherit``), load parts of a recipe
+   from other files (``include`` and ``require``) and export variables
+   to the environment (``export``).
+   The following example shows the use of some of these keywords:
+   ::
+      export POSTCONF = "${STAGING_BINDIR}/postconf"
+      inherit autoconf
+      require otherfile.inc
+-  *Comments (#):* Any lines that begin with the hash character (``#``)
+   are treated as comment lines and are ignored:
+   ::
+      # This is a comment
+This next list summarizes the most important and most commonly used
+parts of the recipe syntax. For more information on these parts of the
+syntax, you can reference the
+:doc:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata` chapter
+in the BitBake User Manual.
+-  *Line Continuation (\\):* Use the backward slash (``\``) character to
+   split a statement over multiple lines. Place the slash character at
+   the end of the line that is to be continued on the next line:
+   ::
+       VAR = "A really long \
+              line"
+   .. note::
+      You cannot have any characters including spaces or tabs after the
+      slash character.
+-  *Using Variables (${VARNAME}):* Use the ``${VARNAME}`` syntax to
+   access the contents of a variable:
+   ::
+      SRC_URI = "${SOURCEFORGE_MIRROR}/libpng/zlib-${PV}.tar.gz"
+   .. note::
+      It is important to understand that the value of a variable
+      expressed in this form does not get substituted automatically. The
+      expansion of these expressions happens on-demand later (e.g.
+      usually when a function that makes reference to the variable
+      executes). This behavior ensures that the values are most
+      appropriate for the context in which they are finally used. On the
+      rare occasion that you do need the variable expression to be
+      expanded immediately, you can use the
+      :=
+      operator instead of
+      =
+      when you make the assignment, but this is not generally needed.
+-  *Quote All Assignments ("value"):* Use double quotes around values in
+   all variable assignments (e.g. ``"value"``). Following is an example:
+   ::
+      VAR1 = "${OTHERVAR}"
+      VAR2 = "The version is ${PV}"
+-  *Conditional Assignment (?=):* Conditional assignment is used to
+   assign a value to a variable, but only when the variable is currently
+   unset. Use the question mark followed by the equal sign (``?=``) to
+   make a "soft" assignment used for conditional assignment. Typically,
+   "soft" assignments are used in the ``local.conf`` file for variables
+   that are allowed to come through from the external environment.
+   Here is an example where ``VAR1`` is set to "New value" if it is
+   currently empty. However, if ``VAR1`` has already been set, it
+   remains unchanged:
+   ::
+      VAR1 ?= "New value"
+   In this next example, ``VAR1`` is left with the value "Original value":
+   ::
+      VAR1 = "Original value"
+      VAR1 ?= "New value"
+-  *Appending (+=):* Use the plus character followed by the equals sign
+   (``+=``) to append values to existing variables.
+   .. note::
+      This operator adds a space between the existing content of the
+      variable and the new content.
+   Here is an example:
+   ::
+      SRC_URI += "file://fix-makefile.patch"
+-  *Prepending (=+):* Use the equals sign followed by the plus character
+   (``=+``) to prepend values to existing variables.
+   .. note::
+      This operator adds a space between the new content and the
+      existing content of the variable.
+   Here is an example:
+   ::
+      VAR =+ "Starts"
+-  *Appending (_append):* Use the ``_append`` operator to append values
+   to existing variables. This operator does not add any additional
+   space. Also, the operator is applied after all the ``+=``, and ``=+``
+   operators have been applied and after all ``=`` assignments have
+   occurred.
+   The following example shows the space being explicitly added to the
+   start to ensure the appended value is not merged with the existing
+   value:
+   ::
+      SRC_URI_append = " file://fix-makefile.patch"
+   You can also use
+   the ``_append`` operator with overrides, which results in the actions
+   only being performed for the specified target or machine:
+   ::
+      SRC_URI_append_sh4 = " file://fix-makefile.patch"
+-  *Prepending (_prepend):* Use the ``_prepend`` operator to prepend
+   values to existing variables. This operator does not add any
+   additional space. Also, the operator is applied after all the ``+=``,
+   and ``=+`` operators have been applied and after all ``=``
+   assignments have occurred.
+   The following example shows the space being explicitly added to the
+   end to ensure the prepended value is not merged with the existing
+   value:
+   ::
+      CFLAGS_prepend = "-I${S}/myincludes "
+   You can also use the
+   ``_prepend`` operator with overrides, which results in the actions
+   only being performed for the specified target or machine:
+   ::
+      CFLAGS_prepend_sh4 = "-I${S}/myincludes "
+-  *Overrides:* You can use overrides to set a value conditionally,
+   typically based on how the recipe is being built. For example, to set
+   the :term:`KBRANCH` variable's
+   value to "standard/base" for any target
+   :term:`MACHINE`, except for
+   qemuarm where it should be set to "standard/arm-versatile-926ejs",
+   you would do the following:
+   ::
+      KBRANCH = "standard/base"
+      KBRANCH_qemuarm = "standard/arm-versatile-926ejs"
+   Overrides are also used to separate
+   alternate values of a variable in other situations. For example, when
+   setting variables such as
+   :term:`FILES` and
+   :term:`RDEPENDS` that are
+   specific to individual packages produced by a recipe, you should
+   always use an override that specifies the name of the package.
+-  *Indentation:* Use spaces for indentation rather than tabs. For
+   shell functions, both currently work. However, it is a policy
+   decision of the Yocto Project to use tabs in shell functions. Realize
+   that some layers have a policy to use spaces for all indentation.
+-  *Using Python for Complex Operations:* For more advanced processing,
+   it is possible to use Python code during variable assignments (e.g.
+   search and replacement on a variable).
+   You indicate Python code using the ``${@python_code}`` syntax for the
+   variable assignment:
+   ::
+      SRC_URI = "ftp://ftp.info-zip.org/pub/infozip/src/zip${@d.getVar('PV',1).replace('.', '')}.tgz
+-  *Shell Function Syntax:* Write shell functions as if you were writing
+   a shell script when you describe a list of actions to take. You
+   should ensure that your script works with a generic ``sh`` and that
+   it does not require any ``bash`` or other shell-specific
+   functionality. The same considerations apply to various system
+   utilities (e.g. ``sed``, ``grep``, ``awk``, and so forth) that you
+   might wish to use. If in doubt, you should check with multiple
+   implementations - including those from BusyBox.
+Adding a New Machine
+====================
+Adding a new machine to the Yocto Project is a straightforward process.
+This section describes how to add machines that are similar to those
+that the Yocto Project already supports.
+.. note::
+   Although well within the capabilities of the Yocto Project, adding a
+   totally new architecture might require changes to ``gcc``/``glibc``
+   and to the site information, which is beyond the scope of this
+   manual.
+For a complete example that shows how to add a new machine, see the
+":ref:`bsp-guide/bsp:creating a new bsp layer using the \`\`bitbake-layers\`\` script`"
+section in the Yocto Project Board Support Package (BSP) Developer's
+Guide.
+Adding the Machine Configuration File
+-------------------------------------
+To add a new machine, you need to add a new machine configuration file
+to the layer's ``conf/machine`` directory. This configuration file
+provides details about the device you are adding.
+The OpenEmbedded build system uses the root name of the machine
+configuration file to reference the new machine. For example, given a
+machine configuration file named ``crownbay.conf``, the build system
+recognizes the machine as "crownbay".
+The most important variables you must set in your machine configuration
+file or include from a lower-level configuration file are as follows:
+-  ``TARGET_ARCH`` (e.g. "arm")
+-  ``PREFERRED_PROVIDER_virtual/kernel``
+-  ``MACHINE_FEATURES`` (e.g. "apm screen wifi")
+You might also need these variables:
+-  ``SERIAL_CONSOLES`` (e.g. "115200;ttyS0 115200;ttyS1")
+-  ``KERNEL_IMAGETYPE`` (e.g. "zImage")
+-  ``IMAGE_FSTYPES`` (e.g. "tar.gz jffs2")
+You can find full details on these variables in the reference section.
+You can leverage existing machine ``.conf`` files from
+``meta-yocto-bsp/conf/machine/``.
+Adding a Kernel for the Machine
+-------------------------------
+The OpenEmbedded build system needs to be able to build a kernel for the
+machine. You need to either create a new kernel recipe for this machine,
+or extend an existing kernel recipe. You can find several kernel recipe
+examples in the Source Directory at ``meta/recipes-kernel/linux`` that
+you can use as references.
+If you are creating a new kernel recipe, normal recipe-writing rules
+apply for setting up a ``SRC_URI``. Thus, you need to specify any
+necessary patches and set ``S`` to point at the source code. You need to
+create a ``do_configure`` task that configures the unpacked kernel with
+a ``defconfig`` file. You can do this by using a ``make defconfig``
+command or, more commonly, by copying in a suitable ``defconfig`` file
+and then running ``make oldconfig``. By making use of ``inherit kernel``
+and potentially some of the ``linux-*.inc`` files, most other
+functionality is centralized and the defaults of the class normally work
+well.
+If you are extending an existing kernel recipe, it is usually a matter
+of adding a suitable ``defconfig`` file. The file needs to be added into
+a location similar to ``defconfig`` files used for other machines in a
+given kernel recipe. A possible way to do this is by listing the file in
+the ``SRC_URI`` and adding the machine to the expression in
+``COMPATIBLE_MACHINE``:
+::
+   COMPATIBLE_MACHINE = '(qemux86|qemumips)'
+For more information on ``defconfig`` files, see the
+":ref:`kernel-dev/kernel-dev-common:changing the configuration`"
+section in the Yocto Project Linux Kernel Development Manual.
+Adding a Formfactor Configuration File
+--------------------------------------
+A formfactor configuration file provides information about the target
+hardware for which the image is being built and information that the
+build system cannot obtain from other sources such as the kernel. Some
+examples of information contained in a formfactor configuration file
+include framebuffer orientation, whether or not the system has a
+keyboard, the positioning of the keyboard in relation to the screen, and
+the screen resolution.
+The build system uses reasonable defaults in most cases. However, if
+customization is necessary, you need to create a ``machconfig`` file in
+the ``meta/recipes-bsp/formfactor/files`` directory. This directory
+contains directories for specific machines such as ``qemuarm`` and
+``qemux86``. For information about the settings available and the
+defaults, see the ``meta/recipes-bsp/formfactor/files/config`` file
+found in the same area.
+Following is an example for "qemuarm" machine:
+::
+   HAVE_TOUCHSCREEN=1
+   HAVE_KEYBOARD=1
+   DISPLAY_CAN_ROTATE=0
+   DISPLAY_ORIENTATION=0
+   #DISPLAY_WIDTH_PIXELS=640
+   #DISPLAY_HEIGHT_PIXELS=480
+   #DISPLAY_BPP=16
+   DISPLAY_DPI=150
+   DISPLAY_SUBPIXEL_ORDER=vrgb
+Upgrading Recipes
+=================
+Over time, upstream developers publish new versions for software built
+by layer recipes. It is recommended to keep recipes up-to-date with
+upstream version releases.
+While several methods exist that allow you upgrade a recipe, you might
+consider checking on the upgrade status of a recipe first. You can do so
+using the ``devtool check-upgrade-status`` command. See the
+":ref:`devtool-checking-on-the-upgrade-status-of-a-recipe`"
+section in the Yocto Project Reference Manual for more information.
+The remainder of this section describes three ways you can upgrade a
+recipe. You can use the Automated Upgrade Helper (AUH) to set up
+automatic version upgrades. Alternatively, you can use
+``devtool upgrade`` to set up semi-automatic version upgrades. Finally,
+you can manually upgrade a recipe by editing the recipe itself.
+Using the Auto Upgrade Helper (AUH)
+-----------------------------------
+The AUH utility works in conjunction with the OpenEmbedded build system
+in order to automatically generate upgrades for recipes based on new
+versions being published upstream. Use AUH when you want to create a
+service that performs the upgrades automatically and optionally sends
+you an email with the results.
+AUH allows you to update several recipes with a single use. You can also
+optionally perform build and integration tests using images with the
+results saved to your hard drive and emails of results optionally sent
+to recipe maintainers. Finally, AUH creates Git commits with appropriate
+commit messages in the layer's tree for the changes made to recipes.
+.. note::
+   Conditions do exist when you should not use AUH to upgrade recipes
+   and you should instead use either ``devtool upgrade`` or upgrade your
+   recipes manually:
+   -  When AUH cannot complete the upgrade sequence. This situation
+      usually results because custom patches carried by the recipe
+      cannot be automatically rebased to the new version. In this case,
+      ``devtool upgrade`` allows you to manually resolve conflicts.
+   -  When for any reason you want fuller control over the upgrade
+      process. For example, when you want special arrangements for
+      testing.
+The following steps describe how to set up the AUH utility:
+1. *Be Sure the Development Host is Set Up:* You need to be sure that
+   your development host is set up to use the Yocto Project. For
+   information on how to set up your host, see the
+   ":ref:`dev-manual/start:Preparing the Build Host`" section.
+2. *Make Sure Git is Configured:* The AUH utility requires Git to be
+   configured because AUH uses Git to save upgrades. Thus, you must have
+   Git user and email configured. The following command shows your
+   configurations:
+   ::
+      $ git config --list
+   If you do not have the user and
+   email configured, you can use the following commands to do so:
+   ::
+      $ git config --global user.name some_name
+      $ git config --global user.email username@domain.com
+3. *Clone the AUH Repository:* To use AUH, you must clone the repository
+   onto your development host. The following command uses Git to create
+   a local copy of the repository on your system:
+   ::
+      $ git clone  git://git.yoctoproject.org/auto-upgrade-helper
+      Cloning into 'auto-upgrade-helper'... remote: Counting objects: 768, done.
+      remote: Compressing objects: 100% (300/300), done.
+      remote: Total 768 (delta 499), reused 703 (delta 434)
+      Receiving objects: 100% (768/768), 191.47 KiB | 98.00 KiB/s, done.
+      Resolving deltas: 100% (499/499), done.
+      Checking connectivity... done.
+   AUH is not part of the :term:`OpenEmbedded-Core (OE-Core)` or
+   :term:`Poky` repositories.
+4. *Create a Dedicated Build Directory:* Run the
+   :ref:`structure-core-script`
+   script to create a fresh build directory that you use exclusively for
+   running the AUH utility:
+   ::
+      $ cd ~/poky
+      $ source oe-init-build-env your_AUH_build_directory
+   Re-using an existing build directory and its configurations is not
+   recommended as existing settings could cause AUH to fail or behave
+   undesirably.
+5. *Make Configurations in Your Local Configuration File:* Several
+   settings need to exist in the ``local.conf`` file in the build
+   directory you just created for AUH. Make these following
+   configurations:
+   -  If you want to enable :ref:`Build
+      History <dev-manual/common-tasks:maintaining build output quality>`,
+      which is optional, you need the following lines in the
+      ``conf/local.conf`` file:
+      ::
+         INHERIT =+ "buildhistory"
+         BUILDHISTORY_COMMIT = "1"
+      With this configuration and a successful
+      upgrade, a build history "diff" file appears in the
+      ``upgrade-helper/work/recipe/buildhistory-diff.txt`` file found in
+      your build directory.
+   -  If you want to enable testing through the
+      :ref:`testimage <ref-classes-testimage*>`
+      class, which is optional, you need to have the following set in
+      your ``conf/local.conf`` file:
+      ::
+         INHERIT += "testimage"
+      .. note::
+         If your distro does not enable by default ptest, which Poky
+         does, you need the following in your ``local.conf`` file:
+         ::
+                 DISTRO_FEATURES_append = " ptest"
+6. *Optionally Start a vncserver:* If you are running in a server
+   without an X11 session, you need to start a vncserver:
+   ::
+      $ vncserver :1
+      $ export DISPLAY=:1
+7. *Create and Edit an AUH Configuration File:* You need to have the
+   ``upgrade-helper/upgrade-helper.conf`` configuration file in your
+   build directory. You can find a sample configuration file in the
+   :yocto_git:`AUH source repository </auto-upgrade-helper/tree/>`.
+   Read through the sample file and make configurations as needed. For
+   example, if you enabled build history in your ``local.conf`` as
+   described earlier, you must enable it in ``upgrade-helper.conf``.
+   Also, if you are using the default ``maintainers.inc`` file supplied
+   with Poky and located in ``meta-yocto`` and you do not set a
+   "maintainers_whitelist" or "global_maintainer_override" in the
+   ``upgrade-helper.conf`` configuration, and you specify "-e all" on
+   the AUH command-line, the utility automatically sends out emails to
+   all the default maintainers. Please avoid this.
+This next set of examples describes how to use the AUH:
+-  *Upgrading a Specific Recipe:* To upgrade a specific recipe, use the
+   following form:
+   ::
+      $ upgrade-helper.py recipe_name
+   For example, this command upgrades the ``xmodmap`` recipe:
+   ::
+      $ upgrade-helper.py xmodmap
+-  *Upgrading a Specific Recipe to a Particular Version:* To upgrade a
+   specific recipe to a particular version, use the following form:
+   ::
+      $ upgrade-helper.py recipe_name -t version
+   For example, this command upgrades the ``xmodmap`` recipe to version 1.2.3:
+   ::
+      $ upgrade-helper.py xmodmap -t 1.2.3
+-  *Upgrading all Recipes to the Latest Versions and Suppressing Email
+   Notifications:* To upgrade all recipes to their most recent versions
+   and suppress the email notifications, use the following command:
+   ::
+      $ upgrade-helper.py all
+-  *Upgrading all Recipes to the Latest Versions and Send Email
+   Notifications:* To upgrade all recipes to their most recent versions
+   and send email messages to maintainers for each attempted recipe as
+   well as a status email, use the following command:
+   ::
+      $ upgrade-helper.py -e all
+Once you have run the AUH utility, you can find the results in the AUH
+build directory:
+::
+   ${BUILDDIR}/upgrade-helper/timestamp
+The AUH utility
+also creates recipe update commits from successful upgrade attempts in
+the layer tree.
+You can easily set up to run the AUH utility on a regular basis by using
+a cron job. See the
+:yocto_git:`weeklyjob.sh </auto-upgrade-helper/tree/weeklyjob.sh>`
+file distributed with the utility for an example.
+Using ``devtool upgrade``
+-------------------------
+As mentioned earlier, an alternative method for upgrading recipes to
+newer versions is to use
+:doc:`devtool upgrade </ref-manual/ref-devtool-reference>`.
+You can read about ``devtool upgrade`` in general in the
+":ref:`sdk-manual/sdk-extensible:use \`\`devtool upgrade\`\` to create a version of the recipe that supports a newer version of the software`"
+section in the Yocto Project Application Development and the Extensible
+Software Development Kit (eSDK) Manual.
+To see all the command-line options available with ``devtool upgrade``,
+use the following help command:
+::
+   $ devtool upgrade -h
+If you want to find out what version a recipe is currently at upstream
+without any attempt to upgrade your local version of the recipe, you can
+use the following command:
+::
+   $ devtool latest-version recipe_name
+As mentioned in the previous section describing AUH, ``devtool upgrade``
+works in a less-automated manner than AUH. Specifically,
+``devtool upgrade`` only works on a single recipe that you name on the
+command line, cannot perform build and integration testing using images,
+and does not automatically generate commits for changes in the source
+tree. Despite all these "limitations", ``devtool upgrade`` updates the
+recipe file to the new upstream version and attempts to rebase custom
+patches contained by the recipe as needed.
+.. note::
+   AUH uses much of ``devtool upgrade`` behind the scenes making AUH somewhat
+   of a "wrapper" application for ``devtool upgrade``.
+A typical scenario involves having used Git to clone an upstream
+repository that you use during build operations. Because you have built the
+recipe in the past, the layer is likely added to your
+configuration already. If for some reason, the layer is not added, you
+could add it easily using the
+":ref:`bitbake-layers <bsp-guide/bsp:creating a new bsp layer using the \`\`bitbake-layers\`\` script>`"
+script. For example, suppose you use the ``nano.bb`` recipe from the
+``meta-oe`` layer in the ``meta-openembedded`` repository. For this
+example, assume that the layer has been cloned into following area:
+::
+   /home/scottrif/meta-openembedded
+The following command from your
+:term:`Build Directory` adds the layer to
+your build configuration (i.e. ``${BUILDDIR}/conf/bblayers.conf``):
+::
+   $ bitbake-layers add-layer /home/scottrif/meta-openembedded/meta-oe
+   NOTE: Starting bitbake server...
+   Parsing recipes: 100% |##########################################| Time: 0:00:55
+   Parsing of 1431 .bb files complete (0 cached, 1431 parsed). 2040 targets, 56 skipped, 0 masked, 0 errors.
+   Removing 12 recipes from the x86_64 sysroot: 100% |##############| Time: 0:00:00
+   Removing 1 recipes from the x86_64_i586 sysroot: 100% |##########| Time: 0:00:00
+   Removing 5 recipes from the i586 sysroot: 100% |#################| Time: 0:00:00
+   Removing 5 recipes from the qemux86 sysroot: 100% |##############| Time: 0:00:00
+For this example, assume that the ``nano.bb`` recipe that
+is upstream has a 2.9.3 version number. However, the version in the
+local repository is 2.7.4. The following command from your build
+directory automatically upgrades the recipe for you:
+.. note::
+   Using the ``-V`` option is not necessary. Omitting the version number causes
+   ``devtool upgrade`` to upgrade the recipe to the most recent version.
+::
+   $ devtool upgrade nano -V 2.9.3
+   NOTE: Starting bitbake server...
+   NOTE: Creating workspace layer in /home/scottrif/poky/build/workspace
+   Parsing recipes: 100% |##########################################| Time: 0:00:46
+   Parsing of 1431 .bb files complete (0 cached, 1431 parsed). 2040 targets, 56 skipped, 0 masked, 0 errors.
+   NOTE: Extracting current version source...
+   NOTE: Resolving any missing task queue dependencies
+          .
+          .
+          .
+   NOTE: Executing SetScene Tasks
+   NOTE: Executing RunQueue Tasks
+   NOTE: Tasks Summary: Attempted 74 tasks of which 72 didn't need to be rerun and all succeeded.
+   Adding changed files: 100% |#####################################| Time: 0:00:00
+   NOTE: Upgraded source extracted to /home/scottrif/poky/build/workspace/sources/nano
+   NOTE: New recipe is /home/scottrif/poky/build/workspace/recipes/nano/nano_2.9.3.bb
+Continuing with this example, you can use ``devtool build`` to build the
+newly upgraded recipe:
+::
+   $ devtool build nano
+   NOTE: Starting bitbake server...
+   Loading cache: 100% |################################################################################################| Time: 0:00:01
+   Loaded 2040 entries from dependency cache.
+   Parsing recipes: 100% |##############################################################################################| Time: 0:00:00
+   Parsing of 1432 .bb files complete (1431 cached, 1 parsed). 2041 targets, 56 skipped, 0 masked, 0 errors.
+   NOTE: Resolving any missing task queue dependencies
+          .
+          .
+          .
+   NOTE: Executing SetScene Tasks
+   NOTE: Executing RunQueue Tasks
+   NOTE: nano: compiling from external source tree /home/scottrif/poky/build/workspace/sources/nano
+   NOTE: Tasks Summary: Attempted 520 tasks of which 304 didn't need to be rerun and all succeeded.
+Within the ``devtool upgrade`` workflow, opportunity
+exists to deploy and test your rebuilt software. For this example,
+however, running ``devtool finish`` cleans up the workspace once the
+source in your workspace is clean. This usually means using Git to stage
+and submit commits for the changes generated by the upgrade process.
+Once the tree is clean, you can clean things up in this example with the
+following command from the ``${BUILDDIR}/workspace/sources/nano``
+directory:
+::
+   $ devtool finish nano meta-oe
+   NOTE: Starting bitbake server...
+   Loading cache: 100% |################################################################################################| Time: 0:00:00
+   Loaded 2040 entries from dependency cache.
+   Parsing recipes: 100% |##############################################################################################| Time: 0:00:01
+   Parsing of 1432 .bb files complete (1431 cached, 1 parsed). 2041 targets, 56 skipped, 0 masked, 0 errors.
+   NOTE: Adding new patch 0001-nano.bb-Stuff-I-changed-when-upgrading-nano.bb.patch
+   NOTE: Updating recipe nano_2.9.3.bb
+   NOTE: Removing file /home/scottrif/meta-openembedded/meta-oe/recipes-support/nano/nano_2.7.4.bb
+   NOTE: Moving recipe file to /home/scottrif/meta-openembedded/meta-oe/recipes-support/nano
+   NOTE: Leaving source tree /home/scottrif/poky/build/workspace/sources/nano as-is; if you no longer need it then please delete it manually
+Using the ``devtool finish`` command cleans up the workspace and creates a patch
+file based on your commits. The tool puts all patch files back into the
+source directory in a sub-directory named ``nano`` in this case.
+Manually Upgrading a Recipe
+---------------------------
+If for some reason you choose not to upgrade recipes using
+:ref:`dev-manual/common-tasks:Using the Auto Upgrade Helper (AUH)` or
+by :ref:`dev-manual/common-tasks:Using \`\`devtool upgrade\`\``,
+you can manually edit the recipe files to upgrade the versions.
+.. note::
+   Manually updating multiple recipes scales poorly and involves many
+   steps. The recommendation to upgrade recipe versions is through AUH
+   or ``devtool upgrade``, both of which automate some steps and provide
+   guidance for others needed for the manual process.
+To manually upgrade recipe versions, follow these general steps:
+1. *Change the Version:* Rename the recipe such that the version (i.e.
+   the :term:`PV` part of the recipe name)
+   changes appropriately. If the version is not part of the recipe name,
+   change the value as it is set for ``PV`` within the recipe itself.
+2. *Update* ``SRCREV`` *if Needed*: If the source code your recipe builds
+   is fetched from Git or some other version control system, update
+   :term:`SRCREV` to point to the
+   commit hash that matches the new version.
+3. *Build the Software:* Try to build the recipe using BitBake. Typical
+   build failures include the following:
+   -  License statements were updated for the new version. For this
+      case, you need to review any changes to the license and update the
+      values of :term:`LICENSE` and
+      :term:`LIC_FILES_CHKSUM`
+      as needed.
+      .. note::
+         License changes are often inconsequential. For example, the
+         license text's copyright year might have changed.
+   -  Custom patches carried by the older version of the recipe might
+      fail to apply to the new version. For these cases, you need to
+      review the failures. Patches might not be necessary for the new
+      version of the software if the upgraded version has fixed those
+      issues. If a patch is necessary and failing, you need to rebase it
+      into the new version.
+4. *Optionally Attempt to Build for Several Architectures:* Once you
+   successfully build the new software for a given architecture, you
+   could test the build for other architectures by changing the
+   :term:`MACHINE` variable and
+   rebuilding the software. This optional step is especially important
+   if the recipe is to be released publicly.
+5. *Check the Upstream Change Log or Release Notes:* Checking both these
+   reveals if new features exist that could break
+   backwards-compatibility. If so, you need to take steps to mitigate or
+   eliminate that situation.
+6. *Optionally Create a Bootable Image and Test:* If you want, you can
+   test the new software by booting it onto actual hardware.
+7. *Create a Commit with the Change in the Layer Repository:* After all
+   builds work and any testing is successful, you can create commits for
+   any changes in the layer holding your upgraded recipe.
+Finding Temporary Source Code
+=============================
+You might find it helpful during development to modify the temporary
+source code used by recipes to build packages. For example, suppose you
+are developing a patch and you need to experiment a bit to figure out
+your solution. After you have initially built the package, you can
+iteratively tweak the source code, which is located in the
+:term:`Build Directory`, and then you can
+force a re-compile and quickly test your altered code. Once you settle
+on a solution, you can then preserve your changes in the form of
+patches.
+During a build, the unpacked temporary source code used by recipes to
+build packages is available in the Build Directory as defined by the
+:term:`S` variable. Below is the default
+value for the ``S`` variable as defined in the
+``meta/conf/bitbake.conf`` configuration file in the
+:term:`Source Directory`:
+::
+   S = "${WORKDIR}/${BP}"
+You should be aware that many recipes override the
+``S`` variable. For example, recipes that fetch their source from Git
+usually set ``S`` to ``${WORKDIR}/git``.
+.. note::
+   The :term:`BP` represents the base recipe name, which consists of the name
+   and version:
+   ::
+           BP = "${BPN}-${PV}"
+The path to the work directory for the recipe
+(:term:`WORKDIR`) is defined as
+follows:
+::
+   ${TMPDIR}/work/${MULTIMACH_TARGET_SYS}/${PN}/${EXTENDPE}${PV}-${PR}
+The actual directory depends on several things:
+-  :term:`TMPDIR`: The top-level build
+   output directory.
+-  :term:`MULTIMACH_TARGET_SYS`:
+   The target system identifier.
+-  :term:`PN`: The recipe name.
+-  :term:`EXTENDPE`: The epoch - (if
+   :term:`PE` is not specified, which is
+   usually the case for most recipes, then ``EXTENDPE`` is blank).
+-  :term:`PV`: The recipe version.
+-  :term:`PR`: The recipe revision.
+As an example, assume a Source Directory top-level folder named
+``poky``, a default Build Directory at ``poky/build``, and a
+``qemux86-poky-linux`` machine target system. Furthermore, suppose your
+recipe is named ``foo_1.3.0.bb``. In this case, the work directory the
+build system uses to build the package would be as follows:
+::
+   poky/build/tmp/work/qemux86-poky-linux/foo/1.3.0-r0
+Using Quilt in Your Workflow
+============================
+`Quilt <https://savannah.nongnu.org/projects/quilt>`__ is a powerful tool
+that allows you to capture source code changes without having a clean
+source tree. This section outlines the typical workflow you can use to
+modify source code, test changes, and then preserve the changes in the
+form of a patch all using Quilt.
+.. note::
+   With regard to preserving changes to source files, if you clean a
+   recipe or have ``rm_work`` enabled, the
+   :ref:`devtool workflow <sdk-manual/sdk-extensible:using \`\`devtool\`\` in your sdk workflow>`
+   as described in the Yocto Project Application Development and the
+   Extensible Software Development Kit (eSDK) manual is a safer
+   development flow than the flow that uses Quilt.
+Follow these general steps:
+1. *Find the Source Code:* Temporary source code used by the
+   OpenEmbedded build system is kept in the
+   :term:`Build Directory`. See the
+   "`Finding Temporary Source
+   Code <#finding-the-temporary-source-code>`__" section to learn how to
+   locate the directory that has the temporary source code for a
+   particular package.
+2. *Change Your Working Directory:* You need to be in the directory that
+   has the temporary source code. That directory is defined by the
+   :term:`S` variable.
+3. *Create a New Patch:* Before modifying source code, you need to
+   create a new patch. To create a new patch file, use ``quilt new`` as
+   below:
+   ::
+      $ quilt new my_changes.patch
+4. *Notify Quilt and Add Files:* After creating the patch, you need to
+   notify Quilt about the files you plan to edit. You notify Quilt by
+   adding the files to the patch you just created:
+   ::
+      $ quilt add file1.c file2.c file3.c
+5. *Edit the Files:* Make your changes in the source code to the files
+   you added to the patch.
+6. *Test Your Changes:* Once you have modified the source code, the
+   easiest way to test your changes is by calling the ``do_compile``
+   task as shown in the following example:
+   ::
+      $ bitbake -c compile -f package
+   The ``-f`` or ``--force`` option forces the specified task to
+   execute. If you find problems with your code, you can just keep
+   editing and re-testing iteratively until things work as expected.
+   .. note::
+      All the modifications you make to the temporary source code disappear
+      once you run the ``do_clean`` or ``do_cleanall`` tasks using BitBake
+      (i.e. ``bitbake -c clean package`` and ``bitbake -c cleanall package``).
+      Modifications will also disappear if you use the ``rm_work`` feature as
+      described in the
+      ":ref:`dev-manual/common-tasks:conserving disk space during builds`"
+      section.
+7. *Generate the Patch:* Once your changes work as expected, you need to
+   use Quilt to generate the final patch that contains all your
+   modifications.
+   ::
+      $ quilt refresh
+   At this point, the
+   ``my_changes.patch`` file has all your edits made to the ``file1.c``,
+   ``file2.c``, and ``file3.c`` files.
+   You can find the resulting patch file in the ``patches/``
+   subdirectory of the source (``S``) directory.
+8. *Copy the Patch File:* For simplicity, copy the patch file into a
+   directory named ``files``, which you can create in the same directory
+   that holds the recipe (``.bb``) file or the append (``.bbappend``)
+   file. Placing the patch here guarantees that the OpenEmbedded build
+   system will find the patch. Next, add the patch into the ``SRC_URI``
+   of the recipe. Here is an example:
+   ::
+      SRC_URI += "file://my_changes.patch"
+Using a Development Shell
+=========================
+When debugging certain commands or even when just editing packages,
+``devshell`` can be a useful tool. When you invoke ``devshell``, all
+tasks up to and including
+:ref:`ref-tasks-patch` are run for the
+specified target. Then, a new terminal is opened and you are placed in
+``${``\ :term:`S`\ ``}``, the source
+directory. In the new terminal, all the OpenEmbedded build-related
+environment variables are still defined so you can use commands such as
+``configure`` and ``make``. The commands execute just as if the
+OpenEmbedded build system were executing them. Consequently, working
+this way can be helpful when debugging a build or preparing software to
+be used with the OpenEmbedded build system.
+Following is an example that uses ``devshell`` on a target named
+``matchbox-desktop``:
+::
+  $ bitbake matchbox-desktop -c devshell
+This command spawns a terminal with a shell prompt within the
+OpenEmbedded build environment. The
+:term:`OE_TERMINAL` variable
+controls what type of shell is opened.
+For spawned terminals, the following occurs:
+-  The ``PATH`` variable includes the cross-toolchain.
+-  The ``pkgconfig`` variables find the correct ``.pc`` files.
+-  The ``configure`` command finds the Yocto Project site files as well
+   as any other necessary files.
+Within this environment, you can run configure or compile commands as if
+they were being run by the OpenEmbedded build system itself. As noted
+earlier, the working directory also automatically changes to the Source
+Directory (:term:`S`).
+To manually run a specific task using ``devshell``, run the
+corresponding ``run.*`` script in the
+``${``\ :term:`WORKDIR`\ ``}/temp``
+directory (e.g., ``run.do_configure.``\ `pid`). If a task's script does
+not exist, which would be the case if the task was skipped by way of the
+sstate cache, you can create the task by first running it outside of the
+``devshell``:
+::
+   $ bitbake -c task
+.. note::
+   -  Execution of a task's ``run.*`` script and BitBake's execution of
+      a task are identical. In other words, running the script re-runs
+      the task just as it would be run using the ``bitbake -c`` command.
+   -  Any ``run.*`` file that does not have a ``.pid`` extension is a
+      symbolic link (symlink) to the most recent version of that file.
+Remember, that the ``devshell`` is a mechanism that allows you to get
+into the BitBake task execution environment. And as such, all commands
+must be called just as BitBake would call them. That means you need to
+provide the appropriate options for cross-compilation and so forth as
+applicable.
+When you are finished using ``devshell``, exit the shell or close the
+terminal window.
+.. note::
+   -  It is worth remembering that when using ``devshell`` you need to
+      use the full compiler name such as ``arm-poky-linux-gnueabi-gcc``
+      instead of just using ``gcc``. The same applies to other
+      applications such as ``binutils``, ``libtool`` and so forth.
+      BitBake sets up environment variables such as ``CC`` to assist
+      applications, such as ``make`` to find the correct tools.
+   -  It is also worth noting that ``devshell`` still works over X11
+      forwarding and similar situations.
+Using a Development Python Shell
+================================
+Similar to working within a development shell as described in the
+previous section, you can also spawn and work within an interactive
+Python development shell. When debugging certain commands or even when
+just editing packages, ``devpyshell`` can be a useful tool. When you
+invoke ``devpyshell``, all tasks up to and including
+:ref:`ref-tasks-patch` are run for the
+specified target. Then a new terminal is opened. Additionally, key
+Python objects and code are available in the same way they are to
+BitBake tasks, in particular, the data store 'd'. So, commands such as
+the following are useful when exploring the data store and running
+functions:
+::
+   pydevshell> d.getVar("STAGING_DIR")
+   '/media/build1/poky/build/tmp/sysroots'
+   pydevshell> d.getVar("STAGING_DIR")
+   '${TMPDIR}/sysroots'
+   pydevshell> d.setVar("FOO", "bar")
+   pydevshell> d.getVar("FOO")
+   'bar'
+   pydevshell> d.delVar("FOO")
+   pydevshell> d.getVar("FOO")
+   pydevshell> bb.build.exec_func("do_unpack", d)
+   pydevshell>
+The commands execute just as if the OpenEmbedded build
+system were executing them. Consequently, working this way can be
+helpful when debugging a build or preparing software to be used with the
+OpenEmbedded build system.
+Following is an example that uses ``devpyshell`` on a target named
+``matchbox-desktop``:
+::
+   $ bitbake matchbox-desktop -c devpyshell
+This command spawns a terminal and places you in an interactive Python
+interpreter within the OpenEmbedded build environment. The
+:term:`OE_TERMINAL` variable
+controls what type of shell is opened.
+When you are finished using ``devpyshell``, you can exit the shell
+either by using Ctrl+d or closing the terminal window.
+Building
+========
+This section describes various build procedures. For example, the steps
+needed for a simple build, a target that uses multiple configurations,
+building an image for more than one machine, and so forth.
+Building a Simple Image
+-----------------------
+In the development environment, you need to build an image whenever you
+change hardware support, add or change system libraries, or add or
+change services that have dependencies. Several methods exist that allow
+you to build an image within the Yocto Project. This section presents
+the basic steps you need to build a simple image using BitBake from a
+build host running Linux.
+.. note::
+   -  For information on how to build an image using
+      :term:`Toaster`, see the
+      :doc:`/toaster-manual/index`.
+   -  For information on how to use ``devtool`` to build images, see the
+      ":ref:`sdk-manual/sdk-extensible:using \`\`devtool\`\` in your sdk workflow`"
+      section in the Yocto Project Application Development and the
+      Extensible Software Development Kit (eSDK) manual.
+   -  For a quick example on how to build an image using the
+      OpenEmbedded build system, see the
+      :doc:`/brief-yoctoprojectqs/index` document.
+The build process creates an entire Linux distribution from source and
+places it in your :term:`Build Directory` under
+``tmp/deploy/images``. For detailed information on the build process
+using BitBake, see the ":ref:`overview-manual/overview-manual-concepts:images`" section in the
+Yocto Project Overview and Concepts Manual.
+The following figure and list overviews the build process:
+.. image:: figures/bitbake-build-flow.png
+   :align: center
+1. *Set up Your Host Development System to Support Development Using the
+   Yocto Project*: See the ":doc:`start`" section for options on how to get a
+   build host ready to use the Yocto Project.
+2. *Initialize the Build Environment:* Initialize the build environment
+   by sourcing the build environment script (i.e.
+   :ref:`structure-core-script`):
+   ::
+      $ source oe-init-build-env [build_dir]
+   When you use the initialization script, the OpenEmbedded build system
+   uses ``build`` as the default :term:`Build Directory` in your current work
+   directory. You can use a `build_dir` argument with the script to
+   specify a different build directory.
+   .. note::
+      A common practice is to use a different Build Directory for
+      different targets. For example, ``~/build/x86`` for a ``qemux86``
+      target, and ``~/build/arm`` for a ``qemuarm`` target.
+3. *Make Sure Your* ``local.conf`` *File is Correct*: Ensure the
+   ``conf/local.conf`` configuration file, which is found in the Build
+   Directory, is set up how you want it. This file defines many aspects
+   of the build environment including the target machine architecture
+   through the ``MACHINE`` variable, the packaging format used during
+   the build
+   (:term:`PACKAGE_CLASSES`),
+   and a centralized tarball download directory through the
+   :term:`DL_DIR` variable.
+4. *Build the Image:* Build the image using the ``bitbake`` command:
+   ::
+      $ bitbake target
+   .. note::
+      For information on BitBake, see the :doc:`bitbake:index`.
+   The target is the name of the recipe you want to build. Common
+   targets are the images in ``meta/recipes-core/images``,
+   ``meta/recipes-sato/images``, and so forth all found in the
+   :term:`Source Directory`. Or, the target
+   can be the name of a recipe for a specific piece of software such as
+   BusyBox. For more details about the images the OpenEmbedded build
+   system supports, see the
+   ":ref:`ref-manual/ref-images:Images`" chapter in the Yocto
+   Project Reference Manual.
