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      <h1>Buildroot</h1>
    </div>

    <p><a href="http://buildroot.net/">Buildroot</a>
    usage and documentation by Thomas Petazzoni. Contributions from
    Karsten Kruse, Ned Ludd, Martin Herren and others. </p>

    <ul>

      <li><a href="#about">About Buildroot</a></li>
      <li><a href="#download">Obtaining Buildroot</a></li>
      <li><a href="#using">Using Buildroot</a></li>
      <li><a href="#custom_targetfs">Customizing the generated target filesystem</a></li>
      <li><a href="#custom_busybox">Customizing the Busybox
      configuration</a></li>
      <li><a href="#custom_uclibc">Customizing the uClibc
      configuration</a></li>
      <li><a href="#custom_linux26">Customizing the Linux kernel
      configuration</a></li>
      <li><a href="#rebuilding_packages">Understanding how to rebuild packages</a></li>
      <li><a href="#buildroot_innards">How Buildroot works</a></li>
      <li><a href="#using_toolchain">Using the uClibc toolchain
      outside Buildroot</a></li>
      <li><a href="#external_toolchain">Use an external toolchain</a></li>
      <li><a href="#downloaded_packages">Location of downloaded packages</a></li>
      <li><a href="#add_packages">Adding new packages to Buildroot</a></li>
      <li><a href="#board_support">Creating your own board support</a></li>
      <li><a href="#links">Resources</a></li>
    </ul>

    <h2><a name="about" id="about"></a>About Buildroot</h2>

    <p>Buildroot is a set of Makefiles and patches that allows you to
    easily generate a cross-compilation toolchain, a root filesystem
    and a Linux kernel image for your target. Buildroot can be used
    for one, two or all of these options, independently.</p>

    <p>Buildroot is useful mainly for people working with embedded systems.
    Embedded systems often use processors that are not the regular x86
    processors everyone is used to having in his PC. They can be PowerPC
    processors, MIPS processors, ARM processors, etc. </p>

    <p>A compilation toolchain is the set of tools that allows you to
    compile code for your system. It consists of a compiler (in our
    case, <code>gcc</code>), binary utils like assembler and linker
    (in our case, <code>binutils</code>) and a C standard library (for
    example <a href="http://www.gnu.org/software/libc/libc.html">GNU
    Libc</a>, <a href="http://www.uclibc.org/">uClibc</a> or <a
    href="http://www.fefe.de/dietlibc/">dietlibc</a>). The system
    installed on your development station certainly already has a
    compilation toolchain that you can use to compile an application that
    runs on your system. If you're using a PC, your compilation
    toolchain runs on an x86 processor and generates code for an x86
    processor. Under most Linux systems, the compilation toolchain
    uses the GNU libc (glibc) as the C standard library.  This compilation
    toolchain is called the &quot;host compilation toolchain&quot;.
    The machine on which it is running, and on which you're
    working, is called the &quot;host system&quot;. The compilation toolchain
    is provided by your distribution, and Buildroot has nothing to do
    with it (other than using it to build a cross-compilation toolchain
    and other tools that are run on the development host). </p>

    <p>As said above, the compilation toolchain that comes with your system
    runs on and generates code for the processor in your host system. As your
    embedded system has a different processor, you need a cross-compilation
    toolchain &mdash; a compilation toolchain that runs on your host system but
    generates code for your target system (and target processor). For
    example, if your host system uses x86 and your target system uses ARM, the
    regular compilation toolchain on your host runs on x86 and generates code
    for x86, while the cross-compilation toolchain runs on x86 and generates
    code for ARM. </p>

    <p>Even if your embedded system uses an x86 processor, you might be interested
    in Buildroot for two reasons:</p>

    <ul>
      <li>The compilation toolchain on your host certainly uses the GNU Libc
      which is a complete but huge C standard library. Instead of using GNU
      Libc on your target system, you can use uClibc which is a tiny C standard
      library. If you want to use this C library, then you need a compilation
      toolchain to generate binaries linked with it. Buildroot can do that for
      you. </li>

      <li>Buildroot automates the building of a root filesystem with all needed
      tools like busybox. That makes it much easier than doing it by hand. </li>
    </ul>

    <p>You might wonder why such a tool is needed when you can compile
    <code>gcc</code>, <code>binutils</code>, <code>uClibc</code> and all
    the other tools by hand.
    Of course doing so is possible. But, dealing with all of the configure options
    and problems of every <code>gcc</code> or <code>binutils</code>
    version is very time-consuming and uninteresting. Buildroot automates this
    process through the use of Makefiles and has a collection of patches for
    each <code>gcc</code> and <code>binutils</code> version to make them work
    on most architectures. </p>

    <p>Moreover, Buildroot provides an infrastructure for reproducing
    the build process of your kernel, cross-toolchain, and embedded root filesystem. Being able to
    reproduce the build process will be useful when a component needs
    to be patched or updated or when another person is supposed to
    take over the project.</p>

    <h2><a name="download" id="download"></a>Obtaining Buildroot</h2>

    <p>Buildroot releases are made approximately every 3
    months. Direct Git access and daily snapshots are also
    available if you want more bleeding edge.</p>

    <p>Releases are available at <a
    href="http://buildroot.net/downloads/">http://buildroot.net/downloads/</a>.</p>

    <p>The latest snapshot is always available at <a
    href="http://buildroot.net/downloads/snapshots/buildroot-snapshot.tar.bz2">http://buildroot.net/downloads/snapshots/buildroot-snapshot.tar.bz2</a>,
    and previous snapshots are also available at <a
    href="http://buildroot.net/downloads/snapshots/">http://buildroot.net/downloads/snapshots/</a>. </p>

    <p>To download Buildroot using Git you can simply follow
    the rules described on the &quot;Accessing Git&quot; page (<a href=
    "http://buildroot.net/git.html">http://buildroot.net/git.html</a>)
    of the Buildroot website (<a href=
    "http://buildroot.net">http://buildroot.net</a>).
    For the impatient, here's a quick
    recipe:</p>

 <pre>
 $ git clone git://git.buildroot.net/buildroot
</pre>

    <h2><a name="using" id="using"></a>Using Buildroot</h2>

    <p>Buildroot has a nice configuration tool similar to the one you can find
    in the Linux kernel (<a href=
    "http://www.kernel.org/">http://www.kernel.org/</a>) or in Busybox
    (<a href="http://www.busybox.org/">http://www.busybox.org/</a>). Note that
    you can (and should) build everything as a normal user. There is no need to be root to
    configure and use Buildroot. The first step is to run the configuration
    assistant:</p>

<pre>
 $ make menuconfig
</pre>

<p>to run the curses-based configurator, or</p>

<pre>
 $ make xconfig
</pre>

    <p>to run the Qt3-based configurator.</p>

    <p>Both of these "make" commands will need to build a configuration
    utility, so you may need to install "development" packages for
    relevent libraries used by the configuration utilities.
    On Debian-like systems, the
    <code>libncurses5-dev</code> package is required to use the
    <i>menuconfig</i> interface, and the <code>libqt3-mt-dev</code> is
    required to use the <i>xconfig</i> interface.</p>

    <p>For each menu entry in the configuration tool, you can find associated help
    that describes the purpose of the entry. </p>

    <p>Once everything is configured, the configuration tool generates a
    <code>.config</code> file that contains the description of your
    configuration. It will be used by the Makefiles to do what's needed. </p>


    <p>Let's go:</p>

<pre>
 $ make
</pre>
    <p>This command will generally perform the following steps:</p>
    <ul>
      <li>Download source files (as required)</li>
      <li>Configure cross-compile toolchain</li>
      <li>Build/install cross-compile toolchain</li>
      <li>Build/install selected target packages</li>
      <li>Build a kernel image</li>
      <li>Create a root filesystem in selected formats</li>
    </ul>
    <p>Some of the above steps might not be performed if they are not
    selected in the Buildroot configuration.
    </p>

    <p>Buildroot output is stored in a single directory,
    <code>output/</code>. This directory contains several
    subdirectories:</p>

    <ul>

      <li><code>images/</code> where all the images (kernel image,
      bootloader and root filesystem images) are stored.</li>

      <li><code>build/</code> where all the components except for the
      cross-compilation toolchain are built
      (this includes tools needed to run Buildroot on the host and packages compiled
      for the target). The <code>build/</code> directory contains one
      subdirectory for each of these components.</li>

      <li><code>staging/</code> which contains a hierarchy similar to
      a root filesystem hierarchy. This directory contains the
      installation of the cross-compilation toolchain and all the
      userspace packages selected for the target. However, this
      directory is <i>not</i> intended to be the root filesystem for
      the target: it contains a lot of development files, unstripped
      binaries and libraries that make it far too big for an embedded
      system. These development files are used to compile libraries
      and applications for the target that depend on other
      libraries.</li>

      <li><code>target/</code> which contains <i>almost</i> the root
      filesystem for the target: everything needed is present except
      the device files in <code>/dev/</code> (Buildroot can't create
      them because Buildroot doesn't run as root and does not want to
      run as root). Therefore, this directory <b>should not be used on
      your target</b>. Instead, you should use one of the images
      built in the <code>images/</code> directory. If you need an
      extracted image of the root filesystem for booting over NFS,
      then use the tarball image generated in <code>images/</code> and
      extract it as root.<br/>Compared to <code>staging/</code>,
      <code>target/</code> contains only the files and libraries needed
      to run the selected target applications: the development files
      (headers, etc.) are not present.</li>

