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+**************************
+Source Directory Structure
+**************************
+
+The `Source Directory <#source-directory>`__ consists of numerous files,
+directories and subdirectories; understanding their locations and
+contents is key to using the Yocto Project effectively. This chapter
+describes the Source Directory and gives information about those files
+and directories.
+
+For information on how to establish a local Source Directory on your
+development system, see the "`Locating Yocto Project Source
+Files <&YOCTO_DOCS_DEV_URL;#locating-yocto-project-source-files>`__"
+section in the Yocto Project Development Tasks Manual.
+
+.. note::
+
+   The OpenEmbedded build system does not support file or directory
+   names that contain spaces. Be sure that the Source Directory you use
+   does not contain these types of names.
+
+.. _structure-core:
+
+Top-Level Core Components
+=========================
+
+This section describes the top-level components of the `Source
+Directory <#source-directory>`__.
+
+.. _structure-core-bitbake:
+
+``bitbake/``
+------------
+
+This directory includes a copy of BitBake for ease of use. The copy
+usually matches the current stable BitBake release from the BitBake
+project. BitBake, a `Metadata <#metadata>`__ interpreter, reads the
+Yocto Project Metadata and runs the tasks defined by that data. Failures
+are usually caused by errors in your Metadata and not from BitBake
+itself; consequently, most users do not need to worry about BitBake.
+
+When you run the ``bitbake`` command, the main BitBake executable (which
+resides in the ``bitbake/bin/`` directory) starts. Sourcing the
+environment setup script (i.e. ````` <#structure-core-script>`__) places
+the ``scripts/`` and ``bitbake/bin/`` directories (in that order) into
+the shell's ``PATH`` environment variable.
+
+For more information on BitBake, see the `BitBake User
+Manual <&YOCTO_DOCS_BB_URL;>`__.
+
+.. _structure-core-build:
+
+``build/``
+----------
+
+This directory contains user configuration files and the output
+generated by the OpenEmbedded build system in its standard configuration
+where the source tree is combined with the output. The `Build
+Directory <#build-directory>`__ is created initially when you ``source``
+the OpenEmbedded build environment setup script (i.e.
+````` <#structure-core-script>`__).
+
+It is also possible to place output and configuration files in a
+directory separate from the `Source Directory <#source-directory>`__ by
+providing a directory name when you ``source`` the setup script. For
+information on separating output from your local Source Directory files
+(commonly described as an "out of tree" build), see the
+"````` <#structure-core-script>`__" section.
+
+.. _handbook:
+
+``documentation/``
+------------------
+
+This directory holds the source for the Yocto Project documentation as
+well as templates and tools that allow you to generate PDF and HTML
+versions of the manuals. Each manual is contained in its own sub-folder;
+for example, the files for this reference manual reside in the
+``ref-manual/`` directory.
+
+.. _structure-core-meta:
+
+``meta/``
+---------
+
+This directory contains the minimal, underlying OpenEmbedded-Core
+metadata. The directory holds recipes, common classes, and machine
+configuration for strictly emulated targets (``qemux86``, ``qemuarm``,
+and so forth.)
+
+.. _structure-core-meta-poky:
+
+``meta-poky/``
+--------------
+
+Designed above the ``meta/`` content, this directory adds just enough
+metadata to define the Poky reference distribution.
+
+.. _structure-core-meta-yocto-bsp:
+
+``meta-yocto-bsp/``
+-------------------
+
+This directory contains the Yocto Project reference hardware Board
+Support Packages (BSPs). For more information on BSPs, see the `Yocto
+Project Board Support Package (BSP) Developer's
+Guide <&YOCTO_DOCS_BSP_URL;>`__.
+
+.. _structure-meta-selftest:
+
+``meta-selftest/``
+------------------
+
+This directory adds additional recipes and append files used by the
+OpenEmbedded selftests to verify the behavior of the build system. You
+do not have to add this layer to your ``bblayers.conf`` file unless you
+want to run the selftests.