+   As an example, the following command builds the
+   ``core-image-minimal`` image:
+   ::
+      $ bitbake core-image-minimal
+   Once an
+   image has been built, it often needs to be installed. The images and
+   kernels built by the OpenEmbedded build system are placed in the
+   Build Directory in ``tmp/deploy/images``. For information on how to
+   run pre-built images such as ``qemux86`` and ``qemuarm``, see the
+   :doc:`/sdk-manual/index` manual. For
+   information about how to install these images, see the documentation
+   for your particular board or machine.
+Building Images for Multiple Targets Using Multiple Configurations
+------------------------------------------------------------------
+You can use a single ``bitbake`` command to build multiple images or
+packages for different targets where each image or package requires a
+different configuration (multiple configuration builds). The builds, in
+this scenario, are sometimes referred to as "multiconfigs", and this
+section uses that term throughout.
+This section describes how to set up for multiple configuration builds
+and how to account for cross-build dependencies between the
+multiconfigs.
+Setting Up and Running a Multiple Configuration Build
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+To accomplish a multiple configuration build, you must define each
+target's configuration separately using a parallel configuration file in
+the :term:`Build Directory`, and you
+must follow a required file hierarchy. Additionally, you must enable the
+multiple configuration builds in your ``local.conf`` file.
+Follow these steps to set up and execute multiple configuration builds:
+-  *Create Separate Configuration Files*: You need to create a single
+   configuration file for each build target (each multiconfig).
+   Minimally, each configuration file must define the machine and the
+   temporary directory BitBake uses for the build. Suggested practice
+   dictates that you do not overlap the temporary directories used
+   during the builds. However, it is possible that you can share the
+   temporary directory
+   (:term:`TMPDIR`). For example,
+   consider a scenario with two different multiconfigs for the same
+   :term:`MACHINE`: "qemux86" built
+   for two distributions such as "poky" and "poky-lsb". In this case,
+   you might want to use the same ``TMPDIR``.
+   Here is an example showing the minimal statements needed in a
+   configuration file for a "qemux86" target whose temporary build
+   directory is ``tmpmultix86``:
+   ::
+      MACHINE = "qemux86"
+      TMPDIR = "${TOPDIR}/tmpmultix86"
+   The location for these multiconfig configuration files is specific.
+   They must reside in the current build directory in a sub-directory of
+   ``conf`` named ``multiconfig``. Following is an example that defines
+   two configuration files for the "x86" and "arm" multiconfigs:
+   .. image:: figures/multiconfig_files.png
+      :align: center
+   The reason for this required file hierarchy is because the ``BBPATH``
+   variable is not constructed until the layers are parsed.
+   Consequently, using the configuration file as a pre-configuration
+   file is not possible unless it is located in the current working
+   directory.
+-  *Add the BitBake Multi-configuration Variable to the Local
+   Configuration File*: Use the
+   :term:`BBMULTICONFIG`
+   variable in your ``conf/local.conf`` configuration file to specify
+   each multiconfig. Continuing with the example from the previous
+   figure, the ``BBMULTICONFIG`` variable needs to enable two
+   multiconfigs: "x86" and "arm" by specifying each configuration file:
+   ::
+      BBMULTICONFIG = "x86 arm"
+   .. note::
+      A "default" configuration already exists by definition. This
+      configuration is named: "" (i.e. empty string) and is defined by
+      the variables coming from your ``local.conf``
+      file. Consequently, the previous example actually adds two
+      additional configurations to your build: "arm" and "x86" along
+      with "".
+-  *Launch BitBake*: Use the following BitBake command form to launch
+   the multiple configuration build:
+   ::
+      $ bitbake [mc:multiconfigname:]target [[[mc:multiconfigname:]target] ... ]
+   For the example in this section, the following command applies:
+   ::
+      $ bitbake mc:x86:core-image-minimal mc:arm:core-image-sato mc::core-image-base
+   The previous BitBake command builds a ``core-image-minimal`` image
+   that is configured through the ``x86.conf`` configuration file, a
+   ``core-image-sato`` image that is configured through the ``arm.conf``
+   configuration file and a ``core-image-base`` that is configured
+   through your ``local.conf`` configuration file.
+.. note::
+   Support for multiple configuration builds in the Yocto Project &DISTRO;
+   (&DISTRO_NAME;) Release does not include Shared State (sstate)
+   optimizations. Consequently, if a build uses the same object twice
+   in, for example, two different ``TMPDIR``
+   directories, the build either loads from an existing sstate cache for
+   that build at the start or builds the object fresh.
+Enabling Multiple Configuration Build Dependencies
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Sometimes dependencies can exist between targets (multiconfigs) in a
+multiple configuration build. For example, suppose that in order to
+build a ``core-image-sato`` image for an "x86" multiconfig, the root
+filesystem of an "arm" multiconfig must exist. This dependency is
+essentially that the
+:ref:`ref-tasks-image` task in the
+``core-image-sato`` recipe depends on the completion of the
+:ref:`ref-tasks-rootfs` task of the
+``core-image-minimal`` recipe.
+To enable dependencies in a multiple configuration build, you must
+declare the dependencies in the recipe using the following statement
+form:
+::
+   task_or_package[mcdepends] = "mc:from_multiconfig:to_multiconfig:recipe_name:task_on_which_to_depend"
+To better show how to use this statement, consider the example scenario
+from the first paragraph of this section. The following statement needs
+to be added to the recipe that builds the ``core-image-sato`` image:
+::
+   do_image[mcdepends] = "mc:x86:arm:core-image-minimal:do_rootfs"
+In this example, the `from_multiconfig` is "x86". The `to_multiconfig` is "arm". The
+task on which the ``do_image`` task in the recipe depends is the
+``do_rootfs`` task from the ``core-image-minimal`` recipe associated
+with the "arm" multiconfig.
+Once you set up this dependency, you can build the "x86" multiconfig
+using a BitBake command as follows:
+::
+   $ bitbake mc:x86:core-image-sato
+This command executes all the tasks needed to create the
+``core-image-sato`` image for the "x86" multiconfig. Because of the
+dependency, BitBake also executes through the ``do_rootfs`` task for the
+"arm" multiconfig build.
+Having a recipe depend on the root filesystem of another build might not
+seem that useful. Consider this change to the statement in the
+``core-image-sato`` recipe:
+::
+   do_image[mcdepends] = "mc:x86:arm:core-image-minimal:do_image"
+In this case, BitBake must
+create the ``core-image-minimal`` image for the "arm" build since the
+"x86" build depends on it.
+Because "x86" and "arm" are enabled for multiple configuration builds
+and have separate configuration files, BitBake places the artifacts for
+each build in the respective temporary build directories (i.e.
+:term:`TMPDIR`).
+Building an Initial RAM Filesystem (initramfs) Image
+----------------------------------------------------
+An initial RAM filesystem (initramfs) image provides a temporary root
+filesystem used for early system initialization (e.g. loading of modules
+needed to locate and mount the "real" root filesystem).
+.. note::
+   The initramfs image is the successor of initial RAM disk (initrd). It
+   is a "copy in and out" (cpio) archive of the initial filesystem that
+   gets loaded into memory during the Linux startup process. Because
+   Linux uses the contents of the archive during initialization, the
+   initramfs image needs to contain all of the device drivers and tools
+   needed to mount the final root filesystem.
+Follow these steps to create an initramfs image:
+1. *Create the initramfs Image Recipe:* You can reference the
+   ``core-image-minimal-initramfs.bb`` recipe found in the
+   ``meta/recipes-core`` directory of the :term:`Source Directory`
+   as an example
+   from which to work.
+2. *Decide if You Need to Bundle the initramfs Image Into the Kernel
+   Image:* If you want the initramfs image that is built to be bundled
+   in with the kernel image, set the
+   :term:`INITRAMFS_IMAGE_BUNDLE`
+   variable to "1" in your ``local.conf`` configuration file and set the
+   :term:`INITRAMFS_IMAGE`
+   variable in the recipe that builds the kernel image.
+   .. note::
+      It is recommended that you do bundle the initramfs image with the
+      kernel image to avoid circular dependencies between the kernel
+      recipe and the initramfs recipe should the initramfs image include
+      kernel modules.
+   Setting the ``INITRAMFS_IMAGE_BUNDLE`` flag causes the initramfs
+   image to be unpacked into the ``${B}/usr/`` directory. The unpacked
+   initramfs image is then passed to the kernel's ``Makefile`` using the
+   :term:`CONFIG_INITRAMFS_SOURCE`
+   variable, allowing the initramfs image to be built into the kernel
+   normally.
+   .. note::
+      If you choose to not bundle the initramfs image with the kernel
+      image, you are essentially using an
+      `Initial RAM Disk (initrd) <https://en.wikipedia.org/wiki/Initrd>`__.
+      Creating an initrd is handled primarily through the :term:`INITRD_IMAGE`,
+      ``INITRD_LIVE``, and ``INITRD_IMAGE_LIVE`` variables. For more
+      information, see the :ref:`ref-classes-image-live` file.
+3. *Optionally Add Items to the initramfs Image Through the initramfs
+   Image Recipe:* If you add items to the initramfs image by way of its
+   recipe, you should use
+   :term:`PACKAGE_INSTALL`
+   rather than
+   :term:`IMAGE_INSTALL`.
+   ``PACKAGE_INSTALL`` gives more direct control of what is added to the
+   image as compared to the defaults you might not necessarily want that
+   are set by the :ref:`image <ref-classes-image>`
+   or :ref:`core-image <ref-classes-core-image>`
+   classes.
+4. *Build the Kernel Image and the initramfs Image:* Build your kernel
+   image using BitBake. Because the initramfs image recipe is a
+   dependency of the kernel image, the initramfs image is built as well
+   and bundled with the kernel image if you used the
+   :term:`INITRAMFS_IMAGE_BUNDLE`
+   variable described earlier.
+Building a Tiny System
+----------------------
+Very small distributions have some significant advantages such as
+requiring less on-die or in-package memory (cheaper), better performance
+through efficient cache usage, lower power requirements due to less
+memory, faster boot times, and reduced development overhead. Some
+real-world examples where a very small distribution gives you distinct
+advantages are digital cameras, medical devices, and small headless
+systems.
+This section presents information that shows you how you can trim your
+distribution to even smaller sizes than the ``poky-tiny`` distribution,
+which is around 5 Mbytes, that can be built out-of-the-box using the
+Yocto Project.
+Tiny System Overview
+~~~~~~~~~~~~~~~~~~~~
+The following list presents the overall steps you need to consider and
+perform to create distributions with smaller root filesystems, achieve
+faster boot times, maintain your critical functionality, and avoid
+initial RAM disks:
+-  `Determine your goals and guiding
+   principles. <#goals-and-guiding-principles>`__
+-  `Understand what contributes to your image
+   size. <#understand-what-gives-your-image-size>`__
+-  `Reduce the size of the root
+   filesystem. <#trim-the-root-filesystem>`__
+-  `Reduce the size of the kernel. <#trim-the-kernel>`__
+-  `Eliminate packaging
+   requirements. <#remove-package-management-requirements>`__
+-  `Look for other ways to minimize
+   size. <#look-for-other-ways-to-minimize-size>`__
+-  `Iterate on the process. <#iterate-on-the-process>`__
+Goals and Guiding Principles
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Before you can reach your destination, you need to know where you are
+going. Here is an example list that you can use as a guide when creating
+very small distributions:
+-  Determine how much space you need (e.g. a kernel that is 1 Mbyte or
+   less and a root filesystem that is 3 Mbytes or less).
+-  Find the areas that are currently taking 90% of the space and
+   concentrate on reducing those areas.
+-  Do not create any difficult "hacks" to achieve your goals.
+-  Leverage the device-specific options.
+-  Work in a separate layer so that you keep changes isolated. For
+   information on how to create layers, see the "`Understanding and
+   Creating Layers <#understanding-and-creating-layers>`__" section.
+Understand What Contributes to Your Image Size
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+It is easiest to have something to start with when creating your own
+distribution. You can use the Yocto Project out-of-the-box to create the
+``poky-tiny`` distribution. Ultimately, you will want to make changes in
+your own distribution that are likely modeled after ``poky-tiny``.
+.. note::
+   To use ``poky-tiny`` in your build, set the ``DISTRO`` variable in your
+   ``local.conf`` file to "poky-tiny" as described in the
+   ":ref:`dev-manual/common-tasks:creating your own distribution`"
+   section.
+Understanding some memory concepts will help you reduce the system size.
+Memory consists of static, dynamic, and temporary memory. Static memory
+is the TEXT (code), DATA (initialized data in the code), and BSS
+(uninitialized data) sections. Dynamic memory represents memory that is
+allocated at runtime: stacks, hash tables, and so forth. Temporary
+memory is recovered after the boot process. This memory consists of
+memory used for decompressing the kernel and for the ``__init__``
+functions.
+To help you see where you currently are with kernel and root filesystem
+sizes, you can use two tools found in the :term:`Source Directory`
+in the
+``scripts/tiny/`` directory:
+-  ``ksize.py``: Reports component sizes for the kernel build objects.
+-  ``dirsize.py``: Reports component sizes for the root filesystem.
+This next tool and command help you organize configuration fragments and
+view file dependencies in a human-readable form:
+-  ``merge_config.sh``: Helps you manage configuration files and
+   fragments within the kernel. With this tool, you can merge individual
+   configuration fragments together. The tool allows you to make
+   overrides and warns you of any missing configuration options. The
+   tool is ideal for allowing you to iterate on configurations, create
+   minimal configurations, and create configuration files for different
+   machines without having to duplicate your process.
+   The ``merge_config.sh`` script is part of the Linux Yocto kernel Git
+   repositories (i.e. ``linux-yocto-3.14``, ``linux-yocto-3.10``,
+   ``linux-yocto-3.8``, and so forth) in the ``scripts/kconfig``
+   directory.
+   For more information on configuration fragments, see the
+   ":ref:`kernel-dev/kernel-dev-common:creating configuration fragments`"
+   section in the Yocto Project Linux Kernel Development Manual.
+-  ``bitbake -u taskexp -g bitbake_target``: Using the BitBake command
+   with these options brings up a Dependency Explorer from which you can
+   view file dependencies. Understanding these dependencies allows you
+   to make informed decisions when cutting out various pieces of the
+   kernel and root filesystem.
+Trim the Root Filesystem
+~~~~~~~~~~~~~~~~~~~~~~~~
+The root filesystem is made up of packages for booting, libraries, and
+applications. To change things, you can configure how the packaging
+happens, which changes the way you build them. You can also modify the
+filesystem itself or select a different filesystem.
+First, find out what is hogging your root filesystem by running the
+``dirsize.py`` script from your root directory:
+::
+   $ cd root-directory-of-image
+   $ dirsize.py 100000 > dirsize-100k.log
+   $ cat dirsize-100k.log
+You can apply a filter to the script to ignore files
+under a certain size. The previous example filters out any files below
+100 Kbytes. The sizes reported by the tool are uncompressed, and thus
+will be smaller by a relatively constant factor in a compressed root
+filesystem. When you examine your log file, you can focus on areas of
+the root filesystem that take up large amounts of memory.
+You need to be sure that what you eliminate does not cripple the
+functionality you need. One way to see how packages relate to each other
+is by using the Dependency Explorer UI with the BitBake command:
+::
+   $ cd image-directory
+   $ bitbake -u taskexp -g image
+Use the interface to
+select potential packages you wish to eliminate and see their dependency
+relationships.
+When deciding how to reduce the size, get rid of packages that result in
+minimal impact on the feature set. For example, you might not need a VGA
+display. Or, you might be able to get by with ``devtmpfs`` and ``mdev``
+instead of ``udev``.
+Use your ``local.conf`` file to make changes. For example, to eliminate
+``udev`` and ``glib``, set the following in the local configuration
+file:
+::
+   VIRTUAL-RUNTIME_dev_manager = ""
+Finally, you should consider exactly the type of root filesystem you
+need to meet your needs while also reducing its size. For example,
+consider ``cramfs``, ``squashfs``, ``ubifs``, ``ext2``, or an
+``initramfs`` using ``initramfs``. Be aware that ``ext3`` requires a 1
+Mbyte journal. If you are okay with running read-only, you do not need
+this journal.
+.. note::
+   After each round of elimination, you need to rebuild your system and
+   then use the tools to see the effects of your reductions.
+Trim the Kernel
+~~~~~~~~~~~~~~~
+The kernel is built by including policies for hardware-independent
+aspects. What subsystems do you enable? For what architecture are you
+building? Which drivers do you build by default?
+.. note::
+   You can modify the kernel source if you want to help with boot time.
+Run the ``ksize.py`` script from the top-level Linux build directory to
+get an idea of what is making up the kernel:
+::
+   $ cd top-level-linux-build-directory
+   $ ksize.py > ksize.log
+   $ cat ksize.log
+When you examine the log, you will see how much space is taken up with
+the built-in ``.o`` files for drivers, networking, core kernel files,
+filesystem, sound, and so forth. The sizes reported by the tool are
+uncompressed, and thus will be smaller by a relatively constant factor
+in a compressed kernel image. Look to reduce the areas that are large
+and taking up around the "90% rule."
+To examine, or drill down, into any particular area, use the ``-d``
+option with the script:
+::
+   $ ksize.py -d > ksize.log
+Using this option
+breaks out the individual file information for each area of the kernel
+(e.g. drivers, networking, and so forth).
+Use your log file to see what you can eliminate from the kernel based on
+features you can let go. For example, if you are not going to need
+sound, you do not need any drivers that support sound.
+After figuring out what to eliminate, you need to reconfigure the kernel
+to reflect those changes during the next build. You could run
+``menuconfig`` and make all your changes at once. However, that makes it
+difficult to see the effects of your individual eliminations and also
+makes it difficult to replicate the changes for perhaps another target
+device. A better method is to start with no configurations using
+``allnoconfig``, create configuration fragments for individual changes,
+and then manage the fragments into a single configuration file using
+``merge_config.sh``. The tool makes it easy for you to iterate using the
+configuration change and build cycle.
+Each time you make configuration changes, you need to rebuild the kernel
+and check to see what impact your changes had on the overall size.
+Remove Package Management Requirements
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Packaging requirements add size to the image. One way to reduce the size
+of the image is to remove all the packaging requirements from the image.
+This reduction includes both removing the package manager and its unique
+dependencies as well as removing the package management data itself.
+To eliminate all the packaging requirements for an image, be sure that
+"package-management" is not part of your
+:term:`IMAGE_FEATURES`
+statement for the image. When you remove this feature, you are removing
+the package manager as well as its dependencies from the root
+filesystem.
+Look for Other Ways to Minimize Size
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Depending on your particular circumstances, other areas that you can
+trim likely exist. The key to finding these areas is through tools and
+methods described here combined with experimentation and iteration. Here
+are a couple of areas to experiment with:
+-  ``glibc``: In general, follow this process:
+   1. Remove ``glibc`` features from
+      :term:`DISTRO_FEATURES`
+      that you think you do not need.
+   2. Build your distribution.
+   3. If the build fails due to missing symbols in a package, determine
+      if you can reconfigure the package to not need those features. For
+      example, change the configuration to not support wide character
+      support as is done for ``ncurses``. Or, if support for those
+      characters is needed, determine what ``glibc`` features provide
+      the support and restore the configuration.
+   4. Rebuild and repeat the process.
+-  ``busybox``: For BusyBox, use a process similar as described for
+   ``glibc``. A difference is you will need to boot the resulting system
+   to see if you are able to do everything you expect from the running
+   system. You need to be sure to integrate configuration fragments into
+   Busybox because BusyBox handles its own core features and then allows
+   you to add configuration fragments on top.
+Iterate on the Process
+~~~~~~~~~~~~~~~~~~~~~~
+If you have not reached your goals on system size, you need to iterate
+on the process. The process is the same. Use the tools and see just what
+is taking up 90% of the root filesystem and the kernel. Decide what you
+can eliminate without limiting your device beyond what you need.
+Depending on your system, a good place to look might be Busybox, which
+provides a stripped down version of Unix tools in a single, executable
+file. You might be able to drop virtual terminal services or perhaps
+ipv6.
+Building Images for More than One Machine
+-----------------------------------------
+A common scenario developers face is creating images for several
+different machines that use the same software environment. In this
+situation, it is tempting to set the tunings and optimization flags for
+each build specifically for the targeted hardware (i.e. "maxing out" the
+tunings). Doing so can considerably add to build times and package feed
+maintenance collectively for the machines. For example, selecting tunes
+that are extremely specific to a CPU core used in a system might enable
+some micro optimizations in GCC for that particular system but would
+otherwise not gain you much of a performance difference across the other
+systems as compared to using a more general tuning across all the builds
+(e.g. setting :term:`DEFAULTTUNE`
+specifically for each machine's build). Rather than "max out" each
+build's tunings, you can take steps that cause the OpenEmbedded build
+system to reuse software across the various machines where it makes
+sense.
+If build speed and package feed maintenance are considerations, you
+should consider the points in this section that can help you optimize
+your tunings to best consider build times and package feed maintenance.
+-  *Share the Build Directory:* If at all possible, share the
+   :term:`TMPDIR` across builds. The
+   Yocto Project supports switching between different
+   :term:`MACHINE` values in the same
+   ``TMPDIR``. This practice is well supported and regularly used by
+   developers when building for multiple machines. When you use the same
+   ``TMPDIR`` for multiple machine builds, the OpenEmbedded build system
+   can reuse the existing native and often cross-recipes for multiple
+   machines. Thus, build time decreases.
+   .. note::
+      If :term:`DISTRO` settings change or fundamental configuration settings
+      such as the filesystem layout, you need to work with a clean ``TMPDIR``.
+      Sharing ``TMPDIR`` under these circumstances might work but since it is
+      not guaranteed, you should use a clean ``TMPDIR``.
+-  *Enable the Appropriate Package Architecture:* By default, the
+   OpenEmbedded build system enables three levels of package
+   architectures: "all", "tune" or "package", and "machine". Any given
+   recipe usually selects one of these package architectures (types) for
+   its output. Depending for what a given recipe creates packages,
+   making sure you enable the appropriate package architecture can
+   directly impact the build time.
+   A recipe that just generates scripts can enable "all" architecture
+   because there are no binaries to build. To specifically enable "all"
+   architecture, be sure your recipe inherits the
+   :ref:`allarch <ref-classes-allarch>` class.
+   This class is useful for "all" architectures because it configures
+   many variables so packages can be used across multiple architectures.
+   If your recipe needs to generate packages that are machine-specific
+   or when one of the build or runtime dependencies is already
+   machine-architecture dependent, which makes your recipe also
+   machine-architecture dependent, make sure your recipe enables the
+   "machine" package architecture through the
+   :term:`MACHINE_ARCH`
+   variable:
+   ::
+      PACKAGE_ARCH = "${MACHINE_ARCH}"
+   When you do not
+   specifically enable a package architecture through the
+   :term:`PACKAGE_ARCH`, The
+   OpenEmbedded build system defaults to the
+   :term:`TUNE_PKGARCH` setting:
+   ::
+      PACKAGE_ARCH = "${TUNE_PKGARCH}"
+-  *Choose a Generic Tuning File if Possible:* Some tunes are more
+   generic and can run on multiple targets (e.g. an ``armv5`` set of
+   packages could run on ``armv6`` and ``armv7`` processors in most
+   cases). Similarly, ``i486`` binaries could work on ``i586`` and
+   higher processors. You should realize, however, that advances on
+   newer processor versions would not be used.
+   If you select the same tune for several different machines, the
+   OpenEmbedded build system reuses software previously built, thus
+   speeding up the overall build time. Realize that even though a new
+   sysroot for each machine is generated, the software is not recompiled
+   and only one package feed exists.
+-  *Manage Granular Level Packaging:* Sometimes cases exist where
+   injecting another level of package architecture beyond the three
+   higher levels noted earlier can be useful. For example, consider how
+   NXP (formerly Freescale) allows for the easy reuse of binary packages
+   in their layer
+   :yocto_git:`meta-freescale </meta-freescale/>`.
+   In this example, the
+   :yocto_git:`fsl-dynamic-packagearch </meta-freescale/tree/classes/fsl-dynamic-packagearch.bbclass>`
+   class shares GPU packages for i.MX53 boards because all boards share
+   the AMD GPU. The i.MX6-based boards can do the same because all
+   boards share the Vivante GPU. This class inspects the BitBake
+   datastore to identify if the package provides or depends on one of
+   the sub-architecture values. If so, the class sets the
+   :term:`PACKAGE_ARCH` value
+   based on the ``MACHINE_SUBARCH`` value. If the package does not
+   provide or depend on one of the sub-architecture values but it
+   matches a value in the machine-specific filter, it sets
+   :term:`MACHINE_ARCH`. This
+   behavior reduces the number of packages built and saves build time by
+   reusing binaries.
+-  *Use Tools to Debug Issues:* Sometimes you can run into situations
+   where software is being rebuilt when you think it should not be. For
+   example, the OpenEmbedded build system might not be using shared
+   state between machines when you think it should be. These types of
+   situations are usually due to references to machine-specific
+   variables such as :term:`MACHINE`,
+   :term:`SERIAL_CONSOLES`,
+   :term:`XSERVER`,
+   :term:`MACHINE_FEATURES`,
+   and so forth in code that is supposed to only be tune-specific or
+   when the recipe depends
+   (:term:`DEPENDS`,
+   :term:`RDEPENDS`,
+   :term:`RRECOMMENDS`,
+   :term:`RSUGGESTS`, and so forth)
+   on some other recipe that already has
+   :term:`PACKAGE_ARCH` defined
+   as "${MACHINE_ARCH}".
+   .. note::
+      Patches to fix any issues identified are most welcome as these
+      issues occasionally do occur.
+   For such cases, you can use some tools to help you sort out the
+   situation:
+   -  ``state-diff-machines.sh``*:* You can find this tool in the
+      ``scripts`` directory of the Source Repositories. See the comments
+      in the script for information on how to use the tool.
+   -  *BitBake's "-S printdiff" Option:* Using this option causes
+      BitBake to try to establish the closest signature match it can
+      (e.g. in the shared state cache) and then run ``bitbake-diffsigs``
+      over the matches to determine the stamps and delta where these two
+      stamp trees diverge.
+Building Software from an External Source
+-----------------------------------------
+By default, the OpenEmbedded build system uses the
+:term:`Build Directory` when building source
+code. The build process involves fetching the source files, unpacking
+them, and then patching them if necessary before the build takes place.
+Situations exist where you might want to build software from source
+files that are external to and thus outside of the OpenEmbedded build
+system. For example, suppose you have a project that includes a new BSP
+with a heavily customized kernel. And, you want to minimize exposing the
+build system to the development team so that they can focus on their
+project and maintain everyone's workflow as much as possible. In this
+case, you want a kernel source directory on the development machine
+where the development occurs. You want the recipe's
+:term:`SRC_URI` variable to point to
+the external directory and use it as is, not copy it.
+To build from software that comes from an external source, all you need
+to do is inherit the
+:ref:`externalsrc <ref-classes-externalsrc>` class
+and then set the
+:term:`EXTERNALSRC` variable to
+point to your external source code. Here are the statements to put in
+your ``local.conf`` file:
+::
+   INHERIT += "externalsrc"
+   EXTERNALSRC_pn-myrecipe = "path-to-your-source-tree"
+This next example shows how to accomplish the same thing by setting
+``EXTERNALSRC`` in the recipe itself or in the recipe's append file:
+::
+   EXTERNALSRC = "path"
+   EXTERNALSRC_BUILD = "path"
+.. note::
+   In order for these settings to take effect, you must globally or
+   locally inherit the :ref:`externalsrc <ref-classes-externalsrc>`
+   class.
+By default, ``externalsrc.bbclass`` builds the source code in a
+directory separate from the external source directory as specified by
+:term:`EXTERNALSRC`. If you need
+to have the source built in the same directory in which it resides, or
+some other nominated directory, you can set
+:term:`EXTERNALSRC_BUILD`
+to point to that directory:
+::
+   EXTERNALSRC_BUILD_pn-myrecipe = "path-to-your-source-tree"
+Replicating a Build Offline
+---------------------------
+It can be useful to take a "snapshot" of upstream sources used in a
+build and then use that "snapshot" later to replicate the build offline.
+To do so, you need to first prepare and populate your downloads
+directory your "snapshot" of files. Once your downloads directory is
+ready, you can use it at any time and from any machine to replicate your
+build.
+Follow these steps to populate your Downloads directory:
+1. *Create a Clean Downloads Directory:* Start with an empty downloads
+   directory (:term:`DL_DIR`). You
+   start with an empty downloads directory by either removing the files
+   in the existing directory or by setting ``DL_DIR`` to point to either
+   an empty location or one that does not yet exist.
+2. *Generate Tarballs of the Source Git Repositories:* Edit your
+   ``local.conf`` configuration file as follows:
+   ::
+      DL_DIR = "/home/your-download-dir/"
+      BB_GENERATE_MIRROR_TARBALLS = "1"
+   During
+   the fetch process in the next step, BitBake gathers the source files
+   and creates tarballs in the directory pointed to by ``DL_DIR``. See
+   the
+   :term:`BB_GENERATE_MIRROR_TARBALLS`
+   variable for more information.
+3. *Populate Your Downloads Directory Without Building:* Use BitBake to
+   fetch your sources but inhibit the build:
+   ::
+      $ bitbake target --runonly=fetch
+   The downloads directory (i.e. ``${DL_DIR}``) now has
+   a "snapshot" of the source files in the form of tarballs, which can
+   be used for the build.
+4. *Optionally Remove Any Git or other SCM Subdirectories From the
+   Downloads Directory:* If you want, you can clean up your downloads
+   directory by removing any Git or other Source Control Management
+   (SCM) subdirectories such as ``${DL_DIR}/git2/*``. The tarballs
+   already contain these subdirectories.
+Once your downloads directory has everything it needs regarding source
+files, you can create your "own-mirror" and build your target.
+Understand that you can use the files to build the target offline from
+any machine and at any time.
+Follow these steps to build your target using the files in the downloads
+directory:
+1. *Using Local Files Only:* Inside your ``local.conf`` file, add the
+   :term:`SOURCE_MIRROR_URL`
+   variable, inherit the
+   :ref:`own-mirrors <ref-classes-own-mirrors>`
+   class, and use the
+   :term:`bitbake:BB_NO_NETWORK`
+   variable to your ``local.conf``.
+   ::
+      SOURCE_MIRROR_URL ?= "file:///home/your-download-dir/"
+      INHERIT += "own-mirrors"
+      BB_NO_NETWORK = "1"
+   The ``SOURCE_MIRROR_URL`` and ``own-mirror``
+   class set up the system to use the downloads directory as your "own
+   mirror". Using the ``BB_NO_NETWORK`` variable makes sure that
+   BitBake's fetching process in step 3 stays local, which means files
+   from your "own-mirror" are used.
+2. *Start With a Clean Build:* You can start with a clean build by
+   removing the
+   ``${``\ :term:`TMPDIR`\ ``}``
+   directory or using a new :term:`Build Directory`.
+3. *Build Your Target:* Use BitBake to build your target:
+   ::
+      $ bitbake target
+   The build completes using the known local "snapshot" of source
+   files from your mirror. The resulting tarballs for your "snapshot" of
+   source files are in the downloads directory.
+   .. note::
+      The offline build does not work if recipes attempt to find the
+      latest version of software by setting
+      :term:`SRCREV` to
+      ``${``\ :term:`AUTOREV`\ ``}``:
+      ::
+         SRCREV = "${AUTOREV}"
+      When a recipe sets ``SRCREV`` to
+      ``${AUTOREV}``, the build system accesses the network in an
+      attempt to determine the latest version of software from the SCM.
+      Typically, recipes that use ``AUTOREV`` are custom or modified
+      recipes. Recipes that reside in public repositories usually do not
+      use ``AUTOREV``.
+      If you do have recipes that use ``AUTOREV``, you can take steps to
+      still use the recipes in an offline build. Do the following:
+      1. Use a configuration generated by enabling `build
+         history <#maintaining-build-output-quality>`__.
+      2. Use the ``buildhistory-collect-srcrevs`` command to collect the
+         stored ``SRCREV`` values from the build's history. For more
+         information on collecting these values, see the "`Build History
+         Package Information <#build-history-package-information>`__"
+         section.
+      3. Once you have the correct source revisions, you can modify
+         those recipes to to set ``SRCREV`` to specific versions of the
+         software.
+Speeding Up a Build
+===================
+Build time can be an issue. By default, the build system uses simple
+controls to try and maximize build efficiency. In general, the default
+settings for all the following variables result in the most efficient
+build times when dealing with single socket systems (i.e. a single CPU).
+If you have multiple CPUs, you might try increasing the default values
+to gain more speed. See the descriptions in the glossary for each
+variable for more information:
+-  :term:`BB_NUMBER_THREADS`:
+   The maximum number of threads BitBake simultaneously executes.
+-  :term:`bitbake:BB_NUMBER_PARSE_THREADS`:
+   The number of threads BitBake uses during parsing.
+-  :term:`PARALLEL_MAKE`: Extra
+   options passed to the ``make`` command during the
+   :ref:`ref-tasks-compile` task in
+   order to specify parallel compilation on the local build host.
+-  :term:`PARALLEL_MAKEINST`:
+   Extra options passed to the ``make`` command during the
+   :ref:`ref-tasks-install` task in
+   order to specify parallel installation on the local build host.
+As mentioned, these variables all scale to the number of processor cores
+available on the build system. For single socket systems, this
+auto-scaling ensures that the build system fundamentally takes advantage
+of potential parallel operations during the build based on the build
+machine's capabilities.
+Following are additional factors that can affect build speed:
+-  File system type: The file system type that the build is being
+   performed on can also influence performance. Using ``ext4`` is
+   recommended as compared to ``ext2`` and ``ext3`` due to ``ext4``
+   improved features such as extents.
+-  Disabling the updating of access time using ``noatime``: The
+   ``noatime`` mount option prevents the build system from updating file
+   and directory access times.
+-  Setting a longer commit: Using the "commit=" mount option increases
+   the interval in seconds between disk cache writes. Changing this
+   interval from the five second default to something longer increases
+   the risk of data loss but decreases the need to write to the disk,
+   thus increasing the build performance.
+-  Choosing the packaging backend: Of the available packaging backends,
+   IPK is the fastest. Additionally, selecting a singular packaging
+   backend also helps.
+-  Using ``tmpfs`` for :term:`TMPDIR`
+   as a temporary file system: While this can help speed up the build,
+   the benefits are limited due to the compiler using ``-pipe``. The
+   build system goes to some lengths to avoid ``sync()`` calls into the
+   file system on the principle that if there was a significant failure,
+   the :term:`Build Directory`
+   contents could easily be rebuilt.
+-  Inheriting the
+   :ref:`rm_work <ref-classes-rm-work>` class:
+   Inheriting this class has shown to speed up builds due to
+   significantly lower amounts of data stored in the data cache as well
+   as on disk. Inheriting this class also makes cleanup of
+   :term:`TMPDIR` faster, at the
+   expense of being easily able to dive into the source code. File
+   system maintainers have recommended that the fastest way to clean up
+   large numbers of files is to reformat partitions rather than delete
+   files due to the linear nature of partitions. This, of course,
+   assumes you structure the disk partitions and file systems in a way
+   that this is practical.
+Aside from the previous list, you should keep some trade offs in mind
+that can help you speed up the build:
+-  Remove items from
+   :term:`DISTRO_FEATURES`
+   that you might not need.
+-  Exclude debug symbols and other debug information: If you do not need
+   these symbols and other debug information, disabling the ``*-dbg``
+   package generation can speed up the build. You can disable this
+   generation by setting the
+   :term:`INHIBIT_PACKAGE_DEBUG_SPLIT`
+   variable to "1".
+-  Disable static library generation for recipes derived from
+   ``autoconf`` or ``libtool``: Following is an example showing how to
+   disable static libraries and still provide an override to handle
+   exceptions:
+   ::
+      STATICLIBCONF = "--disable-static"
+      STATICLIBCONF_sqlite3-native = ""
+      EXTRA_OECONF += "${STATICLIBCONF}"
+   .. note::
+      -  Some recipes need static libraries in order to work correctly
+         (e.g. ``pseudo-native`` needs ``sqlite3-native``). Overrides,
+         as in the previous example, account for these kinds of
+         exceptions.
+      -  Some packages have packaging code that assumes the presence of
+         the static libraries. If so, you might need to exclude them as
+         well.
+Working With Libraries
+======================
+Libraries are an integral part of your system. This section describes
+some common practices you might find helpful when working with libraries
+to build your system:
+-  `How to include static library
+   files <#including-static-library-files>`__
+-  `How to use the Multilib feature to combine multiple versions of
+   library files into a single
+   image <#combining-multiple-versions-library-files-into-one-image>`__
+-  `How to install multiple versions of the same library in parallel on
+   the same
+   system <#installing-multiple-versions-of-the-same-library>`__
+Including Static Library Files
+------------------------------
+If you are building a library and the library offers static linking, you
+can control which static library files (``*.a`` files) get included in
+the built library.
+The :term:`PACKAGES` and
+:term:`FILES_* <FILES>` variables in the
+``meta/conf/bitbake.conf`` configuration file define how files installed
+by the ``do_install`` task are packaged. By default, the ``PACKAGES``
+variable includes ``${PN}-staticdev``, which represents all static
+library files.
+.. note::
+   Some previously released versions of the Yocto Project defined the
+   static library files through ``${PN}-dev``.
+Following is part of the BitBake configuration file, where you can see
+how the static library files are defined:
+::
+   PACKAGE_BEFORE_PN ?= ""
+   PACKAGES = "${PN}-dbg ${PN}-staticdev ${PN}-dev ${PN}-doc ${PN}-locale ${PACKAGE_BEFORE_PN} ${PN}"
+   PACKAGES_DYNAMIC = "^${PN}-locale-.*"
+   FILES = ""
+   FILES_${PN} = "${bindir}/* ${sbindir}/* ${libexecdir}/* ${libdir}/lib*${SOLIBS} \
+               ${sysconfdir} ${sharedstatedir} ${localstatedir} \
+               ${base_bindir}/* ${base_sbindir}/* \
+               ${base_libdir}/*${SOLIBS} \
+               ${base_prefix}/lib/udev/rules.d ${prefix}/lib/udev/rules.d \
+               ${datadir}/${BPN} ${libdir}/${BPN}/* \
+               ${datadir}/pixmaps ${datadir}/applications \
+               ${datadir}/idl ${datadir}/omf ${datadir}/sounds \
+               ${libdir}/bonobo/servers"
+   FILES_${PN}-bin = "${bindir}/* ${sbindir}/*"
+   FILES_${PN}-doc = "${docdir} ${mandir} ${infodir} ${datadir}/gtk-doc \
+               ${datadir}/gnome/help"
+   SECTION_${PN}-doc = "doc"
+   FILES_SOLIBSDEV ?= "${base_libdir}/lib*${SOLIBSDEV} ${libdir}/lib*${SOLIBSDEV}"
+   FILES_${PN}-dev = "${includedir} ${FILES_SOLIBSDEV} ${libdir}/*.la \
+                   ${libdir}/*.o ${libdir}/pkgconfig ${datadir}/pkgconfig \
+                   ${datadir}/aclocal ${base_libdir}/*.o \
+                   ${libdir}/${BPN}/*.la ${base_libdir}/*.la"
+   SECTION_${PN}-dev = "devel"
+   ALLOW_EMPTY_${PN}-dev = "1"
+   RDEPENDS_${PN}-dev = "${PN} (= ${EXTENDPKGV})"
+   FILES_${PN}-staticdev = "${libdir}/*.a ${base_libdir}/*.a ${libdir}/${BPN}/*.a"
+   SECTION_${PN}-staticdev = "devel"
+   RDEPENDS_${PN}-staticdev = "${PN}-dev (= ${EXTENDPKGV})"
+Combining Multiple Versions of Library Files into One Image
+-----------------------------------------------------------
+The build system offers the ability to build libraries with different
+target optimizations or architecture formats and combine these together
+into one system image. You can link different binaries in the image
+against the different libraries as needed for specific use cases. This
+feature is called "Multilib".
+An example would be where you have most of a system compiled in 32-bit
+mode using 32-bit libraries, but you have something large, like a
+database engine, that needs to be a 64-bit application and uses 64-bit
+libraries. Multilib allows you to get the best of both 32-bit and 64-bit
+libraries.