      <li><code>host/</code> contains the installation of tools
      compiled for the host that are needed for the proper execution
      of Buildroot except for the cross-compilation toolchain which is
      installed under <code>staging/</code>.</li>

      <li><code>toolchain/</code> contains the build directories for
      the various components of the cross-compilation toolchain.</li>

    </ul>

    <h3><a name="offline_builds" id="offline_builds"></a>
    Offline builds</h3>

    <p>If you intend to do an offline build and just want to download
    all sources that you previously selected in the configurator
    (<i>menuconfig</i> or <i>xconfig</i>), then issue:</p>
<pre>
 $ make source
</pre>
    <p>You can now disconnect or copy the content of your <code>dl</code>
    directory to the build-host. </p>

    <h3><a name="building_out_of_tree" id="building_out_of_tree"></a>
    Building out-of-tree</h3>

    <p>Buildroot supports building out of tree with a syntax similar
    to the Linux kernel. To use it, add O=&lt;directory&gt; to the
    make command line:</p>

<pre>
 $ make O=/tmp/build
</pre>

    <p>All the output files will be located under
    <code>/tmp/build</code>.</p>

    <h3><a name="environment_variables" id="environment_variables"></a>
    Environment variables</h3>

    <p>Buildroot also honors some environment variables when they are passed
    to <code>make</code>:</p>
    <ul>
    <li><code>HOSTCXX</code>, the host C++ compiler to use</li>
    <li><code>HOSTCC</code>, the host C compiler to use</li>
    <li><code>UCLIBC_CONFIG_FILE=&lt;path/to/.config&gt;</code>, path
    to the uClibc configuration file to use to compile uClibc if an
    internal toolchain is being built</li>
    <li><code>BUSYBOX_CONFIG_FILE=&lt;path/to/.config&gt;</code>, path
    to the Busybox configuration file</li>
    <li><code>LINUX26_KCONFIG=&lt;path/to/.config&gt;</code>, path
    to the Linux kernel configuration file</li>
    <li><code>BUILDROOT_COPYTO</code>, an additional location to which
    the binary images of the root filesystem, kernel, etc. built by
    Buildroot are copied</li>
    <li><code>BUILDROOT_DL_DIR</code> to override the directory in
    which Buildroot stores/retrieves downloaded files</li>
    </ul>

    <p>An example that uses config files located in the toplevel directory and
    in your $HOME:</p>
<pre>
$ make UCLIBC_CONFIG_FILE=uClibc.config BUSYBOX_CONFIG_FILE=$HOME/bb.config
</pre>

    <p>If you want to use a compiler other than the default <code>gcc</code>
    or <code>g++</code> for building helper-binaries on your host, then do</p>
<pre>
$ make HOSTCXX=g++-4.3-HEAD HOSTCC=gcc-4.3-HEAD
</pre>

    <p>If you want the result of your build to be copied to another directory
    like /tftpboot for downloading to a board using tftp, then you
    can use BUILDROOT_COPYTO to specify your location</p>
    <p>Typically, this is set in your ~/.bashrc file

<pre>
$ export BUILDROOT_COPYTO=/tftpboot
</pre>

    <h2><a name="custom_targetfs" id="custom_targetfs"></a>Customizing the
    generated target filesystem</h2>

    <p>There are a few ways to customize the resulting target filesystem:</p>

    <ul>
      <li>Customize the target filesystem directly and rebuild the image. The
      target filesystem is available under <code>output/target/</code>.
      You can simply make your changes here and run make afterwards &mdash; this will
      rebuild the target filesystem image. This method allows you to do anything
      to the target filesystem, but if you decide to completely rebuild your
      toolchain and tools, these changes will be lost. </li>

      <li>Customize the target filesystem skeleton available under
      <code>target/generic/target_skeleton/</code>. You can customize
      configuration files or other stuff here. However, the full file hierarchy
      is not yet present because it's created during the compilation process.
      Therefore, you can't do everything on this target filesystem skeleton, but
      changes to it do remain even if you completely rebuild the cross-compilation
      toolchain and the tools. <br />
      You can also customize the <code>target/generic/device_table.txt</code>
      file which is used by the tools that generate the target filesystem image
      to properly set permissions and create device nodes.<br />
      These customizations are deployed into
      <code>output/target/</code> just before the actual image
      is made. Simply rebuilding the image by running
      make should propagate any new changes to the image. </li>

      <li>Add support for your own target in Buildroot so that you
      have your own target skeleton (see <a href="#board_support">this
      section</a> for details).</li>

      <li>In the Buildroot configuration, you can specify the path to a
      post-build script that gets called <i>after</i> Buildroot builds
      all the selected software but <i>before</i> the the rootfs
      packages are assembled. The destination root filesystem folder
      is given as the first argument to this script, and this script can
      then be used to copy programs, static data or any other needed
      file to your target filesystem.<br/>You should, however, use
      this feature with care. Whenever you find that a certain package
      generates wrong or unneeded files, you should fix that
      package rather than work around it with a post-build cleanup script.</li>

      <li>A special package, <i>customize</i>, stored in
      <code>package/customize</code> can be used. You can put all the
      files that you want to see in the final target root filesystem
      in <code>package/customize/source</code> and then enable this
      special package in the configuration system.</li>

    </ul>

    <h2><a name="custom_busybox" id="custom_busybox"></a>Customizing the
    Busybox configuration</h2>

    <p><a href="http://www.busybox.net/">Busybox</a> is very configurable, and
    you may want to customize it. You can
    follow these simple steps to do so. This method isn't optimal, but it's
    simple and it works:</p>

    <ol>
      <li>Do an initial compilation of Buildroot with busybox without trying to
      customize it. </li>

      <li>Invoke <code>make busybox-menuconfig</code>.
      The nice configuration tool appears, and you can
      customize everything. </li>

      <li>Run the compilation of Buildroot again. </li>
    </ol>

    <p>Otherwise, you can simply change the
    <code>package/busybox/busybox-&lt;version&gt;.config</code> file if you
    know the options you want to change without using the configuration tool.
    </p>
    <p>If you want to use an existing config file for busybox, then see
    section <a href="#environment_variables">environment variables</a>. </p>

    <h2><a name="custom_uclibc" id="custom_uclibc"></a>Customizing the uClibc
    configuration</h2>

    <p>Just like <a href="#custom_busybox">BusyBox</a>, <a
    href="http://www.uclibc.org/">uClibc</a> offers a lot of
    configuration options. They allow you to select various
    functionalities depending on your needs and limitations. </p>

    <p>The easiest way to modify the configuration of uClibc is to
    follow these steps:</p>

    <ol>

      <li>Do an initial compilation of Buildroot without trying to
      customize uClibc. </li>

      <li>Invoke <code>make uclibc-menuconfig</code>.
      The nice configuration assistant, similar to
      the one used in the Linux kernel or Buildroot, appears. Make
      your configuration changes as appropriate. </li>

      <li>Copy the <code>.config</code> file to
      <code>toolchain/uClibc/uClibc.config</code> or
      <code>toolchain/uClibc/uClibc.config-locale</code>. The former
      is used if you haven't selected locale support in Buildroot
      configuration, and the latter is used if you have selected
      locale support. </li>

      <li>Run the compilation of Buildroot again.</li>

    </ol>

    <p>Otherwise, you can simply change
    <code>toolchain/uClibc/uClibc.config</code> or
    <code>toolchain/uClibc/uClibc.config-locale</code> without running
    the configuration assistant. </p>

    <p>If you want to use an existing config file for uclibc, then see
    section <a href="#environment_variables">environment variables</a>. </p>

    <h2><a name="custom_linux26" id="custom_linux26"></a>Customizing
    the Linux kernel configuration</h2>

    <p>The Linux kernel configuration can be customized just like <a
    href="#custom_busybox">BusyBox</a> and <a href="#custom_uclibc">uClibc</a>
    using <code>make linux26-menuconfig</code>. Make sure you have
    enabled the kernel build in <code>make menuconfig</code> first.
    Once done, run <code>make</code> to (re)build everything.</p>

    <p>If you want to use an existing config file for Linux, then see
    section <a href="#environment_variables">environment variables</a>.</p>

    <h2><a name="#rebuilding_packages"
    id="rebuilding_packages">Understanding how to rebuild
    packages</a></h2>

    <p>One of the most common questions asked by Buildroot
    users is how to rebuild a given package or how to
    remove a package without rebuilding everything from scratch.</p>

    <p>Removing a package is currently unsupported by Buildroot
    without rebuilding from scratch. This is because Buildroot doesn't
    keep track of which package installs what files in the
    <code>output/staging</code> and <code>output/target</code>
    directories. However, implementing clean package removal is on the
    TODO-list of Buildroot developers.</p>

    <p>The easiest way to rebuild a single package from scratch is to
    remove its build directory in <code>output/build</code>. Buildroot
    will then re-extract, re-configure, re-compile and re-install this
    package from scratch.</p>