+
+.. _structure-meta-skeleton:
+
+``meta-skeleton/``
+------------------
+
+This directory contains template recipes for BSP and kernel development.
+
+.. _structure-core-scripts:
+
+``scripts/``
+------------
+
+This directory contains various integration scripts that implement extra
+functionality in the Yocto Project environment (e.g. QEMU scripts). The
+````` <#structure-core-script>`__ script prepends this directory to the
+shell's ``PATH`` environment variable.
+
+The ``scripts`` directory has useful scripts that assist in contributing
+back to the Yocto Project, such as ``create-pull-request`` and
+``send-pull-request``.
+
+.. _structure-core-script:
+
+````
+----
+
+This script sets up the OpenEmbedded build environment. Running this
+script with the ``source`` command in a shell makes changes to ``PATH``
+and sets other core BitBake variables based on the current working
+directory. You need to run an environment setup script before running
+BitBake commands. The script uses other scripts within the ``scripts``
+directory to do the bulk of the work.
+
+When you run this script, your Yocto Project environment is set up, a
+`Build Directory <#build-directory>`__ is created, your working
+directory becomes the Build Directory, and you are presented with some
+simple suggestions as to what to do next, including a list of some
+possible targets to build. Here is an example: $ source
+oe-init-build-env ### Shell environment set up for builds. ### You can
+now run 'bitbake <target>' Common targets are: core-image-minimal
+core-image-sato meta-toolchain meta-ide-support You can also run
+generated qemu images with a command like 'runqemu qemux86-64' The
+default output of the ``oe-init-build-env`` script is from the
+``conf-notes.txt`` file, which is found in the ``meta-poky`` directory
+within the `Source Directory <#source-directory>`__. If you design a
+custom distribution, you can include your own version of this
+configuration file to mention the targets defined by your distribution.
+See the "`Creating a Custom Template Configuration
+Directory <&YOCTO_DOCS_DEV_URL;#creating-a-custom-template-configuration-directory>`__"
+section in the Yocto Project Development Tasks Manual for more
+information.
+
+By default, running this script without a Build Directory argument
+creates the ``build/`` directory in your current working directory. If
+you provide a Build Directory argument when you ``source`` the script,
+you direct the OpenEmbedded build system to create a Build Directory of
+your choice. For example, the following command creates a Build
+Directory named ``mybuilds/`` that is outside of the `Source
+Directory <#source-directory>`__: $ source OE_INIT_FILE ~/mybuilds The
+OpenEmbedded build system uses the template configuration files, which
+are found by default in the ``meta-poky/conf/`` directory in the Source
+Directory. See the "`Creating a Custom Template Configuration
+Directory <&YOCTO_DOCS_DEV_URL;#creating-a-custom-template-configuration-directory>`__"
+section in the Yocto Project Development Tasks Manual for more
+information.
+
+.. note::
+
+   The OpenEmbedded build system does not support file or directory
+   names that contain spaces. If you attempt to run the
+   OE_INIT_FILE
+   script from a Source Directory that contains spaces in either the
+   filenames or directory names, the script returns an error indicating
+   no such file or directory. Be sure to use a Source Directory free of
+   names containing spaces.
+
+.. _structure-basic-top-level:
+
+``LICENSE, README, and README.hardware``
+----------------------------------------
+
+These files are standard top-level files.
+
+.. _structure-build:
+
+The Build Directory - ``build/``
+================================
+
+The OpenEmbedded build system creates the `Build
+Directory <#build-directory>`__ when you run the build environment setup
+script ````` <#structure-core-script>`__. If you do not give the Build
+Directory a specific name when you run the setup script, the name
+defaults to ``build/``.
+
+For subsequent parsing and processing, the name of the Build directory
+is available via the ```TOPDIR`` <#var-TOPDIR>`__ variable.