+While the Multilib feature is most commonly used for 32 and 64-bit
+differences, the approach the build system uses facilitates different
+target optimizations. You could compile some binaries to use one set of
+libraries and other binaries to use a different set of libraries. The
+libraries could differ in architecture, compiler options, or other
+optimizations.
+Several examples exist in the ``meta-skeleton`` layer found in the
+:term:`Source Directory`:
+-  ``conf/multilib-example.conf`` configuration file
+-  ``conf/multilib-example2.conf`` configuration file
+-  ``recipes-multilib/images/core-image-multilib-example.bb`` recipe
+Preparing to Use Multilib
+~~~~~~~~~~~~~~~~~~~~~~~~~
+User-specific requirements drive the Multilib feature. Consequently,
+there is no one "out-of-the-box" configuration that likely exists to
+meet your needs.
+In order to enable Multilib, you first need to ensure your recipe is
+extended to support multiple libraries. Many standard recipes are
+already extended and support multiple libraries. You can check in the
+``meta/conf/multilib.conf`` configuration file in the
+:term:`Source Directory` to see how this is
+done using the
+:term:`BBCLASSEXTEND` variable.
+Eventually, all recipes will be covered and this list will not be
+needed.
+For the most part, the Multilib class extension works automatically to
+extend the package name from ``${PN}`` to ``${MLPREFIX}${PN}``, where
+``MLPREFIX`` is the particular multilib (e.g. "lib32-" or "lib64-").
+Standard variables such as
+:term:`DEPENDS`,
+:term:`RDEPENDS`,
+:term:`RPROVIDES`,
+:term:`RRECOMMENDS`,
+:term:`PACKAGES`, and
+:term:`PACKAGES_DYNAMIC` are
+automatically extended by the system. If you are extending any manual
+code in the recipe, you can use the ``${MLPREFIX}`` variable to ensure
+those names are extended correctly. This automatic extension code
+resides in ``multilib.bbclass``.
+Using Multilib
+~~~~~~~~~~~~~~
+After you have set up the recipes, you need to define the actual
+combination of multiple libraries you want to build. You accomplish this
+through your ``local.conf`` configuration file in the
+:term:`Build Directory`. An example
+configuration would be as follows:
+::
+   MACHINE = "qemux86-64"
+   require conf/multilib.conf
+   MULTILIBS = "multilib:lib32"
+   DEFAULTTUNE_virtclass-multilib-lib32 = "x86"
+   IMAGE_INSTALL_append = "lib32-glib-2.0"
+This example enables an additional library named
+``lib32`` alongside the normal target packages. When combining these
+"lib32" alternatives, the example uses "x86" for tuning. For information
+on this particular tuning, see
+``meta/conf/machine/include/ia32/arch-ia32.inc``.
+The example then includes ``lib32-glib-2.0`` in all the images, which
+illustrates one method of including a multiple library dependency. You
+can use a normal image build to include this dependency, for example:
+::
+   $ bitbake core-image-sato
+You can also build Multilib packages
+specifically with a command like this:
+::
+   $ bitbake lib32-glib-2.0
+Additional Implementation Details
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Generic implementation details as well as details that are specific to
+package management systems exist. Following are implementation details
+that exist regardless of the package management system:
+-  The typical convention used for the class extension code as used by
+   Multilib assumes that all package names specified in
+   :term:`PACKAGES` that contain
+   ``${PN}`` have ``${PN}`` at the start of the name. When that
+   convention is not followed and ``${PN}`` appears at the middle or the
+   end of a name, problems occur.
+-  The :term:`TARGET_VENDOR`
+   value under Multilib will be extended to "-vendormlmultilib" (e.g.
+   "-pokymllib32" for a "lib32" Multilib with Poky). The reason for this
+   slightly unwieldy contraction is that any "-" characters in the
+   vendor string presently break Autoconf's ``config.sub``, and other
+   separators are problematic for different reasons.
+For the RPM Package Management System, the following implementation
+details exist:
+-  A unique architecture is defined for the Multilib packages, along
+   with creating a unique deploy folder under ``tmp/deploy/rpm`` in the
+   :term:`Build Directory`. For
+   example, consider ``lib32`` in a ``qemux86-64`` image. The possible
+   architectures in the system are "all", "qemux86_64",
+   "lib32_qemux86_64", and "lib32_x86".
+-  The ``${MLPREFIX}`` variable is stripped from ``${PN}`` during RPM
+   packaging. The naming for a normal RPM package and a Multilib RPM
+   package in a ``qemux86-64`` system resolves to something similar to
+   ``bash-4.1-r2.x86_64.rpm`` and ``bash-4.1.r2.lib32_x86.rpm``,
+   respectively.
+-  When installing a Multilib image, the RPM backend first installs the
+   base image and then installs the Multilib libraries.
+-  The build system relies on RPM to resolve the identical files in the
+   two (or more) Multilib packages.
+For the IPK Package Management System, the following implementation
+details exist:
+-  The ``${MLPREFIX}`` is not stripped from ``${PN}`` during IPK
+   packaging. The naming for a normal RPM package and a Multilib IPK
+   package in a ``qemux86-64`` system resolves to something like
+   ``bash_4.1-r2.x86_64.ipk`` and ``lib32-bash_4.1-rw_x86.ipk``,
+   respectively.
+-  The IPK deploy folder is not modified with ``${MLPREFIX}`` because
+   packages with and without the Multilib feature can exist in the same
+   folder due to the ``${PN}`` differences.
+-  IPK defines a sanity check for Multilib installation using certain
+   rules for file comparison, overridden, etc.
+Installing Multiple Versions of the Same Library
+------------------------------------------------
+Situations can exist where you need to install and use multiple versions
+of the same library on the same system at the same time. These
+situations almost always exist when a library API changes and you have
+multiple pieces of software that depend on the separate versions of the
+library. To accommodate these situations, you can install multiple
+versions of the same library in parallel on the same system.
+The process is straightforward as long as the libraries use proper
+versioning. With properly versioned libraries, all you need to do to
+individually specify the libraries is create separate, appropriately
+named recipes where the :term:`PN` part of
+the name includes a portion that differentiates each library version
+(e.g. the major part of the version number). Thus, instead of having a
+single recipe that loads one version of a library (e.g. ``clutter``),
+you provide multiple recipes that result in different versions of the
+libraries you want. As an example, the following two recipes would allow
+the two separate versions of the ``clutter`` library to co-exist on the
+same system:
+.. code-block:: none
+   clutter-1.6_1.6.20.bb
+   clutter-1.8_1.8.4.bb
+Additionally, if
+you have other recipes that depend on a given library, you need to use
+the :term:`DEPENDS` variable to
+create the dependency. Continuing with the same example, if you want to
+have a recipe depend on the 1.8 version of the ``clutter`` library, use
+the following in your recipe:
+::
+   DEPENDS = "clutter-1.8"
+Using x32 psABI
+===============
+x32 processor-specific Application Binary Interface (`x32
+psABI <https://software.intel.com/en-us/node/628948>`__) is a native
+32-bit processor-specific ABI for Intel 64 (x86-64) architectures. An
+ABI defines the calling conventions between functions in a processing
+environment. The interface determines what registers are used and what
+the sizes are for various C data types.
+Some processing environments prefer using 32-bit applications even when
+running on Intel 64-bit platforms. Consider the i386 psABI, which is a
+very old 32-bit ABI for Intel 64-bit platforms. The i386 psABI does not
+provide efficient use and access of the Intel 64-bit processor
+resources, leaving the system underutilized. Now consider the x86_64
+psABI. This ABI is newer and uses 64-bits for data sizes and program
+pointers. The extra bits increase the footprint size of the programs,
+libraries, and also increases the memory and file system size
+requirements. Executing under the x32 psABI enables user programs to
+utilize CPU and system resources more efficiently while keeping the
+memory footprint of the applications low. Extra bits are used for
+registers but not for addressing mechanisms.
+The Yocto Project supports the final specifications of x32 psABI as
+follows:
+-  You can create packages and images in x32 psABI format on x86_64
+   architecture targets.
+-  You can successfully build recipes with the x32 toolchain.
+-  You can create and boot ``core-image-minimal`` and
+   ``core-image-sato`` images.
+-  RPM Package Manager (RPM) support exists for x32 binaries.
+-  Support for large images exists.
+To use the x32 psABI, you need to edit your ``conf/local.conf``
+configuration file as follows:
+::
+   MACHINE = "qemux86-64"
+   DEFAULTTUNE = "x86-64-x32"
+   baselib = "${@d.getVar('BASE_LIB_tune-' + (d.getVar('DEFAULTTUNE') \
+       or 'INVALID')) or 'lib'}"
+Once you have set
+up your configuration file, use BitBake to build an image that supports
+the x32 psABI. Here is an example:
+::
+   $ bitbake core-image-sato
+Enabling GObject Introspection Support
+======================================
+`GObject
+introspection <https://wiki.gnome.org/Projects/GObjectIntrospection>`__
+is the standard mechanism for accessing GObject-based software from
+runtime environments. GObject is a feature of the GLib library that
+provides an object framework for the GNOME desktop and related software.
+GObject Introspection adds information to GObject that allows objects
+created within it to be represented across different programming
+languages. If you want to construct GStreamer pipelines using Python, or
+control UPnP infrastructure using Javascript and GUPnP, GObject
+introspection is the only way to do it.
+This section describes the Yocto Project support for generating and
+packaging GObject introspection data. GObject introspection data is a
+description of the API provided by libraries built on top of GLib
+framework, and, in particular, that framework's GObject mechanism.
+GObject Introspection Repository (GIR) files go to ``-dev`` packages,
+``typelib`` files go to main packages as they are packaged together with
+libraries that are introspected.
+The data is generated when building such a library, by linking the
+library with a small executable binary that asks the library to describe
+itself, and then executing the binary and processing its output.
+Generating this data in a cross-compilation environment is difficult
+because the library is produced for the target architecture, but its
+code needs to be executed on the build host. This problem is solved with
+the OpenEmbedded build system by running the code through QEMU, which
+allows precisely that. Unfortunately, QEMU does not always work
+perfectly as mentioned in the "`Known Issues <#known-issues>`__"
+section.
+Enabling the Generation of Introspection Data
+---------------------------------------------
+Enabling the generation of introspection data (GIR files) in your
+library package involves the following:
+1. Inherit the
+   :ref:`gobject-introspection <ref-classes-gobject-introspection>`
+   class.
+2. Make sure introspection is not disabled anywhere in the recipe or
+   from anything the recipe includes. Also, make sure that
+   "gobject-introspection-data" is not in
+   :term:`DISTRO_FEATURES_BACKFILL_CONSIDERED`
+   and that "qemu-usermode" is not in
+   :term:`MACHINE_FEATURES_BACKFILL_CONSIDERED`.
+   If either of these conditions exist, nothing will happen.
+3. Try to build the recipe. If you encounter build errors that look like
+   something is unable to find ``.so`` libraries, check where these
+   libraries are located in the source tree and add the following to the
+   recipe:
+   ::
+      GIR_EXTRA_LIBS_PATH = "${B}/something/.libs"
+   .. note::
+      See recipes in the ``oe-core`` repository that use that
+      ``GIR_EXTRA_LIBS_PATH`` variable as an example.
+4. Look for any other errors, which probably mean that introspection
+   support in a package is not entirely standard, and thus breaks down
+   in a cross-compilation environment. For such cases, custom-made fixes
+   are needed. A good place to ask and receive help in these cases is
+   the :ref:`Yocto Project mailing
+   lists <resources-mailinglist>`.
+.. note::
+   Using a library that no longer builds against the latest Yocto
+   Project release and prints introspection related errors is a good
+   candidate for the previous procedure.
+Disabling the Generation of Introspection Data
+----------------------------------------------
+You might find that you do not want to generate introspection data. Or,
+perhaps QEMU does not work on your build host and target architecture
+combination. If so, you can use either of the following methods to
+disable GIR file generations:
+-  Add the following to your distro configuration:
+   ::
+      DISTRO_FEATURES_BACKFILL_CONSIDERED = "gobject-introspection-data"
+   Adding this statement disables generating introspection data using
+   QEMU but will still enable building introspection tools and libraries
+   (i.e. building them does not require the use of QEMU).
+-  Add the following to your machine configuration:
+   ::
+      MACHINE_FEATURES_BACKFILL_CONSIDERED = "qemu-usermode"
+   Adding this statement disables the use of QEMU when building packages for your
+   machine. Currently, this feature is used only by introspection
+   recipes and has the same effect as the previously described option.
+   .. note::
+      Future releases of the Yocto Project might have other features
+      affected by this option.
+If you disable introspection data, you can still obtain it through other
+means such as copying the data from a suitable sysroot, or by generating
+it on the target hardware. The OpenEmbedded build system does not
+currently provide specific support for these techniques.
+Testing that Introspection Works in an Image
+--------------------------------------------
+Use the following procedure to test if generating introspection data is
+working in an image:
+1. Make sure that "gobject-introspection-data" is not in
+   :term:`DISTRO_FEATURES_BACKFILL_CONSIDERED`
+   and that "qemu-usermode" is not in
+   :term:`MACHINE_FEATURES_BACKFILL_CONSIDERED`.
+2. Build ``core-image-sato``.
+3. Launch a Terminal and then start Python in the terminal.
+4. Enter the following in the terminal:
+   ::
+      >>> from gi.repository import GLib
+      >>> GLib.get_host_name()
+5. For something a little more advanced, enter the following see:
+   https://python-gtk-3-tutorial.readthedocs.io/en/latest/introduction.html
+Known Issues
+------------
+The following know issues exist for GObject Introspection Support:
+-  ``qemu-ppc64`` immediately crashes. Consequently, you cannot build
+   introspection data on that architecture.
+-  x32 is not supported by QEMU. Consequently, introspection data is
+   disabled.
+-  musl causes transient GLib binaries to crash on assertion failures.
+   Consequently, generating introspection data is disabled.
+-  Because QEMU is not able to run the binaries correctly, introspection
+   is disabled for some specific packages under specific architectures
+   (e.g. ``gcr``, ``libsecret``, and ``webkit``).
+-  QEMU usermode might not work properly when running 64-bit binaries
+   under 32-bit host machines. In particular, "qemumips64" is known to
+   not work under i686.
+Optionally Using an External Toolchain
+======================================
+You might want to use an external toolchain as part of your development.
+If this is the case, the fundamental steps you need to accomplish are as
+follows:
+-  Understand where the installed toolchain resides. For cases where you
+   need to build the external toolchain, you would need to take separate
+   steps to build and install the toolchain.
+-  Make sure you add the layer that contains the toolchain to your
+   ``bblayers.conf`` file through the
+   :term:`BBLAYERS` variable.
+-  Set the ``EXTERNAL_TOOLCHAIN`` variable in your ``local.conf`` file
+   to the location in which you installed the toolchain.
+A good example of an external toolchain used with the Yocto Project is
+Mentor Graphics Sourcery G++ Toolchain. You can see information on how
+to use that particular layer in the ``README`` file at
+https://github.com/MentorEmbedded/meta-sourcery/. You can find
+further information by reading about the
+:term:`TCMODE` variable in the Yocto
+Project Reference Manual's variable glossary.
+Creating Partitioned Images Using Wic
+=====================================
+Creating an image for a particular hardware target using the
+OpenEmbedded build system does not necessarily mean you can boot that
+image as is on your device. Physical devices accept and boot images in
+various ways depending on the specifics of the device. Usually,
+information about the hardware can tell you what image format the device
+requires. Should your device require multiple partitions on an SD card,
+flash, or an HDD, you can use the OpenEmbedded Image Creator, Wic, to
+create the properly partitioned image.
+The ``wic`` command generates partitioned images from existing
+OpenEmbedded build artifacts. Image generation is driven by partitioning
+commands contained in an Openembedded kickstart file (``.wks``)
+specified either directly on the command line or as one of a selection
+of canned kickstart files as shown with the ``wic list images`` command
+in the "`Using an Existing Kickstart
+File <#using-a-provided-kickstart-file>`__" section. When you apply the
+command to a given set of build artifacts, the result is an image or set
+of images that can be directly written onto media and used on a
+particular system.
+.. note::
+   For a kickstart file reference, see the
+   ":ref:`ref-manual/ref-kickstart:openembedded kickstart (\`\`.wks\`\`) reference`"
+   Chapter in the Yocto Project Reference Manual.
+The ``wic`` command and the infrastructure it is based on is by
+definition incomplete. The purpose of the command is to allow the
+generation of customized images, and as such, was designed to be
+completely extensible through a plugin interface. See the "`Using the
+Wic PlugIn Interface <#wic-using-the-wic-plugin-interface>`__" section
+for information on these plugins.
+This section provides some background information on Wic, describes what
+you need to have in place to run the tool, provides instruction on how
+to use the Wic utility, provides information on using the Wic plugins
+interface, and provides several examples that show how to use Wic.
+Background
+----------
+This section provides some background on the Wic utility. While none of
+this information is required to use Wic, you might find it interesting.
+-  The name "Wic" is derived from OpenEmbedded Image Creator (oeic). The
+   "oe" diphthong in "oeic" was promoted to the letter "w", because
+   "oeic" is both difficult to remember and to pronounce.
+-  Wic is loosely based on the Meego Image Creator (``mic``) framework.
+   The Wic implementation has been heavily modified to make direct use
+   of OpenEmbedded build artifacts instead of package installation and
+   configuration, which are already incorporated within the OpenEmbedded
+   artifacts.
+-  Wic is a completely independent standalone utility that initially
+   provides easier-to-use and more flexible replacements for an existing
+   functionality in OE-Core's
+   :ref:`image-live <ref-classes-image-live>`
+   class. The difference between Wic and those examples is that with Wic
+   the functionality of those scripts is implemented by a
+   general-purpose partitioning language, which is based on Redhat
+   kickstart syntax.
+Requirements
+------------
+In order to use the Wic utility with the OpenEmbedded Build system, your
+system needs to meet the following requirements:
+-  The Linux distribution on your development host must support the
+   Yocto Project. See the ":ref:`detailed-supported-distros`"
+   section in the Yocto Project Reference Manual for the list of
+   distributions that support the Yocto Project.
+-  The standard system utilities, such as ``cp``, must be installed on
+   your development host system.
+-  You must have sourced the build environment setup script (i.e.
+   :ref:`structure-core-script`) found in the
+   :term:`Build Directory`.
+-  You need to have the build artifacts already available, which
+   typically means that you must have already created an image using the
+   Openembedded build system (e.g. ``core-image-minimal``). While it
+   might seem redundant to generate an image in order to create an image
+   using Wic, the current version of Wic requires the artifacts in the
+   form generated by the OpenEmbedded build system.
+-  You must build several native tools, which are built to run on the
+   build system:
+   ::
+      $ bitbake parted-native dosfstools-native mtools-native
+-  Include "wic" as part of the
+   :term:`IMAGE_FSTYPES`
+   variable.
+-  Include the name of the :ref:`wic kickstart file <openembedded-kickstart-wks-reference>`
+   as part of the :term:`WKS_FILE` variable
+Getting Help
+------------
+You can get general help for the ``wic`` command by entering the ``wic``
+command by itself or by entering the command with a help argument as
+follows:
+::
+   $ wic -h
+   $ wic --help
+   $ wic help
+Currently, Wic supports seven commands: ``cp``, ``create``, ``help``,
+``list``, ``ls``, ``rm``, and ``write``. You can get help for all these
+commands except "help" by using the following form:
+::
+   $ wic help command
+For example, the following command returns help for the ``write``
+command:
+::
+   $ wic help write
+Wic supports help for three topics: ``overview``, ``plugins``, and
+``kickstart``. You can get help for any topic using the following form:
+::
+   $ wic help topic
+For example, the following returns overview help for Wic:
+::
+   $ wic help overview
+One additional level of help exists for Wic. You can get help on
+individual images through the ``list`` command. You can use the ``list``
+command to return the available Wic images as follows:
+::
+   $ wic list images
+     genericx86                                 Create an EFI disk image for genericx86*
+     beaglebone-yocto                           Create SD card image for Beaglebone
+     edgerouter                                 Create SD card image for Edgerouter
+     qemux86-directdisk                         Create a qemu machine 'pcbios' direct disk image
+     directdisk-gpt                             Create a 'pcbios' direct disk image
+     mkefidisk                                  Create an EFI disk image
+     directdisk                                 Create a 'pcbios' direct disk image
+     systemd-bootdisk                           Create an EFI disk image with systemd-boot
+     mkhybridiso                                Create a hybrid ISO image
+     sdimage-bootpart                           Create SD card image with a boot partition
+     directdisk-multi-rootfs                    Create multi rootfs image using rootfs plugin
+     directdisk-bootloader-config               Create a 'pcbios' direct disk image with custom bootloader config
+Once you know the list of available
+Wic images, you can use ``help`` with the command to get help on a
+particular image. For example, the following command returns help on the
+"beaglebone-yocto" image:
+::
+   $ wic list beaglebone-yocto help
+   Creates a partitioned SD card image for Beaglebone.
+   Boot files are located in the first vfat partition.
+Operational Modes
+-----------------
+You can use Wic in two different modes, depending on how much control
+you need for specifying the Openembedded build artifacts that are used
+for creating the image: Raw and Cooked:
+-  *Raw Mode:* You explicitly specify build artifacts through Wic
+   command-line arguments.
+-  *Cooked Mode:* The current
+   :term:`MACHINE` setting and image
+   name are used to automatically locate and provide the build
+   artifacts. You just supply a kickstart file and the name of the image
+   from which to use artifacts.
+Regardless of the mode you use, you need to have the build artifacts
+ready and available.
+Raw Mode
+~~~~~~~~
+Running Wic in raw mode allows you to specify all the partitions through
+the ``wic`` command line. The primary use for raw mode is if you have
+built your kernel outside of the Yocto Project
+:term:`Build Directory`. In other words, you
+can point to arbitrary kernel, root filesystem locations, and so forth.
+Contrast this behavior with cooked mode where Wic looks in the Build
+Directory (e.g. ``tmp/deploy/images/``\ machine).
+The general form of the ``wic`` command in raw mode is:
+::
+   $ wic create wks_file options ...
+     Where:
+        wks_file:
+           An OpenEmbedded kickstart file.  You can provide
+           your own custom file or use a file from a set of
+           existing files as described by further options.
+        optional arguments:
+          -h, --help            show this help message and exit
+          -o OUTDIR, --outdir OUTDIR
+                                name of directory to create image in
+          -e IMAGE_NAME, --image-name IMAGE_NAME
+                                name of the image to use the artifacts from e.g. core-
+                                image-sato
+          -r ROOTFS_DIR, --rootfs-dir ROOTFS_DIR
+                                path to the /rootfs dir to use as the .wks rootfs
+                                source
+          -b BOOTIMG_DIR, --bootimg-dir BOOTIMG_DIR
+                                path to the dir containing the boot artifacts (e.g.
+                                /EFI or /syslinux dirs) to use as the .wks bootimg
+                                source
+          -k KERNEL_DIR, --kernel-dir KERNEL_DIR
+                                path to the dir containing the kernel to use in the
+                                .wks bootimg
+          -n NATIVE_SYSROOT, --native-sysroot NATIVE_SYSROOT
+                                path to the native sysroot containing the tools to use
+                                to build the image
+          -s, --skip-build-check
+                                skip the build check
+          -f, --build-rootfs    build rootfs
+          -c {gzip,bzip2,xz}, --compress-with {gzip,bzip2,xz}
+                                compress image with specified compressor
+          -m, --bmap            generate .bmap
+          --no-fstab-update     Do not change fstab file.
+          -v VARS_DIR, --vars VARS_DIR
+                                directory with <image>.env files that store bitbake
+                                variables
+          -D, --debug           output debug information
+.. note::
+   You do not need root privileges to run Wic. In fact, you should not
+   run as root when using the utility.
+Cooked Mode
+~~~~~~~~~~~
+Running Wic in cooked mode leverages off artifacts in the Build
+Directory. In other words, you do not have to specify kernel or root
+filesystem locations as part of the command. All you need to provide is
+a kickstart file and the name of the image from which to use artifacts
+by using the "-e" option. Wic looks in the Build Directory (e.g.
+``tmp/deploy/images/``\ machine) for artifacts.
+The general form of the ``wic`` command using Cooked Mode is as follows:
+::
+   $ wic create wks_file -e IMAGE_NAME
+     Where:
+        wks_file:
+           An OpenEmbedded kickstart file.  You can provide
+           your own custom file or use a file from a set of
+           existing files provided with the Yocto Project
+           release.
+        required argument:
+           -e IMAGE_NAME, --image-name IMAGE_NAME
+                                name of the image to use the artifacts from e.g. core-
+                                image-sato
+Using an Existing Kickstart File
+--------------------------------
+If you do not want to create your own kickstart file, you can use an
+existing file provided by the Wic installation. As shipped, kickstart
+files can be found in the :ref:`overview-manual/overview-manual-development-environment:yocto project source repositories` in the
+following two locations:
+::
+   poky/meta-yocto-bsp/wic
+   poky/scripts/lib/wic/canned-wks
+Use the following command to list the available kickstart files:
+::
+   $ wic list images
+     genericx86                                 Create an EFI disk image for genericx86*
+     beaglebone-yocto                           Create SD card image for Beaglebone
+     edgerouter                                 Create SD card image for Edgerouter
+     qemux86-directdisk                         Create a qemu machine 'pcbios' direct disk image
+     directdisk-gpt                             Create a 'pcbios' direct disk image
+     mkefidisk                                  Create an EFI disk image
+     directdisk                                 Create a 'pcbios' direct disk image
+     systemd-bootdisk                           Create an EFI disk image with systemd-boot
+     mkhybridiso                                Create a hybrid ISO image
+     sdimage-bootpart                           Create SD card image with a boot partition
+     directdisk-multi-rootfs                    Create multi rootfs image using rootfs plugin
+     directdisk-bootloader-config               Create a 'pcbios' direct disk image with custom bootloader config
+When you use an existing file, you
+do not have to use the ``.wks`` extension. Here is an example in Raw
+Mode that uses the ``directdisk`` file:
+::
+   $ wic create directdisk -r rootfs_dir -b bootimg_dir \
+         -k kernel_dir -n native_sysroot
+Here are the actual partition language commands used in the
+``genericx86.wks`` file to generate an image:
+::
+   # short-description: Create an EFI disk image for genericx86*
+   # long-description: Creates a partitioned EFI disk image for genericx86* machines
+   part /boot --source bootimg-efi --sourceparams="loader=grub-efi" --ondisk sda --label msdos --active --align 1024
+   part / --source rootfs --ondisk sda --fstype=ext4 --label platform --align 1024 --use-uuid
+   part swap --ondisk sda --size 44 --label swap1 --fstype=swap
+   bootloader --ptable gpt --timeout=5 --append="rootfstype=ext4 console=ttyS0,115200 console=tty0"
+Using the Wic Plugin Interface
+------------------------------
+You can extend and specialize Wic functionality by using Wic plugins.
+This section explains the Wic plugin interface.
+.. note::
+   Wic plugins consist of "source" and "imager" plugins. Imager plugins
+   are beyond the scope of this section.
+Source plugins provide a mechanism to customize partition content during
+the Wic image generation process. You can use source plugins to map
+values that you specify using ``--source`` commands in kickstart files
+(i.e. ``*.wks``) to a plugin implementation used to populate a given
+partition.
+.. note::
+   If you use plugins that have build-time dependencies (e.g. native
+   tools, bootloaders, and so forth) when building a Wic image, you need
+   to specify those dependencies using the :term:`WKS_FILE_DEPENDS`
+   variable.
+Source plugins are subclasses defined in plugin files. As shipped, the
+Yocto Project provides several plugin files. You can see the source
+plugin files that ship with the Yocto Project
+:yocto_git:`here </poky/tree/scripts/lib/wic/plugins/source>`.
+Each of these plugin files contains source plugins that are designed to
+populate a specific Wic image partition.
+Source plugins are subclasses of the ``SourcePlugin`` class, which is
+defined in the ``poky/scripts/lib/wic/pluginbase.py`` file. For example,
+the ``BootimgEFIPlugin`` source plugin found in the ``bootimg-efi.py``
+file is a subclass of the ``SourcePlugin`` class, which is found in the
+``pluginbase.py`` file.
+You can also implement source plugins in a layer outside of the Source
+Repositories (external layer). To do so, be sure that your plugin files
+are located in a directory whose path is
+``scripts/lib/wic/plugins/source/`` within your external layer. When the
+plugin files are located there, the source plugins they contain are made
+available to Wic.
+When the Wic implementation needs to invoke a partition-specific
+implementation, it looks for the plugin with the same name as the
+``--source`` parameter used in the kickstart file given to that
+partition. For example, if the partition is set up using the following
+command in a kickstart file:
+::
+   part /boot --source bootimg-pcbios --ondisk sda --label boot --active --align 1024
+The methods defined as class
+members of the matching source plugin (i.e. ``bootimg-pcbios``) in the
+``bootimg-pcbios.py`` plugin file are used.
+To be more concrete, here is the corresponding plugin definition from
+the ``bootimg-pcbios.py`` file for the previous command along with an
+example method called by the Wic implementation when it needs to prepare
+a partition using an implementation-specific function:
+::
+                .
+                .
+                .
+   class BootimgPcbiosPlugin(SourcePlugin):
+       """
+       Create MBR boot partition and install syslinux on it.
+       """
+      name = 'bootimg-pcbios'
+                .
+                .
+                .
+       @classmethod
+       def do_prepare_partition(cls, part, source_params, creator, cr_workdir,
+                                oe_builddir, bootimg_dir, kernel_dir,
+                                rootfs_dir, native_sysroot):
+           """
+           Called to do the actual content population for a partition i.e. it
+           'prepares' the partition to be incorporated into the image.
+           In this case, prepare content for legacy bios boot partition.
+           """
+                .
+                .
+                .
+If a
+subclass (plugin) itself does not implement a particular function, Wic
+locates and uses the default version in the superclass. It is for this
+reason that all source plugins are derived from the ``SourcePlugin``
+class.
+The ``SourcePlugin`` class defined in the ``pluginbase.py`` file defines
+a set of methods that source plugins can implement or override. Any
+plugins (subclass of ``SourcePlugin``) that do not implement a
+particular method inherit the implementation of the method from the
+``SourcePlugin`` class. For more information, see the ``SourcePlugin``
+class in the ``pluginbase.py`` file for details:
+The following list describes the methods implemented in the
+``SourcePlugin`` class:
+-  ``do_prepare_partition()``: Called to populate a partition with
+   actual content. In other words, the method prepares the final
+   partition image that is incorporated into the disk image.
+-  ``do_configure_partition()``: Called before
+   ``do_prepare_partition()`` to create custom configuration files for a
+   partition (e.g. syslinux or grub configuration files).
+-  ``do_install_disk()``: Called after all partitions have been
+   prepared and assembled into a disk image. This method provides a hook
+   to allow finalization of a disk image (e.g. writing an MBR).
+-  ``do_stage_partition()``: Special content-staging hook called
+   before ``do_prepare_partition()``. This method is normally empty.
+   Typically, a partition just uses the passed-in parameters (e.g. the
+   unmodified value of ``bootimg_dir``). However, in some cases, things
+   might need to be more tailored. As an example, certain files might
+   additionally need to be taken from ``bootimg_dir + /boot``. This hook
+   allows those files to be staged in a customized fashion.
+   .. note::
+      ``get_bitbake_var()`` allows you to access non-standard variables that
+      you might want to use for this behavior.
+You can extend the source plugin mechanism. To add more hooks, create
+more source plugin methods within ``SourcePlugin`` and the corresponding
+derived subclasses. The code that calls the plugin methods uses the
+``plugin.get_source_plugin_methods()`` function to find the method or
+methods needed by the call. Retrieval of those methods is accomplished
+by filling up a dict with keys that contain the method names of
+interest. On success, these will be filled in with the actual methods.
+See the Wic implementation for examples and details.
+Wic Examples
+------------
+This section provides several examples that show how to use the Wic
+utility. All the examples assume the list of requirements in the
+"`Requirements <#wic-requirements>`__" section have been met. The
+examples assume the previously generated image is
+``core-image-minimal``.
+Generate an Image using an Existing Kickstart File
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+This example runs in Cooked Mode and uses the ``mkefidisk`` kickstart
+file:
+::
+   $ wic create mkefidisk -e core-image-minimal
+   INFO: Building wic-tools...
+             .
+             .
+             .
+   INFO: The new image(s) can be found here:
+     ./mkefidisk-201804191017-sda.direct
+   The following build artifacts were used to create the image(s):
+     ROOTFS_DIR:                   /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs
+     BOOTIMG_DIR:                  /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share
+     KERNEL_DIR:                   /home/stephano/build/master/build/tmp-glibc/deploy/images/qemux86
+     NATIVE_SYSROOT:               /home/stephano/build/master/build/tmp-glibc/work/i586-oe-linux/wic-tools/1.0-r0/recipe-sysroot-native
+   INFO: The image(s) were created using OE kickstart file:
+     /home/stephano/build/master/openembedded-core/scripts/lib/wic/canned-wks/mkefidisk.wks
+The previous example shows the easiest way to create an image by running
+in cooked mode and supplying a kickstart file and the "-e" option to
+point to the existing build artifacts. Your ``local.conf`` file needs to
+have the :term:`MACHINE` variable set
+to the machine you are using, which is "qemux86" in this example.
+Once the image builds, the output provides image location, artifact use,
+and kickstart file information.
+.. note::
+   You should always verify the details provided in the output to make
+   sure that the image was indeed created exactly as expected.
+Continuing with the example, you can now write the image from the Build
+Directory onto a USB stick, or whatever media for which you built your
+image, and boot from the media. You can write the image by using
+``bmaptool`` or ``dd``:
+::
+   $ oe-run-native bmaptool copy mkefidisk-201804191017-sda.direct /dev/sdX
+or ::
+   $ sudo dd if=mkefidisk-201804191017-sda.direct of=/dev/sdX
+.. note::
+   For more information on how to use the ``bmaptool``
+   to flash a device with an image, see the
+   ":ref:`dev-manual/common-tasks:flashing images using \`\`bmaptool\`\``"
+   section.
+Using a Modified Kickstart File
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Because partitioned image creation is driven by the kickstart file, it
+is easy to affect image creation by changing the parameters in the file.
+This next example demonstrates that through modification of the
+``directdisk-gpt`` kickstart file.
+As mentioned earlier, you can use the command ``wic list images`` to
+show the list of existing kickstart files. The directory in which the
+``directdisk-gpt.wks`` file resides is
+``scripts/lib/image/canned-wks/``, which is located in the
+:term:`Source Directory` (e.g. ``poky``).
+Because available files reside in this directory, you can create and add
+your own custom files to the directory. Subsequent use of the
+``wic list images`` command would then include your kickstart files.
+In this example, the existing ``directdisk-gpt`` file already does most
+of what is needed. However, for the hardware in this example, the image
+will need to boot from ``sdb`` instead of ``sda``, which is what the
+``directdisk-gpt`` kickstart file uses.
+The example begins by making a copy of the ``directdisk-gpt.wks`` file
+in the ``scripts/lib/image/canned-wks`` directory and then by changing
+the lines that specify the target disk from which to boot.
+::
+   $ cp /home/stephano/poky/scripts/lib/wic/canned-wks/directdisk-gpt.wks \
+        /home/stephano/poky/scripts/lib/wic/canned-wks/directdisksdb-gpt.wks
+Next, the example modifies the ``directdisksdb-gpt.wks`` file and
+changes all instances of "``--ondisk sda``" to "``--ondisk sdb``". The
+example changes the following two lines and leaves the remaining lines
+untouched:
+::
+   part /boot --source bootimg-pcbios --ondisk sdb --label boot --active --align 1024
+   part / --source rootfs --ondisk sdb --fstype=ext4 --label platform --align 1024 --use-uuid
+Once the lines are changed, the
+example generates the ``directdisksdb-gpt`` image. The command points
+the process at the ``core-image-minimal`` artifacts for the Next Unit of
+Computing (nuc) :term:`MACHINE` the
+``local.conf``.
+::
+   $ wic create directdisksdb-gpt -e core-image-minimal
+   INFO: Building wic-tools...
+              .
+              .
+              .
+   Initialising tasks: 100% |#######################################| Time: 0:00:01
+   NOTE: Executing SetScene Tasks
+   NOTE: Executing RunQueue Tasks
+   NOTE: Tasks Summary: Attempted 1161 tasks of which 1157 didn't need to be rerun and all succeeded.
+   INFO: Creating image(s)...
+   INFO: The new image(s) can be found here:
+     ./directdisksdb-gpt-201710090938-sdb.direct
+   The following build artifacts were used to create the image(s):
+     ROOTFS_DIR:                   /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs
+     BOOTIMG_DIR:                  /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share
+     KERNEL_DIR:                   /home/stephano/build/master/build/tmp-glibc/deploy/images/qemux86
+     NATIVE_SYSROOT:               /home/stephano/build/master/build/tmp-glibc/work/i586-oe-linux/wic-tools/1.0-r0/recipe-sysroot-native
+   INFO: The image(s) were created using OE kickstart file:
+     /home/stephano/poky/scripts/lib/wic/canned-wks/directdisksdb-gpt.wks
+Continuing with the example, you can now directly ``dd`` the image to a
+USB stick, or whatever media for which you built your image, and boot
+the resulting media:
+::
+   $ sudo dd if=directdisksdb-gpt-201710090938-sdb.direct of=/dev/sdb
+   140966+0 records in
+   140966+0 records out
+   72174592 bytes (72 MB, 69 MiB) copied, 78.0282 s, 925 kB/s
+   $ sudo eject /dev/sdb
+Using a Modified Kickstart File and Running in Raw Mode
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+This next example manually specifies each build artifact (runs in Raw
+Mode) and uses a modified kickstart file. The example also uses the
+``-o`` option to cause Wic to create the output somewhere other than the
+default output directory, which is the current directory:
+::
+   $ wic create /home/stephano/my_yocto/test.wks -o /home/stephano/testwic \
+        --rootfs-dir /home/stephano/build/master/build/tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/rootfs \
+        --bootimg-dir /home/stephano/build/master/build/tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share \
+        --kernel-dir /home/stephano/build/master/build/tmp/deploy/images/qemux86 \
+        --native-sysroot /home/stephano/build/master/build/tmp/work/i586-poky-linux/wic-tools/1.0-r0/recipe-sysroot-native
+   INFO: Creating image(s)...
+   INFO: The new image(s) can be found here:
+     /home/stephano/testwic/test-201710091445-sdb.direct
+   The following build artifacts were used to create the image(s):
+     ROOTFS_DIR:                   /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/rootfs
+     BOOTIMG_DIR:                  /home/stephano/build/master/build/tmp-glibc/work/qemux86-oe-linux/core-image-minimal/1.0-r0/recipe-sysroot/usr/share
+     KERNEL_DIR:                   /home/stephano/build/master/build/tmp-glibc/deploy/images/qemux86
+     NATIVE_SYSROOT:               /home/stephano/build/master/build/tmp-glibc/work/i586-oe-linux/wic-tools/1.0-r0/recipe-sysroot-native
+   INFO: The image(s) were created using OE kickstart file:
+     /home/stephano/my_yocto/test.wks
+For this example,
+:term:`MACHINE` did not have to be
+specified in the ``local.conf`` file since the artifact is manually
+specified.
+Using Wic to Manipulate an Image
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Wic image manipulation allows you to shorten turnaround time during
+image development. For example, you can use Wic to delete the kernel
+partition of a Wic image and then insert a newly built kernel. This
+saves you time from having to rebuild the entire image each time you
+modify the kernel.
+.. note::
+   In order to use Wic to manipulate a Wic image as in this example,
+   your development machine must have the ``mtools`` package installed.
+The following example examines the contents of the Wic image, deletes
+the existing kernel, and then inserts a new kernel:
+1. *List the Partitions:* Use the ``wic ls`` command to list all the
+   partitions in the Wic image:
+   ::
+      $ wic ls tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic
+      Num     Start        End          Size      Fstype
+       1       1048576     25041919     23993344  fat16
+       2      25165824     72157183     46991360  ext4
+   The previous output shows two partitions in the
+   ``core-image-minimal-qemux86.wic`` image.
+2. *Examine a Particular Partition:* Use the ``wic ls`` command again
+   but in a different form to examine a particular partition.