    <p>However, if you don't want to rebuild the package completely
    from scratch, a better understanding of the Buildroot internals is
    needed. Internally, to keep track of which steps have been done
    and which steps remain to be done, Buildroot maintains stamp
    files (empty files that just tell whether this or that action
    has been done). The problem is that these stamp files are not
    uniformely named and handled by the different packages, so some
    understanding of the particular package is needed.</p>

    <p>For packages relying on Buildroot packages infrastructures (see
    <a href="#add_packages">this section</a> for details), the
    following stamp files are relevent:</p>

    <ul>

      <li><code>output/build/packagename-version/.stamp_configured</code>. If
      removed, Buildroot will trigger the recompilation of the package
      from the configuration step (execution of
      <code>./configure</code>).</li>

      <li><code>output/build/packagename-version/.stamp_built</code>. If
      removed, Buildroot will trigger the recompilation of the package
      from the compilation step (execution of <code>make</code>).</li>

    </ul>

    <p>For other packages, an analysis of the specific
    <i>package.mk</i> file is needed. For example, the zlib Makefile
    used to look like this (before it was converted to the generic
    package infrastructure):</p>

    <pre>
$(ZLIB_DIR)/.configured: $(ZLIB_DIR)/.patched
        (cd $(ZLIB_DIR); rm -rf config.cache; \
                        [...]
        )
        touch $@

$(ZLIB_DIR)/libz.a: $(ZLIB_DIR)/.configured
        $(MAKE) -C $(ZLIB_DIR) all libz.a
        touch -c $@
    </pre>

    <p>If you want to trigger the reconfiguration, you need to
    remove <code>output/build/zlib-version/.configured</code>. If
    you want to trigger only the recompilation, you need to remove
    <code>output/build/zlib-version/libz.a</code>.</p>

    <p>Note that most packages, if not all, will progressively be
    ported over the generic or the autotools infrastructure, making it
    much easier to rebuild individual packages.</p>

    <h2><a name="buildroot_innards" id="buildroot_innards"></a>How Buildroot
    works</h2>

    <p>As mentioned above, Buildroot is basically a set of Makefiles that downloads,
    configures and compiles software with the correct options. It also includes
    patches for various software packages &mdash;  mainly the ones involved in the
    cross-compilation tool chain (<code>gcc</code>, <code>binutils</code> and
    <code>uClibc</code>). </p>

    <p>There is basically one Makefile per software package, and they are named with
    the <code>.mk</code> extension. Makefiles are split into three main
    sections:</p>

    <ul>
      <li><b>toolchain</b> (in the <code>toolchain/</code> directory) contains
      the Makefiles and associated files for all software related to the
      cross-compilation toolchain: <code>binutils</code>, <code>ccache</code>,
      <code>gcc</code>, <code>gdb</code>, <code>kernel-headers</code> and
      <code>uClibc</code>. </li>

      <li><b>package</b> (in the <code>package/</code> directory) contains the
      Makefiles and associated files for all user-space tools that Buildroot
      can compile and add to the target root filesystem. There is one
      sub-directory per tool. </li>

      <li><b>target</b> (in the <code>target</code> directory) contains the
      Makefiles and associated files for software related to the generation of
      the target root filesystem image. Four types of filesystems are supported:
      ext2, jffs2, cramfs and squashfs. For each of them there is a
      sub-directory with the required files. There is also a
      <code>default/</code> directory that contains the target filesystem
      skeleton. </li>
    </ul>

    <p>Each directory contains at least 2 files:</p>

    <ul>
      <li><code>something.mk</code> is the Makefile that downloads, configures,
      compiles and installs the package <code>something</code>. </li>

      <li><code>Config.in</code> is a part of the configuration tool
      description file. It describes the options related to the 
      package. </li>

    </ul>

    <p>The main Makefile performs the following steps (once the
    configuration is done):</p>

    <ol>

      <li>Create all the output directories: <code>staging</code>,
      <code>target</code>, <code>build</code>, <code>stamps</code>,
      etc. in the output directory (<code>output/</code> by default,
      another value can be specified using <code>O=</code>)</li>

      <li>Generate all the targets listed in the
      <code>BASE_TARGETS</code> variable. When an internal toolchain
      is used, this means generating the cross-compilation
      toolchain. When an external toolchain is used, this means checking
      the features of the external toolchain and importing it into the
      Buildroot environment.</li>

      <li>Generate all the targets listed in the <code>TARGETS</code>
      variable. This variable is filled by all the individual
      components' Makefiles. Generating these targets will
      trigger the compilation of the userspace packages (libraries,
      programs), the kernel, the bootloader and the generation of the
      root filesystem images, depending on the configuration.</li>

    </ol>

    <h2><a name="board_support" id="board_support"></a>
    Creating your own board support</h2>

    <p>Creating your own board support in Buildroot allows you to have
    a convenient place to store your project's target filesystem skeleton
    and configuration files for Buildroot, Busybox, uClibc, and the kernel.

    <p>Follow these steps to integrate your board in Buildroot:</p>

    <ol>

      <li>Create a new directory in <code>target/device/</code> named
      after your company or organization</li>

      <li>Add a line <code>source
      "target/device/yourcompany/Config.in"</code> in
      <code>target/device/Config.in</code> so that your board appears
      in the configuration system</li>

      <li>In <code>target/device/yourcompany/</code>, create a
      directory for your project. This way, you'll be able to store
      several of your company's projects inside Buildroot.</li>

      <li>Create a <code>target/device/yourcompany/Config.in</code>
      file that looks like the following:

      <pre>
menuconfig BR2_TARGET_COMPANY
       bool "Company projects"

if BR2_TARGET_COMPANY

config BR2_TARGET_COMPANY_PROJECT_FOOBAR
       bool "Support for Company project Foobar"
       help
         This option enables support for Company project Foobar

endif
      </pre>

      Of course, you should customize the different values to match your
      company/organization and your project. This file will create a
      menu entry that contains the different projects of your
      company/organization.</li>

      <li>Create a <code>target/device/yourcompany/Makefile.in</code>
      file that looks like the following:

      <pre>
ifeq ($(BR2_TARGET_COMPANY_PROJECT_FOOBAR),y)
include target/device/yourcompany/project-foobar/Makefile.in
endif
      </pre>
      </li>

      <li>Create the
      <code>target/device/yourcompany/project-foobar/Makefile.in</code>
      file. It is recommended that you define a
      <code>BOARD_PATH</code> variable set to
      <code>target/device/yourcompany/project-foobar</code> as it
      will simplify further definitions. Then, the file might define
      one or several of the following variables:

      <ul>

	<li><code>TARGET_SKELETON</code> to a directory that contains
	the target skeleton for your project. If this variable is
	defined, this target skeleton will be used instead of the
	default one. If defined, the convention is to define it to
	<code>$(BOARD_PATH)/target_skeleton</code> so that the target
	skeleton is stored in the board specific directory.</li>

      </ul>

      </li>

      <li>In the
      <code>target/device/yourcompany/project-foobar/</code>
      directory you can store configuration files for the kernel,
      Busybox or uClibc.

      You can furthermore create one or more preconfigured configuration
      files, referencing those files. These config files are named
      <code>something_defconfig</code> and are stored in the toplevel
      <code>configs/</code> directory. Your users will then be able
      to run <code>make something_defconfig</code> and get the right
      configuration for your project</li>

    </ol>

    <h2><a name="using_toolchain" id="using_toolchain"></a>Using the
    generated toolchain outside Buildroot</h2>

    <p>You may want to compile for your target your own programs or other software
    that are not packaged in Buildroot. In order to do this you can
    use the toolchain that was generated by Buildroot. </p>

    <p>The toolchain generated by Buildroot is located by default in
    <code>output/staging/</code>. The simplest way to use it
    is to add <code>output/staging/usr/bin/</code> to your PATH
    environnement variable and then to use
    <code>ARCH-linux-gcc</code>, <code>ARCH-linux-objdump</code>,
    <code>ARCH-linux-ld</code>, etc. </p>

    <p><b>Important</b>: do not try to move a gcc-3.x toolchain to another
    directory &mdash; it won't work because there are some hardcoded paths in the
    gcc-3.x configuration. If you are using a current gcc-4.x, it
    is possible to relocate the toolchain &mdash; but then
    <code>--sysroot</code> must be passed every time the compiler is
    called to tell where the libraries and header files are.</p>

    <p>It is also possible to generate the Buildroot toolchain in
    a directory other than <code>output/staging</code> by using the
    <code>Build options -&gt; Toolchain and header file
    location</code> options. This could be useful if the toolchain
    must be shared with other users.</p>

    <h2><a name="downloaded_packages"
    id="downloaded_packages"></a>Location of downloaded packages</h2>

    <p>It might be useful to know that the various tarballs that are
    downloaded by the Makefiles are all stored in the
    <code>DL_DIR</code> which by default is the <code>dl</code>
    directory. It's useful, for example, if you want to keep a complete
    version of Buildroot which is know to be working with the
    associated tarballs. This will allow you to regenerate the
    toolchain and the target filesystem with exactly the same
    versions. </p>

    <p>If you maintain several Buildroot trees, it might be better to have
    a shared download location. This can be accessed by creating a symbolic link
    from the <code>dl</code> directory to the shared download location: </p>