+
+.. _structure-build-buildhistory:
+
+``build/buildhistory/``
+-----------------------
+
+The OpenEmbedded build system creates this directory when you enable
+build history via the ``buildhistory`` class file. The directory
+organizes build information into image, packages, and SDK
+subdirectories. For information on the build history feature, see the
+"`Maintaining Build Output
+Quality <&YOCTO_DOCS_DEV_URL;#maintaining-build-output-quality>`__"
+section in the Yocto Project Development Tasks Manual.
+
+.. _structure-build-conf-local.conf:
+
+``build/conf/local.conf``
+-------------------------
+
+This configuration file contains all the local user configurations for
+your build environment. The ``local.conf`` file contains documentation
+on the various configuration options. Any variable set here overrides
+any variable set elsewhere within the environment unless that variable
+is hard-coded within a file (e.g. by using '=' instead of '?='). Some
+variables are hard-coded for various reasons but such variables are
+relatively rare.
+
+At a minimum, you would normally edit this file to select the target
+``MACHINE``, which package types you wish to use
+(```PACKAGE_CLASSES`` <#var-PACKAGE_CLASSES>`__), and the location from
+which you want to access downloaded files (``DL_DIR``).
+
+If ``local.conf`` is not present when you start the build, the
+OpenEmbedded build system creates it from ``local.conf.sample`` when you
+``source`` the top-level build environment setup script
+````` <#structure-core-script>`__.
+
+The source ``local.conf.sample`` file used depends on the
+``$TEMPLATECONF`` script variable, which defaults to ``meta-poky/conf/``
+when you are building from the Yocto Project development environment,
+and to ``meta/conf/`` when you are building from the OpenEmbedded-Core
+environment. Because the script variable points to the source of the
+``local.conf.sample`` file, this implies that you can configure your
+build environment from any layer by setting the variable in the
+top-level build environment setup script as follows:
+TEMPLATECONF=your_layer/conf Once the build process gets the sample
+file, it uses ``sed`` to substitute final
+``${``\ ```OEROOT`` <#var-OEROOT>`__\ ``}`` values for all
+``##OEROOT##`` values.
+
+.. note::
+
+   You can see how the
+   TEMPLATECONF
+   variable is used by looking at the
+   scripts/oe-setup-builddir
+   script in the
+   Source Directory
+   . You can find the Yocto Project version of the
+   local.conf.sample
+   file in the
+   meta-poky/conf
+   directory.
+
+.. _structure-build-conf-bblayers.conf:
+
+``build/conf/bblayers.conf``
+----------------------------
+
+This configuration file defines
+`layers <&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers>`__,
+which are directory trees, traversed (or walked) by BitBake. The
+``bblayers.conf`` file uses the ```BBLAYERS`` <#var-BBLAYERS>`__
+variable to list the layers BitBake tries to find.
+
+If ``bblayers.conf`` is not present when you start the build, the
+OpenEmbedded build system creates it from ``bblayers.conf.sample`` when
+you ``source`` the top-level build environment setup script (i.e.
+````` <#structure-core-script>`__).
+
+As with the ``local.conf`` file, the source ``bblayers.conf.sample``
+file used depends on the ``$TEMPLATECONF`` script variable, which
+defaults to ``meta-poky/conf/`` when you are building from the Yocto
+Project development environment, and to ``meta/conf/`` when you are
+building from the OpenEmbedded-Core environment. Because the script
+variable points to the source of the ``bblayers.conf.sample`` file, this
+implies that you can base your build from any layer by setting the
+variable in the top-level build environment setup script as follows:
+TEMPLATECONF=your_layer/conf Once the build process gets the sample
+file, it uses ``sed`` to substitute final
+``${``\ ```OEROOT`` <#var-OEROOT>`__\ ``}`` values for all
+``##OEROOT##`` values.
+
+.. note::
+
+   You can see how the
+   TEMPLATECONF
+   variable
+   scripts/oe-setup-builddir
+   script in the
+   Source Directory
+   . You can find the Yocto Project version of the
+   bblayers.conf.sample
+   file in the
+   meta-poky/conf/
+   directory.