+   .. note::
+      You can get command usage on any Wic command using the following
+      form:
+      ::
+              $ wic help command
+      For example, the following command shows you the various ways to
+      use the
+      wic ls
+      command:
+      ::
+              $ wic help ls
+   The following command shows what is in Partition one:
+   ::
+        $ wic ls tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic:1
+        Volume in drive : is boot
+         Volume Serial Number is E894-1809
+        Directory for ::/
+        libcom32 c32    186500 2017-10-09  16:06
+        libutil  c32     24148 2017-10-09  16:06
+        syslinux cfg       220 2017-10-09  16:06
+        vesamenu c32     27104 2017-10-09  16:06
+        vmlinuz        6904608 2017-10-09  16:06
+                5 files           7 142 580 bytes
+                                 16 582 656 bytes free
+   The previous output shows five files, with the
+   ``vmlinuz`` being the kernel.
+   .. note::
+      If you see the following error, you need to update or create a
+      ``~/.mtoolsrc`` file and be sure to have the line "mtools_skip_check=1"
+      in the file. Then, run the Wic command again:
+      ::
+              ERROR: _exec_cmd: /usr/bin/mdir -i /tmp/wic-parttfokuwra ::/ returned '1' instead of 0
+               output: Total number of sectors (47824) not a multiple of sectors per track (32)!
+               Add mtools_skip_check=1 to your .mtoolsrc file to skip this test
+3. *Remove the Old Kernel:* Use the ``wic rm`` command to remove the
+   ``vmlinuz`` file (kernel):
+   ::
+      $ wic rm tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic:1/vmlinuz
+4. *Add In the New Kernel:* Use the ``wic cp`` command to add the
+   updated kernel to the Wic image. Depending on how you built your
+   kernel, it could be in different places. If you used ``devtool`` and
+   an SDK to build your kernel, it resides in the ``tmp/work`` directory
+   of the extensible SDK. If you used ``make`` to build the kernel, the
+   kernel will be in the ``workspace/sources`` area.
+   The following example assumes ``devtool`` was used to build the
+   kernel:
+   ::
+      cp ~/poky_sdk/tmp/work/qemux86-poky-linux/linux-yocto/4.12.12+git999-r0/linux-yocto-4.12.12+git999/arch/x86/boot/bzImage \
+         ~/poky/build/tmp/deploy/images/qemux86/core-image-minimal-qemux86.wic:1/vmlinuz
+   Once the new kernel is added back into the image, you can use the
+   ``dd`` command or :ref:`bmaptool
+   <dev-manual/common-tasks:flashing images using \`\`bmaptool\`\`>`
+   to flash your wic image onto an SD card or USB stick and test your
+   target.
+   .. note::
+      Using ``bmaptool`` is generally 10 to 20 times faster than using ``dd``.
+Flashing Images Using ``bmaptool``
+==================================
+A fast and easy way to flash an image to a bootable device is to use
+Bmaptool, which is integrated into the OpenEmbedded build system.
+Bmaptool is a generic tool that creates a file's block map (bmap) and
+then uses that map to copy the file. As compared to traditional tools
+such as dd or cp, Bmaptool can copy (or flash) large files like raw
+system image files much faster.
+.. note::
+   -  If you are using Ubuntu or Debian distributions, you can install
+      the ``bmap-tools`` package using the following command and then
+      use the tool without specifying ``PATH`` even from the root
+      account:
+      ::
+         $ sudo apt-get install bmap-tools
+   -  If you are unable to install the ``bmap-tools`` package, you will
+      need to build Bmaptool before using it. Use the following command:
+      ::
+         $ bitbake bmap-tools-native
+Following, is an example that shows how to flash a Wic image. Realize
+that while this example uses a Wic image, you can use Bmaptool to flash
+any type of image. Use these steps to flash an image using Bmaptool:
+1. *Update your local.conf File:* You need to have the following set
+   in your ``local.conf`` file before building your image:
+   ::
+      IMAGE_FSTYPES += "wic wic.bmap"
+2. *Get Your Image:* Either have your image ready (pre-built with the
+   :term:`IMAGE_FSTYPES`
+   setting previously mentioned) or take the step to build the image:
+   ::
+      $ bitbake image
+3. *Flash the Device:* Flash the device with the image by using Bmaptool
+   depending on your particular setup. The following commands assume the
+   image resides in the Build Directory's ``deploy/images/`` area:
+   -  If you have write access to the media, use this command form:
+      ::
+         $ oe-run-native bmap-tools-native bmaptool copy build-directory/tmp/deploy/images/machine/image.wic /dev/sdX
+   -  If you do not have write access to the media, set your permissions
+      first and then use the same command form:
+      ::
+         $ sudo chmod 666 /dev/sdX
+         $ oe-run-native bmap-tools-native bmaptool copy build-directory/tmp/deploy/images/machine/image.wic /dev/sdX
+For help on the ``bmaptool`` command, use the following command:
+::
+   $ bmaptool --help
+Making Images More Secure
+=========================
+Security is of increasing concern for embedded devices. Consider the
+issues and problems discussed in just this sampling of work found across
+the Internet:
+-  *"*\ `Security Risks of Embedded
+   Systems <https://www.schneier.com/blog/archives/2014/01/security_risks_9.html>`__\ *"*
+   by Bruce Schneier
+-  *"*\ `Internet Census
+   2012 <http://census2012.sourceforge.net/paper.html>`__\ *"* by Carna
+   Botnet
+-  *"*\ `Security Issues for Embedded
+   Devices <http://elinux.org/images/6/6f/Security-issues.pdf>`__\ *"*
+   by Jake Edge
+When securing your image is of concern, there are steps, tools, and
+variables that you can consider to help you reach the security goals you
+need for your particular device. Not all situations are identical when
+it comes to making an image secure. Consequently, this section provides
+some guidance and suggestions for consideration when you want to make
+your image more secure.
+.. note::
+   Because the security requirements and risks are different for every
+   type of device, this section cannot provide a complete reference on
+   securing your custom OS. It is strongly recommended that you also
+   consult other sources of information on embedded Linux system
+   hardening and on security.
+General Considerations
+----------------------
+General considerations exist that help you create more secure images.
+You should consider the following suggestions to help make your device
+more secure:
+-  Scan additional code you are adding to the system (e.g. application
+   code) by using static analysis tools. Look for buffer overflows and
+   other potential security problems.
+-  Pay particular attention to the security for any web-based
+   administration interface.
+   Web interfaces typically need to perform administrative functions and
+   tend to need to run with elevated privileges. Thus, the consequences
+   resulting from the interface's security becoming compromised can be
+   serious. Look for common web vulnerabilities such as
+   cross-site-scripting (XSS), unvalidated inputs, and so forth.
+   As with system passwords, the default credentials for accessing a
+   web-based interface should not be the same across all devices. This
+   is particularly true if the interface is enabled by default as it can
+   be assumed that many end-users will not change the credentials.
+-  Ensure you can update the software on the device to mitigate
+   vulnerabilities discovered in the future. This consideration
+   especially applies when your device is network-enabled.
+-  Ensure you remove or disable debugging functionality before producing
+   the final image. For information on how to do this, see the
+   "`Considerations Specific to the OpenEmbedded Build
+   System <#considerations-specific-to-the-openembedded-build-system>`__"
+   section.
+-  Ensure you have no network services listening that are not needed.
+-  Remove any software from the image that is not needed.
+-  Enable hardware support for secure boot functionality when your
+   device supports this functionality.
+Security Flags
+--------------
+The Yocto Project has security flags that you can enable that help make
+your build output more secure. The security flags are in the
+``meta/conf/distro/include/security_flags.inc`` file in your
+:term:`Source Directory` (e.g. ``poky``).
+.. note::
+   Depending on the recipe, certain security flags are enabled and
+   disabled by default.
+Use the following line in your ``local.conf`` file or in your custom
+distribution configuration file to enable the security compiler and
+linker flags for your build:
+::
+   require conf/distro/include/security_flags.inc
+Considerations Specific to the OpenEmbedded Build System
+--------------------------------------------------------
+You can take some steps that are specific to the OpenEmbedded build
+system to make your images more secure:
+-  Ensure "debug-tweaks" is not one of your selected
+   :term:`IMAGE_FEATURES`.
+   When creating a new project, the default is to provide you with an
+   initial ``local.conf`` file that enables this feature using the
+   :term:`EXTRA_IMAGE_FEATURES`
+   variable with the line:
+   ::
+      EXTRA_IMAGE_FEATURES = "debug-tweaks"
+   To disable that feature, simply comment out that line in your
+   ``local.conf`` file, or make sure ``IMAGE_FEATURES`` does not contain
+   "debug-tweaks" before producing your final image. Among other things,
+   leaving this in place sets the root password as blank, which makes
+   logging in for debugging or inspection easy during development but
+   also means anyone can easily log in during production.
+-  It is possible to set a root password for the image and also to set
+   passwords for any extra users you might add (e.g. administrative or
+   service type users). When you set up passwords for multiple images or
+   users, you should not duplicate passwords.
+   To set up passwords, use the
+   :ref:`extrausers <ref-classes-extrausers>`
+   class, which is the preferred method. For an example on how to set up
+   both root and user passwords, see the
+   ":ref:`extrausers.bbclass <ref-classes-extrausers>`"
+   section.
+   .. note::
+      When adding extra user accounts or setting a root password, be
+      cautious about setting the same password on every device. If you
+      do this, and the password you have set is exposed, then every
+      device is now potentially compromised. If you need this access but
+      want to ensure security, consider setting a different, random
+      password for each device. Typically, you do this as a separate
+      step after you deploy the image onto the device.
+-  Consider enabling a Mandatory Access Control (MAC) framework such as
+   SMACK or SELinux and tuning it appropriately for your device's usage.
+   You can find more information in the
+   :yocto_git:`meta-selinux </meta-selinux/>` layer.
+Tools for Hardening Your Image
+------------------------------
+The Yocto Project provides tools for making your image more secure. You
+can find these tools in the ``meta-security`` layer of the
+:yocto_git:`Yocto Project Source Repositories <>`.
+Creating Your Own Distribution
+==============================
+When you build an image using the Yocto Project and do not alter any
+distribution :term:`Metadata`, you are
+creating a Poky distribution. If you wish to gain more control over
+package alternative selections, compile-time options, and other
+low-level configurations, you can create your own distribution.
+To create your own distribution, the basic steps consist of creating
+your own distribution layer, creating your own distribution
+configuration file, and then adding any needed code and Metadata to the
+layer. The following steps provide some more detail:
+-  *Create a layer for your new distro:* Create your distribution layer
+   so that you can keep your Metadata and code for the distribution
+   separate. It is strongly recommended that you create and use your own
+   layer for configuration and code. Using your own layer as compared to
+   just placing configurations in a ``local.conf`` configuration file
+   makes it easier to reproduce the same build configuration when using
+   multiple build machines. See the
+   ":ref:`dev-manual/common-tasks:creating a general layer using the \`\`bitbake-layers\`\` script`"
+   section for information on how to quickly set up a layer.
+-  *Create the distribution configuration file:* The distribution
+   configuration file needs to be created in the ``conf/distro``
+   directory of your layer. You need to name it using your distribution
+   name (e.g. ``mydistro.conf``).
+   .. note::
+      The :term:`DISTRO` variable in your ``local.conf`` file determines the
+      name of your distribution.
+   You can split out parts of your configuration file into include files
+   and then "require" them from within your distribution configuration
+   file. Be sure to place the include files in the
+   ``conf/distro/include`` directory of your layer. A common example
+   usage of include files would be to separate out the selection of
+   desired version and revisions for individual recipes.
+   Your configuration file needs to set the following required
+   variables:
+   - :term:`DISTRO_NAME`
+   - :term:`DISTRO_VERSION`
+   These following variables are optional and you typically set them
+   from the distribution configuration file:
+   - :term:`DISTRO_FEATURES`
+   - :term:`DISTRO_EXTRA_RDEPENDS`
+   - :term:`DISTRO_EXTRA_RRECOMMENDS`
+   - :term:`TCLIBC`
+   .. tip::
+      If you want to base your distribution configuration file on the
+      very basic configuration from OE-Core, you can use
+      ``conf/distro/defaultsetup.conf`` as a reference and just include
+      variables that differ as compared to ``defaultsetup.conf``.
+      Alternatively, you can create a distribution configuration file
+      from scratch using the ``defaultsetup.conf`` file or configuration files
+      from other distributions such as Poky or Angstrom as references.
+-  *Provide miscellaneous variables:* Be sure to define any other
+   variables for which you want to create a default or enforce as part
+   of the distribution configuration. You can include nearly any
+   variable from the ``local.conf`` file. The variables you use are not
+   limited to the list in the previous bulleted item.
+-  *Point to Your distribution configuration file:* In your
+   ``local.conf`` file in the :term:`Build Directory`,
+   set your
+   :term:`DISTRO` variable to point to
+   your distribution's configuration file. For example, if your
+   distribution's configuration file is named ``mydistro.conf``, then
+   you point to it as follows:
+   ::
+      DISTRO = "mydistro"
+-  *Add more to the layer if necessary:* Use your layer to hold other
+   information needed for the distribution:
+   -  Add recipes for installing distro-specific configuration files
+      that are not already installed by another recipe. If you have
+      distro-specific configuration files that are included by an
+      existing recipe, you should add an append file (``.bbappend``) for
+      those. For general information and recommendations on how to add
+      recipes to your layer, see the "`Creating Your Own
+      Layer <#creating-your-own-layer>`__" and "`Following Best
+      Practices When Creating
+      Layers <#best-practices-to-follow-when-creating-layers>`__"
+      sections.
+   -  Add any image recipes that are specific to your distribution.
+   -  Add a ``psplash`` append file for a branded splash screen. For
+      information on append files, see the "`Using .bbappend Files in
+      Your Layer <#using-bbappend-files>`__" section.
+   -  Add any other append files to make custom changes that are
+      specific to individual recipes.
+Creating a Custom Template Configuration Directory
+==================================================
+If you are producing your own customized version of the build system for
+use by other users, you might want to customize the message shown by the
+setup script or you might want to change the template configuration
+files (i.e. ``local.conf`` and ``bblayers.conf``) that are created in a
+new build directory.
+The OpenEmbedded build system uses the environment variable
+``TEMPLATECONF`` to locate the directory from which it gathers
+configuration information that ultimately ends up in the
+:term:`Build Directory` ``conf`` directory.
+By default, ``TEMPLATECONF`` is set as follows in the ``poky``
+repository:
+::
+   TEMPLATECONF=${TEMPLATECONF:-meta-poky/conf}
+This is the
+directory used by the build system to find templates from which to build
+some key configuration files. If you look at this directory, you will
+see the ``bblayers.conf.sample``, ``local.conf.sample``, and
+``conf-notes.txt`` files. The build system uses these files to form the
+respective ``bblayers.conf`` file, ``local.conf`` file, and display the
+list of BitBake targets when running the setup script.
+To override these default configuration files with configurations you
+want used within every new Build Directory, simply set the
+``TEMPLATECONF`` variable to your directory. The ``TEMPLATECONF``
+variable is set in the ``.templateconf`` file, which is in the top-level
+:term:`Source Directory` folder
+(e.g. ``poky``). Edit the ``.templateconf`` so that it can locate your
+directory.
+Best practices dictate that you should keep your template configuration
+directory in your custom distribution layer. For example, suppose you
+have a layer named ``meta-mylayer`` located in your home directory and
+you want your template configuration directory named ``myconf``.
+Changing the ``.templateconf`` as follows causes the OpenEmbedded build
+system to look in your directory and base its configuration files on the
+``*.sample`` configuration files it finds. The final configuration files
+(i.e. ``local.conf`` and ``bblayers.conf`` ultimately still end up in
+your Build Directory, but they are based on your ``*.sample`` files.
+::
+   TEMPLATECONF=${TEMPLATECONF:-meta-mylayer/myconf}
+Aside from the ``*.sample`` configuration files, the ``conf-notes.txt``
+also resides in the default ``meta-poky/conf`` directory. The script
+that sets up the build environment (i.e.
+:ref:`structure-core-script`) uses this file to
+display BitBake targets as part of the script output. Customizing this
+``conf-notes.txt`` file is a good way to make sure your list of custom
+targets appears as part of the script's output.
+Here is the default list of targets displayed as a result of running
+either of the setup scripts:
+::
+   You can now run 'bitbake <target>'
+   Common targets are:
+       core-image-minimal
+       core-image-sato
+       meta-toolchain
+       meta-ide-support
+Changing the listed common targets is as easy as editing your version of
+``conf-notes.txt`` in your custom template configuration directory and
+making sure you have ``TEMPLATECONF`` set to your directory.
+Conserving Disk Space During Builds
+===================================
+To help conserve disk space during builds, you can add the following
+statement to your project's ``local.conf`` configuration file found in
+the :term:`Build Directory`:
+::
+   INHERIT += "rm_work"
+Adding this statement deletes the work directory used for
+building a recipe once the recipe is built. For more information on
+"rm_work", see the
+:ref:`rm_work <ref-classes-rm-work>` class in the
+Yocto Project Reference Manual.
+Working with Packages
+=====================
+This section describes a few tasks that involve packages:
+-  `Excluding packages from an
+   image <#excluding-packages-from-an-image>`__
+-  `Incrementing a binary package
+   version <#incrementing-a-binary-package-version>`__
+-  `Handling optional module
+   packaging <#handling-optional-module-packaging>`__
+-  `Using runtime package
+   management <#using-runtime-package-management>`__
+-  `Generating and using signed
+   packages <#generating-and-using-signed-packages>`__
+-  `Setting up and running package test
+   (ptest) <#testing-packages-with-ptest>`__
+-  `Creating node package manager (NPM)
+   packages <#creating-node-package-manager-npm-packages>`__
+-  `Adding custom metadata to
+   packages <#adding-custom-metadata-to-packages>`__
+Excluding Packages from an Image
+--------------------------------
+You might find it necessary to prevent specific packages from being
+installed into an image. If so, you can use several variables to direct
+the build system to essentially ignore installing recommended packages
+or to not install a package at all.
+The following list introduces variables you can use to prevent packages
+from being installed into your image. Each of these variables only works
+with IPK and RPM package types. Support for Debian packages does not
+exist. Also, you can use these variables from your ``local.conf`` file
+or attach them to a specific image recipe by using a recipe name
+override. For more detail on the variables, see the descriptions in the
+Yocto Project Reference Manual's glossary chapter.
+-  :term:`BAD_RECOMMENDATIONS`:
+   Use this variable to specify "recommended-only" packages that you do
+   not want installed.
+-  :term:`NO_RECOMMENDATIONS`:
+   Use this variable to prevent all "recommended-only" packages from
+   being installed.
+-  :term:`PACKAGE_EXCLUDE`:
+   Use this variable to prevent specific packages from being installed
+   regardless of whether they are "recommended-only" or not. You need to
+   realize that the build process could fail with an error when you
+   prevent the installation of a package whose presence is required by
+   an installed package.
+Incrementing a Package Version
+------------------------------
+This section provides some background on how binary package versioning
+is accomplished and presents some of the services, variables, and
+terminology involved.
+In order to understand binary package versioning, you need to consider
+the following:
+-  Binary Package: The binary package that is eventually built and
+   installed into an image.
+-  Binary Package Version: The binary package version is composed of two
+   components - a version and a revision.
+   .. note::
+      Technically, a third component, the "epoch" (i.e. :term:`PE`) is involved
+      but this discussion for the most part ignores ``PE``.
+   The version and revision are taken from the
+   :term:`PV` and
+   :term:`PR` variables, respectively.
+-  ``PV``: The recipe version. ``PV`` represents the version of the
+   software being packaged. Do not confuse ``PV`` with the binary
+   package version.
+-  ``PR``: The recipe revision.
+-  :term:`SRCPV`: The OpenEmbedded
+   build system uses this string to help define the value of ``PV`` when
+   the source code revision needs to be included in it.
+-  :yocto_wiki:`PR Service </PR_Service>`: A
+   network-based service that helps automate keeping package feeds
+   compatible with existing package manager applications such as RPM,
+   APT, and OPKG.
+Whenever the binary package content changes, the binary package version
+must change. Changing the binary package version is accomplished by
+changing or "bumping" the ``PR`` and/or ``PV`` values. Increasing these
+values occurs one of two ways:
+-  Automatically using a Package Revision Service (PR Service).
+-  Manually incrementing the ``PR`` and/or ``PV`` variables.
+Given a primary challenge of any build system and its users is how to
+maintain a package feed that is compatible with existing package manager
+applications such as RPM, APT, and OPKG, using an automated system is
+much preferred over a manual system. In either system, the main
+requirement is that binary package version numbering increases in a
+linear fashion and that a number of version components exist that
+support that linear progression. For information on how to ensure
+package revisioning remains linear, see the "`Automatically Incrementing
+a Binary Package Revision
+Number <#automatically-incrementing-a-binary-package-revision-number>`__"
+section.
+The following three sections provide related information on the PR
+Service, the manual method for "bumping" ``PR`` and/or ``PV``, and on
+how to ensure binary package revisioning remains linear.
+Working With a PR Service
+~~~~~~~~~~~~~~~~~~~~~~~~~
+As mentioned, attempting to maintain revision numbers in the
+:term:`Metadata` is error prone, inaccurate,
+and causes problems for people submitting recipes. Conversely, the PR
+Service automatically generates increasing numbers, particularly the
+revision field, which removes the human element.
+.. note::
+   For additional information on using a PR Service, you can see the
+   :yocto_wiki:`PR Service </PR_Service>` wiki page.
+The Yocto Project uses variables in order of decreasing priority to
+facilitate revision numbering (i.e.
+:term:`PE`,
+:term:`PV`, and
+:term:`PR` for epoch, version, and
+revision, respectively). The values are highly dependent on the policies
+and procedures of a given distribution and package feed.
+Because the OpenEmbedded build system uses
+":ref:`signatures <overview-manual/overview-manual-concepts:checksums (signatures)>`", which are
+unique to a given build, the build system knows when to rebuild
+packages. All the inputs into a given task are represented by a
+signature, which can trigger a rebuild when different. Thus, the build
+system itself does not rely on the ``PR``, ``PV``, and ``PE`` numbers to
+trigger a rebuild. The signatures, however, can be used to generate
+these values.
+The PR Service works with both ``OEBasic`` and ``OEBasicHash``
+generators. The value of ``PR`` bumps when the checksum changes and the
+different generator mechanisms change signatures under different
+circumstances.
+As implemented, the build system includes values from the PR Service
+into the ``PR`` field as an addition using the form "``.x``" so ``r0``
+becomes ``r0.1``, ``r0.2`` and so forth. This scheme allows existing
+``PR`` values to be used for whatever reasons, which include manual
+``PR`` bumps, should it be necessary.
+By default, the PR Service is not enabled or running. Thus, the packages
+generated are just "self consistent". The build system adds and removes
+packages and there are no guarantees about upgrade paths but images will
+be consistent and correct with the latest changes.
+The simplest form for a PR Service is for it to exist for a single host
+development system that builds the package feed (building system). For
+this scenario, you can enable a local PR Service by setting
+:term:`PRSERV_HOST` in your
+``local.conf`` file in the :term:`Build Directory`:
+::
+   PRSERV_HOST = "localhost:0"
+Once the service is started, packages will automatically
+get increasing ``PR`` values and BitBake takes care of starting and
+stopping the server.
+If you have a more complex setup where multiple host development systems
+work against a common, shared package feed, you have a single PR Service
+running and it is connected to each building system. For this scenario,
+you need to start the PR Service using the ``bitbake-prserv`` command:
+::
+   bitbake-prserv --host ip --port port --start
+In addition to
+hand-starting the service, you need to update the ``local.conf`` file of
+each building system as described earlier so each system points to the
+server and port.
+It is also recommended you use build history, which adds some sanity
+checks to binary package versions, in conjunction with the server that
+is running the PR Service. To enable build history, add the following to
+each building system's ``local.conf`` file:
+::
+   # It is recommended to activate "buildhistory" for testing the PR service
+   INHERIT += "buildhistory"
+   BUILDHISTORY_COMMIT = "1"
+For information on build
+history, see the "`Maintaining Build Output
+Quality <#maintaining-build-output-quality>`__" section.
+.. note::
+   The OpenEmbedded build system does not maintain ``PR`` information as
+   part of the shared state (sstate) packages. If you maintain an sstate
+   feed, its expected that either all your building systems that
+   contribute to the sstate feed use a shared PR Service, or you do not
+   run a PR Service on any of your building systems. Having some systems
+   use a PR Service while others do not leads to obvious problems.
+   For more information on shared state, see the
+   ":ref:`overview-manual/overview-manual-concepts:shared state cache`"
+   section in the Yocto Project Overview and Concepts Manual.
+Manually Bumping PR
+~~~~~~~~~~~~~~~~~~~
+The alternative to setting up a PR Service is to manually "bump" the
+:term:`PR` variable.
+If a committed change results in changing the package output, then the
+value of the PR variable needs to be increased (or "bumped") as part of
+that commit. For new recipes you should add the ``PR`` variable and set
+its initial value equal to "r0", which is the default. Even though the
+default value is "r0", the practice of adding it to a new recipe makes
+it harder to forget to bump the variable when you make changes to the
+recipe in future.
+If you are sharing a common ``.inc`` file with multiple recipes, you can
+also use the ``INC_PR`` variable to ensure that the recipes sharing the
+``.inc`` file are rebuilt when the ``.inc`` file itself is changed. The
+``.inc`` file must set ``INC_PR`` (initially to "r0"), and all recipes
+referring to it should set ``PR`` to "${INC_PR}.0" initially,
+incrementing the last number when the recipe is changed. If the ``.inc``
+file is changed then its ``INC_PR`` should be incremented.
+When upgrading the version of a binary package, assuming the ``PV``
+changes, the ``PR`` variable should be reset to "r0" (or "${INC_PR}.0"
+if you are using ``INC_PR``).
+Usually, version increases occur only to binary packages. However, if
+for some reason ``PV`` changes but does not increase, you can increase
+the ``PE`` variable (Package Epoch). The ``PE`` variable defaults to
+"0".
+Binary package version numbering strives to follow the `Debian Version
+Field Policy
+Guidelines <https://www.debian.org/doc/debian-policy/ch-controlfields.html>`__.
+These guidelines define how versions are compared and what "increasing"
+a version means.
+Automatically Incrementing a Package Version Number
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+When fetching a repository, BitBake uses the
+:term:`SRCREV` variable to determine
+the specific source code revision from which to build. You set the
+``SRCREV`` variable to
+:term:`AUTOREV` to cause the
+OpenEmbedded build system to automatically use the latest revision of
+the software:
+::
+   SRCREV = "${AUTOREV}"
+Furthermore, you need to reference ``SRCPV`` in ``PV`` in order to
+automatically update the version whenever the revision of the source
+code changes. Here is an example:
+::
+   PV = "1.0+git${SRCPV}"
+The OpenEmbedded build system substitutes ``SRCPV`` with the following:
+.. code-block:: none
+   AUTOINC+source_code_revision
+The build system replaces the ``AUTOINC``
+with a number. The number used depends on the state of the PR Service:
+-  If PR Service is enabled, the build system increments the number,
+   which is similar to the behavior of
+   :term:`PR`. This behavior results in
+   linearly increasing package versions, which is desirable. Here is an
+   example:
+   .. code-block:: none
+      hello-world-git_0.0+git0+b6558dd387-r0.0_armv7a-neon.ipk
+      hello-world-git_0.0+git1+dd2f5c3565-r0.0_armv7a-neon.ipk
+-  If PR Service is not enabled, the build system replaces the
+   ``AUTOINC`` placeholder with zero (i.e. "0"). This results in
+   changing the package version since the source revision is included.
+   However, package versions are not increased linearly. Here is an
+   example:
+   .. code-block:: none
+      hello-world-git_0.0+git0+b6558dd387-r0.0_armv7a-neon.ipk
+      hello-world-git_0.0+git0+dd2f5c3565-r0.0_armv7a-neon.ipk
+In summary, the OpenEmbedded build system does not track the history of
+binary package versions for this purpose. ``AUTOINC``, in this case, is
+comparable to ``PR``. If PR server is not enabled, ``AUTOINC`` in the
+package version is simply replaced by "0". If PR server is enabled, the
+build system keeps track of the package versions and bumps the number
+when the package revision changes.
+Handling Optional Module Packaging
+----------------------------------
+Many pieces of software split functionality into optional modules (or
+plugins) and the plugins that are built might depend on configuration
+options. To avoid having to duplicate the logic that determines what
+modules are available in your recipe or to avoid having to package each
+module by hand, the OpenEmbedded build system provides functionality to
+handle module packaging dynamically.
+To handle optional module packaging, you need to do two things:
+-  Ensure the module packaging is actually done.
+-  Ensure that any dependencies on optional modules from other recipes
+   are satisfied by your recipe.
+Making Sure the Packaging is Done
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+To ensure the module packaging actually gets done, you use the
+``do_split_packages`` function within the ``populate_packages`` Python
+function in your recipe. The ``do_split_packages`` function searches for
+a pattern of files or directories under a specified path and creates a
+package for each one it finds by appending to the
+:term:`PACKAGES` variable and
+setting the appropriate values for ``FILES_packagename``,
+``RDEPENDS_packagename``, ``DESCRIPTION_packagename``, and so forth.
+Here is an example from the ``lighttpd`` recipe:
+::
+   python populate_packages_prepend () {
+       lighttpd_libdir = d.expand('${libdir}')
+       do_split_packages(d, lighttpd_libdir, '^mod_(.*).so$',
+                        'lighttpd-module-%s', 'Lighttpd module for %s',
+                         extra_depends='')
+   }
+The previous example specifies a number of things in the call to
+``do_split_packages``.
+-  A directory within the files installed by your recipe through
+   ``do_install`` in which to search.
+-  A regular expression used to match module files in that directory. In
+   the example, note the parentheses () that mark the part of the
+   expression from which the module name should be derived.
+-  A pattern to use for the package names.
+-  A description for each package.
+-  An empty string for ``extra_depends``, which disables the default
+   dependency on the main ``lighttpd`` package. Thus, if a file in
+   ``${libdir}`` called ``mod_alias.so`` is found, a package called
+   ``lighttpd-module-alias`` is created for it and the
+   :term:`DESCRIPTION` is set to
+   "Lighttpd module for alias".
+Often, packaging modules is as simple as the previous example. However,
+more advanced options exist that you can use within
+``do_split_packages`` to modify its behavior. And, if you need to, you
+can add more logic by specifying a hook function that is called for each
+package. It is also perfectly acceptable to call ``do_split_packages``
+multiple times if you have more than one set of modules to package.
+For more examples that show how to use ``do_split_packages``, see the
+``connman.inc`` file in the ``meta/recipes-connectivity/connman/``
+directory of the ``poky`` :ref:`source repository <overview-manual/overview-manual-development-environment:yocto project source repositories>`. You can
+also find examples in ``meta/classes/kernel.bbclass``.
+Following is a reference that shows ``do_split_packages`` mandatory and
+optional arguments:
+::
+   Mandatory arguments
+   root
+      The path in which to search
+   file_regex
+      Regular expression to match searched files.
+      Use parentheses () to mark the part of this
+      expression that should be used to derive the
+      module name (to be substituted where %s is
+      used in other function arguments as noted below)
+   output_pattern
+      Pattern to use for the package names. Must
+      include %s.
+   description
+      Description to set for each package. Must
+      include %s.
+   Optional arguments
+   postinst
+      Postinstall script to use for all packages
+      (as a string)
+   recursive
+      True to perform a recursive search - default
+      False
+   hook
+      A hook function to be called for every match.
+      The function will be called with the following
+      arguments (in the order listed):
+      f
+         Full path to the file/directory match
+      pkg
+         The package name
+      file_regex
+         As above
+      output_pattern
+         As above
+      modulename
+         The module name derived using file_regex
+   extra_depends
+      Extra runtime dependencies (RDEPENDS) to be
+      set for all packages. The default value of None
+      causes a dependency on the main package
+      (${PN}) - if you do not want this, pass empty
+      string '' for this parameter.
+   aux_files_pattern
+      Extra item(s) to be added to FILES for each
+      package. Can be a single string item or a list
+      of strings for multiple items. Must include %s.
+   postrm
+      postrm script to use for all packages (as a
+      string)
+   allow_dirs
+      True to allow directories to be matched -
+      default False
+   prepend
+      If True, prepend created packages to PACKAGES
+      instead of the default False which appends them
+   match_path
+      match file_regex on the whole relative path to
+      the root rather than just the file name
+   aux_files_pattern_verbatim
+      Extra item(s) to be added to FILES for each
+      package, using the actual derived module name
+      rather than converting it to something legal
+      for a package name. Can be a single string item
+      or a list of strings for multiple items. Must
+      include %s.
+   allow_links
+      True to allow symlinks to be matched - default
+      False
+   summary
+      Summary to set for each package. Must include %s;
+      defaults to description if not set.
+Satisfying Dependencies
+~~~~~~~~~~~~~~~~~~~~~~~
+The second part for handling optional module packaging is to ensure that
+any dependencies on optional modules from other recipes are satisfied by
+your recipe. You can be sure these dependencies are satisfied by using
+the :term:`PACKAGES_DYNAMIC`
+variable. Here is an example that continues with the ``lighttpd`` recipe
+shown earlier:
+::
+   PACKAGES_DYNAMIC = "lighttpd-module-.*"
+The name
+specified in the regular expression can of course be anything. In this
+example, it is ``lighttpd-module-`` and is specified as the prefix to
+ensure that any :term:`RDEPENDS` and
+:term:`RRECOMMENDS` on a package
+name starting with the prefix are satisfied during build time. If you
+are using ``do_split_packages`` as described in the previous section,
+the value you put in ``PACKAGES_DYNAMIC`` should correspond to the name
+pattern specified in the call to ``do_split_packages``.
+Using Runtime Package Management
+--------------------------------
+During a build, BitBake always transforms a recipe into one or more
+packages. For example, BitBake takes the ``bash`` recipe and produces a
+number of packages (e.g. ``bash``, ``bash-bashbug``,
+``bash-completion``, ``bash-completion-dbg``, ``bash-completion-dev``,
+``bash-completion-extra``, ``bash-dbg``, and so forth). Not all
+generated packages are included in an image.
+In several situations, you might need to update, add, remove, or query
+the packages on a target device at runtime (i.e. without having to
+generate a new image). Examples of such situations include:
+-  You want to provide in-the-field updates to deployed devices (e.g.
+   security updates).
+-  You want to have a fast turn-around development cycle for one or more
+   applications that run on your device.
+-  You want to temporarily install the "debug" packages of various
+   applications on your device so that debugging can be greatly improved
+   by allowing access to symbols and source debugging.
+-  You want to deploy a more minimal package selection of your device
+   but allow in-the-field updates to add a larger selection for
+   customization.
+In all these situations, you have something similar to a more
+traditional Linux distribution in that in-field devices are able to
+receive pre-compiled packages from a server for installation or update.
+Being able to install these packages on a running, in-field device is
+what is termed "runtime package management".
+In order to use runtime package management, you need a host or server
+machine that serves up the pre-compiled packages plus the required
+metadata. You also need package manipulation tools on the target. The
+build machine is a likely candidate to act as the server. However, that
+machine does not necessarily have to be the package server. The build
+machine could push its artifacts to another machine that acts as the
+server (e.g. Internet-facing). In fact, doing so is advantageous for a
+production environment as getting the packages away from the development
+system's build directory prevents accidental overwrites.
+A simple build that targets just one device produces more than one
+package database. In other words, the packages produced by a build are
+separated out into a couple of different package groupings based on
+criteria such as the target's CPU architecture, the target board, or the
+C library used on the target. For example, a build targeting the
+``qemux86`` device produces the following three package databases:
+``noarch``, ``i586``, and ``qemux86``. If you wanted your ``qemux86``
+device to be aware of all the packages that were available to it, you
+would need to point it to each of these databases individually. In a
+similar way, a traditional Linux distribution usually is configured to
+be aware of a number of software repositories from which it retrieves
+packages.
+Using runtime package management is completely optional and not required
+for a successful build or deployment in any way. But if you want to make
+use of runtime package management, you need to do a couple things above
+and beyond the basics. The remainder of this section describes what you
+need to do.
+Build Considerations
+~~~~~~~~~~~~~~~~~~~~
+This section describes build considerations of which you need to be
+aware in order to provide support for runtime package management.
+When BitBake generates packages, it needs to know what format or formats
+to use. In your configuration, you use the
+:term:`PACKAGE_CLASSES`
+variable to specify the format:
+1. Open the ``local.conf`` file inside your
+   :term:`Build Directory` (e.g.
+   ``~/poky/build/conf/local.conf``).
+2. Select the desired package format as follows:
+   ::
+      PACKAGE_CLASSES ?= "package_packageformat"
+   where packageformat can be "ipk", "rpm",
+   "deb", or "tar" which are the supported package formats.
+   .. note::
+      Because the Yocto Project supports four different package formats,
+      you can set the variable with more than one argument. However, the
+      OpenEmbedded build system only uses the first argument when
+      creating an image or Software Development Kit (SDK).
+If you would like your image to start off with a basic package database
+containing the packages in your current build as well as to have the
+relevant tools available on the target for runtime package management,
+you can include "package-management" in the
+:term:`IMAGE_FEATURES`
+variable. Including "package-management" in this configuration variable
+ensures that when the image is assembled for your target, the image
+includes the currently-known package databases as well as the
+target-specific tools required for runtime package management to be
+performed on the target. However, this is not strictly necessary. You
+could start your image off without any databases but only include the
+required on-target package tool(s). As an example, you could include
+"opkg" in your
+:term:`IMAGE_INSTALL` variable
+if you are using the IPK package format. You can then initialize your
+target's package database(s) later once your image is up and running.
+Whenever you perform any sort of build step that can potentially
+generate a package or modify existing package, it is always a good idea
+to re-generate the package index after the build by using the following
+command:
+::
+   $ bitbake package-index
+It might be tempting to build the
+package and the package index at the same time with a command such as
+the following:
+::
+   $ bitbake some-package package-index
+Do not do this as
+BitBake does not schedule the package index for after the completion of
+the package you are building. Consequently, you cannot be sure of the
+package index including information for the package you just built.
+Thus, be sure to run the package update step separately after building
+any packages.
+You can use the
+:term:`PACKAGE_FEED_ARCHS`,
+:term:`PACKAGE_FEED_BASE_PATHS`,
+and
+:term:`PACKAGE_FEED_URIS`
+variables to pre-configure target images to use a package feed. If you
+do not define these variables, then manual steps as described in the
+subsequent sections are necessary to configure the target. You should
+set these variables before building the image in order to produce a
+correctly configured image.
+When your build is complete, your packages reside in the
+``${TMPDIR}/deploy/packageformat`` directory. For example, if
+``${``\ :term:`TMPDIR`\ ``}`` is
+``tmp`` and your selected package type is RPM, then your RPM packages
+are available in ``tmp/deploy/rpm``.
+Host or Server Machine Setup
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Although other protocols are possible, a server using HTTP typically
+serves packages. If you want to use HTTP, then set up and configure a
+web server such as Apache 2, lighttpd, or Python web server on the
+machine serving the packages.
+To keep things simple, this section describes how to set up a
+Python web server to share package feeds from the developer's
+machine. Although this server might not be the best for a production
+environment, the setup is simple and straight forward. Should you want
+to use a different server more suited for production (e.g. Apache 2,
+Lighttpd, or Nginx), take the appropriate steps to do so.
+From within the build directory where you have built an image based on
+your packaging choice (i.e. the
+:term:`PACKAGE_CLASSES`
+setting), simply start the server. The following example assumes a build
+directory of ``~/poky/build/tmp/deploy/rpm`` and a ``PACKAGE_CLASSES``
+setting of "package_rpm":
+::
+   $ cd ~/poky/build/tmp/deploy/rpm
+   $ python3 -m http.server
+Target Setup
+~~~~~~~~~~~~
+Setting up the target differs depending on the package management
+system. This section provides information for RPM, IPK, and DEB.
+Using RPM
+^^^^^^^^^
+The `Dandified Packaging
+Tool <https://en.wikipedia.org/wiki/DNF_(software)>`__ (DNF) performs
+runtime package management of RPM packages. In order to use DNF for
+runtime package management, you must perform an initial setup on the
+target machine for cases where the ``PACKAGE_FEED_*`` variables were not
+set as part of the image that is running on the target. This means if
+you built your image and did not not use these variables as part of the
+build and your image is now running on the target, you need to perform
+the steps in this section if you want to use runtime package management.