<pre>
ln -s &lt;shared download location&gt; dl
</pre>

    <p>Another way of accessing a shared download location is to
    create the <code>BUILDROOT_DL_DIR</code> environment variable.
    If this is set, then the value of DL_DIR in the project is
    overridden. The following line should be added to
    <code>&quot;~/.bashrc&quot;</code>. <p>

<pre>
export BUILDROOT_DL_DIR &lt;shared download location&gt;
</pre>

    <h2><a name="external_toolchain" id="external_toolchain"></a>Using
    an external toolchain</h2>

<p>It might be useful not to use the toolchain generated by
Buildroot, for example if you already have a toolchain that is known
to work for your specific CPU, or if the toolchain generation feature
of Buildroot is not sufficiently flexible for you (for example if you
need to generate a system with <i>glibc</i> instead of
<i>uClibc</i>). Buildroot supports using an <i>external
toolchain</i>.</p>

<p>To enable the use of an external toolchain, go in the
<code>Toolchain</code> menu, and&nbsp;:</p>

<ul>
  <li>Select the <code>External binary toolchain</code> toolchain
  type</li>
  <li>Adjust the <code>External toolchain path</code>
  appropriately. It should be set to a path where a bin/ directory
  contains your cross-compiling tools</li>
  <li>Adjust the <code>External toolchain prefix</code> so that the
  prefix, suffixed with <code>-gcc</code> or <code>-ld</code> will
  correspond to your cross-compiling tools</li>
</ul>

<p>If you are using an external toolchain based on <i>uClibc</i>, the
<code>Core C library from the external toolchain</code> and
<code>Libraries to copy from the external toolchain</code> options
should already have correct values. However, if your external
toolchain is based on <i>glibc</i>, you'll have to change these values
according to your cross-compiling toolchain.</p>

<p>To generate external toolchains, we recommend using <a
href="http://ymorin.is-a-geek.org/dokuwiki/projects/crosstool">Crosstool-NG</a>.
It allows generating toolchains based on <i>uClibc</i>, <i>glibc</i>
and <i>eglibc</i> for a wide range of architectures and has good
community support.</p>

    <h2><a name="add_packages" id="add_packages"></a>Adding new
    packages to Buildroot</h2>

    <p>This section covers how new packages (userspace libraries or
    applications) can be integrated into Buildroot. It also allows to
    understand how existing packages are integrated, which is needed
    to fix issues or tune their configuration.</p>

    <ul>
      <li><a href="#package-directory">Package directory</a></li>
      <li><a href="#config-in-file"><code>Config.in</code> file</a></li>
      <li><a href="#mk-file">The <code>.mk</code> file</a>
      <ul>
	<li><a href="#generic-tutorial">Makefile for generic
	packages : tutorial</a></li>
	<li><a href="#generic-reference">Makefile for
	generic packages : reference</a></li>
	<li><a href="#autotools-tutorial">Makefile for autotools-based
	packages : tutorial</a></li>
	<li><a href="#autotools-reference">Makefile for autotools-based
	packages : reference</a></li>
	<li><a href="#manual-tutorial">Manual Makefile : tutorial</a></li>
      </ul>
      </li>
      <li><a href="#gettext-integration">Gettext integration and
      interaction with packages</a></li>
    </ul>

    <h3><a name="package-directory"></a>Package directory</h3>

    <p>First of all, create a directory under the <code>package</code>
    directory for your software, for example <code>foo</code>. </p>

    <p>Some packages have been grouped by topic in a sub-directory:
    <code>multimedia</code>, <code>java</code>,
    <code>databases</code>, <code>editors</code>, <code>x11r7</code>,
    <code>games</code>. If your package fits in one of these
    categories, then create your package directory in these.</p>

    <h3><a name="config-in-file"></a><code>Config.in</code> file</h3>

    <p>Then, create a file named <code>Config.in</code>. This file
    will contain the option descriptions related to our
    <code>libfoo</code> software that will be used and displayed in the
    configuration tool. It should basically contain :</p>

<pre>
config BR2_PACKAGE_LIBFOO
        bool "libfoo"
        help
	  This is a comment that explains what libfoo is.

	  http://foosoftware.org/libfoo/
</pre>

    <p>Of course, you can add other options to configure particular
    things in your software. You can look at examples in other
    packages. The syntax of the Config.in file is the same as the one
    for the kernel Kconfig file. The documentation for this syntax is
    available at <a
    href="http://lxr.free-electrons.com/source/Documentation/kbuild/kconfig-language.txt">http://lxr.free-electrons.com/source/Documentation/kbuild/kconfig-language.txt</a></p>

    <p>Finally you have to add your new <code>libfoo/Config.in</code> to
    <code>package/Config.in</code> (or in a category subdirectory if
    you decided to put your package in one of the existing
    categories). The files included there are <em>sorted
    alphabetically</em> per category and are <em>NOT</em> supposed to
    contain anything but the <em>bare</em> name of the package.</p>
<pre>
source "package/libfoo/Config.in"
</pre>

   <h3><a name="mk-file"></a>The <code>.mk</code> file</h3>

   <p>Finally, here's the hardest part. Create a file named
   <code>foo.mk</code>. It describes how the package should be
   downloaded, configured, built, installed, etc.</p>

   <p>Depending on the package type, the <code>.mk</code> file must be
   written in a different way, using different infrastructures:</p>

   <ul>

     <li>Makefiles for generic packages (not using autotools), based
     on an infrastructure similar to the one used for autotools-based
     packages, but which requires a little more work from the
     developer : specify what should be done at for the configuration,
     compilation, installation and cleanup of the package. This
     infrastructure must be used for all packages that do not use the
     autotools as their build system. In the future, other specialized
     infrastructures might be written for other build systems.<br/>We
     cover them through a <a
     href="#generic-tutorial">tutorial</a> and a <a
     href="#generic-reference">reference</a>.</li>

     <li>Makefiles for autotools-based (autoconf, automake, etc.)
     softwares. We provide a dedicated infrastructure for such
     packages, since autotools is a very common build system. This
     infrastructure <i>must</i> be used for new packages that rely on
     the autotools as their build system.<br/>We cover them through a
     <a href="#autotools-tutorial">tutorial</a> and a <a
     href="#autotools-reference">reference</a>.</li>

     <li>Manual Makefiles. These are currently obsolete and no new
     manual Makefiles should be added. However, since there are still
     many of them in the tree and because the , we keep them documented in a <a
     href="#manual-tutorial">tutorial</a>.</li>

   </ul>

   <h4><a name="generic-tutorial"></a>Makefile for generic packages :
   tutorial</h4>

   <pre><tt><span style="color: #000000">01:</span> <span style="font-style: italic"><span style="color: #9A1900">#############################################################</span></span>
<span style="color: #000000">02:</span> <span style="font-style: italic"><span style="color: #9A1900">#</span></span>
<span style="color: #000000">03:</span> <span style="font-style: italic"><span style="color: #9A1900"># libfoo</span></span>
<span style="color: #000000">04:</span> <span style="font-style: italic"><span style="color: #9A1900">#</span></span>
<span style="color: #000000">05:</span> <span style="font-style: italic"><span style="color: #9A1900">#############################################################</span></span>
<span style="color: #000000">06:</span> <span style="color: #990000">LIBFOO_VERSION:=</span>1.0
<span style="color: #000000">07:</span> <span style="color: #990000">LIBFOO_SOURCE:=</span>libfoo-<span style="color: #009900">$(LIBFOO_VERSION)</span>.tar.gz
<span style="color: #000000">08:</span> <span style="color: #990000">LIBFOO_SITE:=</span>http<span style="color: #990000">:</span>//www.foosoftware.org/download
<span style="color: #000000">09:</span> <span style="color: #009900">LIBFOO_INSTALL_STAGING=</span>YES
<span style="color: #000000">10:</span> <span style="color: #009900">LIBFOO_DEPENDENCIES =</span> host-libaaa libbbb
<span style="color: #000000">11:</span> 
<span style="color: #000000">12:</span> define LIBFOO_BUILD_CMDS
<span style="color: #000000">13:</span>         <span style="color: #009900">$(MAKE)</span> <span style="color: #009900">CC</span><span style="color: #990000">=</span><span style="color: #009900">$(TARGET_CC)</span> <span style="color: #009900">LD</span><span style="color: #990000">=</span><span style="color: #009900">$(TARGET_LD)</span> -C <span style="color: #009900">$(@D)</span> all
<span style="color: #000000">14:</span> endef
<span style="color: #000000">15:</span> 
<span style="color: #000000">16:</span> define LIBFOO_INSTALL_STAGING_CMDS
<span style="color: #000000">17:</span>         <span style="color: #009900">$(INSTALL)</span> -D <span style="color: #009900">$(@D)</span>/libfoo.a <span style="color: #009900">$(STAGING_DIR)</span>/usr/lib/libfoo.a
<span style="color: #000000">18:</span>         <span style="color: #009900">$(INSTALL)</span> -D <span style="color: #009900">$(@D)</span>/foo.h <span style="color: #009900">$(STAGING_DIR)</span>/usr/include/foo.h
<span style="color: #000000">19:</span>         cp -dpf <span style="color: #009900">$(@D)</span>/libfoo.so<span style="color: #990000">*</span> <span style="color: #009900">$(STAGING_DIR)</span>/usr/lib
<span style="color: #000000">20:</span> endef
<span style="color: #000000">21:</span> 
<span style="color: #000000">22:</span> define LIBFOO_INSTALL_TARGET_CMDS
<span style="color: #000000">23:</span>         cp -dpf <span style="color: #009900">$(@D)</span>/libfoo.so<span style="color: #990000">*</span> <span style="color: #009900">$(TARGET_DIR)</span>/usr/lib
<span style="color: #000000">24:</span>         -<span style="color: #009900">$(STRIPCMP)</span> <span style="color: #009900">$(STRIP_STRIP_UNNEEDED)</span> <span style="color: #009900">$(TARGET_DIR)</span>/isr/lib/libfoo.so<span style="color: #990000">*</span>
<span style="color: #000000">25:</span> endef
<span style="color: #000000">26:</span> 
<span style="color: #000000">27:</span> <span style="color: #009900">$(</span><span style="font-weight: bold"><span style="color: #0000FF">eval</span></span> <span style="color: #009900">$(</span>call GENTARGETS<span style="color: #990000">,</span>package<span style="color: #990000">,</span>libfoo<span style="color: #990000">))</span></tt></pre>

