d41e115395
Signed-off-by: Samuel MARTIN <s.martin49@gmail.com> Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be> Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
184 lines
6.4 KiB
Plaintext
184 lines
6.4 KiB
Plaintext
Using Buildroot
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===============
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Configuration and general usage
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-------------------------------
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Buildroot has a nice configuration tool similar to the one you can
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find in the http://www.kernel.org/[Linux kernel] or in
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http://www.busybox.net/[Busybox]. Note that you can (and should) build
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everything as a normal user. There is no need to be root to configure
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and use Buildroot. The first step is to run the configuration
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assistant:
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--------------------
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$ make menuconfig
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--------------------
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to run the curses-based configurator, or
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$ make xconfig
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--------------------
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or
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--------------------
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$ make gconfig
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--------------------
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to run the Qt or GTK-based configurators.
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All of these "make" commands will need to build a configuration
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utility, so you may need to install "development" packages for
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relevant libraries used by the configuration utilities. On Debian-like
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systems, the +libncurses5-dev+ package is required to use the
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'menuconfig' interface, +libqt4-dev+ is required to use the 'xconfig'
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interface, and +libglib2.0-dev, libgtk2.0-dev and libglade2-dev+ are
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needed to use the 'gconfig' interface.
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For each menu entry in the configuration tool, you can find associated
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help that describes the purpose of the entry.
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Once everything is configured, the configuration tool generates a
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+.config+ file that contains the description of your
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configuration. It will be used by the Makefiles to do what's needed.
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Let's go:
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--------------------
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$ make
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--------------------
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You *should never* use +make -jN+ with Buildroot: it does not support
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'top-level parallel make'. Instead, use the +BR2_JLEVEL+ option to
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tell Buildroot to run each package compilation with +make -jN+.
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This command will generally perform the following steps:
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* Download source files (as required)
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* Configure, build and install the cross-compiling toolchain if an
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internal toolchain is used, or import a toolchain if an external
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toolchain is used
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* Build/install selected target packages
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* Build a kernel image, if selected
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* Build a bootloader image, if selected
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* Create a root filesystem in selected formats
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Buildroot output is stored in a single directory, +output/+.
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This directory contains several subdirectories:
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* +images/+ where all the images (kernel image, bootloader and root
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filesystem images) are stored.
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* +build/+ where all the components except for the cross-compilation
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toolchain are built (this includes tools needed to run Buildroot on
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the host and packages compiled for the target). The +build/+
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directory contains one subdirectory for each of these components.
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* +staging/+ which contains a hierarchy similar to a root filesystem
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hierarchy. This directory contains the installation of the
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cross-compilation toolchain and all the userspace packages selected
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for the target. However, this directory is 'not' intended to be
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the root filesystem for the target: it contains a lot of development
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files, unstripped binaries and libraries that make it far too big
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for an embedded system. These development files are used to compile
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libraries and applications for the target that depend on other
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libraries.
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* +target/+ which contains 'almost' the complete root filesystem for
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the target: everything needed is present except the device files in
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+/dev/+ (Buildroot can't create them because Buildroot doesn't run
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as root and doesn't want to run as root). Therefore, this directory
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*should not be used on your target*. Instead, you should use one of
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the images built in the +images/+ directory. If you need an
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extracted image of the root filesystem for booting over NFS, then
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use the tarball image generated in +images/+ and extract it as
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root. Compared to +staging/+, +target/+ contains only the files and
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libraries needed to run the selected target applications: the
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development files (headers, etc.) are not present, unless the
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+development files in target filesystem+ option is selected.
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* +host/+ contains the installation of tools compiled for the host
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that are needed for the proper execution of Buildroot, including the
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cross-compilation toolchain.
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* +toolchain/+ contains the build directories for the various
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components of the cross-compilation toolchain.
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Offline builds
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--------------
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If you intend to do an offline build and just want to download
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all sources that you previously selected in the configurator
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('menuconfig', 'xconfig' or 'gconfig'), then issue:
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$ make source
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You can now disconnect or copy the content of your +dl+
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directory to the build-host.
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Building out-of-tree
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--------------------
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Buildroot supports building out of tree with a syntax similar to the
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Linux kernel. To use it, add +O=<directory>+ to the make command line:
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$ make O=/tmp/build
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Or:
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$ cd /tmp/build; make O=$PWD -C path/to/buildroot
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--------------------
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All the output files will be located under +/tmp/build+.
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When using out-of-tree builds, the Buildroot +.config+ and temporary
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files are also stored in the output directory. This means that you can
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safely run multiple builds in parallel using the same source tree as
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long as they use unique output directories.
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For ease of use, Buildroot generates a Makefile wrapper in the output
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directory - So after the first run, you no longer need to pass +O=..+
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and +-C ..+, simply run (in the output directory):
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$ make <target>
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Environment variables
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---------------------
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[[env-vars]]
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Buildroot also honors some environment variables, when they are passed
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to +make+ or set in the environment:
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* +HOSTCXX+, the host C++ compiler to use
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* +HOSTCC+, the host C compiler to use
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* +UCLIBC_CONFIG_FILE=<path/to/.config>+, path to
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the uClibc configuration file, used to compile uClibc, if an
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internal toolchain is being built
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* +BUSYBOX_CONFIG_FILE=<path/to/.config>+, path to
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the Busybox configuration file
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* +BUILDROOT_DL_DIR+ to override the directory in which
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Buildroot stores/retrieves downloaded files
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An example that uses config files located in the toplevel directory and
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in your $HOME:
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$ make UCLIBC_CONFIG_FILE=uClibc.config BUSYBOX_CONFIG_FILE=$HOME/bb.config
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--------------------
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If you want to use a compiler other than the default +gcc+
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or +g+++ for building helper-binaries on your host, then do
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$ make HOSTCXX=g++-4.3-HEAD HOSTCC=gcc-4.3-HEAD
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--------------------
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