+.. note::
+   For information on the ``PACKAGE_FEED_*`` variables, see
+   :term:`PACKAGE_FEED_ARCHS`, :term:`PACKAGE_FEED_BASE_PATHS`, and
+   :term:`PACKAGE_FEED_URIS` in the Yocto Project Reference Manual variables
+   glossary.
+On the target, you must inform DNF that package databases are available.
+You do this by creating a file named
+``/etc/yum.repos.d/oe-packages.repo`` and defining the ``oe-packages``.
+As an example, assume the target is able to use the following package
+databases: ``all``, ``i586``, and ``qemux86`` from a server named
+``my.server``. The specifics for setting up the web server are up to
+you. The critical requirement is that the URIs in the target repository
+configuration point to the correct remote location for the feeds.
+.. note::
+   For development purposes, you can point the web server to the build
+   system's ``deploy`` directory. However, for production use, it is better to
+   copy the package directories to a location outside of the build area and use
+   that location. Doing so avoids situations where the build system
+   overwrites or changes the ``deploy`` directory.
+When telling DNF where to look for the package databases, you must
+declare individual locations per architecture or a single location used
+for all architectures. You cannot do both:
+-  *Create an Explicit List of Architectures:* Define individual base
+   URLs to identify where each package database is located:
+   .. code-block:: none
+      [oe-packages]
+      baseurl=http://my.server/rpm/i586  http://my.server/rpm/qemux86 http://my.server/rpm/all
+   This example
+   informs DNF about individual package databases for all three
+   architectures.
+-  *Create a Single (Full) Package Index:* Define a single base URL that
+   identifies where a full package database is located:
+   ::
+      [oe-packages]
+      baseurl=http://my.server/rpm
+   This example informs DNF about a single
+   package database that contains all the package index information for
+   all supported architectures.
+Once you have informed DNF where to find the package databases, you need
+to fetch them:
+.. code-block:: none
+   # dnf makecache
+DNF is now able to find, install, and
+upgrade packages from the specified repository or repositories.
+.. note::
+   See the `DNF documentation <https://dnf.readthedocs.io/en/latest/>`__ for
+   additional information.
+Using IPK
+^^^^^^^^^
+The ``opkg`` application performs runtime package management of IPK
+packages. You must perform an initial setup for ``opkg`` on the target
+machine if the
+:term:`PACKAGE_FEED_ARCHS`,
+:term:`PACKAGE_FEED_BASE_PATHS`,
+and
+:term:`PACKAGE_FEED_URIS`
+variables have not been set or the target image was built before the
+variables were set.
+The ``opkg`` application uses configuration files to find available
+package databases. Thus, you need to create a configuration file inside
+the ``/etc/opkg/`` direction, which informs ``opkg`` of any repository
+you want to use.
+As an example, suppose you are serving packages from a ``ipk/``
+directory containing the ``i586``, ``all``, and ``qemux86`` databases
+through an HTTP server named ``my.server``. On the target, create a
+configuration file (e.g. ``my_repo.conf``) inside the ``/etc/opkg/``
+directory containing the following:
+.. code-block:: none
+   src/gz all http://my.server/ipk/all
+   src/gz i586 http://my.server/ipk/i586
+   src/gz qemux86 http://my.server/ipk/qemux86
+Next, instruct ``opkg`` to fetch the
+repository information:
+.. code-block:: none
+   # opkg update
+The ``opkg`` application is now able to find, install, and upgrade packages
+from the specified repository.
+Using DEB
+^^^^^^^^^
+The ``apt`` application performs runtime package management of DEB
+packages. This application uses a source list file to find available
+package databases. You must perform an initial setup for ``apt`` on the
+target machine if the
+:term:`PACKAGE_FEED_ARCHS`,
+:term:`PACKAGE_FEED_BASE_PATHS`,
+and
+:term:`PACKAGE_FEED_URIS`
+variables have not been set or the target image was built before the
+variables were set.
+To inform ``apt`` of the repository you want to use, you might create a
+list file (e.g. ``my_repo.list``) inside the
+``/etc/apt/sources.list.d/`` directory. As an example, suppose you are
+serving packages from a ``deb/`` directory containing the ``i586``,
+``all``, and ``qemux86`` databases through an HTTP server named
+``my.server``. The list file should contain:
+.. code-block:: none
+   deb http://my.server/deb/all ./
+   deb http://my.server/deb/i586 ./
+   deb http://my.server/deb/qemux86 ./
+Next, instruct the ``apt`` application
+to fetch the repository information:
+.. code-block:: none
+  # apt-get update
+After this step,
+``apt`` is able to find, install, and upgrade packages from the
+specified repository.
+Generating and Using Signed Packages
+------------------------------------
+In order to add security to RPM packages used during a build, you can
+take steps to securely sign them. Once a signature is verified, the
+OpenEmbedded build system can use the package in the build. If security
+fails for a signed package, the build system aborts the build.
+This section describes how to sign RPM packages during a build and how
+to use signed package feeds (repositories) when doing a build.
+Signing RPM Packages
+~~~~~~~~~~~~~~~~~~~~
+To enable signing RPM packages, you must set up the following
+configurations in either your ``local.config`` or ``distro.config``
+file:
+::
+   # Inherit sign_rpm.bbclass to enable signing functionality
+   INHERIT += " sign_rpm"
+   # Define the GPG key that will be used for signing.
+   RPM_GPG_NAME = "key_name"
+   # Provide passphrase for the key
+   RPM_GPG_PASSPHRASE = "passphrase"
+.. note::
+   Be sure to supply appropriate values for both `key_name` and
+   `passphrase`.
+Aside from the ``RPM_GPG_NAME`` and ``RPM_GPG_PASSPHRASE`` variables in
+the previous example, two optional variables related to signing exist:
+-  *GPG_BIN:* Specifies a ``gpg`` binary/wrapper that is executed
+   when the package is signed.
+-  *GPG_PATH:* Specifies the ``gpg`` home directory used when the
+   package is signed.
+Processing Package Feeds
+~~~~~~~~~~~~~~~~~~~~~~~~
+In addition to being able to sign RPM packages, you can also enable
+signed package feeds for IPK and RPM packages.
+The steps you need to take to enable signed package feed use are similar
+to the steps used to sign RPM packages. You must define the following in
+your ``local.config`` or ``distro.config`` file:
+::
+   INHERIT += "sign_package_feed"
+   PACKAGE_FEED_GPG_NAME = "key_name"
+   PACKAGE_FEED_GPG_PASSPHRASE_FILE = "path_to_file_containing_passphrase"
+For signed package feeds, the passphrase must exist in a separate file,
+which is pointed to by the ``PACKAGE_FEED_GPG_PASSPHRASE_FILE``
+variable. Regarding security, keeping a plain text passphrase out of the
+configuration is more secure.
+Aside from the ``PACKAGE_FEED_GPG_NAME`` and
+``PACKAGE_FEED_GPG_PASSPHRASE_FILE`` variables, three optional variables
+related to signed package feeds exist:
+-  *GPG_BIN* Specifies a ``gpg`` binary/wrapper that is executed
+   when the package is signed.
+-  *GPG_PATH:* Specifies the ``gpg`` home directory used when the
+   package is signed.
+-  *PACKAGE_FEED_GPG_SIGNATURE_TYPE:* Specifies the type of ``gpg``
+   signature. This variable applies only to RPM and IPK package feeds.
+   Allowable values for the ``PACKAGE_FEED_GPG_SIGNATURE_TYPE`` are
+   "ASC", which is the default and specifies ascii armored, and "BIN",
+   which specifies binary.
+Testing Packages With ptest
+---------------------------
+A Package Test (ptest) runs tests against packages built by the
+OpenEmbedded build system on the target machine. A ptest contains at
+least two items: the actual test, and a shell script (``run-ptest``)
+that starts the test. The shell script that starts the test must not
+contain the actual test - the script only starts the test. On the other
+hand, the test can be anything from a simple shell script that runs a
+binary and checks the output to an elaborate system of test binaries and
+data files.
+The test generates output in the format used by Automake:
+::
+   result: testname
+where the result can be ``PASS``, ``FAIL``, or ``SKIP``, and
+the testname can be any identifying string.
+For a list of Yocto Project recipes that are already enabled with ptest,
+see the :yocto_wiki:`Ptest </Ptest>` wiki page.
+.. note::
+   A recipe is "ptest-enabled" if it inherits the
+   :ref:`ptest <ref-classes-ptest>` class.
+Adding ptest to Your Build
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+To add package testing to your build, add the
+:term:`DISTRO_FEATURES` and
+:term:`EXTRA_IMAGE_FEATURES`
+variables to your ``local.conf`` file, which is found in the
+:term:`Build Directory`:
+::
+   DISTRO_FEATURES_append = " ptest"
+   EXTRA_IMAGE_FEATURES += "ptest-pkgs"
+Once your build is complete, the ptest files are installed into the
+``/usr/lib/package/ptest`` directory within the image, where ``package``
+is the name of the package.
+Running ptest
+~~~~~~~~~~~~~
+The ``ptest-runner`` package installs a shell script that loops through
+all installed ptest test suites and runs them in sequence. Consequently,
+you might want to add this package to your image.
+Getting Your Package Ready
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+In order to enable a recipe to run installed ptests on target hardware,
+you need to prepare the recipes that build the packages you want to
+test. Here is what you have to do for each recipe:
+-  *Be sure the recipe inherits
+   the* :ref:`ptest <ref-classes-ptest>` *class:*
+   Include the following line in each recipe:
+   ::
+      inherit ptest
+-  *Create run-ptest:* This script starts your test. Locate the
+   script where you will refer to it using
+   :term:`SRC_URI`. Here is an
+   example that starts a test for ``dbus``:
+   ::
+      #!/bin/sh
+      cd test
+      make -k runtest-TESTS
+-  *Ensure dependencies are met:* If the test adds build or runtime
+   dependencies that normally do not exist for the package (such as
+   requiring "make" to run the test suite), use the
+   :term:`DEPENDS` and
+   :term:`RDEPENDS` variables in
+   your recipe in order for the package to meet the dependencies. Here
+   is an example where the package has a runtime dependency on "make":
+   ::
+      RDEPENDS_${PN}-ptest += "make"
+-  *Add a function to build the test suite:* Not many packages support
+   cross-compilation of their test suites. Consequently, you usually
+   need to add a cross-compilation function to the package.
+   Many packages based on Automake compile and run the test suite by
+   using a single command such as ``make check``. However, the host
+   ``make check`` builds and runs on the same computer, while
+   cross-compiling requires that the package is built on the host but
+   executed for the target architecture (though often, as in the case
+   for ptest, the execution occurs on the host). The built version of
+   Automake that ships with the Yocto Project includes a patch that
+   separates building and execution. Consequently, packages that use the
+   unaltered, patched version of ``make check`` automatically
+   cross-compiles.
+   Regardless, you still must add a ``do_compile_ptest`` function to
+   build the test suite. Add a function similar to the following to your
+   recipe:
+   ::
+      do_compile_ptest() {
+          oe_runmake buildtest-TESTS
+      }
+-  *Ensure special configurations are set:* If the package requires
+   special configurations prior to compiling the test code, you must
+   insert a ``do_configure_ptest`` function into the recipe.
+-  *Install the test suite:* The ``ptest`` class automatically copies
+   the file ``run-ptest`` to the target and then runs make
+   ``install-ptest`` to run the tests. If this is not enough, you need
+   to create a ``do_install_ptest`` function and make sure it gets
+   called after the "make install-ptest" completes.
+Creating Node Package Manager (NPM) Packages
+--------------------------------------------
+`NPM <https://en.wikipedia.org/wiki/Npm_(software)>`__ is a package
+manager for the JavaScript programming language. The Yocto Project
+supports the NPM :ref:`fetcher <bitbake:bitbake-user-manual/bitbake-user-manual-fetching:fetchers>`. You can
+use this fetcher in combination with
+:doc:`devtool </ref-manual/ref-devtool-reference>` to create
+recipes that produce NPM packages.
+Two workflows exist that allow you to create NPM packages using
+``devtool``: the NPM registry modules method and the NPM project code
+method.
+.. note::
+   While it is possible to create NPM recipes manually, using
+   ``devtool`` is far simpler.
+Additionally, some requirements and caveats exist.
+Requirements and Caveats
+~~~~~~~~~~~~~~~~~~~~~~~~
+You need to be aware of the following before using ``devtool`` to create
+NPM packages:
+-  Of the two methods that you can use ``devtool`` to create NPM
+   packages, the registry approach is slightly simpler. However, you
+   might consider the project approach because you do not have to
+   publish your module in the NPM registry
+   (`npm-registry <https://docs.npmjs.com/misc/registry>`_), which
+   is NPM's public registry.
+-  Be familiar with
+   :doc:`devtool </ref-manual/ref-devtool-reference>`.
+-  The NPM host tools need the native ``nodejs-npm`` package, which is
+   part of the OpenEmbedded environment. You need to get the package by
+   cloning the https://github.com/openembedded/meta-openembedded
+   repository out of GitHub. Be sure to add the path to your local copy
+   to your ``bblayers.conf`` file.
+-  ``devtool`` cannot detect native libraries in module dependencies.
+   Consequently, you must manually add packages to your recipe.
+-  While deploying NPM packages, ``devtool`` cannot determine which
+   dependent packages are missing on the target (e.g. the node runtime
+   ``nodejs``). Consequently, you need to find out what files are
+   missing and be sure they are on the target.
+-  Although you might not need NPM to run your node package, it is
+   useful to have NPM on your target. The NPM package name is
+   ``nodejs-npm``.
+Using the Registry Modules Method
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+This section presents an example that uses the ``cute-files`` module,
+which is a file browser web application.
+.. note::
+   You must know the ``cute-files`` module version.
+The first thing you need to do is use ``devtool`` and the NPM fetcher to
+create the recipe:
+::
+   $ devtool add "npm://registry.npmjs.org;package=cute-files;version=1.0.2"
+The
+``devtool add`` command runs ``recipetool create`` and uses the same
+fetch URI to download each dependency and capture license details where
+possible. The result is a generated recipe.
+The recipe file is fairly simple and contains every license that
+``recipetool`` finds and includes the licenses in the recipe's
+:term:`LIC_FILES_CHKSUM`
+variables. You need to examine the variables and look for those with
+"unknown" in the :term:`LICENSE`
+field. You need to track down the license information for "unknown"
+modules and manually add the information to the recipe.
+``recipetool`` creates a "shrinkwrap" file for your recipe. Shrinkwrap
+files capture the version of all dependent modules. Many packages do not
+provide shrinkwrap files. ``recipetool`` create a shrinkwrap file as it
+runs.
+.. note::
+   A package is created for each sub-module. This policy is the only
+   practical way to have the licenses for all of the dependencies
+   represented in the license manifest of the image.
+The ``devtool edit-recipe`` command lets you take a look at the recipe:
+::
+   $ devtool edit-recipe cute-files
+   SUMMARY = "Turn any folder on your computer into a cute file browser, available on the local network."
+   LICENSE = "MIT & ISC & Unknown"
+   LIC_FILES_CHKSUM = "file://LICENSE;md5=71d98c0a1db42956787b1909c74a86ca \
+       file://node_modules/toidentifier/LICENSE;md5=1a261071a044d02eb6f2bb47f51a3502 \
+       file://node_modules/debug/LICENSE;md5=ddd815a475e7338b0be7a14d8ee35a99 \
+       ...
+   SRC_URI = " \
+       npm://registry.npmjs.org/;package=cute-files;version=${PV} \
+       npmsw://${THISDIR}/${BPN}/npm-shrinkwrap.json \
+       "
+   S = "${WORKDIR}/npm"
+   inherit npm LICENSE_${PN} = "MIT"
+   LICENSE_${PN}-accepts = "MIT"
+   LICENSE_${PN}-array-flatten = "MIT"
+   ...
+   LICENSE_${PN}-vary = "MIT"
+Three key points exist in the previous example:
+-  :term:`SRC_URI` uses the NPM
+   scheme so that the NPM fetcher is used.
+-  ``recipetool`` collects all the license information. If a
+   sub-module's license is unavailable, the sub-module's name appears in
+   the comments.
+-  The ``inherit npm`` statement causes the
+   :ref:`npm <ref-classes-npm>` class to package
+   up all the modules.
+You can run the following command to build the ``cute-files`` package:
+::
+   $ devtool build cute-files
+Remember that ``nodejs`` must be installed on
+the target before your package.
+Assuming 192.168.7.2 for the target's IP address, use the following
+command to deploy your package:
+::
+   $ devtool deploy-target -s cute-files root@192.168.7.2
+Once the package is installed on the target, you can
+test the application:
+.. note::
+   Because of a known issue, you cannot simply run ``cute-files`` as you would
+   if you had run ``npm install``.
+::
+  $ cd /usr/lib/node_modules/cute-files
+  $ node cute-files.js
+On a browser,
+go to ``http://192.168.7.2:3000`` and you see the following:
+.. image:: figures/cute-files-npm-example.png
+   :align: center
+You can find the recipe in ``workspace/recipes/cute-files``. You can use
+the recipe in any layer you choose.
+Using the NPM Projects Code Method
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Although it is useful to package modules already in the NPM registry,
+adding ``node.js`` projects under development is a more common developer
+use case.
+This section covers the NPM projects code method, which is very similar
+to the "registry" approach described in the previous section. In the NPM
+projects method, you provide ``devtool`` with an URL that points to the
+source files.
+Replicating the same example, (i.e. ``cute-files``) use the following
+command:
+::
+   $ devtool add https://github.com/martinaglv/cute-files.git
+The
+recipe this command generates is very similar to the recipe created in
+the previous section. However, the ``SRC_URI`` looks like the following:
+::
+   SRC_URI = " \
+       git://github.com/martinaglv/cute-files.git;protocol=https \
+       npmsw://${THISDIR}/${BPN}/npm-shrinkwrap.json \
+       "
+In this example,
+the main module is taken from the Git repository and dependencies are
+taken from the NPM registry. Other than those differences, the recipe is
+basically the same between the two methods. You can build and deploy the
+package exactly as described in the previous section that uses the
+registry modules method.
+Adding custom metadata to packages
+----------------------------------
+The variable
+:term:`PACKAGE_ADD_METADATA`
+can be used to add additional metadata to packages. This is reflected in
+the package control/spec file. To take the ipk format for example, the
+CONTROL file stored inside would contain the additional metadata as
+additional lines.
+The variable can be used in multiple ways, including using suffixes to
+set it for a specific package type and/or package. Note that the order
+of precedence is the same as this list:
+-  ``PACKAGE_ADD_METADATA_<PKGTYPE>_<PN>``
+-  ``PACKAGE_ADD_METADATA_<PKGTYPE>``
+-  ``PACKAGE_ADD_METADATA_<PN>``
+-  ``PACKAGE_ADD_METADATA``
+`<PKGTYPE>` is a parameter and expected to be a distinct name of specific
+package type:
+-  IPK for .ipk packages
+-  DEB for .deb packages
+-  RPM for .rpm packages
+`<PN>` is a parameter and expected to be a package name.
+The variable can contain multiple [one-line] metadata fields separated
+by the literal sequence '\\n'. The separator can be redefined using the
+variable flag ``separator``.
+The following is an example that adds two custom fields for ipk
+packages:
+::
+   PACKAGE_ADD_METADATA_IPK = "Vendor: CustomIpk\nGroup:Applications/Spreadsheets"
+Efficiently Fetching Source Files During a Build
+================================================
+The OpenEmbedded build system works with source files located through
+the :term:`SRC_URI` variable. When
+you build something using BitBake, a big part of the operation is
+locating and downloading all the source tarballs. For images,
+downloading all the source for various packages can take a significant
+amount of time.
+This section shows you how you can use mirrors to speed up fetching
+source files and how you can pre-fetch files all of which leads to more
+efficient use of resources and time.
+Setting up Effective Mirrors
+----------------------------
+A good deal that goes into a Yocto Project build is simply downloading
+all of the source tarballs. Maybe you have been working with another
+build system (OpenEmbedded or Angstrom) for which you have built up a
+sizable directory of source tarballs. Or, perhaps someone else has such
+a directory for which you have read access. If so, you can save time by
+adding statements to your configuration file so that the build process
+checks local directories first for existing tarballs before checking the
+Internet.
+Here is an efficient way to set it up in your ``local.conf`` file:
+::
+   SOURCE_MIRROR_URL ?= "file:///home/you/your-download-dir/"
+   INHERIT += "own-mirrors"
+   BB_GENERATE_MIRROR_TARBALLS = "1"
+   # BB_NO_NETWORK = "1"
+In the previous example, the
+:term:`BB_GENERATE_MIRROR_TARBALLS`
+variable causes the OpenEmbedded build system to generate tarballs of
+the Git repositories and store them in the
+:term:`DL_DIR` directory. Due to
+performance reasons, generating and storing these tarballs is not the
+build system's default behavior.
+You can also use the
+:term:`PREMIRRORS` variable. For
+an example, see the variable's glossary entry in the Yocto Project
+Reference Manual.
+Getting Source Files and Suppressing the Build
+----------------------------------------------
+Another technique you can use to ready yourself for a successive string
+of build operations, is to pre-fetch all the source files without
+actually starting a build. This technique lets you work through any
+download issues and ultimately gathers all the source files into your
+download directory :ref:`structure-build-downloads`,
+which is located with :term:`DL_DIR`.
+Use the following BitBake command form to fetch all the necessary
+sources without starting the build:
+::
+   $ bitbake target --runall=fetch
+This
+variation of the BitBake command guarantees that you have all the
+sources for that BitBake target should you disconnect from the Internet
+and want to do the build later offline.
+Selecting an Initialization Manager
+===================================
+By default, the Yocto Project uses SysVinit as the initialization
+manager. However, support also exists for systemd, which is a full
+replacement for init with parallel starting of services, reduced shell
+overhead and other features that are used by many distributions.
+Within the system, SysVinit treats system components as services. These
+services are maintained as shell scripts stored in the ``/etc/init.d/``
+directory. Services organize into different run levels. This
+organization is maintained by putting links to the services in the
+``/etc/rcN.d/`` directories, where `N/` is one of the following options:
+"S", "0", "1", "2", "3", "4", "5", or "6".
+.. note::
+   Each runlevel has a dependency on the previous runlevel. This
+   dependency allows the services to work properly.
+In comparison, systemd treats components as units. Using units is a
+broader concept as compared to using a service. A unit includes several
+different types of entities. Service is one of the types of entities.
+The runlevel concept in SysVinit corresponds to the concept of a target
+in systemd, where target is also a type of supported unit.
+In a SysVinit-based system, services load sequentially (i.e. one by one)
+during init and parallelization is not supported. With systemd, services
+start in parallel. Needless to say, the method can have an impact on
+system startup performance.
+If you want to use SysVinit, you do not have to do anything. But, if you
+want to use systemd, you must take some steps as described in the
+following sections.
+Using systemd Exclusively
+-------------------------
+Set these variables in your distribution configuration file as follows:
+::
+   DISTRO_FEATURES_append = " systemd"
+   VIRTUAL-RUNTIME_init_manager = "systemd"
+You can also prevent the SysVinit distribution feature from
+being automatically enabled as follows:
+::
+   DISTRO_FEATURES_BACKFILL_CONSIDERED = "sysvinit"
+Doing so removes any
+redundant SysVinit scripts.
+To remove initscripts from your image altogether, set this variable
+also:
+::
+   VIRTUAL-RUNTIME_initscripts = ""
+For information on the backfill variable, see
+:term:`DISTRO_FEATURES_BACKFILL_CONSIDERED`.
+Using systemd for the Main Image and Using SysVinit for the Rescue Image
+------------------------------------------------------------------------
+Set these variables in your distribution configuration file as follows:
+::
+   DISTRO_FEATURES_append = " systemd"
+   VIRTUAL-RUNTIME_init_manager = "systemd"
+Doing so causes your main image to use the
+``packagegroup-core-boot.bb`` recipe and systemd. The rescue/minimal
+image cannot use this package group. However, it can install SysVinit
+and the appropriate packages will have support for both systemd and
+SysVinit.
+Selecting a Device Manager
+==========================
+The Yocto Project provides multiple ways to manage the device manager
+(``/dev``):
+-  Persistent and Pre-Populated\ ``/dev``: For this case, the ``/dev``
+   directory is persistent and the required device nodes are created
+   during the build.
+-  Use ``devtmpfs`` with a Device Manager: For this case, the ``/dev``
+   directory is provided by the kernel as an in-memory file system and
+   is automatically populated by the kernel at runtime. Additional
+   configuration of device nodes is done in user space by a device
+   manager like ``udev`` or ``busybox-mdev``.
+Using Persistent and Pre-Populated\ ``/dev``
+--------------------------------------------
+To use the static method for device population, you need to set the
+:term:`USE_DEVFS` variable to "0"
+as follows:
+::
+   USE_DEVFS = "0"
+The content of the resulting ``/dev`` directory is defined in a Device
+Table file. The
+:term:`IMAGE_DEVICE_TABLES`
+variable defines the Device Table to use and should be set in the
+machine or distro configuration file. Alternatively, you can set this
+variable in your ``local.conf`` configuration file.
+If you do not define the ``IMAGE_DEVICE_TABLES`` variable, the default
+``device_table-minimal.txt`` is used:
+::
+   IMAGE_DEVICE_TABLES = "device_table-mymachine.txt"
+The population is handled by the ``makedevs`` utility during image
+creation:
+Using ``devtmpfs`` and a Device Manager
+---------------------------------------
+To use the dynamic method for device population, you need to use (or be
+sure to set) the :term:`USE_DEVFS`
+variable to "1", which is the default:
+::
+   USE_DEVFS = "1"
+With this
+setting, the resulting ``/dev`` directory is populated by the kernel
+using ``devtmpfs``. Make sure the corresponding kernel configuration
+variable ``CONFIG_DEVTMPFS`` is set when building you build a Linux
+kernel.
+All devices created by ``devtmpfs`` will be owned by ``root`` and have
+permissions ``0600``.
+To have more control over the device nodes, you can use a device manager
+like ``udev`` or ``busybox-mdev``. You choose the device manager by
+defining the ``VIRTUAL-RUNTIME_dev_manager`` variable in your machine or
+distro configuration file. Alternatively, you can set this variable in
+your ``local.conf`` configuration file:
+::
+   VIRTUAL-RUNTIME_dev_manager = "udev"
+   # Some alternative values
+   # VIRTUAL-RUNTIME_dev_manager = "busybox-mdev"
+   # VIRTUAL-RUNTIME_dev_manager = "systemd"
+Using an External SCM
+=====================
+If you're working on a recipe that pulls from an external Source Code
+Manager (SCM), it is possible to have the OpenEmbedded build system
+notice new recipe changes added to the SCM and then build the resulting
+packages that depend on the new recipes by using the latest versions.
+This only works for SCMs from which it is possible to get a sensible
+revision number for changes. Currently, you can do this with Apache
+Subversion (SVN), Git, and Bazaar (BZR) repositories.
+To enable this behavior, the :term:`PV` of
+the recipe needs to reference
+:term:`SRCPV`. Here is an example:
+::
+   PV = "1.2.3+git${SRCPV}"
+Then, you can add the following to your
+``local.conf``:
+::
+   SRCREV_pn-PN = "${AUTOREV}"
+:term:`PN` is the name of the recipe for
+which you want to enable automatic source revision updating.
+If you do not want to update your local configuration file, you can add
+the following directly to the recipe to finish enabling the feature:
+::
+   SRCREV = "${AUTOREV}"
+The Yocto Project provides a distribution named ``poky-bleeding``, whose
+configuration file contains the line:
+::
+   require conf/distro/include/poky-floating-revisions.inc
+This line pulls in the
+listed include file that contains numerous lines of exactly that form:
+::
+   #SRCREV_pn-opkg-native ?= "${AUTOREV}"
+   #SRCREV_pn-opkg-sdk ?= "${AUTOREV}"
+   #SRCREV_pn-opkg ?= "${AUTOREV}"
+   #SRCREV_pn-opkg-utils-native ?= "${AUTOREV}"
+   #SRCREV_pn-opkg-utils ?= "${AUTOREV}"
+   SRCREV_pn-gconf-dbus ?= "${AUTOREV}"
+   SRCREV_pn-matchbox-common ?= "${AUTOREV}"
+   SRCREV_pn-matchbox-config-gtk ?= "${AUTOREV}"
+   SRCREV_pn-matchbox-desktop ?= "${AUTOREV}"
+   SRCREV_pn-matchbox-keyboard ?= "${AUTOREV}"
+   SRCREV_pn-matchbox-panel-2 ?= "${AUTOREV}"
+   SRCREV_pn-matchbox-themes-extra ?= "${AUTOREV}"
+   SRCREV_pn-matchbox-terminal ?= "${AUTOREV}"
+   SRCREV_pn-matchbox-wm ?= "${AUTOREV}"
+   SRCREV_pn-settings-daemon ?= "${AUTOREV}"
+   SRCREV_pn-screenshot ?= "${AUTOREV}"
+   . . .
+These lines allow you to
+experiment with building a distribution that tracks the latest
+development source for numerous packages.
+.. note::
+   The ``poky-bleeding`` distribution is not tested on a regular basis. Keep
+   this in mind if you use it.
+Creating a Read-Only Root Filesystem
+====================================
+Suppose, for security reasons, you need to disable your target device's
+root filesystem's write permissions (i.e. you need a read-only root
+filesystem). Or, perhaps you are running the device's operating system
+from a read-only storage device. For either case, you can customize your
+image for that behavior.
+.. note::
+   Supporting a read-only root filesystem requires that the system and
+   applications do not try to write to the root filesystem. You must
+   configure all parts of the target system to write elsewhere, or to
+   gracefully fail in the event of attempting to write to the root
+   filesystem.
+Creating the Root Filesystem
+----------------------------
+To create the read-only root filesystem, simply add the
+"read-only-rootfs" feature to your image, normally in one of two ways.
+The first way is to add the "read-only-rootfs" image feature in the
+image's recipe file via the ``IMAGE_FEATURES`` variable:
+::
+   IMAGE_FEATURES += "read-only-rootfs"
+As an alternative, you can add the same feature
+from within your build directory's ``local.conf`` file with the
+associated ``EXTRA_IMAGE_FEATURES`` variable, as in:
+::
+   EXTRA_IMAGE_FEATURES = "read-only-rootfs"
+For more information on how to use these variables, see the
+":ref:`dev-manual/common-tasks:Customizing Images Using Custom \`\`IMAGE_FEATURES\`\` and \`\`EXTRA_IMAGE_FEATURES\`\``"
+section. For information on the variables, see
+:term:`IMAGE_FEATURES` and
+:term:`EXTRA_IMAGE_FEATURES`.
+Post-Installation Scripts and Read-Only Root Filesystem
+-------------------------------------------------------
+It is very important that you make sure all post-Installation
+(``pkg_postinst``) scripts for packages that are installed into the
+image can be run at the time when the root filesystem is created during
+the build on the host system. These scripts cannot attempt to run during
+first-boot on the target device. With the "read-only-rootfs" feature
+enabled, the build system checks during root filesystem creation to make
+sure all post-installation scripts succeed. If any of these scripts
+still need to be run after the root filesystem is created, the build
+immediately fails. These build-time checks ensure that the build fails
+rather than the target device fails later during its initial boot
+operation.
+Most of the common post-installation scripts generated by the build
+system for the out-of-the-box Yocto Project are engineered so that they
+can run during root filesystem creation (e.g. post-installation scripts
+for caching fonts). However, if you create and add custom scripts, you
+need to be sure they can be run during this file system creation.
+Here are some common problems that prevent post-installation scripts
+from running during root filesystem creation:
+-  *Not using $D in front of absolute paths:* The build system defines
+   ``$``\ :term:`D` when the root
+   filesystem is created. Furthermore, ``$D`` is blank when the script
+   is run on the target device. This implies two purposes for ``$D``:
+   ensuring paths are valid in both the host and target environments,
+   and checking to determine which environment is being used as a method
+   for taking appropriate actions.
+-  *Attempting to run processes that are specific to or dependent on the
+   target architecture:* You can work around these attempts by using
+   native tools, which run on the host system, to accomplish the same
+   tasks, or by alternatively running the processes under QEMU, which
+   has the ``qemu_run_binary`` function. For more information, see the
+   :ref:`qemu <ref-classes-qemu>` class.
+Areas With Write Access
+-----------------------
+With the "read-only-rootfs" feature enabled, any attempt by the target
+to write to the root filesystem at runtime fails. Consequently, you must
+make sure that you configure processes and applications that attempt
+these types of writes do so to directories with write access (e.g.
+``/tmp`` or ``/var/run``).
+Maintaining Build Output Quality
+================================
+Many factors can influence the quality of a build. For example, if you
+upgrade a recipe to use a new version of an upstream software package or
+you experiment with some new configuration options, subtle changes can
+occur that you might not detect until later. Consider the case where
+your recipe is using a newer version of an upstream package. In this
+case, a new version of a piece of software might introduce an optional
+dependency on another library, which is auto-detected. If that library
+has already been built when the software is building, the software will
+link to the built library and that library will be pulled into your
+image along with the new software even if you did not want the library.
+The :ref:`buildhistory <ref-classes-buildhistory>`
+class exists to help you maintain the quality of your build output. You
+can use the class to highlight unexpected and possibly unwanted changes
+in the build output. When you enable build history, it records
+information about the contents of each package and image and then
+commits that information to a local Git repository where you can examine
+the information.
+The remainder of this section describes the following:
+-  :ref:`How you can enable and disable build history <dev-manual/common-tasks:enabling and disabling build history>`
+-  :ref:`How to understand what the build history contains <dev-manual/common-tasks:understanding what the build history contains>`
+-  :ref:`How to limit the information used for build history <dev-manual/common-tasks:using build history to gather image information only>`
+-  :ref:`How to examine the build history from both a command-line and web interface <dev-manual/common-tasks:examining build history information>`
+Enabling and Disabling Build History
+------------------------------------
+Build history is disabled by default. To enable it, add the following
+``INHERIT`` statement and set the
+:term:`BUILDHISTORY_COMMIT`
+variable to "1" at the end of your ``conf/local.conf`` file found in the
+:term:`Build Directory`:
+::
+   INHERIT += "buildhistory"
+   BUILDHISTORY_COMMIT = "1"
+Enabling build history as
+previously described causes the OpenEmbedded build system to collect
+build output information and commit it as a single commit to a local
+:ref:`overview-manual/overview-manual-development-environment:git` repository.
+.. note::
+   Enabling build history increases your build times slightly,
+   particularly for images, and increases the amount of disk space used
+   during the build.
+You can disable build history by removing the previous statements from
+your ``conf/local.conf`` file.
+Understanding What the Build History Contains
+---------------------------------------------
+Build history information is kept in
+``${``\ :term:`TOPDIR`\ ``}/buildhistory``
+in the Build Directory as defined by the
+:term:`BUILDHISTORY_DIR`
+variable. The following is an example abbreviated listing:
+.. image:: figures/buildhistory.png
+   :align: center
+At the top level, a ``metadata-revs`` file exists that lists the
+revisions of the repositories for the enabled layers when the build was
+produced. The rest of the data splits into separate ``packages``,
+``images`` and ``sdk`` directories, the contents of which are described
+as follows.
+Build History Package Information
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The history for each package contains a text file that has name-value
+pairs with information about the package. For example,
+``buildhistory/packages/i586-poky-linux/busybox/busybox/latest``
+contains the following:
+.. code-block:: none
+   PV = 1.22.1
+   PR = r32
+   RPROVIDES =
+   RDEPENDS = glibc (>= 2.20) update-alternatives-opkg
+   RRECOMMENDS = busybox-syslog busybox-udhcpc update-rc.d
+   PKGSIZE = 540168
+   FILES = /usr/bin/* /usr/sbin/* /usr/lib/busybox/* /usr/lib/lib*.so.* \
+      /etc /com /var /bin/* /sbin/* /lib/*.so.* /lib/udev/rules.d \
+      /usr/lib/udev/rules.d /usr/share/busybox /usr/lib/busybox/* \
+      /usr/share/pixmaps /usr/share/applications /usr/share/idl \
+      /usr/share/omf /usr/share/sounds /usr/lib/bonobo/servers
+   FILELIST = /bin/busybox /bin/busybox.nosuid /bin/busybox.suid /bin/sh \
+      /etc/busybox.links.nosuid /etc/busybox.links.suid
+Most of these
+name-value pairs correspond to variables used to produce the package.
+The exceptions are ``FILELIST``, which is the actual list of files in
+the package, and ``PKGSIZE``, which is the total size of files in the
+package in bytes.
+A file also exists that corresponds to the recipe from which the package
+came (e.g. ``buildhistory/packages/i586-poky-linux/busybox/latest``):
+.. code-block:: none
+   PV = 1.22.1
+   PR = r32
+   DEPENDS = initscripts kern-tools-native update-rc.d-native \
+      virtual/i586-poky-linux-compilerlibs virtual/i586-poky-linux-gcc \
+      virtual/libc virtual/update-alternatives
+   PACKAGES = busybox-ptest busybox-httpd busybox-udhcpd busybox-udhcpc \
+      busybox-syslog busybox-mdev busybox-hwclock busybox-dbg \
+      busybox-staticdev busybox-dev busybox-doc busybox-locale busybox
+Finally, for those recipes fetched from a version control system (e.g.,
+Git), a file exists that lists source revisions that are specified in
+the recipe and lists the actual revisions used during the build. Listed
+and actual revisions might differ when
+:term:`SRCREV` is set to
+${:term:`AUTOREV`}. Here is an
+example assuming
+``buildhistory/packages/qemux86-poky-linux/linux-yocto/latest_srcrev``):
+::
+   # SRCREV_machine = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1"
+   SRCREV_machine = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1"
+   # SRCREV_meta = "a227f20eff056e511d504b2e490f3774ab260d6f"
+   SRCREV_meta ="a227f20eff056e511d504b2e490f3774ab260d6f"
+You can use the
+``buildhistory-collect-srcrevs`` command with the ``-a`` option to
+collect the stored ``SRCREV`` values from build history and report them
+in a format suitable for use in global configuration (e.g.,
+``local.conf`` or a distro include file) to override floating
+``AUTOREV`` values to a fixed set of revisions. Here is some example
+output from this command:
+::
+   $ buildhistory-collect-srcrevs -a
+   # i586-poky-linux
+   SRCREV_pn-glibc = "b8079dd0d360648e4e8de48656c5c38972621072"
+   SRCREV_pn-glibc-initial = "b8079dd0d360648e4e8de48656c5c38972621072"
+   SRCREV_pn-opkg-utils = "53274f087565fd45d8452c5367997ba6a682a37a"
+   SRCREV_pn-kmod = "fd56638aed3fe147015bfa10ed4a5f7491303cb4"
+   # x86_64-linux
+   SRCREV_pn-gtk-doc-stub-native = "1dea266593edb766d6d898c79451ef193eb17cfa"
+   SRCREV_pn-dtc-native = "65cc4d2748a2c2e6f27f1cf39e07a5dbabd80ebf"
+   SRCREV_pn-update-rc.d-native = "eca680ddf28d024954895f59a241a622dd575c11"
+   SRCREV_glibc_pn-cross-localedef-native = "b8079dd0d360648e4e8de48656c5c38972621072"
+   SRCREV_localedef_pn-cross-localedef-native = "c833367348d39dad7ba018990bfdaffaec8e9ed3"
+   SRCREV_pn-prelink-native = "faa069deec99bf61418d0bab831c83d7c1b797ca"
+   SRCREV_pn-opkg-utils-native = "53274f087565fd45d8452c5367997ba6a682a37a"
+   SRCREV_pn-kern-tools-native = "23345b8846fe4bd167efdf1bd8a1224b2ba9a5ff"
+   SRCREV_pn-kmod-native = "fd56638aed3fe147015bfa10ed4a5f7491303cb4"
+   # qemux86-poky-linux
+   SRCREV_machine_pn-linux-yocto = "38cd560d5022ed2dbd1ab0dca9642e47c98a0aa1"
+   SRCREV_meta_pn-linux-yocto = "a227f20eff056e511d504b2e490f3774ab260d6f"
+   # all-poky-linux
+   SRCREV_pn-update-rc.d = "eca680ddf28d024954895f59a241a622dd575c11"
+.. note::
+   Here are some notes on using the ``buildhistory-collect-srcrevs`` command:
+   -  By default, only values where the ``SRCREV`` was not hardcoded
+      (usually when ``AUTOREV`` is used) are reported. Use the ``-a``
+      option to see all ``SRCREV`` values.
