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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>
or
<pre>
$ make gconfig
</pre>
<p>to run the Qt3 or GTK-based configurators.</p>
<p>All 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, <code>libqt3-mt-dev</code> is
required to use the <i>xconfig</i> interface, and
<code>libglib2.0-dev, libgtk2.0-dev and libglade2-dev</code> are
needed to used the <i>gconfig</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>
<p>When using out-of-tree builds, the Buildroot
<code>.config</code> and temporary files are also stored in the
output directory. This means that you can safely run multiple
builds in parallel using the same source tree as long as they use
unique output directories.</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>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>
<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 $(call GENTARGETS,package,libfoo,host))
</pre>
<p>This might be useful if the compilation of the target package
requires some tools to be installed on the host. If the package
name is <code>libfoo</code>, then the name of the package for the
target is also <code>libfoo</code>, while the name of the package
for the host is <code>host-libfoo</code>. These names should be
used in the DEPENDENCIES variables of other packages if they depend
on <code>libfoo</code> or <code>host-libfoo</code>.</p>
<p>The call to the <code>GENTARGETS</code> macro <b>must</b> be at
the end of the <code>.mk</code> file, after all variable
definitions.</p>
<p>For the target package, the <code>GENTARGETS</code> uses the
variables defined by the .mk file and prefixed by the uppercased
package name: <code>LIBFOO_*</code>. For the host package, it uses
the <code>HOST_LIBFOO_*</code>. For <i>some</i> variables, if the
<code>HOST_LIBFOO_</code> prefixed variable doesn't exist, the
package infrastructure uses the corresponding variable prefixed by
<code>LIBFOO_</code>. This is done for variables that are likely to
have the same value for both the target and host packages. See
below for details.</p>
<p>The list of variables that can be set in a <code>.mk</code> file
to give metadata informations is (assuming the package name is
<code>libfoo</code>) :</p>
<ul>
<li><code>LIBFOO_VERSION</code>, mandatory, must contain the
version of the package. Note that if
<code>HOST_LIBFOO_VERSION</code> doesn't exist, it is assumed to
be the same as <code>LIBFOO_VERSION</code>.<br/>Example:
<code>LIBFOO_VERSION=0.1.2</code></li>
<li><code>LIBFOO_SOURCE</code> may contain the name of the
tarball of the package. If <code>HOST_LIBFOO_SOURCE</code> is not
specified, it defaults to <code>LIBFOO_VERSION</code>. If none
are specified, then the value is assumed to be
<code>packagename-$(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_GETTEXT 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 $(BR2_NEEDS_GETTEXT),gettext)</code> in the
package <code>DEPENDENCIES</code> variable</li>
</ol>
<p>Packages that need gettext only when locale support is enabled
should:</p>
<ol>
<li>Use <code>select BR2_PACKAGE_GETTEXT if
BR2_NEEDS_GETTEXT_IF_LOCALE</code> and possibly <code>select
BR2_PACKAGE_LIBINTL if BR2_NEEDS_GETTEXT_IF_LOCALE</code> if
libintl is also needed</li>
<li>Use <code>$(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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