+
+.. _structure-build-conf-sanity_info:
+
+``build/cache/sanity_info``
+---------------------------
+
+This file indicates the state of the sanity checks and is created during
+the build.
+
+.. _structure-build-downloads:
+
+``build/downloads/``
+--------------------
+
+This directory contains downloaded upstream source tarballs. You can
+reuse the directory for multiple builds or move the directory to another
+location. You can control the location of this directory through the
+``DL_DIR`` variable.
+
+.. _structure-build-sstate-cache:
+
+``build/sstate-cache/``
+-----------------------
+
+This directory contains the shared state cache. You can reuse the
+directory for multiple builds or move the directory to another location.
+You can control the location of this directory through the
+``SSTATE_DIR`` variable.
+
+.. _structure-build-tmp:
+
+``build/tmp/``
+--------------
+
+The OpenEmbedded build system creates and uses this directory for all
+the build system's output. The ```TMPDIR`` <#var-TMPDIR>`__ variable
+points to this directory.
+
+BitBake creates this directory if it does not exist. As a last resort,
+to clean up a build and start it from scratch (other than the
+downloads), you can remove everything in the ``tmp`` directory or get
+rid of the directory completely. If you do, you should also completely
+remove the ``build/sstate-cache`` directory.
+
+.. _structure-build-tmp-buildstats:
+
+``build/tmp/buildstats/``
+-------------------------
+
+This directory stores the build statistics.
+
+.. _structure-build-tmp-cache:
+
+``build/tmp/cache/``
+--------------------
+
+When BitBake parses the metadata (recipes and configuration files), it
+caches the results in ``build/tmp/cache/`` to speed up future builds.
+The results are stored on a per-machine basis.
+
+During subsequent builds, BitBake checks each recipe (together with, for
+example, any files included or appended to it) to see if they have been
+modified. Changes can be detected, for example, through file
+modification time (mtime) changes and hashing of file contents. If no
+changes to the file are detected, then the parsed result stored in the
+cache is reused. If the file has changed, it is reparsed.
+
+.. _structure-build-tmp-deploy:
+
+``build/tmp/deploy/``
+---------------------
+
+This directory contains any "end result" output from the OpenEmbedded
+build process. The ```DEPLOY_DIR`` <#var-DEPLOY_DIR>`__ variable points
+to this directory. For more detail on the contents of the ``deploy``
+directory, see the
+"`Images <&YOCTO_DOCS_OM_URL;#images-dev-environment>`__" and
+"`Application Development
+SDK <&YOCTO_DOCS_OM_URL;#sdk-dev-environment>`__" sections in the Yocto
+Project Overview and Concepts Manual.
+
+.. _structure-build-tmp-deploy-deb:
+
+``build/tmp/deploy/deb/``
+-------------------------
+
+This directory receives any ``.deb`` packages produced by the build
+process. The packages are sorted into feeds for different architecture
+types.
+
+.. _structure-build-tmp-deploy-rpm:
+
+``build/tmp/deploy/rpm/``
+-------------------------
+
+This directory receives any ``.rpm`` packages produced by the build
+process. The packages are sorted into feeds for different architecture
+types.
+
+.. _structure-build-tmp-deploy-ipk:
+
+``build/tmp/deploy/ipk/``
+-------------------------
+
+This directory receives ``.ipk`` packages produced by the build process.
+
+.. _structure-build-tmp-deploy-licenses:
+
+``build/tmp/deploy/licenses/``
+------------------------------
+
+This directory receives package licensing information. For example, the
+directory contains sub-directories for ``bash``, ``busybox``, and
+``glibc`` (among others) that in turn contain appropriate ``COPYING``
+license files with other licensing information. For information on
+licensing, see the "`Maintaining Open Source License Compliance During
+Your Product's
+Lifecycle <&YOCTO_DOCS_DEV_URL;#maintaining-open-source-license-compliance-during-your-products-lifecycle>`__"
+section in the Yocto Project Development Tasks Manual.