+   -  The output statements might not have any effect if overrides are
+      applied elsewhere in the build system configuration. Use the
+      ``-f`` option to add the ``forcevariable`` override to each output
+      line if you need to work around this restriction.
+   -  The script does apply special handling when building for multiple
+      machines. However, the script does place a comment before each set
+      of values that specifies which triplet to which they belong as
+      previously shown (e.g., ``i586-poky-linux``).
+Build History Image Information
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The files produced for each image are as follows:
+-  ``image-files:`` A directory containing selected files from the root
+   filesystem. The files are defined by
+   :term:`BUILDHISTORY_IMAGE_FILES`.
+-  ``build-id.txt:`` Human-readable information about the build
+   configuration and metadata source revisions. This file contains the
+   full build header as printed by BitBake.
+-  ``*.dot:`` Dependency graphs for the image that are compatible with
+   ``graphviz``.
+-  ``files-in-image.txt:`` A list of files in the image with
+   permissions, owner, group, size, and symlink information.
+-  ``image-info.txt:`` A text file containing name-value pairs with
+   information about the image. See the following listing example for
+   more information.
+-  ``installed-package-names.txt:`` A list of installed packages by name
+   only.
+-  ``installed-package-sizes.txt:`` A list of installed packages ordered
+   by size.
+-  ``installed-packages.txt:`` A list of installed packages with full
+   package filenames.
+.. note::
+   Installed package information is able to be gathered and produced
+   even if package management is disabled for the final image.
+Here is an example of ``image-info.txt``:
+.. code-block:: none
+   DISTRO = poky
+   DISTRO_VERSION = 1.7
+   USER_CLASSES = buildstats image-mklibs image-prelink
+   IMAGE_CLASSES = image_types
+   IMAGE_FEATURES = debug-tweaks
+   IMAGE_LINGUAS =
+   IMAGE_INSTALL = packagegroup-core-boot run-postinsts
+   BAD_RECOMMENDATIONS =
+   NO_RECOMMENDATIONS =
+   PACKAGE_EXCLUDE =
+   ROOTFS_POSTPROCESS_COMMAND = write_package_manifest; license_create_manifest; \
+      write_image_manifest ; buildhistory_list_installed_image ; \
+      buildhistory_get_image_installed ; ssh_allow_empty_password;  \
+      postinst_enable_logging; rootfs_update_timestamp ; ssh_disable_dns_lookup ;
+   IMAGE_POSTPROCESS_COMMAND =   buildhistory_get_imageinfo ;
+   IMAGESIZE = 6900
+Other than ``IMAGESIZE``,
+which is the total size of the files in the image in Kbytes, the
+name-value pairs are variables that may have influenced the content of
+the image. This information is often useful when you are trying to
+determine why a change in the package or file listings has occurred.
+Using Build History to Gather Image Information Only
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+As you can see, build history produces image information, including
+dependency graphs, so you can see why something was pulled into the
+image. If you are just interested in this information and not interested
+in collecting specific package or SDK information, you can enable
+writing only image information without any history by adding the
+following to your ``conf/local.conf`` file found in the
+:term:`Build Directory`:
+::
+   INHERIT += "buildhistory"
+   BUILDHISTORY_COMMIT = "0"
+   BUILDHISTORY_FEATURES = "image"
+Here, you set the
+:term:`BUILDHISTORY_FEATURES`
+variable to use the image feature only.
+Build History SDK Information
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Build history collects similar information on the contents of SDKs (e.g.
+``bitbake -c populate_sdk imagename``) as compared to information it
+collects for images. Furthermore, this information differs depending on
+whether an extensible or standard SDK is being produced.
+The following list shows the files produced for SDKs:
+-  ``files-in-sdk.txt:`` A list of files in the SDK with permissions,
+   owner, group, size, and symlink information. This list includes both
+   the host and target parts of the SDK.
+-  ``sdk-info.txt:`` A text file containing name-value pairs with
+   information about the SDK. See the following listing example for more
+   information.
+-  ``sstate-task-sizes.txt:`` A text file containing name-value pairs
+   with information about task group sizes (e.g. ``do_populate_sysroot``
+   tasks have a total size). The ``sstate-task-sizes.txt`` file exists
+   only when an extensible SDK is created.
+-  ``sstate-package-sizes.txt:`` A text file containing name-value pairs
+   with information for the shared-state packages and sizes in the SDK.
+   The ``sstate-package-sizes.txt`` file exists only when an extensible
+   SDK is created.
+-  ``sdk-files:`` A folder that contains copies of the files mentioned
+   in ``BUILDHISTORY_SDK_FILES`` if the files are present in the output.
+   Additionally, the default value of ``BUILDHISTORY_SDK_FILES`` is
+   specific to the extensible SDK although you can set it differently if
+   you would like to pull in specific files from the standard SDK.
+   The default files are ``conf/local.conf``, ``conf/bblayers.conf``,
+   ``conf/auto.conf``, ``conf/locked-sigs.inc``, and
+   ``conf/devtool.conf``. Thus, for an extensible SDK, these files get
+   copied into the ``sdk-files`` directory.
+-  The following information appears under each of the ``host`` and
+   ``target`` directories for the portions of the SDK that run on the
+   host and on the target, respectively:
+   .. note::
+      The following files for the most part are empty when producing an
+      extensible SDK because this type of SDK is not constructed from
+      packages as is the standard SDK.
+   -  ``depends.dot:`` Dependency graph for the SDK that is compatible
+      with ``graphviz``.
+   -  ``installed-package-names.txt:`` A list of installed packages by
+      name only.
+   -  ``installed-package-sizes.txt:`` A list of installed packages
+      ordered by size.
+   -  ``installed-packages.txt:`` A list of installed packages with full
+      package filenames.
+Here is an example of ``sdk-info.txt``:
+.. code-block:: none
+   DISTRO = poky
+   DISTRO_VERSION = 1.3+snapshot-20130327
+   SDK_NAME = poky-glibc-i686-arm
+   SDK_VERSION = 1.3+snapshot
+   SDKMACHINE =
+   SDKIMAGE_FEATURES = dev-pkgs dbg-pkgs
+   BAD_RECOMMENDATIONS =
+   SDKSIZE = 352712
+Other than ``SDKSIZE``, which is
+the total size of the files in the SDK in Kbytes, the name-value pairs
+are variables that might have influenced the content of the SDK. This
+information is often useful when you are trying to determine why a
+change in the package or file listings has occurred.
+Examining Build History Information
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+You can examine build history output from the command line or from a web
+interface.
+To see any changes that have occurred (assuming you have
+:term:`BUILDHISTORY_COMMIT` = "1"),
+you can simply use any Git command that allows you to view the history
+of a repository. Here is one method:
+::
+   $ git log -p
+You need to realize,
+however, that this method does show changes that are not significant
+(e.g. a package's size changing by a few bytes).
+A command-line tool called ``buildhistory-diff`` does exist, though,
+that queries the Git repository and prints just the differences that
+might be significant in human-readable form. Here is an example:
+::
+   $ ~/poky/poky/scripts/buildhistory-diff . HEAD^
+   Changes to images/qemux86_64/glibc/core-image-minimal (files-in-image.txt):
+      /etc/anotherpkg.conf was added
+      /sbin/anotherpkg was added
+      * (installed-package-names.txt):
+      *   anotherpkg was added
+   Changes to images/qemux86_64/glibc/core-image-minimal (installed-package-names.txt):
+      anotherpkg was added
+   packages/qemux86_64-poky-linux/v86d: PACKAGES: added "v86d-extras"
+      * PR changed from "r0" to "r1"
+      * PV changed from "0.1.10" to "0.1.12"
+   packages/qemux86_64-poky-linux/v86d/v86d: PKGSIZE changed from 110579 to 144381 (+30%)
+      * PR changed from "r0" to "r1"
+      * PV changed from "0.1.10" to "0.1.12"
+.. note::
+   The ``buildhistory-diff`` tool requires the ``GitPython``
+   package. Be sure to install it using Pip3 as follows:
+   ::
+         $ pip3 install GitPython --user
+   Alternatively, you can install ``python3-git`` using the appropriate
+   distribution package manager (e.g. ``apt-get``, ``dnf``, or ``zipper``).
+To see changes to the build history using a web interface, follow the
+instruction in the ``README`` file
+:yocto_git:`here </buildhistory-web/>`.
+Here is a sample screenshot of the interface:
+.. image:: figures/buildhistory-web.png
+   :align: center
+Performing Automated Runtime Testing
+====================================
+The OpenEmbedded build system makes available a series of automated
+tests for images to verify runtime functionality. You can run these
+tests on either QEMU or actual target hardware. Tests are written in
+Python making use of the ``unittest`` module, and the majority of them
+run commands on the target system over SSH. This section describes how
+you set up the environment to use these tests, run available tests, and
+write and add your own tests.
+For information on the test and QA infrastructure available within the
+Yocto Project, see the ":ref:`ref-manual/ref-release-process:testing and quality assurance`"
+section in the Yocto Project Reference Manual.
+Enabling Tests
+--------------
+Depending on whether you are planning to run tests using QEMU or on the
+hardware, you have to take different steps to enable the tests. See the
+following subsections for information on how to enable both types of
+tests.
+Enabling Runtime Tests on QEMU
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+In order to run tests, you need to do the following:
+-  *Set up to avoid interaction with sudo for networking:* To
+   accomplish this, you must do one of the following:
+   -  Add ``NOPASSWD`` for your user in ``/etc/sudoers`` either for all
+      commands or just for ``runqemu-ifup``. You must provide the full
+      path as that can change if you are using multiple clones of the
+      source repository.
+      .. note::
+         On some distributions, you also need to comment out "Defaults
+         requiretty" in ``/etc/sudoers``.
+   -  Manually configure a tap interface for your system.
+   -  Run as root the script in ``scripts/runqemu-gen-tapdevs``, which
+      should generate a list of tap devices. This is the option
+      typically chosen for Autobuilder-type environments.
+      .. note::
+         -  Be sure to use an absolute path when calling this script
+            with sudo.
+         -  The package recipe ``qemu-helper-native`` is required to run
+            this script. Build the package using the following command:
+            ::
+               $ bitbake qemu-helper-native
+-  *Set the DISPLAY variable:* You need to set this variable so that
+   you have an X server available (e.g. start ``vncserver`` for a
+   headless machine).
+-  *Be sure your host's firewall accepts incoming connections from
+   192.168.7.0/24:* Some of the tests (in particular DNF tests) start an
+   HTTP server on a random high number port, which is used to serve
+   files to the target. The DNF module serves
+   ``${WORKDIR}/oe-rootfs-repo`` so it can run DNF channel commands.
+   That means your host's firewall must accept incoming connections from
+   192.168.7.0/24, which is the default IP range used for tap devices by
+   ``runqemu``.
+-  *Be sure your host has the correct packages installed:* Depending
+   your host's distribution, you need to have the following packages
+   installed:
+   -  Ubuntu and Debian: ``sysstat`` and ``iproute2``
+   -  OpenSUSE: ``sysstat`` and ``iproute2``
+   -  Fedora: ``sysstat`` and ``iproute``
+   -  CentOS: ``sysstat`` and ``iproute``
+Once you start running the tests, the following happens:
+1. A copy of the root filesystem is written to ``${WORKDIR}/testimage``.
+2. The image is booted under QEMU using the standard ``runqemu`` script.
+3. A default timeout of 500 seconds occurs to allow for the boot process
+   to reach the login prompt. You can change the timeout period by
+   setting
+   :term:`TEST_QEMUBOOT_TIMEOUT`
+   in the ``local.conf`` file.
+4. Once the boot process is reached and the login prompt appears, the
+   tests run. The full boot log is written to
+   ``${WORKDIR}/testimage/qemu_boot_log``.
+5. Each test module loads in the order found in ``TEST_SUITES``. You can
+   find the full output of the commands run over SSH in
+   ``${WORKDIR}/testimgage/ssh_target_log``.
+6. If no failures occur, the task running the tests ends successfully.
+   You can find the output from the ``unittest`` in the task log at
+   ``${WORKDIR}/temp/log.do_testimage``.
+Enabling Runtime Tests on Hardware
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The OpenEmbedded build system can run tests on real hardware, and for
+certain devices it can also deploy the image to be tested onto the
+device beforehand.
+For automated deployment, a "master image" is installed onto the
+hardware once as part of setup. Then, each time tests are to be run, the
+following occurs:
+1. The master image is booted into and used to write the image to be
+   tested to a second partition.
+2. The device is then rebooted using an external script that you need to
+   provide.
+3. The device boots into the image to be tested.
+When running tests (independent of whether the image has been deployed
+automatically or not), the device is expected to be connected to a
+network on a pre-determined IP address. You can either use static IP
+addresses written into the image, or set the image to use DHCP and have
+your DHCP server on the test network assign a known IP address based on
+the MAC address of the device.
+In order to run tests on hardware, you need to set ``TEST_TARGET`` to an
+appropriate value. For QEMU, you do not have to change anything, the
+default value is "qemu". For running tests on hardware, the following
+options exist:
+-  *"simpleremote":* Choose "simpleremote" if you are going to run tests
+   on a target system that is already running the image to be tested and
+   is available on the network. You can use "simpleremote" in
+   conjunction with either real hardware or an image running within a
+   separately started QEMU or any other virtual machine manager.
+-  *"SystemdbootTarget":* Choose "SystemdbootTarget" if your hardware is
+   an EFI-based machine with ``systemd-boot`` as bootloader and
+   ``core-image-testmaster`` (or something similar) is installed. Also,
+   your hardware under test must be in a DHCP-enabled network that gives
+   it the same IP address for each reboot.
+   If you choose "SystemdbootTarget", there are additional requirements
+   and considerations. See the "`Selecting
+   SystemdbootTarget <#selecting-systemdboottarget>`__" section, which
+   follows, for more information.
+-  *"BeagleBoneTarget":* Choose "BeagleBoneTarget" if you are deploying
+   images and running tests on the BeagleBone "Black" or original
+   "White" hardware. For information on how to use these tests, see the
+   comments at the top of the BeagleBoneTarget
+   ``meta-yocto-bsp/lib/oeqa/controllers/beaglebonetarget.py`` file.
+-  *"EdgeRouterTarget":* Choose "EdgeRouterTarget" if you are deploying
+   images and running tests on the Ubiquiti Networks EdgeRouter Lite.
+   For information on how to use these tests, see the comments at the
+   top of the EdgeRouterTarget
+   ``meta-yocto-bsp/lib/oeqa/controllers/edgeroutertarget.py`` file.
+-  *"GrubTarget":* Choose "GrubTarget" if you are deploying images and running
+   tests on any generic PC that boots using GRUB. For information on how
+   to use these tests, see the comments at the top of the GrubTarget
+   ``meta-yocto-bsp/lib/oeqa/controllers/grubtarget.py`` file.
+-  *"your-target":* Create your own custom target if you want to run
+   tests when you are deploying images and running tests on a custom
+   machine within your BSP layer. To do this, you need to add a Python
+   unit that defines the target class under ``lib/oeqa/controllers/``
+   within your layer. You must also provide an empty ``__init__.py``.
+   For examples, see files in ``meta-yocto-bsp/lib/oeqa/controllers/``.
+Selecting SystemdbootTarget
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+If you did not set ``TEST_TARGET`` to "SystemdbootTarget", then you do
+not need any information in this section. You can skip down to the
+"`Running Tests <#qemu-image-running-tests>`__" section.
+If you did set ``TEST_TARGET`` to "SystemdbootTarget", you also need to
+perform a one-time setup of your master image by doing the following:
+1. *Set EFI_PROVIDER:* Be sure that ``EFI_PROVIDER`` is as follows:
+   ::
+      EFI_PROVIDER = "systemd-boot"
+2. *Build the master image:* Build the ``core-image-testmaster`` image.
+   The ``core-image-testmaster`` recipe is provided as an example for a
+   "master" image and you can customize the image recipe as you would
+   any other recipe.
+   Here are the image recipe requirements:
+   -  Inherits ``core-image`` so that kernel modules are installed.
+   -  Installs normal linux utilities not busybox ones (e.g. ``bash``,
+      ``coreutils``, ``tar``, ``gzip``, and ``kmod``).
+   -  Uses a custom Initial RAM Disk (initramfs) image with a custom
+      installer. A normal image that you can install usually creates a
+      single rootfs partition. This image uses another installer that
+      creates a specific partition layout. Not all Board Support
+      Packages (BSPs) can use an installer. For such cases, you need to
+      manually create the following partition layout on the target:
+      -  First partition mounted under ``/boot``, labeled "boot".
+      -  The main rootfs partition where this image gets installed,
+         which is mounted under ``/``.
+      -  Another partition labeled "testrootfs" where test images get
+         deployed.
+3. *Install image:* Install the image that you just built on the target
+   system.
+The final thing you need to do when setting ``TEST_TARGET`` to
+"SystemdbootTarget" is to set up the test image:
+1. *Set up your local.conf file:* Make sure you have the following
+   statements in your ``local.conf`` file:
+   ::
+      IMAGE_FSTYPES += "tar.gz"
+      INHERIT += "testimage"
+      TEST_TARGET = "SystemdbootTarget"
+      TEST_TARGET_IP = "192.168.2.3"
+2. *Build your test image:* Use BitBake to build the image:
+   ::
+      $ bitbake core-image-sato
+Power Control
+~~~~~~~~~~~~~
+For most hardware targets other than "simpleremote", you can control
+power:
+-  You can use ``TEST_POWERCONTROL_CMD`` together with
+   ``TEST_POWERCONTROL_EXTRA_ARGS`` as a command that runs on the host
+   and does power cycling. The test code passes one argument to that
+   command: off, on or cycle (off then on). Here is an example that
+   could appear in your ``local.conf`` file:
+   ::
+      TEST_POWERCONTROL_CMD = "powercontrol.exp test 10.11.12.1 nuc1"
+   In this example, the expect
+   script does the following:
+   .. code-block:: shell
+      ssh test@10.11.12.1 "pyctl nuc1 arg"
+   It then runs a Python script that controls power for a label called
+   ``nuc1``.
+   .. note::
+      You need to customize ``TEST_POWERCONTROL_CMD`` and
+      ``TEST_POWERCONTROL_EXTRA_ARGS`` for your own setup. The one requirement
+      is that it accepts "on", "off", and "cycle" as the last argument.
+-  When no command is defined, it connects to the device over SSH and
+   uses the classic reboot command to reboot the device. Classic reboot
+   is fine as long as the machine actually reboots (i.e. the SSH test
+   has not failed). It is useful for scenarios where you have a simple
+   setup, typically with a single board, and where some manual
+   interaction is okay from time to time.
+If you have no hardware to automatically perform power control but still
+wish to experiment with automated hardware testing, you can use the
+``dialog-power-control`` script that shows a dialog prompting you to perform
+the required power action. This script requires either KDialog or Zenity
+to be installed. To use this script, set the
+:term:`TEST_POWERCONTROL_CMD`
+variable as follows:
+::
+   TEST_POWERCONTROL_CMD = "${COREBASE}/scripts/contrib/dialog-power-control"
+Serial Console Connection
+~~~~~~~~~~~~~~~~~~~~~~~~~
+For test target classes requiring a serial console to interact with the
+bootloader (e.g. BeagleBoneTarget, EdgeRouterTarget, and GrubTarget),
+you need to specify a command to use to connect to the serial console of
+the target machine by using the
+:term:`TEST_SERIALCONTROL_CMD`
+variable and optionally the
+:term:`TEST_SERIALCONTROL_EXTRA_ARGS`
+variable.
+These cases could be a serial terminal program if the machine is
+connected to a local serial port, or a ``telnet`` or ``ssh`` command
+connecting to a remote console server. Regardless of the case, the
+command simply needs to connect to the serial console and forward that
+connection to standard input and output as any normal terminal program
+does. For example, to use the picocom terminal program on serial device
+``/dev/ttyUSB0`` at 115200bps, you would set the variable as follows:
+::
+   TEST_SERIALCONTROL_CMD = "picocom /dev/ttyUSB0 -b 115200"
+For local
+devices where the serial port device disappears when the device reboots,
+an additional "serdevtry" wrapper script is provided. To use this
+wrapper, simply prefix the terminal command with
+``${COREBASE}/scripts/contrib/serdevtry``:
+::
+   TEST_SERIALCONTROL_CMD = "${COREBASE}/scripts/contrib/serdevtry picocom -b 115200 /dev/ttyUSB0"
+Running Tests
+-------------
+You can start the tests automatically or manually:
+-  *Automatically running tests:* To run the tests automatically after
+   the OpenEmbedded build system successfully creates an image, first
+   set the
+   :term:`TESTIMAGE_AUTO`
+   variable to "1" in your ``local.conf`` file in the
+   :term:`Build Directory`:
+   ::
+      TESTIMAGE_AUTO = "1"
+   Next, build your image. If the image successfully builds, the
+   tests run:
+   ::
+      bitbake core-image-sato
+-  *Manually running tests:* To manually run the tests, first globally
+   inherit the
+   :ref:`testimage <ref-classes-testimage*>` class
+   by editing your ``local.conf`` file:
+   ::
+      INHERIT += "testimage"
+   Next, use BitBake to run the tests:
+   ::
+      bitbake -c testimage image
+All test files reside in ``meta/lib/oeqa/runtime`` in the
+:term:`Source Directory`. A test name maps
+directly to a Python module. Each test module may contain a number of
+individual tests. Tests are usually grouped together by the area tested
+(e.g tests for systemd reside in ``meta/lib/oeqa/runtime/systemd.py``).
+You can add tests to any layer provided you place them in the proper
+area and you extend :term:`BBPATH` in
+the ``local.conf`` file as normal. Be sure that tests reside in
+``layer/lib/oeqa/runtime``.
+.. note::
+   Be sure that module names do not collide with module names used in
+   the default set of test modules in ``meta/lib/oeqa/runtime``.
+You can change the set of tests run by appending or overriding
+:term:`TEST_SUITES` variable in
+``local.conf``. Each name in ``TEST_SUITES`` represents a required test
+for the image. Test modules named within ``TEST_SUITES`` cannot be
+skipped even if a test is not suitable for an image (e.g. running the
+RPM tests on an image without ``rpm``). Appending "auto" to
+``TEST_SUITES`` causes the build system to try to run all tests that are
+suitable for the image (i.e. each test module may elect to skip itself).
+The order you list tests in ``TEST_SUITES`` is important and influences
+test dependencies. Consequently, tests that depend on other tests should
+be added after the test on which they depend. For example, since the
+``ssh`` test depends on the ``ping`` test, "ssh" needs to come after
+"ping" in the list. The test class provides no re-ordering or dependency
+handling.
+.. note::
+   Each module can have multiple classes with multiple test methods.
+   And, Python ``unittest`` rules apply.
+Here are some things to keep in mind when running tests:
+-  The default tests for the image are defined as:
+   ::
+      DEFAULT_TEST_SUITES_pn-image = "ping ssh df connman syslog xorg scp vnc date rpm dnf dmesg"
+-  Add your own test to the list of the by using the following:
+   ::
+      TEST_SUITES_append = " mytest"
+-  Run a specific list of tests as follows:
+   ::
+     TEST_SUITES = "test1 test2 test3"
+   Remember, order is important. Be sure to place a test that is
+   dependent on another test later in the order.
+Exporting Tests
+---------------
+You can export tests so that they can run independently of the build
+system. Exporting tests is required if you want to be able to hand the
+test execution off to a scheduler. You can only export tests that are
+defined in :term:`TEST_SUITES`.
+If your image is already built, make sure the following are set in your
+``local.conf`` file:
+::
+   INHERIT += "testexport"
+   TEST_TARGET_IP = "IP-address-for-the-test-target"
+   TEST_SERVER_IP = "IP-address-for-the-test-server"
+You can then export the tests with the
+following BitBake command form:
+::
+   $ bitbake image -c testexport
+Exporting the tests places them in the
+:term:`Build Directory` in
+``tmp/testexport/``\ image, which is controlled by the
+``TEST_EXPORT_DIR`` variable.
+You can now run the tests outside of the build environment:
+::
+   $ cd tmp/testexport/image
+   $ ./runexported.py testdata.json
+Here is a complete example that shows IP addresses and uses the
+``core-image-sato`` image:
+::
+   INHERIT += "testexport"
+   TEST_TARGET_IP = "192.168.7.2"
+   TEST_SERVER_IP = "192.168.7.1"
+Use BitBake to export the tests:
+::
+   $ bitbake core-image-sato -c testexport
+Run the tests outside of
+the build environment using the following:
+::
+   $ cd tmp/testexport/core-image-sato
+   $ ./runexported.py testdata.json
+Writing New Tests
+-----------------
+As mentioned previously, all new test files need to be in the proper
+place for the build system to find them. New tests for additional
+functionality outside of the core should be added to the layer that adds
+the functionality, in ``layer/lib/oeqa/runtime`` (as long as
+:term:`BBPATH` is extended in the
+layer's ``layer.conf`` file as normal). Just remember the following:
+-  Filenames need to map directly to test (module) names.
+-  Do not use module names that collide with existing core tests.
+-  Minimally, an empty ``__init__.py`` file must exist in the runtime
+   directory.
+To create a new test, start by copying an existing module (e.g.
+``syslog.py`` or ``gcc.py`` are good ones to use). Test modules can use
+code from ``meta/lib/oeqa/utils``, which are helper classes.
+.. note::
+   Structure shell commands such that you rely on them and they return a
+   single code for success. Be aware that sometimes you will need to
+   parse the output. See the ``df.py`` and ``date.py`` modules for examples.
+You will notice that all test classes inherit ``oeRuntimeTest``, which
+is found in ``meta/lib/oetest.py``. This base class offers some helper
+attributes, which are described in the following sections:
+Class Methods
+~~~~~~~~~~~~~
+Class methods are as follows:
+-  *hasPackage(pkg):* Returns "True" if ``pkg`` is in the installed
+   package list of the image, which is based on the manifest file that
+   is generated during the ``do_rootfs`` task.
+-  *hasFeature(feature):* Returns "True" if the feature is in
+   :term:`IMAGE_FEATURES` or
+   :term:`DISTRO_FEATURES`.
+Class Attributes
+~~~~~~~~~~~~~~~~
+Class attributes are as follows:
+-  *pscmd:* Equals "ps -ef" if ``procps`` is installed in the image.
+   Otherwise, ``pscmd`` equals "ps" (busybox).
+-  *tc:* The called test context, which gives access to the
+   following attributes:
+   -  *d:* The BitBake datastore, which allows you to use stuff such
+      as ``oeRuntimeTest.tc.d.getVar("VIRTUAL-RUNTIME_init_manager")``.
+   -  *testslist and testsrequired:* Used internally. The tests
+      do not need these.
+   -  *filesdir:* The absolute path to
+      ``meta/lib/oeqa/runtime/files``, which contains helper files for
+      tests meant for copying on the target such as small files written
+      in C for compilation.
+   -  *target:* The target controller object used to deploy and
+      start an image on a particular target (e.g. Qemu, SimpleRemote,
+      and SystemdbootTarget). Tests usually use the following:
+      -  *ip:* The target's IP address.
+      -  *server_ip:* The host's IP address, which is usually used
+         by the DNF test suite.
+      -  *run(cmd, timeout=None):* The single, most used method.
+         This command is a wrapper for: ``ssh root@host "cmd"``. The
+         command returns a tuple: (status, output), which are what their
+         names imply - the return code of "cmd" and whatever output it
+         produces. The optional timeout argument represents the number
+         of seconds the test should wait for "cmd" to return. If the
+         argument is "None", the test uses the default instance's
+         timeout period, which is 300 seconds. If the argument is "0",
+         the test runs until the command returns.
+      -  *copy_to(localpath, remotepath):*
+         ``scp localpath root@ip:remotepath``.
+      -  *copy_from(remotepath, localpath):*
+         ``scp root@host:remotepath localpath``.
+Instance Attributes
+~~~~~~~~~~~~~~~~~~~
+A single instance attribute exists, which is ``target``. The ``target``
+instance attribute is identical to the class attribute of the same name,
+which is described in the previous section. This attribute exists as
+both an instance and class attribute so tests can use
+``self.target.run(cmd)`` in instance methods instead of
+``oeRuntimeTest.tc.target.run(cmd)``.
+Installing Packages in the DUT Without the Package Manager
+----------------------------------------------------------
+When a test requires a package built by BitBake, it is possible to
+install that package. Installing the package does not require a package
+manager be installed in the device under test (DUT). It does, however,
+require an SSH connection and the target must be using the
+``sshcontrol`` class.
+.. note::
+   This method uses ``scp`` to copy files from the host to the target, which
+   causes permissions and special attributes to be lost.
+A JSON file is used to define the packages needed by a test. This file
+must be in the same path as the file used to define the tests.
+Furthermore, the filename must map directly to the test module name with
+a ``.json`` extension.
+The JSON file must include an object with the test name as keys of an
+object or an array. This object (or array of objects) uses the following
+data:
+-  "pkg" - A mandatory string that is the name of the package to be
+   installed.
+-  "rm" - An optional boolean, which defaults to "false", that specifies
+   to remove the package after the test.
+-  "extract" - An optional boolean, which defaults to "false", that
+   specifies if the package must be extracted from the package format.
+   When set to "true", the package is not automatically installed into
+   the DUT.
+Following is an example JSON file that handles test "foo" installing
+package "bar" and test "foobar" installing packages "foo" and "bar".
+Once the test is complete, the packages are removed from the DUT.
+::
+     {
+         "foo": {
+             "pkg": "bar"
+         },
+         "foobar": [
+             {
+                 "pkg": "foo",
+                 "rm": true
+             },
+             {
+                 "pkg": "bar",
+                 "rm": true
+             }
+         ]
+     }
+Debugging Tools and Techniques
+==============================
+The exact method for debugging build failures depends on the nature of
+the problem and on the system's area from which the bug originates.
+Standard debugging practices such as comparison against the last known
+working version with examination of the changes and the re-application
+of steps to identify the one causing the problem are valid for the Yocto
+Project just as they are for any other system. Even though it is
+impossible to detail every possible potential failure, this section
+provides some general tips to aid in debugging given a variety of
+situations.
+.. note::
+   A useful feature for debugging is the error reporting tool.
+   Configuring the Yocto Project to use this tool causes the
+   OpenEmbedded build system to produce error reporting commands as part
+   of the console output. You can enter the commands after the build
+   completes to log error information into a common database, that can
+   help you figure out what might be going wrong. For information on how
+   to enable and use this feature, see the
+   ":ref:`dev-manual/common-tasks:using the error reporting tool`"
+   section.
+The following list shows the debugging topics in the remainder of this
+section:
+-  "`Viewing Logs from Failed
+   Tasks <#dev-debugging-viewing-logs-from-failed-tasks>`__" describes
+   how to find and view logs from tasks that failed during the build
+   process.
+-  "`Viewing Variable
+   Values <#dev-debugging-viewing-variable-values>`__" describes how to
+   use the BitBake ``-e`` option to examine variable values after a
+   recipe has been parsed.
+-  ":ref:`dev-manual/common-tasks:viewing package information with \`\`oe-pkgdata-util\`\``"
+   describes how to use the ``oe-pkgdata-util`` utility to query
+   :term:`PKGDATA_DIR` and
+   display package-related information for built packages.
+-  "`Viewing Dependencies Between Recipes and
+   Tasks <#dev-viewing-dependencies-between-recipes-and-tasks>`__"
+   describes how to use the BitBake ``-g`` option to display recipe
+   dependency information used during the build.
+-  "`Viewing Task Variable
+   Dependencies <#dev-viewing-task-variable-dependencies>`__" describes
+   how to use the ``bitbake-dumpsig`` command in conjunction with key
+   subdirectories in the
+   :term:`Build Directory` to determine
+   variable dependencies.
+-  "`Running Specific Tasks <#dev-debugging-taskrunning>`__" describes
+   how to use several BitBake options (e.g. ``-c``, ``-C``, and ``-f``)
+   to run specific tasks in the build chain. It can be useful to run
+   tasks "out-of-order" when trying isolate build issues.
+-  "`General BitBake Problems <#dev-debugging-bitbake>`__" describes how
+   to use BitBake's ``-D`` debug output option to reveal more about what
+   BitBake is doing during the build.
+-  "`Building with No Dependencies <#dev-debugging-buildfile>`__"
+   describes how to use the BitBake ``-b`` option to build a recipe
+   while ignoring dependencies.
+-  "`Recipe Logging Mechanisms <#recipe-logging-mechanisms>`__"
+   describes how to use the many recipe logging functions to produce
+   debugging output and report errors and warnings.
+-  "`Debugging Parallel Make Races <#debugging-parallel-make-races>`__"
+   describes how to debug situations where the build consists of several
+   parts that are run simultaneously and when the output or result of
+   one part is not ready for use with a different part of the build that
+   depends on that output.
+-  "`Debugging With the GNU Project Debugger (GDB)
+   Remotely <#platdev-gdb-remotedebug>`__" describes how to use GDB to
+   allow you to examine running programs, which can help you fix
+   problems.
+-  "`Debugging with the GNU Project Debugger (GDB) on the
+   Target <#debugging-with-the-gnu-project-debugger-gdb-on-the-target>`__"
+   describes how to use GDB directly on target hardware for debugging.
+-  "`Other Debugging Tips <#dev-other-debugging-others>`__" describes
+   miscellaneous debugging tips that can be useful.
+Viewing Logs from Failed Tasks
+------------------------------
+You can find the log for a task in the file
+``${``\ :term:`WORKDIR`\ ``}/temp/log.do_``\ `taskname`.
+For example, the log for the
+:ref:`ref-tasks-compile` task of the
+QEMU minimal image for the x86 machine (``qemux86``) might be in
+``tmp/work/qemux86-poky-linux/core-image-minimal/1.0-r0/temp/log.do_compile``.
+To see the commands :term:`BitBake` ran
+to generate a log, look at the corresponding ``run.do_``\ `taskname` file
+in the same directory.
+``log.do_``\ `taskname` and ``run.do_``\ `taskname` are actually symbolic
+links to ``log.do_``\ `taskname`\ ``.``\ `pid` and
+``log.run_``\ `taskname`\ ``.``\ `pid`, where `pid` is the PID the task had
+when it ran. The symlinks always point to the files corresponding to the
+most recent run.
+Viewing Variable Values
+-----------------------
+Sometimes you need to know the value of a variable as a result of
+BitBake's parsing step. This could be because some unexpected behavior
+occurred in your project. Perhaps an attempt to :ref:`modify a variable
+<bitbake:bitbake-user-manual/bitbake-user-manual-metadata:modifying existing
+variables>` did not work out as expected.
+BitBake's ``-e`` option is used to display variable values after
+parsing. The following command displays the variable values after the
+configuration files (i.e. ``local.conf``, ``bblayers.conf``,
+``bitbake.conf`` and so forth) have been parsed:
+::
+   $ bitbake -e
+The following command displays variable values after a specific recipe has
+been parsed. The variables include those from the configuration as well:
+::
+   $ bitbake -e recipename
+.. note::
+   Each recipe has its own private set of variables (datastore).
+   Internally, after parsing the configuration, a copy of the resulting
+   datastore is made prior to parsing each recipe. This copying implies
+   that variables set in one recipe will not be visible to other
+   recipes.
+   Likewise, each task within a recipe gets a private datastore based on
+   the recipe datastore, which means that variables set within one task
+   will not be visible to other tasks.
+In the output of ``bitbake -e``, each variable is preceded by a
+description of how the variable got its value, including temporary
+values that were later overridden. This description also includes
+variable flags (varflags) set on the variable. The output can be very
+helpful during debugging.
+Variables that are exported to the environment are preceded by
+``export`` in the output of ``bitbake -e``. See the following example:
+::
+   export CC="i586-poky-linux-gcc -m32 -march=i586 --sysroot=/home/ulf/poky/build/tmp/sysroots/qemux86"
+In addition to variable values, the output of the ``bitbake -e`` and
+``bitbake -e`` recipe commands includes the following information:
+-  The output starts with a tree listing all configuration files and
+   classes included globally, recursively listing the files they include
+   or inherit in turn. Much of the behavior of the OpenEmbedded build
+   system (including the behavior of the :ref:`ref-manual/ref-tasks:normal recipe build tasks`) is
+   implemented in the
+   :ref:`base <ref-classes-base>` class and the
+   classes it inherits, rather than being built into BitBake itself.
+-  After the variable values, all functions appear in the output. For
+   shell functions, variables referenced within the function body are
+   expanded. If a function has been modified using overrides or using
+   override-style operators like ``_append`` and ``_prepend``, then the
+   final assembled function body appears in the output.
+Viewing Package Information with ``oe-pkgdata-util``
+----------------------------------------------------
+You can use the ``oe-pkgdata-util`` command-line utility to query
+:term:`PKGDATA_DIR` and display
+various package-related information. When you use the utility, you must
+use it to view information on packages that have already been built.
+Following are a few of the available ``oe-pkgdata-util`` subcommands.
+.. note::
+   You can use the standard \* and ? globbing wildcards as part of
+   package names and paths.
+-  ``oe-pkgdata-util list-pkgs [pattern]``: Lists all packages
+   that have been built, optionally limiting the match to packages that
+   match pattern.
+-  ``oe-pkgdata-util list-pkg-files package ...``: Lists the
+   files and directories contained in the given packages.
+   .. note::
+      A different way to view the contents of a package is to look at
+      the
+      ``${``\ :term:`WORKDIR`\ ``}/packages-split``
+      directory of the recipe that generates the package. This directory
+      is created by the
+      :ref:`ref-tasks-package` task
+      and has one subdirectory for each package the recipe generates,
+      which contains the files stored in that package.
+      If you want to inspect the ``${WORKDIR}/packages-split``
+      directory, make sure that
+      :ref:`rm_work <ref-classes-rm-work>` is not
+      enabled when you build the recipe.
+-  ``oe-pkgdata-util find-path path ...``: Lists the names of
+   the packages that contain the given paths. For example, the following
+   tells us that ``/usr/share/man/man1/make.1`` is contained in the
+   ``make-doc`` package:
+   ::
+      $ oe-pkgdata-util find-path /usr/share/man/man1/make.1
+      make-doc: /usr/share/man/man1/make.1
+-  ``oe-pkgdata-util lookup-recipe package ...``: Lists the name
+   of the recipes that produce the given packages.
+For more information on the ``oe-pkgdata-util`` command, use the help
+facility:
+::
+   $ oe-pkgdata-util --help
+   $ oe-pkgdata-util subcommand --help
+Viewing Dependencies Between Recipes and Tasks
+----------------------------------------------
+Sometimes it can be hard to see why BitBake wants to build other recipes
+before the one you have specified. Dependency information can help you
+understand why a recipe is built.
+To generate dependency information for a recipe, run the following
+command:
+::
+   $ bitbake -g recipename
+This command writes the following files in the current directory:
+-  ``pn-buildlist``: A list of recipes/targets involved in building
+   `recipename`. "Involved" here means that at least one task from the
+   recipe needs to run when building `recipename` from scratch. Targets
+   that are in
+   :term:`ASSUME_PROVIDED`
+   are not listed.
+-  ``task-depends.dot``: A graph showing dependencies between tasks.
+The graphs are in
+`DOT <https://en.wikipedia.org/wiki/DOT_%28graph_description_language%29>`__
+format and can be converted to images (e.g. using the ``dot`` tool from
+`Graphviz <https://www.graphviz.org/>`__).
+.. note::
+   -  DOT files use a plain text format. The graphs generated using the
+      ``bitbake -g`` command are often so large as to be difficult to
+      read without special pruning (e.g. with Bitbake's ``-I`` option)
+      and processing. Despite the form and size of the graphs, the
+      corresponding ``.dot`` files can still be possible to read and
+      provide useful information.
+      As an example, the ``task-depends.dot`` file contains lines such
+      as the following:
+      ::
+         "libxslt.do_configure" -> "libxml2.do_populate_sysroot"
+      The above example line reveals that the
+      :ref:`ref-tasks-configure`
+      task in ``libxslt`` depends on the
+      :ref:`ref-tasks-populate_sysroot`
+      task in ``libxml2``, which is a normal
+      :term:`DEPENDS` dependency
+      between the two recipes.
+   -  For an example of how ``.dot`` files can be processed, see the
+      ``scripts/contrib/graph-tool`` Python script, which finds and
+      displays paths between graph nodes.
