path: root/documentation/poky-ref-manual/ref-structure.xml

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<appendix id='ref-structure'>

<title>Reference: Directory Structure</title>

<para>
    Poky consists of several components.
    Understanding them and knowing where they are located is key to using Poky well.
    This appendix describes the Poky directory structure and gives information about the various 
    files and directories.
</para>

<section id='structure-core'>
    <title>Top level core components</title>

    <section id='structure-core-bitbake'>
        <title><filename class="directory">bitbake/</filename></title>

        <para>
            Poky 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 interpreter, reads the Poky metadata and runs the tasks 
            defined by that data. 
            Failures are usually from the metadata and not 
            from BitBake itself.
            Consequently, most users do not need to worry about BitBake.
            The <filename class="directory">bitbake/bin/</filename> directory is placed 
            into the PATH environment variable by the 
            <link linkend="structure-core-script">poky-init-build-env</link> script.
        </para>

        <para>
            For more information on BitBake, see the BitBake project site at 
            <ulink url="http://bitbake.berlios.de/"/> 
            and the BitBake on-line manual at <ulink url="http://bitbake.berlios.de/manual/"/>.
        </para>
    </section>

    <section id='structure-core-build'>
        <title><filename class="directory">build/</filename></title>

        <para>
            This directory contains user configuration files and the output 
            generated by Poky in its standard configuration where the source tree is 
            combined with the output. 
            It is also possible to place output and configuration 
            files in a directory separate from the Poky source.
            For information on separating output from the Poky source, see <link 
            linkend='structure-core-script'>poky-init-build-env</link>.
        </para>
    </section>

    <section id='structure-core-meta'>
        <title><filename class="directory">meta/</filename></title>

        <para>
            This directory contains the core metadata, which is a key part of Poky. 
            This directory contains the machine definitions, the Poky distribution, 
            and the packages that make up a given system.
        </para>
    </section>

    <section id='structure-core-meta-extras'>
        <title><filename class="directory">meta-extras/</filename></title>

        <para>
            This directory is similar to <filename class="directory">meta/</filename>.
            The directory contains extra metadata not included in standard Poky.
            This metadata is disabled by default and is not supported as part of Poky.
        </para>
    </section>

    <section id='structure-core-meta-***'>
        <title><filename class="directory">meta-***/</filename></title>

        <para>
            These directories are optional layers that are added to core metadata.
            The layers are enabled by adding them to the <filename>conf/bblayers.conf</filename> file.
        </para>
    </section>

    <section id='structure-core-scripts'>
        <title><filename class="directory">scripts/</filename></title>

        <para>
            This directory contains various integration scripts that implement 
            extra functionality in the Poky environment (e.g. QEMU scripts).
            The <link linkend="structure-core-script">poky-init-build-env</link> script appends this
            directory to the PATH environment variable.
        </para>
    </section>

    <section id='structure-core-sources'>
        <title><filename class="directory">sources/</filename></title>

        <para>
            This directory receives downloads as specified by the 
            <glossterm><link linkend='var-DL_DIR'>DL_DIR</link></glossterm> variable.
            Even though the directory is not part of a checkout, Poky creates it during a build.
            You can use this directory to share downloading files between Poky builds.
            This practice can save you from downloading files multiple times.
            <note><para>
                You can override the location for this directory by setting 
                the DL_DIR variable in <filename>local.conf</filename>.
            </para></note>
        </para>

        <para> 
            This directory also contains SCM checkouts (e.g. <filename class="directory">sources/svn/
            </filename>, <filename class="directory">sources/cvs/</filename> or 
            <filename class="directory">sources/git/</filename>).
            The <filename class="directory">sources</filename> directory can contain archives of 
            checkouts for various revisions or dates.
        </para>

        <para>
            It's worth noting that BitBake creates <filename class="extension">.md5 
            </filename> stamp files for downloads. 
            BitBake uses these files to mark downloads as 
            complete as well as for checksum and access accounting purposes. 
            If you manually add a file to the directory, you need to touch the corresponding 
            <filename class="extension">.md5</filename> file as well.
        </para>
    </section>

    <section id='handbook'>
        <title><filename class="directory">documentation</filename></title>

        <para>
            This directory holds the source for the documentation.  Each manual is contained in 
            a sub-folder.  For example, the files for this manual reside in 
            <filename class="directory">poky-ref-manual</filename>.
        </para>
    </section>