+
+.. _structure-build-tmp-deploy-images:
+
+``build/tmp/deploy/images/``
+----------------------------
+
+This directory is populated with the basic output objects of the build
+(think of them as the "generated artifacts" of the build process),
+including things like the boot loader image, kernel, root filesystem and
+more. If you want to flash the resulting image from a build onto a
+device, look here for the necessary components.
+
+Be careful when deleting files in this directory. You can safely delete
+old images from this directory (e.g. ``core-image-*``). However, the
+kernel (``*zImage*``, ``*uImage*``, etc.), bootloader and other
+supplementary files might be deployed here prior to building an image.
+Because these files are not directly produced from the image, if you
+delete them they will not be automatically re-created when you build the
+image again.
+
+If you do accidentally delete files here, you will need to force them to
+be re-created. In order to do that, you will need to know the target
+that produced them. For example, these commands rebuild and re-create
+the kernel files: $ bitbake -c clean virtual/kernel $ bitbake
+virtual/kernel
+
+.. _structure-build-tmp-deploy-sdk:
+
+``build/tmp/deploy/sdk/``
+-------------------------
+
+The OpenEmbedded build system creates this directory to hold toolchain
+installer scripts which, when executed, install the sysroot that matches
+your target hardware. You can find out more about these installers in
+the "`Building an SDK
+Installer <&YOCTO_DOCS_SDK_URL;#sdk-building-an-sdk-installer>`__"
+section in the Yocto Project Application Development and the Extensible
+Software Development Kit (eSDK) manual.
+
+.. _structure-build-tmp-sstate-control:
+
+``build/tmp/sstate-control/``
+-----------------------------
+
+The OpenEmbedded build system uses this directory for the shared state
+manifest files. The shared state code uses these files to record the
+files installed by each sstate task so that the files can be removed
+when cleaning the recipe or when a newer version is about to be
+installed. The build system also uses the manifests to detect and
+produce a warning when files from one task are overwriting those from
+another.
+
+.. _structure-build-tmp-sysroots-components:
+
+``build/tmp/sysroots-components/``
+----------------------------------
+
+This directory is the location of the sysroot contents that the task
+```do_prepare_recipe_sysroot`` <#ref-tasks-prepare_recipe_sysroot>`__
+links or copies into the recipe-specific sysroot for each recipe listed
+in ```DEPENDS`` <#var-DEPENDS>`__. Population of this directory is
+handled through shared state, while the path is specified by the
+```COMPONENTS_DIR`` <#var-COMPONENTS_DIR>`__ variable. Apart from a few
+unusual circumstances, handling of the ``sysroots-components`` directory
+should be automatic, and recipes should not directly reference
+``build/tmp/sysroots-components``.
+
+.. _structure-build-tmp-sysroots:
+
+``build/tmp/sysroots/``
+-----------------------
+
+Previous versions of the OpenEmbedded build system used to create a
+global shared sysroot per machine along with a native sysroot. Beginning
+with the DISTRO version of the Yocto Project, sysroots exist in
+recipe-specific ```WORKDIR`` <#var-WORKDIR>`__ directories. Thus, the
+``build/tmp/sysroots/`` directory is unused.
+
+.. note::
+
+   The
+   build/tmp/sysroots/
+   directory can still be populated using the
+   bitbake build-sysroots
+   command and can be used for compatibility in some cases. However, in
+   general it is not recommended to populate this directory. Individual
+   recipe-specific sysroots should be used.
+
+.. _structure-build-tmp-stamps:
+
+``build/tmp/stamps/``
+---------------------
+
+This directory holds information that BitBake uses for accounting
+purposes to track what tasks have run and when they have run. The
+directory is sub-divided by architecture, package name, and version.
+Following is an example:
+stamps/all-poky-linux/distcc-config/1.0-r0.do_build-2fdd....2do Although
+the files in the directory are empty of data, BitBake uses the filenames
+and timestamps for tracking purposes.