+You can use a different method to view dependency information by using
+the following command:
+::
+   $ bitbake -g -u taskexp recipename
+This command
+displays a GUI window from which you can view build-time and runtime
+dependencies for the recipes involved in building recipename.
+Viewing Task Variable Dependencies
+----------------------------------
+As mentioned in the
+":ref:`bitbake:bitbake-user-manual/bitbake-user-manual-execution:checksums (signatures)`" section of the BitBake
+User Manual, BitBake tries to automatically determine what variables a
+task depends on so that it can rerun the task if any values of the
+variables change. This determination is usually reliable. However, if
+you do things like construct variable names at runtime, then you might
+have to manually declare dependencies on those variables using
+``vardeps`` as described in the
+":ref:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata:variable flags`" section of the BitBake
+User Manual.
+If you are unsure whether a variable dependency is being picked up
+automatically for a given task, you can list the variable dependencies
+BitBake has determined by doing the following:
+1. Build the recipe containing the task:
+::
+   $ bitbake recipename
+2. Inside the :term:`STAMPS_DIR`
+   directory, find the signature data (``sigdata``) file that
+   corresponds to the task. The ``sigdata`` files contain a pickled
+   Python database of all the metadata that went into creating the input
+   checksum for the task. As an example, for the
+   :ref:`ref-tasks-fetch` task of the
+   ``db`` recipe, the ``sigdata`` file might be found in the following
+   location:
+   ::
+      ${BUILDDIR}/tmp/stamps/i586-poky-linux/db/6.0.30-r1.do_fetch.sigdata.7c048c18222b16ff0bcee2000ef648b1
+   For tasks that are accelerated through the shared state
+   (:ref:`sstate <overview-manual/overview-manual-concepts:shared state cache>`) cache, an
+   additional ``siginfo`` file is written into
+   :term:`SSTATE_DIR` along with
+   the cached task output. The ``siginfo`` files contain exactly the
+   same information as ``sigdata`` files.
+3. Run ``bitbake-dumpsig`` on the ``sigdata`` or ``siginfo`` file. Here
+   is an example:
+   ::
+      $ bitbake-dumpsig ${BUILDDIR}/tmp/stamps/i586-poky-linux/db/6.0.30-r1.do_fetch.sigdata.7c048c18222b16ff0bcee2000ef648b1
+   In the output of the above command, you will find a line like the
+   following, which lists all the (inferred) variable dependencies for
+   the task. This list also includes indirect dependencies from
+   variables depending on other variables, recursively.
+   ::
+      Task dependencies: ['PV', 'SRCREV', 'SRC_URI', 'SRC_URI[md5sum]', 'SRC_URI[sha256sum]', 'base_do_fetch']
+   .. note::
+      Functions (e.g. ``base_do_fetch``) also count as variable dependencies.
+      These functions in turn depend on the variables they reference.
+   The output of ``bitbake-dumpsig`` also includes the value each
+   variable had, a list of dependencies for each variable, and
+   :term:`bitbake:BB_HASHBASE_WHITELIST`
+   information.
+There is also a ``bitbake-diffsigs`` command for comparing two
+``siginfo`` or ``sigdata`` files. This command can be helpful when
+trying to figure out what changed between two versions of a task. If you
+call ``bitbake-diffsigs`` with just one file, the command behaves like
+``bitbake-dumpsig``.
+You can also use BitBake to dump out the signature construction
+information without executing tasks by using either of the following
+BitBake command-line options:
+::
+   ‐‐dump-signatures=SIGNATURE_HANDLER
+   -S SIGNATURE_HANDLER
+.. note::
+   Two common values for `SIGNATURE_HANDLER` are "none" and "printdiff", which
+   dump only the signature or compare the dumped signature with the cached one,
+   respectively.
+Using BitBake with either of these options causes BitBake to dump out
+``sigdata`` files in the ``stamps`` directory for every task it would
+have executed instead of building the specified target package.
+Viewing Metadata Used to Create the Input Signature of a Shared State Task
+--------------------------------------------------------------------------
+Seeing what metadata went into creating the input signature of a shared
+state (sstate) task can be a useful debugging aid. This information is
+available in signature information (``siginfo``) files in
+:term:`SSTATE_DIR`. For
+information on how to view and interpret information in ``siginfo``
+files, see the "`Viewing Task Variable
+Dependencies <#dev-viewing-task-variable-dependencies>`__" section.
+For conceptual information on shared state, see the
+":ref:`overview-manual/overview-manual-concepts:shared state`"
+section in the Yocto Project Overview and Concepts Manual.
+Invalidating Shared State to Force a Task to Run
+------------------------------------------------
+The OpenEmbedded build system uses
+:ref:`checksums <overview-manual/overview-manual-concepts:checksums (signatures)>` and
+:ref:`overview-manual/overview-manual-concepts:shared state` cache to avoid unnecessarily
+rebuilding tasks. Collectively, this scheme is known as "shared state
+code".
+As with all schemes, this one has some drawbacks. It is possible that
+you could make implicit changes to your code that the checksum
+calculations do not take into account. These implicit changes affect a
+task's output but do not trigger the shared state code into rebuilding a
+recipe. Consider an example during which a tool changes its output.
+Assume that the output of ``rpmdeps`` changes. The result of the change
+should be that all the ``package`` and ``package_write_rpm`` shared
+state cache items become invalid. However, because the change to the
+output is external to the code and therefore implicit, the associated
+shared state cache items do not become invalidated. In this case, the
+build process uses the cached items rather than running the task again.
+Obviously, these types of implicit changes can cause problems.
+To avoid these problems during the build, you need to understand the
+effects of any changes you make. Realize that changes you make directly
+to a function are automatically factored into the checksum calculation.
+Thus, these explicit changes invalidate the associated area of shared
+state cache. However, you need to be aware of any implicit changes that
+are not obvious changes to the code and could affect the output of a
+given task.
+When you identify an implicit change, you can easily take steps to
+invalidate the cache and force the tasks to run. The steps you can take
+are as simple as changing a function's comments in the source code. For
+example, to invalidate package shared state files, change the comment
+statements of
+:ref:`ref-tasks-package` or the
+comments of one of the functions it calls. Even though the change is
+purely cosmetic, it causes the checksum to be recalculated and forces
+the build system to run the task again.
+.. note::
+   For an example of a commit that makes a cosmetic change to invalidate
+   shared state, see this
+   :yocto_git:`commit </poky/commit/meta/classes/package.bbclass?id=737f8bbb4f27b4837047cb9b4fbfe01dfde36d54>`.
+Running Specific Tasks
+----------------------
+Any given recipe consists of a set of tasks. The standard BitBake
+behavior in most cases is: ``do_fetch``, ``do_unpack``, ``do_patch``,
+``do_configure``, ``do_compile``, ``do_install``, ``do_package``,
+``do_package_write_*``, and ``do_build``. The default task is
+``do_build`` and any tasks on which it depends build first. Some tasks,
+such as ``do_devshell``, are not part of the default build chain. If you
+wish to run a task that is not part of the default build chain, you can
+use the ``-c`` option in BitBake. Here is an example:
+::
+   $ bitbake matchbox-desktop -c devshell
+The ``-c`` option respects task dependencies, which means that all other
+tasks (including tasks from other recipes) that the specified task
+depends on will be run before the task. Even when you manually specify a
+task to run with ``-c``, BitBake will only run the task if it considers
+it "out of date". See the
+":ref:`overview-manual/overview-manual-concepts:stamp files and the rerunning of tasks`"
+section in the Yocto Project Overview and Concepts Manual for how
+BitBake determines whether a task is "out of date".
+If you want to force an up-to-date task to be rerun (e.g. because you
+made manual modifications to the recipe's
+:term:`WORKDIR` that you want to try
+out), then you can use the ``-f`` option.
+.. note::
+   The reason ``-f`` is never required when running the
+   :ref:`ref-tasks-devshell` task is because the
+   [\ :ref:`nostamp <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:variable flags>`\ ]
+   variable flag is already set for the task.
+The following example shows one way you can use the ``-f`` option:
+::
+   $ bitbake matchbox-desktop
+             .
+             .
+   make some changes to the source code in the work directory
+             .
+             .
+   $ bitbake matchbox-desktop -c compile -f
+   $ bitbake matchbox-desktop
+This sequence first builds and then recompiles ``matchbox-desktop``. The
+last command reruns all tasks (basically the packaging tasks) after the
+compile. BitBake recognizes that the ``do_compile`` task was rerun and
+therefore understands that the other tasks also need to be run again.
+Another, shorter way to rerun a task and all
+:ref:`ref-manual/ref-tasks:normal recipe build tasks`
+that depend on it is to use the ``-C`` option.
+.. note::
+   This option is upper-cased and is separate from the ``-c``
+   option, which is lower-cased.
+Using this option invalidates the given task and then runs the
+:ref:`ref-tasks-build` task, which is
+the default task if no task is given, and the tasks on which it depends.
+You could replace the final two commands in the previous example with
+the following single command:
+::
+   $ bitbake matchbox-desktop -C compile
+Internally, the ``-f`` and ``-C`` options work by tainting (modifying)
+the input checksum of the specified task. This tainting indirectly
+causes the task and its dependent tasks to be rerun through the normal
+task dependency mechanisms.
+.. note::
+   BitBake explicitly keeps track of which tasks have been tainted in
+   this fashion, and will print warnings such as the following for
+   builds involving such tasks:
+   .. code-block:: none
+      WARNING: /home/ulf/poky/meta/recipes-sato/matchbox-desktop/matchbox-desktop_2.1.bb.do_compile is tainted from a forced run
+   The purpose of the warning is to let you know that the work directory
+   and build output might not be in the clean state they would be in for
+   a "normal" build, depending on what actions you took. To get rid of
+   such warnings, you can remove the work directory and rebuild the
+   recipe, as follows:
+   ::
+      $ bitbake matchbox-desktop -c clean
+      $ bitbake matchbox-desktop
+You can view a list of tasks in a given package by running the
+``do_listtasks`` task as follows:
+::
+   $ bitbake matchbox-desktop -c listtasks
+The results appear as output to the console and are also in
+the file ``${WORKDIR}/temp/log.do_listtasks``.
+General BitBake Problems
+------------------------
+You can see debug output from BitBake by using the ``-D`` option. The
+debug output gives more information about what BitBake is doing and the
+reason behind it. Each ``-D`` option you use increases the logging
+level. The most common usage is ``-DDD``.
+The output from ``bitbake -DDD -v targetname`` can reveal why BitBake
+chose a certain version of a package or why BitBake picked a certain
+provider. This command could also help you in a situation where you
+think BitBake did something unexpected.
+Building with No Dependencies
+-----------------------------
+To build a specific recipe (``.bb`` file), you can use the following
+command form:
+::
+   $ bitbake -b somepath/somerecipe.bb
+This command form does
+not check for dependencies. Consequently, you should use it only when
+you know existing dependencies have been met.
+.. note::
+   You can also specify fragments of the filename. In this case, BitBake
+   checks for a unique match.
+Recipe Logging Mechanisms
+-------------------------
+The Yocto Project provides several logging functions for producing
+debugging output and reporting errors and warnings. For Python
+functions, the following logging functions exist. All of these functions
+log to ``${T}/log.do_``\ `task`, and can also log to standard output
+(stdout) with the right settings:
+-  ``bb.plain(msg)``: Writes msg as is to the log while also
+   logging to stdout.
+-  ``bb.note(msg)``: Writes "NOTE: msg" to the log. Also logs to
+   stdout if BitBake is called with "-v".
+-  ``bb.debug(level, msg)``: Writes "DEBUG: msg" to the
+   log. Also logs to stdout if the log level is greater than or equal to
+   level. See the ":ref:`-D <bitbake:bitbake-user-manual/bitbake-user-manual-intro:usage and syntax>`" option
+   in the BitBake User Manual for more information.
+-  ``bb.warn(msg)``: Writes "WARNING: msg" to the log while also
+   logging to stdout.
+-  ``bb.error(msg)``: Writes "ERROR: msg" to the log while also
+   logging to standard out (stdout).
+   .. note::
+      Calling this function does not cause the task to fail.
+-  ``bb.fatal(``\ msg\ ``)``: This logging function is similar to
+   ``bb.error(``\ msg\ ``)`` but also causes the calling task to fail.
+   .. note::
+      ``bb.fatal()`` raises an exception, which means you do not need to put a
+      "return" statement after the function.
+The same logging functions are also available in shell functions, under
+the names ``bbplain``, ``bbnote``, ``bbdebug``, ``bbwarn``, ``bberror``,
+and ``bbfatal``. The
+:ref:`logging <ref-classes-logging>` class
+implements these functions. See that class in the ``meta/classes``
+folder of the :term:`Source Directory` for information.
+Logging With Python
+~~~~~~~~~~~~~~~~~~~
+When creating recipes using Python and inserting code that handles build
+logs, keep in mind the goal is to have informative logs while keeping
+the console as "silent" as possible. Also, if you want status messages
+in the log, use the "debug" loglevel.
+Following is an example written in Python. The code handles logging for
+a function that determines the number of tasks needed to be run. See the
+":ref:`ref-tasks-listtasks`"
+section for additional information:
+::
+   python do_listtasks() {
+       bb.debug(2, "Starting to figure out the task list")
+       if noteworthy_condition:
+           bb.note("There are 47 tasks to run")
+       bb.debug(2, "Got to point xyz")
+       if warning_trigger:
+           bb.warn("Detected warning_trigger, this might be a problem later.")
+       if recoverable_error:
+           bb.error("Hit recoverable_error, you really need to fix this!")
+       if fatal_error:
+           bb.fatal("fatal_error detected, unable to print the task list")
+       bb.plain("The tasks present are abc")
+       bb.debug(2, "Finished figuring out the tasklist")
+   }
+Logging With Bash
+~~~~~~~~~~~~~~~~~
+When creating recipes using Bash and inserting code that handles build
+logs, you have the same goals - informative with minimal console output.
+The syntax you use for recipes written in Bash is similar to that of
+recipes written in Python described in the previous section.
+Following is an example written in Bash. The code logs the progress of
+the ``do_my_function`` function.
+::
+   do_my_function() {
+       bbdebug 2 "Running do_my_function"
+       if [ exceptional_condition ]; then
+           bbnote "Hit exceptional_condition"
+       fi
+       bbdebug 2  "Got to point xyz"
+       if [ warning_trigger ]; then
+           bbwarn "Detected warning_trigger, this might cause a problem later."
+       fi
+       if [ recoverable_error ]; then
+           bberror "Hit recoverable_error, correcting"
+       fi
+       if [ fatal_error ]; then
+           bbfatal "fatal_error detected"
+       fi
+       bbdebug 2 "Completed do_my_function"
+   }
+Debugging Parallel Make Races
+-----------------------------
+A parallel ``make`` race occurs when the build consists of several parts
+that are run simultaneously and a situation occurs when the output or
+result of one part is not ready for use with a different part of the
+build that depends on that output. Parallel make races are annoying and
+can sometimes be difficult to reproduce and fix. However, some simple
+tips and tricks exist that can help you debug and fix them. This section
+presents a real-world example of an error encountered on the Yocto
+Project autobuilder and the process used to fix it.
+.. note::
+   If you cannot properly fix a ``make`` race condition, you can work around it
+   by clearing either the :term:`PARALLEL_MAKE` or :term:`PARALLEL_MAKEINST`
+   variables.
+The Failure
+~~~~~~~~~~~
+For this example, assume that you are building an image that depends on
+the "neard" package. And, during the build, BitBake runs into problems
+and creates the following output.
+.. note::
+   This example log file has longer lines artificially broken to make
+   the listing easier to read.
+If you examine the output or the log file, you see the failure during
+``make``:
+.. code-block:: none
+   | DEBUG: SITE files ['endian-little', 'bit-32', 'ix86-common', 'common-linux', 'common-glibc', 'i586-linux', 'common']
+   | DEBUG: Executing shell function do_compile
+   | NOTE: make -j 16
+   | make --no-print-directory all-am
+   | /bin/mkdir -p include/near
+   | /bin/mkdir -p include/near
+   | /bin/mkdir -p include/near
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/types.h include/near/types.h
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/log.h include/near/log.h
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/plugin.h include/near/plugin.h
+   | /bin/mkdir -p include/near
+   | /bin/mkdir -p include/near
+   | /bin/mkdir -p include/near
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/tag.h include/near/tag.h
+   | /bin/mkdir -p include/near
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/adapter.h include/near/adapter.h
+   | /bin/mkdir -p include/near
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/ndef.h include/near/ndef.h
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/tlv.h include/near/tlv.h
+   | /bin/mkdir -p include/near
+   | /bin/mkdir -p include/near
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/setting.h include/near/setting.h
+   | /bin/mkdir -p include/near
+   | /bin/mkdir -p include/near
+   | /bin/mkdir -p include/near
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/device.h include/near/device.h
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/nfc_copy.h include/near/nfc_copy.h
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/snep.h include/near/snep.h
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/version.h include/near/version.h
+   | ln -s /home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/work/i586-poky-linux/neard/
+     0.14-r0/neard-0.14/include/dbus.h include/near/dbus.h
+   | ./src/genbuiltin nfctype1 nfctype2 nfctype3 nfctype4 p2p > src/builtin.h
+   | i586-poky-linux-gcc  -m32 -march=i586 --sysroot=/home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/
+     build/build/tmp/sysroots/qemux86 -DHAVE_CONFIG_H -I. -I./include -I./src -I./gdbus  -I/home/pokybuild/
+     yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/sysroots/qemux86/usr/include/glib-2.0
+     -I/home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/tmp/sysroots/qemux86/usr/
+     lib/glib-2.0/include  -I/home/pokybuild/yocto-autobuilder/yocto-slave/nightly-x86/build/build/
+     tmp/sysroots/qemux86/usr/include/dbus-1.0 -I/home/pokybuild/yocto-autobuilder/yocto-slave/
+     nightly-x86/build/build/tmp/sysroots/qemux86/usr/lib/dbus-1.0/include  -I/home/pokybuild/yocto-autobuilder/
+     yocto-slave/nightly-x86/build/build/tmp/sysroots/qemux86/usr/include/libnl3
+     -DNEAR_PLUGIN_BUILTIN -DPLUGINDIR=\""/usr/lib/near/plugins"\"
+     -DCONFIGDIR=\""/etc/neard\"" -O2 -pipe -g -feliminate-unused-debug-types -c
+     -o tools/snep-send.o tools/snep-send.c
+   | In file included from tools/snep-send.c:16:0:
+   | tools/../src/near.h:41:23: fatal error: near/dbus.h: No such file or directory
+   |  #include <near/dbus.h>
+   |                        ^
+   | compilation terminated.
+   | make[1]: *** [tools/snep-send.o] Error 1
+   | make[1]: *** Waiting for unfinished jobs....
+   | make: *** [all] Error 2
+   | ERROR: oe_runmake failed
+Reproducing the Error
+~~~~~~~~~~~~~~~~~~~~~
+Because race conditions are intermittent, they do not manifest
+themselves every time you do the build. In fact, most times the build
+will complete without problems even though the potential race condition
+exists. Thus, once the error surfaces, you need a way to reproduce it.
+In this example, compiling the "neard" package is causing the problem.
+So the first thing to do is build "neard" locally. Before you start the
+build, set the
+:term:`PARALLEL_MAKE` variable
+in your ``local.conf`` file to a high number (e.g. "-j 20"). Using a
+high value for ``PARALLEL_MAKE`` increases the chances of the race
+condition showing up:
+::
+   $ bitbake neard
+Once the local build for "neard" completes, start a ``devshell`` build:
+::
+   $ bitbake neard -c devshell
+For information on how to use a
+``devshell``, see the "`Using a Development
+Shell <#platdev-appdev-devshell>`__" section.
+In the ``devshell``, do the following:
+::
+   $ make clean
+   $ make tools/snep-send.o
+The ``devshell`` commands cause the failure to clearly
+be visible. In this case, a missing dependency exists for the "neard"
+Makefile target. Here is some abbreviated, sample output with the
+missing dependency clearly visible at the end:
+::
+   i586-poky-linux-gcc  -m32 -march=i586 --sysroot=/home/scott-lenovo/......
+      .
+      .
+      .
+   tools/snep-send.c
+   In file included from tools/snep-send.c:16:0:
+   tools/../src/near.h:41:23: fatal error: near/dbus.h: No such file or directory
+    #include <near/dbus.h>
+                     ^
+   compilation terminated.
+   make: *** [tools/snep-send.o] Error 1
+   $
+Creating a Patch for the Fix
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Because there is a missing dependency for the Makefile target, you need
+to patch the ``Makefile.am`` file, which is generated from
+``Makefile.in``. You can use Quilt to create the patch:
+::
+   $ quilt new parallelmake.patch
+   Patch patches/parallelmake.patch is now on top
+   $ quilt add Makefile.am
+   File Makefile.am added to patch patches/parallelmake.patch
+For more information on using Quilt, see the
+"`Using Quilt in Your Workflow <#using-a-quilt-workflow>`__" section.
+At this point you need to make the edits to ``Makefile.am`` to add the
+missing dependency. For our example, you have to add the following line
+to the file:
+::
+   tools/snep-send.$(OBJEXT): include/near/dbus.h
+Once you have edited the file, use the ``refresh`` command to create the
+patch:
+::
+   $ quilt refresh
+   Refreshed patch patches/parallelmake.patch
+Once
+the patch file exists, you need to add it back to the originating recipe
+folder. Here is an example assuming a top-level
+:term:`Source Directory` named ``poky``:
+::
+   $ cp patches/parallelmake.patch poky/meta/recipes-connectivity/neard/neard
+The final thing you need to do to implement the fix in the build is to
+update the "neard" recipe (i.e. ``neard-0.14.bb``) so that the
+:term:`SRC_URI` statement includes
+the patch file. The recipe file is in the folder above the patch. Here
+is what the edited ``SRC_URI`` statement would look like:
+::
+   SRC_URI = "${KERNELORG_MIRROR}/linux/network/nfc/${BPN}-${PV}.tar.xz \
+              file://neard.in \
+              file://neard.service.in \
+              file://parallelmake.patch \
+             "
+With the patch complete and moved to the correct folder and the
+``SRC_URI`` statement updated, you can exit the ``devshell``:
+::
+   $ exit
+Testing the Build
+~~~~~~~~~~~~~~~~~
+With everything in place, you can get back to trying the build again
+locally:
+::
+   $ bitbake neard
+This build should succeed.
+Now you can open up a ``devshell`` again and repeat the clean and make
+operations as follows:
+::
+   $ bitbake neard -c devshell
+   $ make clean
+   $ make tools/snep-send.o
+The build should work without issue.
+As with all solved problems, if they originated upstream, you need to
+submit the fix for the recipe in OE-Core and upstream so that the
+problem is taken care of at its source. See the "`Submitting a Change to
+the Yocto Project <#how-to-submit-a-change>`__" section for more
+information.
+Debugging With the GNU Project Debugger (GDB) Remotely
+------------------------------------------------------
+GDB allows you to examine running programs, which in turn helps you to
+understand and fix problems. It also allows you to perform post-mortem
+style analysis of program crashes. GDB is available as a package within
+the Yocto Project and is installed in SDK images by default. See the
+":ref:`ref-manual/ref-images:Images`" chapter in the Yocto
+Project Reference Manual for a description of these images. You can find
+information on GDB at https://sourceware.org/gdb/.
+.. note::
+   For best results, install debug (``-dbg``) packages for the applications you
+   are going to debug. Doing so makes extra debug symbols available that give
+   you more meaningful output.
+Sometimes, due to memory or disk space constraints, it is not possible
+to use GDB directly on the remote target to debug applications. These
+constraints arise because GDB needs to load the debugging information
+and the binaries of the process being debugged. Additionally, GDB needs
+to perform many computations to locate information such as function
+names, variable names and values, stack traces and so forth - even
+before starting the debugging process. These extra computations place
+more load on the target system and can alter the characteristics of the
+program being debugged.
+To help get past the previously mentioned constraints, you can use
+gdbserver, which runs on the remote target and does not load any
+debugging information from the debugged process. Instead, a GDB instance
+processes the debugging information that is run on a remote computer -
+the host GDB. The host GDB then sends control commands to gdbserver to
+make it stop or start the debugged program, as well as read or write
+memory regions of that debugged program. All the debugging information
+loaded and processed as well as all the heavy debugging is done by the
+host GDB. Offloading these processes gives the gdbserver running on the
+target a chance to remain small and fast.
+Because the host GDB is responsible for loading the debugging
+information and for doing the necessary processing to make actual
+debugging happen, you have to make sure the host can access the
+unstripped binaries complete with their debugging information and also
+be sure the target is compiled with no optimizations. The host GDB must
+also have local access to all the libraries used by the debugged
+program. Because gdbserver does not need any local debugging
+information, the binaries on the remote target can remain stripped.
+However, the binaries must also be compiled without optimization so they
+match the host's binaries.
+To remain consistent with GDB documentation and terminology, the binary
+being debugged on the remote target machine is referred to as the
+"inferior" binary. For documentation on GDB see the `GDB
+site <https://sourceware.org/gdb/documentation/>`__.
+The following steps show you how to debug using the GNU project
+debugger.
+1. *Configure your build system to construct the companion debug
+   filesystem:*
+   In your ``local.conf`` file, set the following:
+   ::
+      IMAGE_GEN_DEBUGFS = "1"
+      IMAGE_FSTYPES_DEBUGFS = "tar.bz2"
+   These options cause the
+   OpenEmbedded build system to generate a special companion filesystem
+   fragment, which contains the matching source and debug symbols to
+   your deployable filesystem. The build system does this by looking at
+   what is in the deployed filesystem, and pulling the corresponding
+   ``-dbg`` packages.
+   The companion debug filesystem is not a complete filesystem, but only
+   contains the debug fragments. This filesystem must be combined with
+   the full filesystem for debugging. Subsequent steps in this procedure
+   show how to combine the partial filesystem with the full filesystem.
+2. *Configure the system to include gdbserver in the target filesystem:*
+   Make the following addition in either your ``local.conf`` file or in
+   an image recipe:
+   ::
+      IMAGE_INSTALL_append = " gdbserver"
+   The change makes
+   sure the ``gdbserver`` package is included.
+3. *Build the environment:*
+   Use the following command to construct the image and the companion
+   Debug Filesystem:
+   ::
+      $ bitbake image
+   Build the cross GDB component and
+   make it available for debugging. Build the SDK that matches the
+   image. Building the SDK is best for a production build that can be
+   used later for debugging, especially during long term maintenance:
+   ::
+      $ bitbake -c populate_sdk image
+   Alternatively, you can build the minimal toolchain components that
+   match the target. Doing so creates a smaller than typical SDK and
+   only contains a minimal set of components with which to build simple
+   test applications, as well as run the debugger:
+   ::
+      $ bitbake meta-toolchain
+   A final method is to build Gdb itself within the build system:
+   ::
+      $ bitbake gdb-cross-<architecture>
+   Doing so produces a temporary copy of
+   ``cross-gdb`` you can use for debugging during development. While
+   this is the quickest approach, the two previous methods in this step
+   are better when considering long-term maintenance strategies.
+   .. note::
+      If you run ``bitbake gdb-cross``, the OpenEmbedded build system suggests
+      the actual image (e.g. ``gdb-cross-i586``). The suggestion is usually the
+      actual name you want to use.
+4. *Set up the* ``debugfs``\ *:*
+   Run the following commands to set up the ``debugfs``:
+   ::
+      $ mkdir debugfs
+      $ cd debugfs
+      $ tar xvfj build-dir/tmp-glibc/deploy/images/machine/image.rootfs.tar.bz2
+      $ tar xvfj build-dir/tmp-glibc/deploy/images/machine/image-dbg.rootfs.tar.bz2
+5. *Set up GDB:*
+   Install the SDK (if you built one) and then source the correct
+   environment file. Sourcing the environment file puts the SDK in your
+   ``PATH`` environment variable.
+   If you are using the build system, Gdb is located in
+   `build-dir`\ ``/tmp/sysroots/``\ `host`\ ``/usr/bin/``\ `architecture`\ ``/``\ `architecture`\ ``-gdb``
+6. *Boot the target:*
+   For information on how to run QEMU, see the `QEMU
+   Documentation <https://wiki.qemu.org/Documentation/GettingStartedDevelopers>`__.
+   .. note::
+      Be sure to verify that your host can access the target via TCP.
+7. *Debug a program:*
+   Debugging a program involves running gdbserver on the target and then
+   running Gdb on the host. The example in this step debugs ``gzip``:
+   .. code-block:: shell
+      root@qemux86:~# gdbserver localhost:1234 /bin/gzip —help
+   For
+   additional gdbserver options, see the `GDB Server
+   Documentation <https://www.gnu.org/software/gdb/documentation/>`__.
+   After running gdbserver on the target, you need to run Gdb on the
+   host and configure it and connect to the target. Use these commands:
+   ::
+      $ cd directory-holding-the-debugfs-directory
+      $ arch-gdb
+      (gdb) set sysroot debugfs
+      (gdb) set substitute-path /usr/src/debug debugfs/usr/src/debug
+      (gdb) target remote IP-of-target:1234
+   At this
+   point, everything should automatically load (i.e. matching binaries,
+   symbols and headers).
+   .. note::
+      The Gdb ``set`` commands in the previous example can be placed into the
+      users ``~/.gdbinit`` file. Upon starting, Gdb automatically runs whatever
+      commands are in that file.
+8. *Deploying without a full image rebuild:*
+   In many cases, during development you want a quick method to deploy a
+   new binary to the target and debug it, without waiting for a full
+   image build.
+   One approach to solving this situation is to just build the component
+   you want to debug. Once you have built the component, copy the
+   executable directly to both the target and the host ``debugfs``.
+   If the binary is processed through the debug splitting in
+   OpenEmbedded, you should also copy the debug items (i.e. ``.debug``
+   contents and corresponding ``/usr/src/debug`` files) from the work
+   directory. Here is an example:
+   ::
+      $ bitbake bash
+      $ bitbake -c devshell bash
+      $ cd ..
+      $ scp packages-split/bash/bin/bash target:/bin/bash
+      $ cp -a packages-split/bash-dbg/\* path/debugfs
+Debugging with the GNU Project Debugger (GDB) on the Target
+-----------------------------------------------------------
+The previous section addressed using GDB remotely for debugging
+purposes, which is the most usual case due to the inherent hardware
+limitations on many embedded devices. However, debugging in the target
+hardware itself is also possible with more powerful devices. This
+section describes what you need to do in order to support using GDB to
+debug on the target hardware.
+To support this kind of debugging, you need do the following:
+-  Ensure that GDB is on the target. You can do this by adding "gdb" to
+   :term:`IMAGE_INSTALL`:
+   ::
+      IMAGE_INSTALL_append = " gdb"
+   Alternatively, you can add "tools-debug" to :term:`IMAGE_FEATURES`:
+   ::
+      IMAGE_FEATURES_append = " tools-debug"
+-  Ensure that debug symbols are present. You can make sure these
+   symbols are present by installing ``-dbg``:
+   ::
+      IMAGE_INSTALL_append = "packagename-dbg"
+   Alternatively, you can do the following to include
+   all the debug symbols:
+   ::
+      IMAGE_FEATURES_append = " dbg-pkgs"
+.. note::
+   To improve the debug information accuracy, you can reduce the level
+   of optimization used by the compiler. For example, when adding the
+   following line to your ``local.conf`` file, you will reduce optimization
+   from :term:`FULL_OPTIMIZATION` of "-O2" to :term:`DEBUG_OPTIMIZATION`
+   of "-O -fno-omit-frame-pointer":
+   ::
+           DEBUG_BUILD = "1"
+   Consider that this will reduce the application's performance and is
+   recommended only for debugging purposes.
+Other Debugging Tips
+--------------------
+Here are some other tips that you might find useful:
+-  When adding new packages, it is worth watching for undesirable items
+   making their way into compiler command lines. For example, you do not
+   want references to local system files like ``/usr/lib/`` or
+   ``/usr/include/``.
+-  If you want to remove the ``psplash`` boot splashscreen, add
+   ``psplash=false`` to the kernel command line. Doing so prevents
+   ``psplash`` from loading and thus allows you to see the console. It
+   is also possible to switch out of the splashscreen by switching the
+   virtual console (e.g. Fn+Left or Fn+Right on a Zaurus).
+-  Removing :term:`TMPDIR` (usually
+   ``tmp/``, within the
+   :term:`Build Directory`) can often fix
+   temporary build issues. Removing ``TMPDIR`` is usually a relatively
+   cheap operation, because task output will be cached in
+   :term:`SSTATE_DIR` (usually
+   ``sstate-cache/``, which is also in the Build Directory).
+   .. note::
+      Removing ``TMPDIR`` might be a workaround rather than a fix.
+      Consequently, trying to determine the underlying cause of an issue before
+      removing the directory is a good idea.
+-  Understanding how a feature is used in practice within existing
+   recipes can be very helpful. It is recommended that you configure
+   some method that allows you to quickly search through files.
+   Using GNU Grep, you can use the following shell function to
+   recursively search through common recipe-related files, skipping
+   binary files, ``.git`` directories, and the Build Directory (assuming
+   its name starts with "build"):
+   ::
+      g() {
+          grep -Ir \
+               --exclude-dir=.git \
+               --exclude-dir='build*' \
+               --include='*.bb*' \
+               --include='*.inc*' \
+               --include='*.conf*' \
+               --include='*.py*' \
+               "$@"
+      }
+   Following are some usage examples:
+   ::
+      $ g FOO # Search recursively for "FOO"
+      $ g -i foo # Search recursively for "foo", ignoring case
+      $ g -w FOO # Search recursively for "FOO" as a word, ignoring e.g. "FOOBAR"
+   If figuring
+   out how some feature works requires a lot of searching, it might
+   indicate that the documentation should be extended or improved. In
+   such cases, consider filing a documentation bug using the Yocto
+   Project implementation of
+   :yocto_bugs:`Bugzilla <>`. For information on
+   how to submit a bug against the Yocto Project, see the Yocto Project
+   Bugzilla :yocto_wiki:`wiki page </Bugzilla_Configuration_and_Bug_Tracking>`
+   and the "`Submitting a Defect Against the Yocto
+   Project <#submitting-a-defect-against-the-yocto-project>`__" section.
+   .. note::
+      The manuals might not be the right place to document variables
+      that are purely internal and have a limited scope (e.g. internal
+      variables used to implement a single ``.bbclass`` file).
+Making Changes to the Yocto Project
+===================================
+Because the Yocto Project is an open-source, community-based project,
+you can effect changes to the project. This section presents procedures
+that show you how to submit a defect against the project and how to
+submit a change.
+Submitting a Defect Against the Yocto Project
+---------------------------------------------
+Use the Yocto Project implementation of
+`Bugzilla <https://www.bugzilla.org/about/>`__ to submit a defect (bug)
+against the Yocto Project. For additional information on this
+implementation of Bugzilla see the ":ref:`Yocto Project
+Bugzilla <resources-bugtracker>`" section in the
+Yocto Project Reference Manual. For more detail on any of the following
+steps, see the Yocto Project
+:yocto_wiki:`Bugzilla wiki page </Bugzilla_Configuration_and_Bug_Tracking>`.
+Use the following general steps to submit a bug:
+1.  Open the Yocto Project implementation of :yocto_bugs:`Bugzilla <>`.
+2.  Click "File a Bug" to enter a new bug.
+3.  Choose the appropriate "Classification", "Product", and "Component"
+    for which the bug was found. Bugs for the Yocto Project fall into
+    one of several classifications, which in turn break down into
+    several products and components. For example, for a bug against the
+    ``meta-intel`` layer, you would choose "Build System, Metadata &
+    Runtime", "BSPs", and "bsps-meta-intel", respectively.
+4.  Choose the "Version" of the Yocto Project for which you found the
+    bug (e.g. &DISTRO;).
+5.  Determine and select the "Severity" of the bug. The severity
+    indicates how the bug impacted your work.
+6.  Choose the "Hardware" that the bug impacts.
+7.  Choose the "Architecture" that the bug impacts.
+8.  Choose a "Documentation change" item for the bug. Fixing a bug might
+    or might not affect the Yocto Project documentation. If you are
+    unsure of the impact to the documentation, select "Don't Know".
+9.  Provide a brief "Summary" of the bug. Try to limit your summary to
+    just a line or two and be sure to capture the essence of the bug.
+10. Provide a detailed "Description" of the bug. You should provide as
+    much detail as you can about the context, behavior, output, and so
+    forth that surrounds the bug. You can even attach supporting files
+    for output from logs by using the "Add an attachment" button.
+11. Click the "Submit Bug" button submit the bug. A new Bugzilla number
+    is assigned to the bug and the defect is logged in the bug tracking
+    system.
+Once you file a bug, the bug is processed by the Yocto Project Bug
+Triage Team and further details concerning the bug are assigned (e.g.
+priority and owner). You are the "Submitter" of the bug and any further
+categorization, progress, or comments on the bug result in Bugzilla
+sending you an automated email concerning the particular change or
+progress to the bug.
+Submitting a Change to the Yocto Project
+----------------------------------------
+Contributions to the Yocto Project and OpenEmbedded are very welcome.
+Because the system is extremely configurable and flexible, we recognize
+that developers will want to extend, configure or optimize it for their
+specific uses.
+The Yocto Project uses a mailing list and a patch-based workflow that is
+similar to the Linux kernel but contains important differences. In
+general, a mailing list exists through which you can submit patches. You
+should send patches to the appropriate mailing list so that they can be
+reviewed and merged by the appropriate maintainer. The specific mailing
+list you need to use depends on the location of the code you are
+changing. Each component (e.g. layer) should have a ``README`` file that
+indicates where to send the changes and which process to follow.
+You can send the patch to the mailing list using whichever approach you
+feel comfortable with to generate the patch. Once sent, the patch is
+usually reviewed by the community at large. If somebody has concerns
+with the patch, they will usually voice their concern over the mailing
+list. If a patch does not receive any negative reviews, the maintainer
+of the affected layer typically takes the patch, tests it, and then
+based on successful testing, merges the patch.
+The "poky" repository, which is the Yocto Project's reference build
+environment, is a hybrid repository that contains several individual
+pieces (e.g. BitBake, Metadata, documentation, and so forth) built using
+the combo-layer tool. The upstream location used for submitting changes
+varies by component:
+-  *Core Metadata:* Send your patch to the
+   :oe_lists:`openembedded-core </g/openembedded-core>`
+   mailing list. For example, a change to anything under the ``meta`` or
+   ``scripts`` directories should be sent to this mailing list.
+-  *BitBake:* For changes to BitBake (i.e. anything under the
+   ``bitbake`` directory), send your patch to the
+   :oe_lists:`bitbake-devel </g/bitbake-devel>`
+   mailing list.
+-  *"meta-\*" trees:* These trees contain Metadata. Use the
+   :yocto_lists:`poky </g/poky>` mailing list.
+-  *Documentation*: For changes to the Yocto Project documentation, use the
+   :yocto_lists:`docs </g/docs>` mailing list.
+For changes to other layers hosted in the Yocto Project source
+repositories (i.e. ``yoctoproject.org``) and tools use the
+:yocto_lists:`Yocto Project </g/yocto/>` general mailing list.
+.. note::
+   Sometimes a layer's documentation specifies to use a particular
+   mailing list. If so, use that list.
+For additional recipes that do not fit into the core Metadata, you
+should determine which layer the recipe should go into and submit the
+change in the manner recommended by the documentation (e.g. the
+``README`` file) supplied with the layer. If in doubt, please ask on the
+Yocto general mailing list or on the openembedded-devel mailing list.
+You can also push a change upstream and request a maintainer to pull the
+change into the component's upstream repository. You do this by pushing
+to a contribution repository that is upstream. See the
+":ref:`overview-manual/overview-manual-development-environment:git workflows and the yocto project`"
+section in the Yocto Project Overview and Concepts Manual for additional
+concepts on working in the Yocto Project development environment.
+Maintainers commonly use ``-next`` branches to test submissions prior to
+merging patches. Thus, you can get an idea of the status of a patch based on
+whether the patch has been merged into one of these branches. The commonly
+used testing branches for OpenEmbedded-Core are as follows:
+-  *openembedded-core "master-next" branch:* This branch is part of the
+   :oe_git:`openembedded-core </openembedded-core/>` repository and contains
+   proposed changes to the core metadata.
+-  *poky "master-next" branch:* This branch is part of the
+   :yocto_git:`poky </poky/>` repository and combines proposed
+   changes to bitbake, the core metadata and the poky distro.