    <section id='structure-core-script'>
        <title><filename>poky-init-build-env</filename></title>

        <para>
            This script sets up the Poky build environment. 
            Sourcing this file in
            a shell makes changes to PATH and sets other core BitBake variables based on the
            current working directory. 
            You need to run this script before running Poky commands.
            The script uses other scripts within the <filename class="directory">scripts/ 
            </filename> directory to do the bulk of the work. 
            You can use this script to specify any directory for the build's output by doing the following:
        </para>

        <literallayout class='monospaced'>
     $ source POKY_SRC/poky-init-build-env [BUILDDIR]
        </literallayout>

        <para>
            You can enter the above command from any directory, as long as POKY_SRC points to
            the desired Poky source tree. 
            The optional BUILDDIR can be any directory into which you would
            like Poky to generate the build output.
        </para>
    </section>
</section>

<section id='structure-build'>
    <title>The Build Directory - <filename class="directory">build/</filename></title>

    <section id='structure-build-conf-local.conf'>
        <title><filename>build/conf/local.conf</filename></title>

        <para>
            This file contains all the local user configuration of Poky. 
            If there is no <filename>local.conf</filename> present, it is created from 
            <filename>local.conf.sample</filename>. 
            The <filename>local.conf</filename> file contains documentation on the various configuration options.  
            Any variable set here overrides any variable set elsewhere within Poky unless 
            that variable is hard-coded within Poky (e.g. by using '=' instead of '?='). 
            Some variables are hard-coded for various reasons but these variables are 
            relatively rare.
        </para>

        <para>
            Edit this file to set the <glossterm><link linkend='var-MACHINE'>MACHINE</link></glossterm> 
            for which you want to build, which package types you
            wish to use (PACKAGE_CLASSES) or where you want to downloaded files
            (<glossterm><link linkend='var-DL_DIR'>DL_DIR</link></glossterm>).
        </para>
    </section>

    <section id='structure-build-conf-bblayers.conf'>
        <title><filename>build/conf/bblayers.conf</filename></title>

        <para>
            This file defines layers, which is a directory tree, traversed (or walked) by BitBake. 
            If <filename>bblayers.conf</filename> 
            is not present, it is created from <filename>bblayers.conf.sample</filename> when the environment 
            setup script is sourced.
        </para>
    </section>

    <section id='structure-build-tmp'>
        <title><filename class="directory">build/tmp/</filename></title>

        <para>
            This directory receives all the Poky output.
            BitBake creates this directory if it does not exist. 
            To clean Poky and start a build from scratch (other than downloads), 
            you can remove everything in this directory or get rid of the directory completely.
            The <filename class="directory">tmp/</filename> directory has some important 
            sub-components detailed below.
        </para>
    </section>

    <section id='structure-build-tmp-cache'>
        <title><filename class="directory">build/tmp/cache/</filename></title>

        <para>
            When BitBake parses the metadata it creates a cache file of the result that can
            be used when subsequently running commands. 
            These results are stored here on a per-machine basis.
        </para>
    </section>

    <section id='structure-build-tmp-deploy'>
        <title><filename class="directory">build/tmp/deploy/</filename></title>

        <para>This directory contains any 'end result' output from Poky.</para>
    </section>

    <section id='structure-build-tmp-deploy-deb'>
        <title><filename class="directory">build/tmp/deploy/deb/</filename></title>

        <para>
            This directory receives any .deb packages produced by Poky.
            The packages are sorted into feeds for different architecture types.
        </para>
    </section>

    <section id='structure-build-tmp-deploy-rpm'>
        <title><filename class="directory">build/tmp/deploy/rpm/</filename></title>

        <para>
            This directory receives any .rpm packages produced by Poky.  
            The packages re sorted into feeds for different architecture types.
        </para>
    </section>

    <section id='structure-build-tmp-deploy-images'>
        <title><filename class="directory">build/tmp/deploy/images/</filename></title>

        <para>
            This directory receives complete filesystem images. 
            If you want to flash the resulting image from a build onto a device, look here for the image.
        </para>
    </section>

    <section id='structure-build-tmp-deploy-ipk'>
        <title><filename class="directory">build/tmp/deploy/ipk/</filename></title>

        <para>This directory receives .ipk packages produced by Poky.</para>
    </section>