+
+For information on how BitBake uses stamp files to determine if a task
+should be rerun, see the "`Stamp Files and the Rerunning of
+Tasks <&YOCTO_DOCS_OM_URL;#stamp-files-and-the-rerunning-of-tasks>`__"
+section in the Yocto Project Overview and Concepts Manual.
+
+.. _structure-build-tmp-log:
+
+``build/tmp/log/``
+------------------
+
+This directory contains general logs that are not otherwise placed using
+the package's ``WORKDIR``. Examples of logs are the output from the
+``do_check_pkg`` or ``do_distro_check`` tasks. Running a build does not
+necessarily mean this directory is created.
+
+.. _structure-build-tmp-work:
+
+``build/tmp/work/``
+-------------------
+
+This directory contains architecture-specific work sub-directories for
+packages built by BitBake. All tasks execute from the appropriate work
+directory. For example, the source for a particular package is unpacked,
+patched, configured and compiled all within its own work directory.
+Within the work directory, organization is based on the package group
+and version for which the source is being compiled as defined by the
+```WORKDIR`` <#var-WORKDIR>`__.
+
+It is worth considering the structure of a typical work directory. As an
+example, consider ``linux-yocto-kernel-3.0`` on the machine ``qemux86``
+built within the Yocto Project. For this package, a work directory of
+``tmp/work/qemux86-poky-linux/linux-yocto/3.0+git1+<.....>``, referred
+to as the ``WORKDIR``, is created. Within this directory, the source is
+unpacked to ``linux-qemux86-standard-build`` and then patched by Quilt.
+(See the "`Using Quilt in Your
+Workflow <&YOCTO_DOCS_DEV_URL;#using-a-quilt-workflow>`__" section in
+the Yocto Project Development Tasks Manual for more information.) Within
+the ``linux-qemux86-standard-build`` directory, standard Quilt
+directories ``linux-3.0/patches`` and ``linux-3.0/.pc`` are created, and
+standard Quilt commands can be used.
+
+There are other directories generated within ``WORKDIR``. The most
+important directory is ``WORKDIR/temp/``, which has log files for each
+task (``log.do_*.pid``) and contains the scripts BitBake runs for each
+task (``run.do_*.pid``). The ``WORKDIR/image/`` directory is where "make
+install" places its output that is then split into sub-packages within
+``WORKDIR/packages-split/``.
+
+.. _structure-build-tmp-work-tunearch-recipename-version:
+
+``build/tmp/work/tunearch/recipename/version/``
+-----------------------------------------------
+
+The recipe work directory - ``${WORKDIR}``.
+
+As described earlier in the
+"```build/tmp/sysroots/`` <#structure-build-tmp-sysroots>`__" section,
+beginning with the DISTRO release of the Yocto Project, the OpenEmbedded
+build system builds each recipe in its own work directory (i.e.
+```WORKDIR`` <#var-WORKDIR>`__). The path to the work directory is
+constructed using the architecture of the given build (e.g.
+```TUNE_PKGARCH`` <#var-TUNE_PKGARCH>`__,
+```MACHINE_ARCH`` <#var-MACHINE_ARCH>`__, or "allarch"), the recipe
+name, and the version of the recipe (i.e.
+```PE`` <#var-PE>`__\ ``:``\ ```PV`` <#var-PV>`__\ ``-``\ ```PR`` <#var-PR>`__).
+
+A number of key subdirectories exist within each recipe work directory:
+
+-  ``${WORKDIR}/temp``: Contains the log files of each task executed for
+   this recipe, the "run" files for each executed task, which contain
+   the code run, and a ``log.task_order`` file, which lists the order in
+   which tasks were executed.
+
+-  ``${WORKDIR}/image``: Contains the output of the
+   ```do_install`` <#ref-tasks-install>`__ task, which corresponds to
+   the ``${``\ ```D`` <#var-D>`__\ ``}`` variable in that task.
+
+-  ``${WORKDIR}/pseudo``: Contains the pseudo database and log for any
+   tasks executed under pseudo for the recipe.