   <p>The Makefile begins on line 6 to 8 by metadata informations: the
   version of the package (<code>LIBFOO_VERSION</code>), the name of
   the tarball containing the package (<code>LIBFOO_SOURCE</code>) and
   the Internet location at which the tarball can be downloaded
   (<code>LIBFOO_SITE</code>). All variables must start with the same
   prefix, <code>LIBFOO_</code> in this case. This prefix is always
   the uppercased version of the package name (see below to understand
   where the package name is defined).</p>

   <p>On line 9, we specify that this package wants to install
   something to the staging space. This is often needed for libraries
   since they must install header files and other development files in
   the staging space. This will ensure that the commands listed in the
   <code>LIBFOO_INSTALL_STAGING_CMDS</code> variable will be
   executed.</p>

   <p>On line 10, we specify the list of dependencies this package
   relies on. These dependencies are listed in terms of lower-case
   package names, which can be packages for the target (without the
   <code>host-</code> prefix) or packages for the host (with the
   <code>host-</code>) prefix). Buildroot will ensure that all these
   packages are built and installed <i>before</i> the current package
   starts its configuration.</p>

   <p>The rest of the Makefile defines what should be done at the
   different steps of the package configuration, compilation and
   installation. <code>LIBFOO_BUILD_CMDS</code> tells what steps
   should be performed to build the
   package. <code>LIBFOO_INSTALL_STAGING_CMDS</code> tells what steps
   should be performed to install the package in the staging
   space. <code>LIBFOO_INSTALL_TARGET_CMDS</code> tells what steps
   should be performed to install the package in the target space.</p>

   <p>All these steps rely on the <code>$(@D)</code> variable, which
   contains the directory where the source code of the package has
   been extracted.</p>

   <p>Finally, on line 27, we call the <code>GENTARGETS</code> which
   generates, according to the variables defined previously, all the
   Makefile code necessary to make your package working.</p>

   <h4><a name="generic-reference"></a>Makefile for generic packages :
   reference</h4>

   <p>The <code>GENTARGETS</code> macro takes three arguments:</p>

   <ul>

     <li>The first argument is the package directory prefix. If your
     package is in <code>package/libfoo</code>, then the directory
     prefix is <code>package</code>. If your package is in
     <code>package/editors/foo</code>, then the directory prefix must
     be <code>package/editors</code>.</li>

     <li>The second argument is the lower-cased package name. It must
     match the prefix of the variables in the <code>.mk</code> file
     and must match the configuration option name in the
     <code>Config.in</code> file. For example, if the package name is
     <code>libfoo</code>, so the variables in the <code>.mk</code>
     must start with <code>LIBFOO_</code> and the configuration option
     in the <code>Config.in</code> file must be
     <code>BR2_PACKAGE_LIBFOO</code>.</li>

     <li>The third argument is optional. It can be used to tell if the
     package if a target package (cross-compiled for the target) or a
     host package (natively compiled for the host). If unspecified, it
     is assumed that it is a target package. See below for
     details.</li>

   </ul>

   <p>For a given package, in a single <code>.mk</code> file, it is
   possible to call GENTARGETS twice, once to create the rules to
   generate a target package and once to create the rules to generate
   a host package:</p>

<pre>
$(eval $(call GENTARGETS,package,libfoo))
$(eval $(call GENTARGETS,package,libfoo,host))
</pre>

   <p>This might be useful if the compilation of the target package
   requires some tools to be installed on the host. If the package
   name is <code>libfoo</code>, then the name of the package for the
   target is also <code>libfoo</code>, while the name of the package
   for the host is <code>host-libfoo</code>. These names should be
   used in the DEPENDENCIES variables of other packages if they depend
   on <code>libfoo</code> or <code>host-libfoo</code>.</p>

   <p>The call to the <code>GENTARGETS</code> macro <b>must</b> be at
   the end of the <code>.mk</code> file, after all variable
   definitions.</p>

   <p>For the target package, the <code>GENTARGETS</code> uses the
   variables defined by the .mk file and prefixed by the uppercased
   package name: <code>LIBFOO_*</code>. For target package, it uses
   the <code>HOST_LIBFOO_*</code>. For <i>some</i> variables, if the
   <code>HOST_LIBFOO_</code> prefixed variable doesn't exist, the
   package infrastructure uses the corresponding variable prefixed by
   <code>LIBFOO_</code>. This is done for variables that are likely to
   have the same value for both the target and host packages. See
   below for details.</p>

   <p>The list of variables that can be set in a <code>.mk</code> file
   to give metadata informations is (assuming the package name is
   <code>libfoo</code>) :</p>

   <ul>

     <li><code>LIBFOO_VERSION</code>, mandatory, must contain the
     version of the package. Note that if
     <code>HOST_LIBFOO_VERSION</code> doesn't exist, it is assumed to
     be the same as <code>LIBFOO_VERSION</code>.<br/>Example:
     <code>LIBFOO_VERSION=0.1.2</code></li>

     <li><code>LIBFOO_SOURCE</code> may contain the name of the
     tarball of the package. If <code>HOST_LIBFOO_SOURCE</code> is not
     specified, it defaults to <code>LIBFOO_VERSION</code>. If none
     are specified, then the value is assumed to be
     <code>packagename-$(LIBFOO_VERSION).tar.gz</code>.<br/>Example:
     <code>LIBFOO_SOURCE =
     foobar-$(LIBFOO_VERSION).tar.bz2</code></li>

     <li><code>LIBFOO_PATCH</code> may contain the name of a patch,
     that will be downloaded from the same location as the tarball
     indicated in <code>LIBFOO_SOURCE</code>. If
     <code>HOST_LIBFOO_PATCH</code> is not specified, it defaults to
     <code>LIBFOO_PATCH</code>. Also note that another mechanism is
     available to patch a package: all files of the form
     <code>packagename-packageversion-description.patch</code> present
     in the package directory inside Buildroot will be applied to the
     package after extraction.</li>

     <li><code>LIBFOO_SITE</code> may contain the Internet location of
     the tarball of the package. If <code>HOST_LIBFOO_SITE</code> is
     not specified, it defaults to <code>LIBFOO_SITE</code>. If none
     are specified, then the location is assumed to be
     <code>http://$$(BR2_SOURCEFORGE_MIRROR).dl.sourceforge.net/sourceforge/packagename</code>.<br/>Example:
     <code>LIBFOO_SITE=http://www.foosoftware.org/libfoo</code>.</li>

     <li><code>LIBFOO_DEPENDENCIES</code> lists the dependencies (in
     terms of package name) that are required for the current target
     package to compile. These dependencies are guaranteed to be
     compiled and installed before the configuration of the current
     package starts. In a similar way,
     <code>HOST_LIBFOO_DEPENDENCIES</code> lists the dependency for
     the current host package.</li>

     <li><code>LIBFOO_INSTALL_STAGING</code> can be set to
     <code>YES</code> or <code>NO</code> (default). If set to
     <code>YES</code>, then the commands in the
     <code>LIBFOO_INSTALL_STAGING_CMDS</code> variables are executed
     to install the package into the staging directory.</p>

     <li><code>LIBFOO_INSTALL_TARGET</code> can be set to
     <code>YES</code> (default) or <code>NO</code>. If set to
     <code>YES</code>, then the commands in the
     <code>LIBFOO_INSTALL_TARGET_CMDS</code> variables are executed
     to install the package into the target directory.</p>

     </ul>

     <p>The recommended way to define these variables is to use the
     following syntax:</p>

<pre>
LIBFOO_VERSION=2.32
</pre>

     <p>Now, the variables that define what should be performed at the
     different steps of the build process.</p>

     <ul>

       <li><code>LIBFOO_CONFIGURE_CMDS</code>, used to list the
       actions to be performed to configure the package before its
       compilation</li>

       <li><code>LIBFOO_BUILD_CMDS</code>, used to list the actions to
       be performed to compile the package</li>