    <section id='structure-build-tmp-sysroots'>
        <title><filename class="directory">build/tmp/sysroots/</filename></title>

        <para>
            This directory contains shared header files and libraries as well as other shared 
            data.  
            Packages that need to share output with other packages do so within this directory. 
            The directory is subdivided by architecture so multiple builds can run within
            the one build directory.
        </para>
    </section>

    <section id='structure-build-tmp-stamps'>
        <title><filename class="directory">build/tmp/stamps/</filename></title>

        <para>
            This directory holds information that that BitBake uses for accounting purposes 
            to track what tasks have run and when they have run.
            The directory is sub-divided by architecture. 
            The files in the directory are empty of data.
            However, BitBake uses the filenames and timestamps for tracking purposes.
        </para>
    </section>

    <section id='structure-build-tmp-log'>
        <title><filename class="directory">build/tmp/log/</filename></title>

        <para>
            This directory contains general logs that are not otherwise placed using the 
            package's <glossterm><link linkend='var-WORKDIR'>WORKDIR</link></glossterm>.
            Examples of logs are the output from the "check_pkg" or "distro_check" tasks.
        </para>
    </section>

    <section id='structure-build-tmp-pkgdata'>
        <title><filename class="directory">build/tmp/pkgdata/</filename></title>

        <para>
            This directory contains intermediate packaging data that is used later in the packaging process. 
            For more information, see <link linkend='ref-classes-package'>package.bbclass</link>.
        </para>
    </section>

    <section id='structure-build-tmp-pstagelogs'>
        <title><filename class="directory">build/tmp/pstagelogs/</filename></title>

        <para>
            This directory contains manifest for task-based pre-built. 
            Each manifest is basically a file list for installed files from a given task.
            Manifests are useful for later packaging or cleanup processes.
        </para>
    </section>

    <section id='structure-build-tmp-work'>
        <title><filename class="directory">build/tmp/work/</filename></title>

        <para>
            This directory contains architecture-specific work sub-directories for packages built by BitBake. 
            All tasks execute from a work directory.
            For example, the source for a particular package is unpacked, patched, configured and compiled all
            within its own work directory.
        </para>

        <para>
            It is worth considering the structure of a typical work directory. 
            As an example consider the linux-rp kernel, version 2.6.20 r7 on the machine spitz 
            built within Poky.  
            For this package a work directory of 
            <filename class="directory">tmp/work/spitz-poky-linux-gnueabi/linux-rp-2.6.20-r7/</filename>, 
            referred to as <glossterm><link linkend='var-WORKDIR'>WORKDIR</link></glossterm>, is created.  
            Within this directory, the source is unpacked to linux-2.6.20 and then patched by quilt 
            (see <link linkend="usingpoky-modifying-packages-quilt">Section 3.5.1</link>).   
            Within the <filename class="directory">linux-2.6.20</filename> directory, 
            standard quilt directories <filename class="directory">linux-2.6.20/patches</filename>
            and <filename class="directory">linux-2.6.20/.pc</filename> are created,
            and standard quilt commands can be used.
        </para>

        <para>
            There are other directories generated within WORKDIR. 
            The most important directory is WORKDIR
            <filename class="directory">/temp/</filename>, which has log files for each 
            task (<filename>log.do_*.pid</filename>) and contains the scripts BitBake runs for 
            each task (<filename>run.do_*.pid</filename>). 
            The WORKDIR<filename class="directory">/image/</filename> directory is where "make 
            install" places its output that is then split into sub-packages 
            within WORKDIR<filename class="directory">/packages-split/</filename>.
        </para>
    </section>
</section>

<section id='structure-meta'>
    <title>The Metadata - <filename class="directory">meta/</filename></title>

    <para>
        As mentioned previously, metadata is the core of Poky. 
        Metadata has several important subdivisions:
    </para>

    <section id='structure-meta-classes'>
        <title><filename class="directory">meta/classes/</filename></title>

        <para>
            This directory contains the <filename class="extension">*.bbclass</filename> files. 
            Class files are used to abstract common code so it can be reused by multiple 
            packages. 
            Every package inherits the <filename>base.bbclass</filename> file.
            Examples of other important classes are <filename>autotools.bbclass</filename>, which 
            in theory allows any Autotool-enabled package to work with Poky with minimal effort.
            Another example is <filename>kernel.bbclass</filename> 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 <filename>image.bbclass</filename>, <filename>rootfs_*.bbclass</filename> and 
            <filename>package*.bbclass</filename>.
        </para>
    </section>