+
+-  ``${WORKDIR}/sysroot-destdir``: Contains the output of the
+   ```do_populate_sysroot`` <#ref-tasks-populate_sysroot>`__ task.
+
+-  ``${WORKDIR}/package``: Contains the output of the
+   ```do_package`` <#ref-tasks-package>`__ task before the output is
+   split into individual packages.
+
+-  ``${WORKDIR}/packages-split``: Contains the output of the
+   ``do_package`` task after the output has been split into individual
+   packages. Subdirectories exist for each individual package created by
+   the recipe.
+
+-  ``${WORKDIR}/recipe-sysroot``: A directory populated with the target
+   dependencies of the recipe. This directory looks like the target
+   filesystem and contains libraries that the recipe might need to link
+   against (e.g. the C library).
+
+-  ``${WORKDIR}/recipe-sysroot-native``: A directory populated with the
+   native dependencies of the recipe. This directory contains the tools
+   the recipe needs to build (e.g. the compiler, Autoconf, libtool, and
+   so forth).
+
+-  ``${WORKDIR}/build``: This subdirectory applies only to recipes that
+   support builds where the source is separate from the build artifacts.
+   The OpenEmbedded build system uses this directory as a separate build
+   directory (i.e. ``${``\ ```B`` <#var-B>`__\ ``}``).
+
+.. _structure-build-work-shared:
+
+``build/tmp/work-shared/``
+--------------------------
+
+For efficiency, the OpenEmbedded build system creates and uses this
+directory to hold recipes that share a work directory with other
+recipes. In practice, this is only used for ``gcc`` and its variants
+(e.g. ``gcc-cross``, ``libgcc``, ``gcc-runtime``, and so forth).
+
+.. _structure-meta:
+
+The Metadata - ``meta/``
+========================
+
+As mentioned previously, `Metadata <#metadata>`__ is the core of the
+Yocto Project. Metadata has several important subdivisions:
+
+.. _structure-meta-classes:
+
+``meta/classes/``
+-----------------
+
+This directory contains the ``*.bbclass`` files. Class files are used to
+abstract common code so it can be reused by multiple packages. Every
+package inherits the ``base.bbclass`` file. Examples of other important
+classes are ``autotools.bbclass``, which in theory allows any
+Autotool-enabled package to work with the Yocto Project with minimal
+effort. Another example is ``kernel.bbclass`` that contains common code
+and functions for working with the Linux kernel. Functions like image
+generation or packaging also have their specific class files such as
+``image.bbclass``, ``rootfs_*.bbclass`` and ``package*.bbclass``.
+
+For reference information on classes, see the
+"`Classes <#ref-classes>`__" chapter.
+
+.. _structure-meta-conf:
+
+``meta/conf/``
+--------------
+
+This directory contains the core set of configuration files that start
+from ``bitbake.conf`` and from which all other configuration files are
+included. See the include statements at the end of the ``bitbake.conf``
+file and you will note that even ``local.conf`` is loaded from there.
+While ``bitbake.conf`` sets up the defaults, you can often override
+these by using the (``local.conf``) file, machine file or the
+distribution configuration file.
+
+.. _structure-meta-conf-machine:
+
+``meta/conf/machine/``
+----------------------
+
+This directory contains all the machine configuration files. If you set
+``MACHINE = "qemux86"``, the OpenEmbedded build system looks for a
+``qemux86.conf`` file in this directory. The ``include`` directory
+contains various data common to multiple machines. If you want to add
+support for a new machine to the Yocto Project, look in this directory.
+
+.. _structure-meta-conf-distro:
+
+``meta/conf/distro/``
+---------------------
+
+The contents of this directory controls any distribution-specific
+configurations. For the Yocto Project, the ``defaultsetup.conf`` is the
+main file here. This directory includes the versions and the ``SRCDATE``
+definitions for applications that are configured here. An example of an
+alternative configuration might be ``poky-bleeding.conf``. Although this
+file mainly inherits its configuration from Poky.