       <li><code>HOST_LIBFOO_INSTALL_CMDS</code>, used to list the
       actions to be performed to install the package, when the
       package is a host package. The package must install its files
       to the directory given by <code>$(HOST_DIR)</code>. All files,
       including development files such as headers should be
       installed, since other packages might be compiled on top of
       this package.</li>

       <li><code>LIBFOO_INSTALL_TARGET_CMDS</code>, used to list the
       actions to be performed to install the package to the target
       directory, when the package is a target package. The package
       must install its files to the directory given by
       <code>$(TARGET_DIR)</code>. Only the files required for
       <i>execution</i> of the package should be installed. Header
       files and documentation should not be installed.</li>

       <li><code>LIBFOO_INSTALL_STAGING_CMDS</code>, used to list the
       actions to be performed to install the package to the staging
       directory, when the package is a target package. The package
       must install its files to the directory given by
       <code>$(STAGING_DIR)</code>. All development files should be
       installed, since they might be needed to compile other
       packages.</li>

       <li><code>LIBFOO_CLEAN_CMDS</code>, used to list the actions to
       perform to clean up the build directory of the package.</li>

       <li><code>LIBFOO_UNINSTALL_TARGET_CMDS</code>, used to list the
       actions to uninstall the package from the target directory
       <code>$(TARGET_DIR)</code></li>

       <li><code>LIBFOO_UNINSTALL_STAGING_CMDS</code></li>, used to
       list the actions to uninstall the package from the staging
       directory <code>$(STAGING_DIR)</code>.</li>

     </ul>

     <p>The preferred way to define these variables is:</p>

<pre>
define LIBFOO_CONFIGURE_CMDS
 action 1
 action 2
 action 3
endef</pre>

     <p>In the action definitions, you can use the following
     variables:</p>

     <ul>

       <li><code>$(@D)</code>, which contains the directory in which
       the package source code has been uncompressed.</li>

       <li><code>$(TARGET_CC)</code>, <code>$(TARGET_LD)</code>,
       etc. to get the target cross-compilation utilities</li>

       <li><code>$(TARGET_CROSS)</code> to get the cross-compilation
       toolchain prefix</li>

       <li>Of course the <code>$(HOST_DIR)</code>,
       <code>$(STAGING_DIR)</code> and <code>$(TARGET_DIR)</code>
       variables to install the packages properly.</li>

     </ul>


     <p>The last feature of the generic infrastructure is the ability
     to add hook more actions after existing steps. These hooks aren't
     really useful for generic packages, since the <code>.mk</code>
     file already has full control over the actions performed in each
     step of the package construction. The hooks are more useful for
     packages using the autotools infrastructure described below. But
     since they are provided by the generic infrastructure, they are
     documented here.</p>

     <p>The following hook points are available:</p>

     <ul>
       <li><code>LIBFOO_POST_PATCH_HOOKS</code></li>
       <li><code>LIBFOO_POST_CONFIGURE_HOOKS</code></li>
       <li><code>LIBFOO_POST_BUILD_HOOKS</code></li>
       <li><code>LIBFOO_POST_INSTALL_HOOKS</code> (for host packages only)</li>
       <li><code>LIBFOO_POST_INSTALL_STAGING_HOOKS</code> (for target packages only)</li>
       <li><code>LIBFOO_POST_INSTALL_TARGET_HOOKS</code> (for target packages only)</li>
     </ul>

     <p>This variables are <i>lists</i> of variable names containing
     actions to be performed at this hook point. This allows several
     hooks to be registered at a given hook point. Here is an
     example:</p>

     <pre>
define LIBFOO_POST_PATCH_FIXUP
  action1
  action2
endef

LIBFOO_POST_PATCH_HOOKS += LIBFOO_POST_PATCH_FIXUP
</pre>

   <h4><a name="autotools-tutorial"></a>Makefile for autotools-based
   packages : tutorial</h4>

   <p>First, let's see how to write a <code>.mk</code> file for an
   autotools-based package, with an example&nbsp;:</p>

<pre><tt><span style="color: #000000">01:</span> <span style="font-style: italic"><span style="color: #9A1900">#############################################################</span></span>
<span style="color: #000000">02:</span> <span style="font-style: italic"><span style="color: #9A1900">#</span></span>
<span style="color: #000000">03:</span> <span style="font-style: italic"><span style="color: #9A1900"># foo</span></span>
<span style="color: #000000">04:</span> <span style="font-style: italic"><span style="color: #9A1900">#</span></span>
<span style="color: #000000">05:</span> <span style="font-style: italic"><span style="color: #9A1900">#############################################################</span></span>
<span style="color: #000000">06:</span> 
<span style="color: #000000">07:</span> <span style="color: #990000">FOO_VERSION:=</span>1.0
<span style="color: #000000">08:</span> <span style="color: #990000">FOO_SOURCE:=</span>foo-<span style="color: #009900">$(FOO_VERSION)</span>.tar.gz
<span style="color: #000000">09:</span> <span style="color: #990000">FOO_SITE:=</span>http<span style="color: #990000">:</span>//www.foosoftware.org/downloads
<span style="color: #000000">10:</span> <span style="color: #009900">FOO_INSTALL_STAGING =</span> YES
<span style="color: #000000">11:</span> <span style="color: #009900">FOO_INSTALL_TARGET =</span> YES
<span style="color: #000000">12:</span> <span style="color: #009900">FOO_CONF_OPT =</span>  --enable-shared
<span style="color: #000000">13:</span> <span style="color: #009900">FOO_DEPENDENCIES =</span> libglib2 host-pkg-config
<span style="color: #000000">14:</span> 
<span style="color: #000000">15:</span> <span style="color: #009900">$(</span><span style="font-weight: bold"><span style="color: #0000FF">eval</span></span> <span style="color: #009900">$(</span>call AUTOTARGETS<span style="color: #990000">,</span>package<span style="color: #990000">,</span>foo<span style="color: #990000">))</span></tt></pre>

    <p>On line 7, we declare the version of the package. On line 8 and
    9, we declare the name of the tarball and the location of the
    tarball on the Web. Buildroot will automatically download the
    tarball from this location.</p>

    <p>On line 10, we tell Buildroot to install the package to the
    staging directory. The staging directory, located in
    <code>output/staging/</code> is the directory where all the
    packages are installed, including their development files, etc. By
    default, packages are not installed to the staging directory,
    since usually, only libraries need to be installed in the staging
    directory: their development files are needed to compile other
    libraries or applications depending on them. Also by default, when
    staging installation is enabled, packages are installed in this
    location using the <code>make install</code> command.</p>

    <p>On line 11, we tell Buildroot to also install the package to
    the target directory. This directory contains what will become the
    root filesystem running on the target. Usually, we try not to
    install the documentation and to install stripped versions of the
    binary. By default, target installation is enabled, so in fact,
    this line is not strictly necessary. Also by default, packages are
    installed in this location using the <code>make
    install-strip</code> command.</p>

    <p>On line 12, we tell Buildroot to pass a custom configure
    option, that will be passed to the <code>./configure</code> script
    before configuring and building the package.</p>

    <p>On line 13, we declare our dependencies, so that they are built
    before the build process of our package starts.</p>

    <p>Finally, on line line 14, we invoke the
    <code>AUTOTARGETS</code> macro that generates all the Makefile
    rules that actually allows the package to be built.</p>

    <h4><a name="autotools-reference"></a>Makefile for autotools
    packages : reference</h4>

    <p>The main macro of the autotools package infrastructure is
    <code>AUTOTARGETS</code>. It has the same number of arguments and
    the same semantic as the <code>GENTARGETS</code> macro, which is
    the main macro of the generic package infrastructure. For
    autotools packages, the ability to have target and host packages
    is also available (and is actually widely used).</p>

    <p>Just like the generic infrastructure, the autotools
    infrastructure works by defining a number of variables before
    calling the <code>AUTOTARGETS</code> macro.</p>

    <p>First, all the package meta-information variables that exist in
    the generic infrastructure also exist in the autotools
    infrastructure: <code>LIBFOO_VERSION</code>,
    <code>LIBFOO_SOURCE</code>, <code>LIBFOO_PATCH</code>,
    <code>LIBFOO_SITE</code>, <code>LIBFOO_SUBDIR</code>,
    <code>LIBFOO_DEPENDENCIES</code>,
    <code>LIBFOO_INSTALL_STAGING</code>,
    <code>LIBFOO_INSTALL_TARGET</code>.</p>

    <p>A few additional variables, specific to the autotools
    infrastructure, can also be defined. Many of them are only useful
    in very specific cases, typical packages will therefore only use a
    few of them.</p>

    <ul>

      <li><code>LIBFOO_SUBDIR</code> may contain the name of a
      subdirectory inside the package that contains the configure
      script. This is useful, if for example, the main configure
      script is not at the root of the tree extracted by the
      tarball. If <code>HOST_LIBFOO_SUBDIR</code> is not specified, it
      defaults to <code>LIBFOO_SUBDIR</code>.</li>

      <li><code>LIBFOO_CONF_ENV</code>, to specify additional
      environment variables to pass to the configure script. By
      default, empty.</li>

      <li><code>LIBFOO_CONF_OPT</code>, to specify additional
      configure options to pass to the configure script. By default,
      empty.</li>