    <section id='structure-meta-conf'>
        <title><filename class="directory">meta/conf/</filename></title>

        <para>
            This directory contains the core set of configuration files that start from 
            <filename>bitbake.conf</filename> and from which all other configuration 
            files are included.
            See the includes at the end of the file and you will note that even 
            <filename>local.conf</filename> is loaded from there! 
            While <filename>bitbake.conf</filename> sets up the defaults, you can often override 
            these by using the (<filename>local.conf</filename>) file, machine file or 
            the distribution configuration file.
        </para>
    </section>

    <section id='structure-meta-conf-machine'>
        <title><filename class="directory">meta/conf/machine/</filename></title>

        <para>
            This directory contains all the machine configuration files. 
            If you set MACHINE="spitz", Poky looks for a <filename>spitz.conf</filename> file in this 
            directory. 
            The includes directory contains various data common to multiple machines. 
            If you want to add support for a new machine to Poky, look in this directory.
        </para>
    </section>

    <section id='structure-meta-conf-distro'>
        <title><filename class="directory">meta/conf/distro/</filename></title>

        <para>
            Any distribution-specific configuration is controlled from this directory. 
            Poky only contains the Poky distribution so <filename>poky.conf</filename>
            is the main file here.  
            This directory includes the versions and SRCDATES for applications that are configured here. 
            An example of an alternative configuration is <filename>poky-bleeding.conf</filename>
            although this file mainly inherits its configuration from Poky itself.
        </para>
    </section>

    <section id='structure-meta-recipes-bsp'>
        <title><filename class="directory">meta/recipes-bsp/</filename></title>

        <para>
            This directory contains anything linking to specific hardware or hardware configuration information
            such as "uboot" and "grub".
        </para>
    </section>

    <section id='structure-meta-recipes-connectivity'>
        <title><filename class="directory">meta/recipes-connectivity/</filename></title>

        <para>
            This directory contains libraries and applications related to communication with other devices.
        </para>
    </section>

    <section id='structure-meta-recipes-core'>
        <title><filename class="directory">meta/recipes-core/</filename></title>

        <para>
            This directory contains what is needed to build a basic working Linux image 
            including commonly used dependencies.
        </para>
    </section>

    <section id='structure-meta-recipes-devtools'>
        <title><filename class="directory">meta/recipes-devtools/</filename></title>

        <para>
            This directory contains tools that are primarily used by the build system.
            The tools, however, can also be used on targets.
        </para>
    </section>

    <section id='structure-meta-recipes-extended'>
        <title><filename class="directory">meta/recipes-extended/</filename></title>

        <para>
            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.
        </para>
    </section>

    <section id='structure-meta-recipes-gnome'>
        <title><filename class="directory">meta/recipes-gnome/</filename></title>

        <para>
            This directory contains all things related to the GTK+ application framework.
        </para>
    </section>

    <section id='structure-meta-recipes-graphics'>
        <title><filename class="directory">meta/recipes-graphics/</filename></title>

        <para>
            This directory contains X and other graphically related system libraries
        </para>
    </section>

    <section id='structure-meta-recipes-kernel'>
        <title><filename class="directory">meta/recipes-kernel/</filename></title>

        <para>
            This directory contains the kernel and generic applications and libraries that 
            have strong kernel dependencies.
        </para>
    </section>

    <section id='structure-meta-recipes-multimedia'>
        <title><filename class="directory">meta/recipes-multimedia/</filename></title>

        <para>
            This directory contains codecs and support utilities for audio, images and video.
        </para>
    </section>

    <section id='structure-meta-recipes-qt'>
        <title><filename class="directory">meta/recipes-qt/</filename></title>

        <para>
            This directory contains all things related to the QT application framework.
        </para>
    </section>

    <section id='structure-meta-recipes-sato'>
        <title><filename class="directory">meta/recipes-sato/</filename></title>

        <para>
            This directory contains the Sato demo/reference UI/UX and its associated applications
            and configuration data.
        </para>
    </section>

    <section id='structure-meta-site'>
        <title><filename class="directory">meta/site/</filename></title>

        <para>
            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. 
        </para>
    </section>
</section>

</appendix>
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