+
+.. _structure-meta-conf-machine-sdk:
+
+``meta/conf/machine-sdk/``
+--------------------------
+
+The OpenEmbedded build system searches this directory for configuration
+files that correspond to the value of
+```SDKMACHINE`` <#var-SDKMACHINE>`__. By default, 32-bit and 64-bit x86
+files ship with the Yocto Project that support some SDK hosts. However,
+it is possible to extend that support to other SDK hosts by adding
+additional configuration files in this subdirectory within another
+layer.
+
+.. _structure-meta-files:
+
+``meta/files/``
+---------------
+
+This directory contains common license files and several text files used
+by the build system. The text files contain minimal device information
+and lists of files and directories with known permissions.
+
+.. _structure-meta-lib:
+
+``meta/lib/``
+-------------
+
+This directory contains OpenEmbedded Python library code used during the
+build process.
+
+.. _structure-meta-recipes-bsp:
+
+``meta/recipes-bsp/``
+---------------------
+
+This directory contains anything linking to specific hardware or
+hardware configuration information such as "u-boot" and "grub".
+
+.. _structure-meta-recipes-connectivity:
+
+``meta/recipes-connectivity/``
+------------------------------
+
+This directory contains libraries and applications related to
+communication with other devices.
+
+.. _structure-meta-recipes-core:
+
+``meta/recipes-core/``
+----------------------
+
+This directory contains what is needed to build a basic working Linux
+image including commonly used dependencies.
+
+.. _structure-meta-recipes-devtools:
+
+``meta/recipes-devtools/``
+--------------------------
+
+This directory contains tools that are primarily used by the build
+system. The tools, however, can also be used on targets.
+
+.. _structure-meta-recipes-extended:
+
+``meta/recipes-extended/``
+--------------------------
+
+This directory contains non-essential applications that add features
+compared to the alternatives in core. You might need this directory for
+full tool functionality or for Linux Standard Base (LSB) compliance.
+
+.. _structure-meta-recipes-gnome:
+
+``meta/recipes-gnome/``
+-----------------------
+
+This directory contains all things related to the GTK+ application
+framework.
+
+.. _structure-meta-recipes-graphics:
+
+``meta/recipes-graphics/``
+--------------------------
+
+This directory contains X and other graphically related system
+libraries.
+
+.. _structure-meta-recipes-kernel:
+
+``meta/recipes-kernel/``
+------------------------
+
+This directory contains the kernel and generic applications and
+libraries that have strong kernel dependencies.
+
+.. _structure-meta-recipes-lsb4:
+
+``meta/recipes-lsb4/``
+----------------------
+
+This directory contains recipes specifically added to support the Linux
+Standard Base (LSB) version 4.x.
+
+.. _structure-meta-recipes-multimedia:
+
+``meta/recipes-multimedia/``
+----------------------------
+
+This directory contains codecs and support utilities for audio, images
+and video.
+
+.. _structure-meta-recipes-rt:
+
+``meta/recipes-rt/``
+--------------------
+
+This directory contains package and image recipes for using and testing
+the ``PREEMPT_RT`` kernel.
+
+.. _structure-meta-recipes-sato:
+
+``meta/recipes-sato/``
+----------------------
+
+This directory contains the Sato demo/reference UI/UX and its associated
+applications and configuration data.
+
+.. _structure-meta-recipes-support:
+
+``meta/recipes-support/``
+-------------------------
+
+This directory contains recipes used by other recipes, but that are not
+directly included in images (i.e. dependencies of other recipes).
+
+.. _structure-meta-site:
+
+``meta/site/``
+--------------
+
+This directory contains a list of cached results for various
+architectures. Because certain "autoconf" test results cannot be
+determined when cross-compiling due to the tests not able to run on a
+live system, the information in this directory is passed to "autoconf"
+for the various architectures.
+
+.. _structure-meta-recipes-txt:
+
+``meta/recipes.txt``
+--------------------
+
+This file is a description of the contents of ``recipes-*``.