      <li><code>LIBFOO_MAKE</code>, to specify an
      alternate <code>make</code> command. This is typically useful
      when parallel make it enabled in the configuration
      (using <code>BR2_JLEVEL</code>) but that this feature should be
      disabled for the given package, for one reason or another. By
      default, set to <code>$(MAKE)</code>. If parallel building is
      not supported by the package, then it should
      do <code>LIBFOO_MAKE=$(MAKE1)</code>.</li>

      <li><code>LIBFOO_MAKE_ENV</code>, to specify additional
      environment variables to pass to make in the build step. These
      are passed before the <code>make</code> command. By default,
      empty.</li>

      <li><code>LIBFOO_MAKE_OPT</code>, to specify additional
      variables to pass to make in the build step. These are passed
      after the <code>make</code> command. By default, empty.</li>

      <li><code>LIBFOO_AUTORECONF</code>, tells whether the package
      should be autoreconfigured or not (i.e, if the configure script
      and Makefile.in files should be re-generated by re-running
      autoconf, automake, libtool, etc.). Valid values
      are <code>YES</code> and <code>NO</code>. By default, the value
      is <code>NO</code></li>

      <li><code>LIBFOO_AUTORECONF_OPT</code> to specify additional
      options passed to the <i>autoreconf</i> program
      if <code>LIBFOO_AUTORECONF=YES</code>. By default, empty.</li>

      <li><code>LIBFOO_LIBTOOL_PATCH</code> tells whether the
      Buildroot patch to fix libtool cross-compilation issues should
      be applied or not. Valid values are <code>YES</code>
      and <code>NO</code>. By default, the value
      is <code>YES</code></li>

      <li><code>LIBFOO_USE_CONFIG_CACHE</code> tells whether the
      configure script should really on a cache file that caches test
      results from previous configure script. Usually, this variable
      should be left to its default value. Only for specific packages
      having issues with the configure cache can set this variable to
      the <code>NO</code> value (but this is more a work-around than a
      really fix)</li>

      <li><code>LIBFOO_INSTALL_STAGING_OPT</code> contains the make
      options used to install the package to the staging directory. By
      default, the value is <code>DESTDIR=$$(STAGING_DIR)
      install</code>, which is correct for most autotools packages. It
      is still possible to override it.</li>

      <li><code>LIBFOO_INSTALL_TARGET_OPT</code> contains the make
      options used to install the package to the target directory. By
      default, the value is <code>DESTDIR=$$(TARGET_DIR)
      install-strip</code> if <code>BR2_ENABLE_DEBUG</code> is not
      set, and <code>DESTDIR=$$(TARGET_DIR) install-exec</code>
      if <code>BR2_ENABLE_DEBUG</code> is set. These default values
      are correct for most autotools packages, but it is still
      possible to override them if needed.</li>

      <li><code>LIBFOO_CLEAN_OPT</code> contains the make options used
      to clean the package. By default, the value
      is <code>clean</code>.</li>

      <li><code>LIBFOO_UNINSTALL_STAGING_OPT</code>, contains the make
      options used to uninstall the package from the staging
      directory. By default, the value is
      <code>DESTDIR=$$(STAGING_DIR) uninstall</code>.</li>

      <li><code>LIBFOO_UNINSTALL_TARGET_OPT</code>, contains the make
      options used to uninstall the package from the target
      directory. By default, the value is
      <code>DESTDIR=$$(TARGET_DIR) uninstall</code>.</li>

    </ul>

    <p>With the autotools infrastructure, all the steps required to
    build and install the packages are already defined, and they
    generally work well for most autotools-based packages. However,
    when required, it is still possible to customize what is done in
    particular step:</p>

    <ul>

      <li>By adding a post-operation hook (after extract, patch,
      configure, build or install). See the reference documentation of
      the generic infrastructure for details.</li>

      <li>By overriding one of the steps. For example, even if the
      autotools infrastructure is used, if the package
      <code>.mk</code> defines its own
      <code>LIBFOO_CONFIGURE_CMDS</code> variable, it will be used
      instead of the default autotools one. However, using this method
      should be restricted to very specific cases. Do not use it in
      the general case.</li>

    </ul>

    <h4><a name="manual-tutorial"></a>Manual Makefile : tutorial</h4>

    <p><b>NOTE: new manual makefiles should not be created, and
    existing manual makefiles should be converted either to the
    generic infrastructure or the autotools infrastructure. This
    section is only kept to document the existing manual makefiles and
    help understanding how they work.</b></p>

<pre>
     <a name="ex2line1" id="ex2line1">1</a>  #############################################################
     <a name="ex2line2" id="ex2line2">2</a>  #
     <a name="ex2line3" id="ex2line3">3</a>  # foo
     <a name="ex2line4" id="ex2line4">4</a>  #
     <a name="ex2line5" id="ex2line5">5</a>  #############################################################
     <a name="ex2line6" id="ex2line6">6</a>  FOO_VERSION:=1.0
     <a name="ex2line7" id="ex2line7">7</a>  FOO_SOURCE:=foo-$(FOO_VERSION).tar.gz
     <a name="ex2line8" id="ex2line8">8</a>  FOO_SITE:=http://www.foosoftware.org/downloads
     <a name="ex2line9" id="ex2line9">9</a>  FOO_DIR:=$(BUILD_DIR)/foo-$(FOO_VERSION)
    <a name="ex2line10" id="ex2line10">10</a>  FOO_BINARY:=foo
    <a name="ex2line11" id="ex2line11">11</a>  FOO_TARGET_BINARY:=usr/bin/foo
    <a name="ex2line12" id="ex2line12">12</a>
    <a name="ex2line13" id="ex2line13">13</a>  $(DL_DIR)/$(FOO_SOURCE):
    <a name="ex2line14" id="ex2line14">14</a>          $(call DOWNLOAD,$(FOO_SITE),$(FOO_SOURCE))
    <a name="ex2line15" id="ex2line15">15</a>
    <a name="ex2line16" id="ex2line16">16</a>  $(FOO_DIR)/.source: $(DL_DIR)/$(FOO_SOURCE)
    <a name="ex2line17" id="ex2line17">17</a>          $(ZCAT) $(DL_DIR)/$(FOO_SOURCE) | tar -C $(BUILD_DIR) $(TAR_OPTIONS) -
    <a name="ex2line18" id="ex2line18">18</a>          touch $@
    <a name="ex2line19" id="ex2line19">19</a>
    <a name="ex2line20" id="ex2line20">20</a>  $(FOO_DIR)/.configured: $(FOO_DIR)/.source
    <a name="ex2line21" id="ex2line21">21</a>          (cd $(FOO_DIR); rm -rf config.cache; \
    <a name="ex2line22" id="ex2line22">22</a>                  $(TARGET_CONFIGURE_OPTS) \
    <a name="ex2line23" id="ex2line23">23</a>                  $(TARGET_CONFIGURE_ARGS) \
    <a name="ex2line24" id="ex2line24">24</a>                  ./configure \
    <a name="ex2line25" id="ex2line25">25</a>                  --target=$(GNU_TARGET_NAME) \
    <a name="ex2line26" id="ex2line26">26</a>                  --host=$(GNU_TARGET_NAME) \
    <a name="ex2line27" id="ex2line27">27</a>                  --build=$(GNU_HOST_NAME) \
    <a name="ex2line28" id="ex2line28">28</a>                  --prefix=/usr \
    <a name="ex2line29" id="ex2line29">29</a>                  --sysconfdir=/etc \
    <a name="ex2line30" id="ex2line30">30</a>          )
    <a name="ex2line31" id="ex2line31">31</a>          touch $@
    <a name="ex2line32" id="ex2line32">32</a>
    <a name="ex2line33" id="ex2line33">33</a>  $(FOO_DIR)/$(FOO_BINARY): $(FOO_DIR)/.configured
    <a name="ex2line34" id="ex2line34">34</a>          $(MAKE) CC=$(TARGET_CC) -C $(FOO_DIR)
    <a name="ex2line35" id="ex2line35">35</a>
    <a name="ex2line36" id="ex2line36">36</a>  $(TARGET_DIR)/$(FOO_TARGET_BINARY): $(FOO_DIR)/$(FOO_BINARY)
    <a name="ex2line37" id="ex2line37">37</a>          $(MAKE) DESTDIR=$(TARGET_DIR) -C $(FOO_DIR) install-strip
    <a name="ex2line38" id="ex2line38">38</a>          rm -Rf $(TARGET_DIR)/usr/man
    <a name="ex2line39" id="ex2line39">39</a>
    <a name="ex2line40" id="ex2line40">40</a>  foo: uclibc ncurses $(TARGET_DIR)/$(FOO_TARGET_BINARY)
    <a name="ex2line41" id="ex2line41">41</a>
    <a name="ex2line42" id="ex2line42">42</a>  foo-source: $(DL_DIR)/$(FOO_SOURCE)
    <a name="ex2line43" id="ex2line43">43</a>
    <a name="ex2line44" id="ex2line44">44</a>  foo-clean:
    <a name="ex2line45" id="ex2line45">45</a>          $(MAKE) prefix=$(TARGET_DIR)/usr -C $(FOO_DIR) uninstall
    <a name="ex2line46" id="ex2line46">46</a>          -$(MAKE) -C $(FOO_DIR) clean
    <a name="ex2line47" id="ex2line47">47</a>
    <a name="ex2line48" id="ex2line48">48</a>  foo-dirclean:
    <a name="ex2line49" id="ex2line49">49</a>          rm -rf $(FOO_DIR)
    <a name="ex2line50" id="ex2line50">50</a>
    <a name="ex2line51" id="ex2line51">51</a> #############################################################
    <a name="ex2line52" id="ex2line52">52</a> #
    <a name="ex2line53" id="ex2line53">53</a> # Toplevel Makefile options
    <a name="ex2line54" id="ex2line54">54</a> #
    <a name="ex2line55" id="ex2line55">55</a> #############################################################
    <a name="ex2line56" id="ex2line56">56</a> ifeq ($(BR2_PACKAGE_FOO),y)
    <a name="ex2line57" id="ex2line57">57</a> TARGETS+=foo
    <a name="ex2line58" id="ex2line58">58</a> endif

