<?xml version="1.0" encoding="iso-8859-1"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Buildroot - Usage and documentation</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <link rel="stylesheet" type="text/css" href="stylesheet.css" /> </head> <body> <div class="main"> <div class="titre"> <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_software">Extending Buildroot with more Software</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 "host compilation toolchain". The machine on which it is running, and on which you're working, is called the "host system". 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 — 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 "Accessing Git" 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.</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=<directory> 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=<path/to/.config></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=<path/to/.config></code>, path to the Busybox configuration file</li> <li><code>LINUX26_KCONFIG=<path/to/.config></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 — 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-<version>.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 the <i>autotools</i> Buildroot infrastructure (see <a href="#add_software">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 looks like:</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> <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 — 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 four 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>$(BOARD_PATH)/target_skeleton</code> so that the target skeleton is stored in the board specific directory.</li> <li><code>TARGET_DEVICE_TABLE</code> to a file that contains the target device table — the list of device files (in <code>/dev/</code>) to be created by the root filesystem build procedure. If this variable is defined, the given device table will be used instead of the default one. If defined, the convention is to define it to <code>$(BOARD_PATH)/target_device_table.txt</code>. See <code>target/generic/device_table.txt</code> for an example file.</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 — 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 — 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 -> 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 <shared download location> 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>"~/.bashrc"</code>. <p> <pre> export BUILDROOT_DL_DIR <shared download location> </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 :</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_software" id="add_software"></a>Extending Buildroot with more software</h2> <p>This section will only consider the case in which you want to add user-space software. </p> <h3>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> <h3><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>foo</code> software that will be used and displayed in the configuration tool. It should basically contain:</p> <pre> config BR2_PACKAGE_FOO bool "foo" help This is a comment that explains what foo is. http://foosoftware.org/foo/ </pre> <p>Of course, you can add other options to configure particular things in your software. </p> <p>Finally you have to add your new <code>foo/Config.in</code> to <code>package/Config.in</code>. 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/procps/Config.in" </pre> <p><strong>Note:</strong><br> Generally all packages should live <em>directly</em> in the <code>package</code> directory to make it easier to find them. </p> <h3>The real Makefile</h3> <p>Finally, here's the hardest part. Create a file named <code>foo.mk</code>. It will contain the Makefile rules that are in charge of downloading, configuring, compiling and installing the software.</p> <p>Two types of Makefiles can be written :</p> <ul> <li>Makefiles for autotools-based (autoconf, automake, etc.) software are very easy to write thanks to the infrastructure available in <code>package/Makefile.autotools.in</code>.</li> <li>Makefiles for other types of packages are a little bit more complex to write.</li> </ul> <p>First, let's see how to write a Makefile for an autotools-based package, with an example :</p> <pre> <a name="ex1line1" id="ex1line1">1</a> ############################################################# <a name="ex1line2" id="ex1line2">2</a> # <a name="ex1line3" id="ex1line3">3</a> # foo <a name="ex1line4" id="ex1line4">4</a> # <a name="ex1line5" id="ex1line5">5</a> ############################################################# <a name="ex1line6" id="ex1line6">6</a> FOO_VERSION:=1.0 <a name="ex1line7" id="ex1line7">7</a> FOO_SOURCE:=foo-$(FOO_VERSION).tar.gz <a name="ex1line8" id="ex1line8">8</a> FOO_SITE:=http://www.foosoftware.org/downloads <a name="ex1line9" id="ex1line9">9</a> FOO_INSTALL_STAGING = YES <a name="ex1line10" id="ex1line10">10</a> FOO_INSTALL_TARGET = YES <a name="ex1line11" id="ex1line11">11</a> FOO_CONF_OPT = --enable-shared <a name="ex1line12" id="ex1line12">12</a> FOO_DEPENDENCIES = libglib2 host-pkgconfig <a name="ex1line13" id="ex1line13">13</a> $(eval $(call AUTOTARGETS,package,foo)) </pre> <p>On <a href="#ex1line6">line 6</a>, we declare the version of the package. On lines <a href="#ex1line7">7</a> and <a href="#ex1line8">8</a>, 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 <a href="#ex1line9">line 9</a>, we tell Buildroot to install the application to the staging directory. The staging directory, located in <code>output/staging/</code> is the directory where all the packages are installed, including their documentation, etc. By default, packages are installed in this location using the <code>make install</code> command.</p> <p>On <a href="#ex1line10">line 10</a>, we tell Buildroot to also install the application to the target directory. This directory contains what will become the root filesystem running on the target. Usually, we try to install stripped binaries and to not install the documentation. By default, packages are installed in this location using the <code>make install-strip</code> command.</p> <p>On <a href="#ex1line11">line 11</a>, we tell Buildroot to pass a custom configure option to the <code>./configure</code> script when configuring the the package.</p> <p>On <a href="#ex1line12">line 12</a>, we declare our dependencies so that they are built before the build process of our package starts.</p> <p>Finally, on line <a href="#ex1line13">line 13</a>, we invoke the <code>package/Makefile.autotools.in</code> magic to get things working.</p> <p>For more details about the available variables and options, see the comment at the top of <code>package/Makefile.autotools.in</code> and the examples in all the available packages.</p> <p>The second solution, suitable for every type of package, looks like this :</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 — 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 "subscribes" 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>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> </div> <!-- <a href="http://validator.w3.org/check?uri=referer"><img border="0" height="31" width="88" src="images/valid-html401.png" alt="Valid HTML"></img></a> --> </body> </html>