+Similarly, stable branches maintained by the project may have corresponding
+``-next`` branches which collect proposed changes. For example,
+``&DISTRO_NAME_NO_CAP;-next`` and ``&DISTRO_NAME_NO_CAP_MINUS_ONE;-next``
+branches in both the "openembdedded-core" and "poky" repositories.
+Other layers may have similar testing branches but there is no formal
+requirement or standard for these so please check the documentation for the
+layers you are contributing to.
+The following sections provide procedures for submitting a change.
+Preparing Changes for Submission
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+1. *Make Your Changes Locally:* Make your changes in your local Git
+   repository. You should make small, controlled, isolated changes.
+   Keeping changes small and isolated aids review, makes
+   merging/rebasing easier and keeps the change history clean should
+   anyone need to refer to it in future.
+2. *Stage Your Changes:* Stage your changes by using the ``git add``
+   command on each file you changed.
+3. *Commit Your Changes:* Commit the change by using the ``git commit``
+   command. Make sure your commit information follows standards by
+   following these accepted conventions:
+   -  Be sure to include a "Signed-off-by:" line in the same style as
+      required by the Linux kernel. Adding this line signifies that you,
+      the submitter, have agreed to the Developer's Certificate of
+      Origin 1.1 as follows:
+      .. code-block:: none
+         Developer's Certificate of Origin 1.1
+         By making a contribution to this project, I certify that:
+         (a) The contribution was created in whole or in part by me and I
+             have the right to submit it under the open source license
+             indicated in the file; or
+         (b) The contribution is based upon previous work that, to the best
+             of my knowledge, is covered under an appropriate open source
+             license and I have the right under that license to submit that
+             work with modifications, whether created in whole or in part
+             by me, under the same open source license (unless I am
+             permitted to submit under a different license), as indicated
+             in the file; or
+         (c) The contribution was provided directly to me by some other
+             person who certified (a), (b) or (c) and I have not modified
+             it.
+         (d) I understand and agree that this project and the contribution
+             are public and that a record of the contribution (including all
+             personal information I submit with it, including my sign-off) is
+             maintained indefinitely and may be redistributed consistent with
+             this project or the open source license(s) involved.
+   -  Provide a single-line summary of the change and, if more
+      explanation is needed, provide more detail in the body of the
+      commit. This summary is typically viewable in the "shortlist" of
+      changes. Thus, providing something short and descriptive that
+      gives the reader a summary of the change is useful when viewing a
+      list of many commits. You should prefix this short description
+      with the recipe name (if changing a recipe), or else with the
+      short form path to the file being changed.
+   -  For the body of the commit message, provide detailed information
+      that describes what you changed, why you made the change, and the
+      approach you used. It might also be helpful if you mention how you
+      tested the change. Provide as much detail as you can in the body
+      of the commit message.
+      .. note::
+         You do not need to provide a more detailed explanation of a
+         change if the change is minor to the point of the single line
+         summary providing all the information.
+   -  If the change addresses a specific bug or issue that is associated
+      with a bug-tracking ID, include a reference to that ID in your
+      detailed description. For example, the Yocto Project uses a
+      specific convention for bug references - any commit that addresses
+      a specific bug should use the following form for the detailed
+      description. Be sure to use the actual bug-tracking ID from
+      Bugzilla for bug-id:
+      ::
+         Fixes [YOCTO #bug-id]
+         detailed description of change
+Using Email to Submit a Patch
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Depending on the components changed, you need to submit the email to a
+specific mailing list. For some guidance on which mailing list to use,
+see the `list <#figuring-out-the-mailing-list-to-use>`__ at the
+beginning of this section. For a description of all the available
+mailing lists, see the ":ref:`Mailing Lists <resources-mailinglist>`" section in the
+Yocto Project Reference Manual.
+Here is the general procedure on how to submit a patch through email
+without using the scripts once the steps in
+:ref:`dev-manual/common-tasks:preparing changes for submission` have been followed:
+1. *Format the Commit:* Format the commit into an email message. To
+   format commits, use the ``git format-patch`` command. When you
+   provide the command, you must include a revision list or a number of
+   patches as part of the command. For example, either of these two
+   commands takes your most recent single commit and formats it as an
+   email message in the current directory:
+   ::
+      $ git format-patch -1
+   or ::
+      $ git format-patch HEAD~
+   After the command is run, the current directory contains a numbered
+   ``.patch`` file for the commit.
+   If you provide several commits as part of the command, the
+   ``git format-patch`` command produces a series of numbered files in
+   the current directory – one for each commit. If you have more than
+   one patch, you should also use the ``--cover`` option with the
+   command, which generates a cover letter as the first "patch" in the
+   series. You can then edit the cover letter to provide a description
+   for the series of patches. For information on the
+   ``git format-patch`` command, see ``GIT_FORMAT_PATCH(1)`` displayed
+   using the ``man git-format-patch`` command.
+   .. note::
+      If you are or will be a frequent contributor to the Yocto Project
+      or to OpenEmbedded, you might consider requesting a contrib area
+      and the necessary associated rights.
+2. *Send the patches via email:* Send the patches to the recipients and
+   relevant mailing lists by using the ``git send-email`` command.
+   .. note::
+      In order to use ``git send-email``, you must have the proper Git packages
+      installed on your host.
+      For Ubuntu, Debian, and Fedora the package is ``git-email``.
+   The ``git send-email`` command sends email by using a local or remote
+   Mail Transport Agent (MTA) such as ``msmtp``, ``sendmail``, or
+   through a direct ``smtp`` configuration in your Git ``~/.gitconfig``
+   file. If you are submitting patches through email only, it is very
+   important that you submit them without any whitespace or HTML
+   formatting that either you or your mailer introduces. The maintainer
+   that receives your patches needs to be able to save and apply them
+   directly from your emails. A good way to verify that what you are
+   sending will be applicable by the maintainer is to do a dry run and
+   send them to yourself and then save and apply them as the maintainer
+   would.
+   The ``git send-email`` command is the preferred method for sending
+   your patches using email since there is no risk of compromising
+   whitespace in the body of the message, which can occur when you use
+   your own mail client. The command also has several options that let
+   you specify recipients and perform further editing of the email
+   message. For information on how to use the ``git send-email``
+   command, see ``GIT-SEND-EMAIL(1)`` displayed using the
+   ``man git-send-email`` command.
+The Yocto Project uses a `Patchwork instance <https://patchwork.openembedded.org/>`__
+to track the status of patches submitted to the various mailing lists and to
+support automated patch testing. Each submitted patch is checked for common
+mistakes and deviations from the expected patch format and submitters are
+notified by patchtest if such mistakes are found. This process helps to
+reduce the burden of patch review on maintainers.
+.. note::
+   This system is imperfect and changes can sometimes get lost in the flow.
+   Asking about the status of a patch or change is reasonable if the change
+   has been idle for a while with no feedback.
+Using Scripts to Push a Change Upstream and Request a Pull
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+For larger patch series it is preferable to send a pull request which not
+only includes the patch but also a pointer to a branch that can be pulled
+from. This involves making a local branch for your changes, pushing this
+branch to an accessible repository and then using the ``create-pull-request``
+and ``send-pull-request`` scripts from openembedded-core to create and send a
+patch series with a link to the branch for review.
+Follow this procedure to push a change to an upstream "contrib" Git
+repository once the steps in :ref:`dev-manual/common-tasks:preparing changes for submission` have
+been followed:
+.. note::
+   You can find general Git information on how to push a change upstream
+   in the
+   `Git Community Book <https://git-scm.com/book/en/v2/Distributed-Git-Distributed-Workflows>`__.
+1. *Push Your Commits to a "Contrib" Upstream:* If you have arranged for
+   permissions to push to an upstream contrib repository, push the
+   change to that repository:
+   ::
+      $ git push upstream_remote_repo local_branch_name
+   For example, suppose you have permissions to push
+   into the upstream ``meta-intel-contrib`` repository and you are
+   working in a local branch named `your_name`\ ``/README``. The following
+   command pushes your local commits to the ``meta-intel-contrib``
+   upstream repository and puts the commit in a branch named
+   `your_name`\ ``/README``:
+   ::
+      $ git push meta-intel-contrib your_name/README
+2. *Determine Who to Notify:* Determine the maintainer or the mailing
+   list that you need to notify for the change.
+   Before submitting any change, you need to be sure who the maintainer
+   is or what mailing list that you need to notify. Use either these
+   methods to find out:
+   -  *Maintenance File:* Examine the ``maintainers.inc`` file, which is
+      located in the :term:`Source Directory` at
+      ``meta/conf/distro/include``, to see who is responsible for code.
+   -  *Search by File:* Using :ref:`overview-manual/overview-manual-development-environment:git`, you can
+      enter the following command to bring up a short list of all
+      commits against a specific file:
+      ::
+         git shortlog -- filename
+      Just provide the name of the file for which you are interested. The
+      information returned is not ordered by history but does include a
+      list of everyone who has committed grouped by name. From the list,
+      you can see who is responsible for the bulk of the changes against
+      the file.
+   -  *Examine the List of Mailing Lists:* For a list of the Yocto
+      Project and related mailing lists, see the ":ref:`Mailing
+      lists <resources-mailinglist>`" section in
+      the Yocto Project Reference Manual.
+3. *Make a Pull Request:* Notify the maintainer or the mailing list that
+   you have pushed a change by making a pull request.
+   The Yocto Project provides two scripts that conveniently let you
+   generate and send pull requests to the Yocto Project. These scripts
+   are ``create-pull-request`` and ``send-pull-request``. You can find
+   these scripts in the ``scripts`` directory within the
+   :term:`Source Directory` (e.g.
+   ``~/poky/scripts``).
+   Using these scripts correctly formats the requests without
+   introducing any whitespace or HTML formatting. The maintainer that
+   receives your patches either directly or through the mailing list
+   needs to be able to save and apply them directly from your emails.
+   Using these scripts is the preferred method for sending patches.
+   First, create the pull request. For example, the following command
+   runs the script, specifies the upstream repository in the contrib
+   directory into which you pushed the change, and provides a subject
+   line in the created patch files:
+   ::
+      $ ~/poky/scripts/create-pull-request -u meta-intel-contrib -s "Updated Manual Section Reference in README"
+   Running this script forms ``*.patch`` files in a folder named
+   ``pull-``\ `PID` in the current directory. One of the patch files is a
+   cover letter.
+   Before running the ``send-pull-request`` script, you must edit the
+   cover letter patch to insert information about your change. After
+   editing the cover letter, send the pull request. For example, the
+   following command runs the script and specifies the patch directory
+   and email address. In this example, the email address is a mailing
+   list:
+   ::
+      $ ~/poky/scripts/send-pull-request -p ~/meta-intel/pull-10565 -t meta-intel@yoctoproject.org
+   You need to follow the prompts as the script is interactive.
+   .. note::
+      For help on using these scripts, simply provide the ``-h``
+      argument as follows:
+      ::
+              $ poky/scripts/create-pull-request -h
+              $ poky/scripts/send-pull-request -h
+Responding to Patch Review
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+You may get feedback on your submitted patches from other community members
+or from the automated patchtest service. If issues are identified in your
+patch then it is usually necessary to address these before the patch will be
+accepted into the project. In this case you should amend the patch according
+to the feedback and submit an updated version to the relevant mailing list,
+copying in the reviewers who provided feedback to the previous version of the
+patch.
+The patch should be amended using ``git commit --amend`` or perhaps ``git
+rebase`` for more expert git users. You should also modify the ``[PATCH]``
+tag in the email subject line when sending the revised patch to mark the new
+iteration as ``[PATCH v2]``, ``[PATCH v3]``, etc as appropriate. This can be
+done by passing the ``-v`` argument to ``git format-patch`` with a version
+number.
+Lastly please ensure that you also test your revised changes. In particular
+please don't just edit the patch file written out by ``git format-patch`` and
+resend it.
+Submitting Changes to Stable Release Branches
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The process for proposing changes to a Yocto Project stable branch differs
+from the steps described above. Changes to a stable branch must address
+identified bugs or CVEs and should be made carefully in order to avoid the
+risk of introducing new bugs or breaking backwards compatibility. Typically
+bug fixes must already be accepted into the master branch before they can be
+backported to a stable branch unless the bug in question does not affect the
+master branch or the fix on the master branch is unsuitable for backporting.
+The list of stable branches along with the status and maintainer for each
+branch can be obtained from the
+:yocto_wiki:`Releases wiki page </Releases>`.
+.. note::
+   Changes will not typically be accepted for branches which are marked as
+   End-Of-Life (EOL).
+With this in mind, the steps to submit a change for a stable branch are as
+follows:
+1. *Identify the bug or CVE to be fixed:* This information should be
+   collected so that it can be included in your submission.
+2. *Check if the fix is already present in the master branch:* This will
+   result in the most straightforward path into the stable branch for the
+   fix.
+   a. *If the fix is present in the master branch - Submit a backport request
+      by email:* You should send an email to the relevant stable branch
+      maintainer and the mailing list with details of the bug or CVE to be
+      fixed, the commit hash on the master branch that fixes the issue and
+      the stable branches which you would like this fix to be backported to.
+   b. *If the fix is not present in the master branch - Submit the fix to the
+      master branch first:* This will ensure that the fix passes through the
+      project's usual patch review and test processes before being accepted.
+      It will also ensure that bugs are not left unresolved in the master
+      branch itself. Once the fix is accepted in the master branch a backport
+      request can be submitted as above.
+   c. *If the fix is unsuitable for the master branch - Submit a patch
+      directly for the stable branch:* This method should be considered as a
+      last resort. It is typically necessary when the master branch is using
+      a newer version of the software which includes an upstream fix for the
+      issue or when the issue has been fixed on the master branch in a way
+      that introduces backwards incompatible changes. In this case follow the
+      steps in :ref:`dev-manual/common-tasks:preparing changes for submission` and
+      :ref:`dev-manual/common-tasks:using email to submit a patch` but modify the subject header of your patch
+      email to include the name of the stable branch which you are
+      targetting. This can be done using the ``--subject-prefix`` argument to
+      ``git format-patch``, for example to submit a patch to the dunfell
+      branch use
+      ``git format-patch --subject-prefix='&DISTRO_NAME_NO_CAP_MINUS_ONE;][PATCH' ...``.
+Working With Licenses
+=====================
+As mentioned in the ":ref:`overview-manual/overview-manual-development-environment:licensing`"
+section in the Yocto Project Overview and Concepts Manual, open source
+projects are open to the public and they consequently have different
+licensing structures in place. This section describes the mechanism by
+which the :term:`OpenEmbedded Build System`
+tracks changes to
+licensing text and covers how to maintain open source license compliance
+during your project's lifecycle. The section also describes how to
+enable commercially licensed recipes, which by default are disabled.
+Tracking License Changes
+------------------------
+The license of an upstream project might change in the future. In order
+to prevent these changes going unnoticed, the
+:term:`LIC_FILES_CHKSUM`
+variable tracks changes to the license text. The checksums are validated
+at the end of the configure step, and if the checksums do not match, the
+build will fail.
+Specifying the ``LIC_FILES_CHKSUM`` Variable
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The ``LIC_FILES_CHKSUM`` variable contains checksums of the license text
+in the source code for the recipe. Following is an example of how to
+specify ``LIC_FILES_CHKSUM``:
+::
+   LIC_FILES_CHKSUM = "file://COPYING;md5=xxxx \
+                       file://licfile1.txt;beginline=5;endline=29;md5=yyyy \
+                       file://licfile2.txt;endline=50;md5=zzzz \
+                       ..."
+.. note::
+   -  When using "beginline" and "endline", realize that line numbering
+      begins with one and not zero. Also, the included lines are
+      inclusive (i.e. lines five through and including 29 in the
+      previous example for ``licfile1.txt``).
+   -  When a license check fails, the selected license text is included
+      as part of the QA message. Using this output, you can determine
+      the exact start and finish for the needed license text.
+The build system uses the :term:`S`
+variable as the default directory when searching files listed in
+``LIC_FILES_CHKSUM``. The previous example employs the default
+directory.
+Consider this next example:
+::
+   LIC_FILES_CHKSUM = "file://src/ls.c;beginline=5;endline=16;\
+                                       md5=bb14ed3c4cda583abc85401304b5cd4e"
+   LIC_FILES_CHKSUM = "file://${WORKDIR}/license.html;md5=5c94767cedb5d6987c902ac850ded2c6"
+The first line locates a file in ``${S}/src/ls.c`` and isolates lines
+five through 16 as license text. The second line refers to a file in
+:term:`WORKDIR`.
+Note that ``LIC_FILES_CHKSUM`` variable is mandatory for all recipes,
+unless the ``LICENSE`` variable is set to "CLOSED".
+Explanation of Syntax
+~~~~~~~~~~~~~~~~~~~~~
+As mentioned in the previous section, the ``LIC_FILES_CHKSUM`` variable
+lists all the important files that contain the license text for the
+source code. It is possible to specify a checksum for an entire file, or
+a specific section of a file (specified by beginning and ending line
+numbers with the "beginline" and "endline" parameters, respectively).
+The latter is useful for source files with a license notice header,
+README documents, and so forth. If you do not use the "beginline"
+parameter, then it is assumed that the text begins on the first line of
+the file. Similarly, if you do not use the "endline" parameter, it is
+assumed that the license text ends with the last line of the file.
+The "md5" parameter stores the md5 checksum of the license text. If the
+license text changes in any way as compared to this parameter then a
+mismatch occurs. This mismatch triggers a build failure and notifies the
+developer. Notification allows the developer to review and address the
+license text changes. Also note that if a mismatch occurs during the
+build, the correct md5 checksum is placed in the build log and can be
+easily copied to the recipe.
+There is no limit to how many files you can specify using the
+``LIC_FILES_CHKSUM`` variable. Generally, however, every project
+requires a few specifications for license tracking. Many projects have a
+"COPYING" file that stores the license information for all the source
+code files. This practice allows you to just track the "COPYING" file as
+long as it is kept up to date.
+.. note::
+   -  If you specify an empty or invalid "md5" parameter,
+      :term:`BitBake` returns an md5
+      mis-match error and displays the correct "md5" parameter value
+      during the build. The correct parameter is also captured in the
+      build log.
+   -  If the whole file contains only license text, you do not need to
+      use the "beginline" and "endline" parameters.
+Enabling Commercially Licensed Recipes
+--------------------------------------
+By default, the OpenEmbedded build system disables components that have
+commercial or other special licensing requirements. Such requirements
+are defined on a recipe-by-recipe basis through the
+:term:`LICENSE_FLAGS` variable
+definition in the affected recipe. For instance, the
+``poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly`` recipe
+contains the following statement:
+::
+   LICENSE_FLAGS = "commercial"
+Here is a
+slightly more complicated example that contains both an explicit recipe
+name and version (after variable expansion):
+::
+   LICENSE_FLAGS = "license_${PN}_${PV}"
+In order for a component restricted by a
+``LICENSE_FLAGS`` definition to be enabled and included in an image, it
+needs to have a matching entry in the global
+:term:`LICENSE_FLAGS_WHITELIST`
+variable, which is a variable typically defined in your ``local.conf``
+file. For example, to enable the
+``poky/meta/recipes-multimedia/gstreamer/gst-plugins-ugly`` package, you
+could add either the string "commercial_gst-plugins-ugly" or the more
+general string "commercial" to ``LICENSE_FLAGS_WHITELIST``. See the
+"`License Flag Matching <#license-flag-matching>`__" section for a full
+explanation of how ``LICENSE_FLAGS`` matching works. Here is the
+example:
+::
+   LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly"
+Likewise, to additionally enable the package built from the recipe
+containing ``LICENSE_FLAGS = "license_${PN}_${PV}"``, and assuming that
+the actual recipe name was ``emgd_1.10.bb``, the following string would
+enable that package as well as the original ``gst-plugins-ugly``
+package:
+::
+   LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly license_emgd_1.10"
+As a convenience, you do not need to specify the
+complete license string in the whitelist for every package. You can use
+an abbreviated form, which consists of just the first portion or
+portions of the license string before the initial underscore character
+or characters. A partial string will match any license that contains the
+given string as the first portion of its license. For example, the
+following whitelist string will also match both of the packages
+previously mentioned as well as any other packages that have licenses
+starting with "commercial" or "license".
+::
+   LICENSE_FLAGS_WHITELIST = "commercial license"
+License Flag Matching
+~~~~~~~~~~~~~~~~~~~~~
+License flag matching allows you to control what recipes the
+OpenEmbedded build system includes in the build. Fundamentally, the
+build system attempts to match ``LICENSE_FLAGS`` strings found in
+recipes against ``LICENSE_FLAGS_WHITELIST`` strings found in the
+whitelist. A match causes the build system to include a recipe in the
+build, while failure to find a match causes the build system to exclude
+a recipe.
+In general, license flag matching is simple. However, understanding some
+concepts will help you correctly and effectively use matching.
+Before a flag defined by a particular recipe is tested against the
+contents of the whitelist, the expanded string ``_${PN}`` is appended to
+the flag. This expansion makes each ``LICENSE_FLAGS`` value
+recipe-specific. After expansion, the string is then matched against the
+whitelist. Thus, specifying ``LICENSE_FLAGS = "commercial"`` in recipe
+"foo", for example, results in the string ``"commercial_foo"``. And, to
+create a match, that string must appear in the whitelist.
+Judicious use of the ``LICENSE_FLAGS`` strings and the contents of the
+``LICENSE_FLAGS_WHITELIST`` variable allows you a lot of flexibility for
+including or excluding recipes based on licensing. For example, you can
+broaden the matching capabilities by using license flags string subsets
+in the whitelist.
+.. note::
+   When using a string subset, be sure to use the part of the expanded
+   string that precedes the appended underscore character (e.g.
+   ``usethispart_1.3``, ``usethispart_1.4``, and so forth).
+For example, simply specifying the string "commercial" in the whitelist
+matches any expanded ``LICENSE_FLAGS`` definition that starts with the
+string "commercial" such as "commercial_foo" and "commercial_bar", which
+are the strings the build system automatically generates for
+hypothetical recipes named "foo" and "bar" assuming those recipes simply
+specify the following:
+::
+   LICENSE_FLAGS = "commercial"
+Thus, you can choose
+to exhaustively enumerate each license flag in the whitelist and allow
+only specific recipes into the image, or you can use a string subset
+that causes a broader range of matches to allow a range of recipes into
+the image.
+This scheme works even if the ``LICENSE_FLAGS`` string already has
+``_${PN}`` appended. For example, the build system turns the license
+flag "commercial_1.2_foo" into "commercial_1.2_foo_foo" and would match
+both the general "commercial" and the specific "commercial_1.2_foo"
+strings found in the whitelist, as expected.
+Here are some other scenarios:
+-  You can specify a versioned string in the recipe such as
+   "commercial_foo_1.2" in a "foo" recipe. The build system expands this
+   string to "commercial_foo_1.2_foo". Combine this license flag with a
+   whitelist that has the string "commercial" and you match the flag
+   along with any other flag that starts with the string "commercial".
+-  Under the same circumstances, you can use "commercial_foo" in the
+   whitelist and the build system not only matches "commercial_foo_1.2"
+   but also matches any license flag with the string "commercial_foo",
+   regardless of the version.
+-  You can be very specific and use both the package and version parts
+   in the whitelist (e.g. "commercial_foo_1.2") to specifically match a
+   versioned recipe.
+Other Variables Related to Commercial Licenses
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Other helpful variables related to commercial license handling exist and
+are defined in the
+``poky/meta/conf/distro/include/default-distrovars.inc`` file:
+::
+   COMMERCIAL_AUDIO_PLUGINS ?= ""
+   COMMERCIAL_VIDEO_PLUGINS ?= ""
+If you
+want to enable these components, you can do so by making sure you have
+statements similar to the following in your ``local.conf`` configuration
+file:
+::
+   COMMERCIAL_AUDIO_PLUGINS = "gst-plugins-ugly-mad \
+       gst-plugins-ugly-mpegaudioparse"
+   COMMERCIAL_VIDEO_PLUGINS = "gst-plugins-ugly-mpeg2dec \
+       gst-plugins-ugly-mpegstream gst-plugins-bad-mpegvideoparse"
+   LICENSE_FLAGS_WHITELIST = "commercial_gst-plugins-ugly commercial_gst-plugins-bad commercial_qmmp"
+Of course, you could also create a matching whitelist for those
+components using the more general "commercial" in the whitelist, but
+that would also enable all the other packages with ``LICENSE_FLAGS``
+containing "commercial", which you may or may not want:
+::
+   LICENSE_FLAGS_WHITELIST = "commercial"
+Specifying audio and video plugins as part of the
+``COMMERCIAL_AUDIO_PLUGINS`` and ``COMMERCIAL_VIDEO_PLUGINS`` statements
+(along with the enabling ``LICENSE_FLAGS_WHITELIST``) includes the
+plugins or components into built images, thus adding support for media
+formats or components.
+Maintaining Open Source License Compliance During Your Product's Lifecycle
+--------------------------------------------------------------------------
+One of the concerns for a development organization using open source
+software is how to maintain compliance with various open source
+licensing during the lifecycle of the product. While this section does
+not provide legal advice or comprehensively cover all scenarios, it does
+present methods that you can use to assist you in meeting the compliance
+requirements during a software release.
+With hundreds of different open source licenses that the Yocto Project
+tracks, it is difficult to know the requirements of each and every
+license. However, the requirements of the major FLOSS licenses can begin
+to be covered by assuming that three main areas of concern exist:
+-  Source code must be provided.
+-  License text for the software must be provided.
+-  Compilation scripts and modifications to the source code must be
+   provided.
+-  spdx files can be provided.
+There are other requirements beyond the scope of these three and the
+methods described in this section (e.g. the mechanism through which
+source code is distributed).
+As different organizations have different methods of complying with open
+source licensing, this section is not meant to imply that there is only
+one single way to meet your compliance obligations, but rather to
+describe one method of achieving compliance. The remainder of this
+section describes methods supported to meet the previously mentioned
+three requirements. Once you take steps to meet these requirements, and
+prior to releasing images, sources, and the build system, you should
+audit all artifacts to ensure completeness.
+.. note::
+   The Yocto Project generates a license manifest during image creation
+   that is located in ``${DEPLOY_DIR}/licenses/``\ `image_name`\ ``-``\ `datestamp`
+   to assist with any audits.
+Providing the Source Code
+~~~~~~~~~~~~~~~~~~~~~~~~~
+Compliance activities should begin before you generate the final image.
+The first thing you should look at is the requirement that tops the list
+for most compliance groups - providing the source. The Yocto Project has
+a few ways of meeting this requirement.
+One of the easiest ways to meet this requirement is to provide the
+entire :term:`DL_DIR` used by the
+build. This method, however, has a few issues. The most obvious is the
+size of the directory since it includes all sources used in the build
+and not just the source used in the released image. It will include
+toolchain source, and other artifacts, which you would not generally
+release. However, the more serious issue for most companies is
+accidental release of proprietary software. The Yocto Project provides
+an :ref:`archiver <ref-classes-archiver>` class to
+help avoid some of these concerns.
+Before you employ ``DL_DIR`` or the ``archiver`` class, you need to
+decide how you choose to provide source. The source ``archiver`` class
+can generate tarballs and SRPMs and can create them with various levels
+of compliance in mind.
+One way of doing this (but certainly not the only way) is to release
+just the source as a tarball. You can do this by adding the following to
+the ``local.conf`` file found in the
+:term:`Build Directory`:
+::
+   INHERIT += "archiver"
+   ARCHIVER_MODE[src] = "original"
+During the creation of your
+image, the source from all recipes that deploy packages to the image is
+placed within subdirectories of ``DEPLOY_DIR/sources`` based on the
+:term:`LICENSE` for each recipe.
+Releasing the entire directory enables you to comply with requirements
+concerning providing the unmodified source. It is important to note that
+the size of the directory can get large.
+A way to help mitigate the size issue is to only release tarballs for
+licenses that require the release of source. Let us assume you are only
+concerned with GPL code as identified by running the following script:
+.. code-block:: shell
+   # Script to archive a subset of packages matching specific license(s)
+   # Source and license files are copied into sub folders of package folder
+   # Must be run from build folder
+   #!/bin/bash
+   src_release_dir="source-release"
+   mkdir -p $src_release_dir
+   for a in tmp/deploy/sources/*; do
+      for d in $a/*; do
+         # Get package name from path
+         p=`basename $d`
+         p=${p%-*}
+         p=${p%-*}
+         # Only archive GPL packages (update *GPL* regex for your license check)
+         numfiles=`ls tmp/deploy/licenses/$p/*GPL* 2> /dev/null | wc -l`
+         if [ $numfiles -gt 1 ]; then
+            echo Archiving $p
+            mkdir -p $src_release_dir/$p/source
+            cp $d/* $src_release_dir/$p/source 2> /dev/null
+            mkdir -p $src_release_dir/$p/license
+            cp tmp/deploy/licenses/$p/* $src_release_dir/$p/license 2> /dev/null
+         fi
+      done
+   done
+At this point, you
+could create a tarball from the ``gpl_source_release`` directory and
+provide that to the end user. This method would be a step toward
+achieving compliance with section 3a of GPLv2 and with section 6 of
+GPLv3.
+Providing License Text
+~~~~~~~~~~~~~~~~~~~~~~
+One requirement that is often overlooked is inclusion of license text.
+This requirement also needs to be dealt with prior to generating the
+final image. Some licenses require the license text to accompany the
+binary. You can achieve this by adding the following to your
+``local.conf`` file:
+::
+   COPY_LIC_MANIFEST = "1"
+   COPY_LIC_DIRS = "1"
+   LICENSE_CREATE_PACKAGE = "1"
+Adding these statements to the
+configuration file ensures that the licenses collected during package
+generation are included on your image.
+.. note::
+   Setting all three variables to "1" results in the image having two
+   copies of the same license file. One copy resides in
+   ``/usr/share/common-licenses`` and the other resides in
+   ``/usr/share/license``.
+   The reason for this behavior is because
+   :term:`COPY_LIC_DIRS` and
+   :term:`COPY_LIC_MANIFEST`
+   add a copy of the license when the image is built but do not offer a
+   path for adding licenses for newly installed packages to an image.
+   :term:`LICENSE_CREATE_PACKAGE`
+   adds a separate package and an upgrade path for adding licenses to an
+   image.
+As the source ``archiver`` class has already archived the original
+unmodified source that contains the license files, you would have
+already met the requirements for inclusion of the license information
+with source as defined by the GPL and other open source licenses.
+Providing Compilation Scripts and Source Code Modifications
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+At this point, we have addressed all we need to prior to generating the
+image. The next two requirements are addressed during the final
+packaging of the release.
+By releasing the version of the OpenEmbedded build system and the layers
+used during the build, you will be providing both compilation scripts
+and the source code modifications in one step.
+If the deployment team has a :ref:`overview-manual/overview-manual-concepts:bsp layer`
+and a distro layer, and those
+those layers are used to patch, compile, package, or modify (in any way)
+any open source software included in your released images, you might be
+required to release those layers under section 3 of GPLv2 or section 1
+of GPLv3. One way of doing that is with a clean checkout of the version
+of the Yocto Project and layers used during your build. Here is an
+example:
+.. code-block:: shell
+   # We built using the dunfell branch of the poky repo
+   $ git clone -b dunfell git://git.yoctoproject.org/poky
+   $ cd poky
+   # We built using the release_branch for our layers
+   $ git clone -b release_branch git://git.mycompany.com/meta-my-bsp-layer
+   $ git clone -b release_branch git://git.mycompany.com/meta-my-software-layer
+   # clean up the .git repos
+   $ find . -name ".git" -type d -exec rm -rf {} \;
+One
+thing a development organization might want to consider for end-user
+convenience is to modify ``meta-poky/conf/bblayers.conf.sample`` to
+ensure that when the end user utilizes the released build system to
+build an image, the development organization's layers are included in
+the ``bblayers.conf`` file automatically:
+::
+   # POKY_BBLAYERS_CONF_VERSION is increased each time build/conf/bblayers.conf
+   # changes incompatibly
+   POKY_BBLAYERS_CONF_VERSION = "2"
+   BBPATH = "${TOPDIR}"
+   BBFILES ?= ""
+   BBLAYERS ?= " \
+     ##OEROOT##/meta \
+     ##OEROOT##/meta-poky \
+     ##OEROOT##/meta-yocto-bsp \
+     ##OEROOT##/meta-mylayer \
+     "
+Creating and
+providing an archive of the :term:`Metadata`
+layers (recipes, configuration files, and so forth) enables you to meet
+your requirements to include the scripts to control compilation as well
+as any modifications to the original source.
+Providing spdx files
+~~~~~~~~~~~~~~~~~~~~~~~~~
+The spdx module has been integrated to a layer named meta-spdxscanner.
+meta-spdxscanner provides several kinds of scanner. If you want to enable
+this function, you have to follow the following steps:
+1. Add meta-spdxscanner layer into ``bblayers.conf``. 
+2. Refer to the README in meta-spdxscanner to setup the environment (e.g, 
+   setup a fossology server) needed for the scanner.
+3. Meta-spdxscanner provides several methods within the bbclass to create spdx files.
+   Please choose one that you want to use and enable the spdx task. You have to
+   add some config options in ``local.conf`` file in your :term:`Build
+   Directory`. The following is an example showing how to generate spdx files
+   during bitbake using the fossology-python.bbclass::
+      # Select fossology-python.bbclass.
+      INHERIT += "fossology-python"
+      # For fossology-python.bbclass, TOKEN is necessary, so, after setup a
+      # Fossology server, you have to create a token.
+      TOKEN = "eyJ0eXAiO..."
+      # The fossology server is necessary for fossology-python.bbclass.
+      FOSSOLOGY_SERVER = "http://xx.xx.xx.xx:8081/repo"
+      # If you want to upload the source code to a special folder:
+      FOLDER_NAME = "xxxx" //Optional
+      # If you don't want to put spdx files in tmp/deploy/spdx, you can enable:
+      SPDX_DEPLOY_DIR = "${DEPLOY_DIR}" //Optional
+For more usage information refer to :yocto_git:`the meta-spdxscanner repository
+</meta-spdxscanner/>`.
+Copying Licenses that Do Not Exist
+----------------------------------
+Some packages, such as the linux-firmware package, have many licenses
+that are not in any way common. You can avoid adding a lot of these
+types of common license files, which are only applicable to a specific
+package, by using the
+:term:`NO_GENERIC_LICENSE`
+variable. Using this variable also avoids QA errors when you use a
+non-common, non-CLOSED license in a recipe.
+The following is an example that uses the ``LICENSE.Abilis.txt`` file as
+the license from the fetched source:
+::
+   NO_GENERIC_LICENSE[Firmware-Abilis] = "LICENSE.Abilis.txt"
+Using the Error Reporting Tool
+==============================
+The error reporting tool allows you to submit errors encountered during
+builds to a central database. Outside of the build environment, you can
+use a web interface to browse errors, view statistics, and query for
+errors. The tool works using a client-server system where the client
+portion is integrated with the installed Yocto Project
+:term:`Source Directory` (e.g. ``poky``).
+The server receives the information collected and saves it in a
+database.
+A live instance of the error reporting server exists at
+https://errors.yoctoproject.org. This server exists so that when
+you want to get help with build failures, you can submit all of the
+information on the failure easily and then point to the URL in your bug
+report or send an email to the mailing list.
+.. note::
+   If you send error reports to this server, the reports become publicly
+   visible.
+Enabling and Using the Tool
+---------------------------
+By default, the error reporting tool is disabled. You can enable it by
+inheriting the
+:ref:`report-error <ref-classes-report-error>`
+class by adding the following statement to the end of your
+``local.conf`` file in your
+:term:`Build Directory`.
+::
+   INHERIT += "report-error"
+By default, the error reporting feature stores information in
+``${``\ :term:`LOG_DIR`\ ``}/error-report``.
+However, you can specify a directory to use by adding the following to
+your ``local.conf`` file:
+::
+   ERR_REPORT_DIR = "path"
+Enabling error
+reporting causes the build process to collect the errors and store them
+in a file as previously described. When the build system encounters an
+error, it includes a command as part of the console output. You can run
+the command to send the error file to the server. For example, the
+following command sends the errors to an upstream server:
+::
+   $ send-error-report /home/brandusa/project/poky/build/tmp/log/error-report/error_report_201403141617.txt
+In the previous example, the errors are sent to a public database
+available at https://errors.yoctoproject.org, which is used by the
+entire community. If you specify a particular server, you can send the
+errors to a different database. Use the following command for more
+information on available options:
+::
+   $ send-error-report --help
+When sending the error file, you are prompted to review the data being
+sent as well as to provide a name and optional email address. Once you
+satisfy these prompts, the command returns a link from the server that
+corresponds to your entry in the database. For example, here is a
+typical link: https://errors.yoctoproject.org/Errors/Details/9522/
+Following the link takes you to a web interface where you can browse,
+query the errors, and view statistics.
+Disabling the Tool
+------------------
+To disable the error reporting feature, simply remove or comment out the
+following statement from the end of your ``local.conf`` file in your
+:term:`Build Directory`.
+::
+   INHERIT += "report-error"
+Setting Up Your Own Error Reporting Server
+------------------------------------------
+If you want to set up your own error reporting server, you can obtain
+the code from the Git repository at :yocto_git:`/error-report-web/`.
+Instructions on how to set it up are in the README document.
+Using Wayland and Weston
+========================
+`Wayland <https://en.wikipedia.org/wiki/Wayland_(display_server_protocol)>`__
+is a computer display server protocol that provides a method for
+compositing window managers to communicate directly with applications
+and video hardware and expects them to communicate with input hardware
+using other libraries. Using Wayland with supporting targets can result
+in better control over graphics frame rendering than an application
+might otherwise achieve.
+The Yocto Project provides the Wayland protocol libraries and the
+reference
+`Weston <https://en.wikipedia.org/wiki/Wayland_(display_server_protocol)#Weston>`__
+compositor as part of its release. You can find the integrated packages
+in the ``meta`` layer of the :term:`Source Directory`.
+Specifically, you
+can find the recipes that build both Wayland and Weston at
+``meta/recipes-graphics/wayland``.
+You can build both the Wayland and Weston packages for use only with
+targets that accept the `Mesa 3D and Direct Rendering
+Infrastructure <https://en.wikipedia.org/wiki/Mesa_(computer_graphics)>`__,
+which is also known as Mesa DRI. This implies that you cannot build and
+use the packages if your target uses, for example, the Intel Embedded
+Media and Graphics Driver (Intel EMGD) that overrides Mesa DRI.
+.. note::
+   Due to lack of EGL support, Weston 1.0.3 will not run directly on the
+   emulated QEMU hardware. However, this version of Weston will run
+   under X emulation without issues.
+This section describes what you need to do to implement Wayland and use
+the Weston compositor when building an image for a supporting target.
+Enabling Wayland in an Image
+----------------------------
+To enable Wayland, you need to enable it to be built and enable it to be
+included (installed) in the image.
+Building Wayland
+~~~~~~~~~~~~~~~~
+To cause Mesa to build the ``wayland-egl`` platform and Weston to build
+Wayland with Kernel Mode Setting
+(`KMS <https://wiki.archlinux.org/index.php/Kernel_Mode_Setting>`__)
+support, include the "wayland" flag in the
+:term:`DISTRO_FEATURES`
+statement in your ``local.conf`` file:
+::
+   DISTRO_FEATURES_append = " wayland"
+.. note::
+   If X11 has been enabled elsewhere, Weston will build Wayland with X11
+   support
+Installing Wayland and Weston
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+To install the Wayland feature into an image, you must include the
+following
+:term:`CORE_IMAGE_EXTRA_INSTALL`
+statement in your ``local.conf`` file:
+::
+   CORE_IMAGE_EXTRA_INSTALL += "wayland weston"
+Running Weston
+--------------
+To run Weston inside X11, enabling it as described earlier and building
+a Sato image is sufficient. If you are running your image under Sato, a
+Weston Launcher appears in the "Utility" category.
+Alternatively, you can run Weston through the command-line interpretor
+(CLI), which is better suited for development work. To run Weston under
+the CLI, you need to do the following after your image is built:
+1. Run these commands to export ``XDG_RUNTIME_DIR``:
+   ::
+      mkdir -p /tmp/$USER-weston
+      chmod 0700 /tmp/$USER-weston
+      export XDG_RUNTIME_DIR=/tmp/$USER-weston
+2. Launch Weston in the shell:
+   ::
+      weston