</pre>

    <p>First of all, this Makefile example works for a package which comprises a single
    binary executable. For other software, such as libraries or more
    complex stuff with multiple binaries, it must be adapted. For examples look at
    the other <code>*.mk</code> files in the <code>package</code>
    directory. </p>

    <p>At lines <a href="#ex2line6">6-11</a>, a couple of useful variables are
    defined:</p>

    <ul>

     <li><code>FOO_VERSION</code>: The version of <i>foo</i> that
     should be downloaded. </li>

     <li><code>FOO_SOURCE</code>: The name of the tarball of
     <i>foo</i> on the download website or FTP site. As you can see
     <code>FOO_VERSION</code> is used. </li>

     <li><code>FOO_SITE</code>: The HTTP or FTP site from which
     <i>foo</i> archive is downloaded. It must include the complete
     path to the directory where <code>FOO_SOURCE</code> can be
     found. </li>

     <li><code>FOO_DIR</code>: The directory into which the software
     will be configured and compiled. Basically, it's a subdirectory
     of <code>BUILD_DIR</code> which is created upon decompression of
     the tarball. </li>

     <li><code>FOO_BINARY</code>: Software binary name. As said
     previously, this is an example for a package with a single binary.</li>

     <li><code>FOO_TARGET_BINARY</code>: The full path of the binary
     inside the target filesystem. </li>

    </ul>

    <p>Lines <a href="#ex2line13">13-14</a> define a target that downloads the
    tarball from the remote site to the download directory
    (<code>DL_DIR</code>). </p>

    <p>Lines <a href="#ex2line16">16-18</a> define a target and associated rules
    that uncompress the downloaded tarball. As you can see, this target
    depends on the tarball file so that the previous target (lines
    <a href="#ex2line13">13-14</a>) is called before executing the rules of the
    current target. Uncompressing is followed by <i>touching</i> a hidden file
    to mark the software as having been uncompressed. This trick is
    used everywhere in a Buildroot Makefile to split steps
    (download, uncompress, configure, compile, install) while still
    having correct dependencies. </p>

    <p>Lines <a href="#ex2line20">20-31</a> define a target and associated rules
    that configure the software. It depends on the previous target (the
    hidden <code>.source</code> file) so that we are sure the software has
    been uncompressed. In order to configure the package, it basically runs the
    well-known <code>./configure</code> script. As we may be doing
    cross-compilation, <code>target</code>, <code>host</code> and
    <code>build</code> arguments are given. The prefix is also set to
    <code>/usr</code>, not because the software will be installed in
    <code>/usr</code> on your host system, but because the software will
    bin installed in <code>/usr</code> on the target
    filesystem. Finally it creates a <code>.configured</code> file to
    mark the software as configured. </p>

    <p>Lines <a href="#ex2line33">33-34</a> define a target and a rule that
    compile the software. This target will create the binary file in the
    compilation directory and depends on the software being already
    configured (hence the reference to the <code>.configured</code>
    file). It basically runs <code>make</code> inside the source
    directory. </p>

    <p>Lines <a href="#ex2line36">36-38</a> define a target and associated rules
    that install the software inside the target filesystem. They depend on the
    binary file in the source directory to make sure the software has
    been compiled. They use the <code>install-strip</code> target of the
    software <code>Makefile</code> by passing a <code>DESTDIR</code>
    argument so that the <code>Makefile</code> doesn't try to install
    the software in the host <code>/usr</code> but rather in the target
    <code>/usr</code>. After the installation, the
    <code>/usr/man</code> directory inside the target filesystem is
    removed to save space. </p>

    <p>Line <a href="#ex2line40">40</a> defines the main target of the software &mdash;
    the one that will be eventually be used by the top level
    <code>Makefile</code> to download, compile, and then install
    this package. This target should first of all depend on all
    needed dependencies of the software (in our example,
    <i>uclibc</i> and <i>ncurses</i>) and also depend on the
    final binary. This last dependency will call all previous
    dependencies in the correct order. </p>

    <p>Line <a href="#ex2line42">42</a> defines a simple target that only
    downloads the code source. This is not used during normal operation of
    Buildroot, but is needed if you intend to download all required sources at
    once for later offline build. Note that if you add a new package providing
    a <code>foo-source</code> target is <i>mandatory</i> to support
    users that wish to do offline-builds. Furthermore it eases checking
    if all package-sources are downloadable. </p>

    <p>Lines <a href="#ex2line44">44-46</a> define a simple target to clean the
    software build by calling the Makefiles with the appropriate option.
    The <code>-clean</code> target should run <code>make clean</code>
    on $(BUILD_DIR)/package-version and MUST uninstall all files of the
    package from $(STAGING_DIR) and from $(TARGET_DIR). </p>

    <p>Lines <a href="#ex2line48">48-49</a> define a simple target to completely
    remove the directory in which the software was uncompressed, configured and
    compiled. The <code>-dirclean</code> target MUST completely rm $(BUILD_DIR)/
    package-version. </p>

    <p>Lines <a href="#ex2line51">51-58</a> add the target <code>foo</code> to
    the list of targets to be compiled by Buildroot by first checking if
    the configuration option for this package has been enabled
    using the configuration tool. If so, it then &quot;subscribes&quot;
    this package to be compiled by adding the package to the TARGETS
    global variable.  The name added to the TARGETS global
    variable is the name of this package's target, as defined on
    line <a href="#ex2line40">40</a>, which is used by Buildroot to download,
    compile, and then install this package. </p>

    <h3><a name="gettext-integration"></a>Gettext integration and
    interaction with packages</h3>

    <p>Many packages that support internationalization use the gettext
    library. Dependency on this library are fairly complicated and
    therefore deserves a few explanations.</p>

    <p>The <i>uClibc</i> C library doesn't implement gettext
    functionality, therefore with this C library, a separate gettext
    must be compiled. On the other hand, the <i>glibc</i> C library
    does integrate its own gettext, and in this case, the separate
    gettext library should not be compiled, because it creates various
    kind of build failures.</p>

    <p>Additionnaly, some packages (such as libglib2) do require
    gettext unconditionnally, while other packages (those who
    support <code>--disable-nls</code> in general) only require
    gettext when locale support is enabled.</p>

    <p>Therefore, Buildroot defines two configuration options:</p>

    <ul>
      <li><code>BR2_NEEDS_GETTEXT</code>, which is true as soon as the
      toolchain doesn't provide its own gettext implementation</li>

      <li><code>BR2_NEEDS_GETTEXT_IF_LOCALE</code>, which is true if
      the toolchain doesn't provide its own gettext implementation and
      if locale support is enabled</li>

    </ul>

    <p>Therefore, packages that unconditionnally need gettext should:</p>

    <ol>
      <li>Use <code>select BR2_PACKAGE_GNUTTEXT if
      BR2_NEEDS_GETTEXT</code> and possibly <code>select
      BR2_PACKAGE_LIBINTL if BR2_NEEDS_GETTEXT</code> if libintl is
      also needed</li>

      <li>Use <code>$(if $(BR2_NEEDS_GETTEXT),gettext)</code> in the
      package <code>DEPENDENCIES</code> variable</li>
    </ol>

    <p>Packages that need gettext only when locale support is enabled
    should:</p>

    <ol>
      <li>Use <code>select BR2_PACKAGE_GNUTTEXT if
      BR2_NEEDS_GETTEXT_IF_LOCALE</code> and possibly <code>select
      BR2_PACKAGE_LIBINTL if BR2_NEEDS_GETTEXT_IF_LOCALE</code> if
      libintl is also needed</li>

      <li>Use <code>$(if
      $(BR2_NEEDS_GETTEXT_IF_LOCALE),gettext)</code> in the
      package <code>DEPENDENCIES</code> variable</li>
    </ol>

    <h3>Conclusion</h3>

    <p>As you can see, adding a software package to Buildroot is simply a
    matter of writing a Makefile using an  existing
    example and modifying it according to the compilation process required by
    the package. </p>

    <p>If you package software that might be useful for other people,
    don't forget to send a patch to Buildroot developers!</p>

     <h2><a name="links" id="links"></a>Resources</h2>

    <p>To learn more about Buildroot you can visit these
    websites:</p>

    <ul>
      <li><a href="http://www.uclibc.org/">http://www.uclibc.org/</a></li>
      <li><a href="http://www.busybox.net/">http://www.busybox.net/</a></li>
    </ul>
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