6527f8a31d
This small patch adds references to the section on 'recommended directory structure' from sections explaining the post-build script and rootfs overlay. Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
108 lines
4.9 KiB
Plaintext
108 lines
4.9 KiB
Plaintext
// -*- mode:doc; -*-
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// vim: set syntax=asciidoc:
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[[rootfs-custom]]
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=== Customizing the generated target filesystem
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Besides changing the configuration through +make *config+,
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there are a few other ways to customize the resulting target filesystem.
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The two recommended methods, which can co-exist, are root filesystem
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overlay(s) and post build script(s).
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Root filesystem overlays (+BR2_ROOTFS_OVERLAY+)::
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+
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A filesystem overlay is a tree of files that is copied directly
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over the target filesystem after it has been built. To enable this
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feature, set config option +BR2_ROOTFS_OVERLAY+ (in the +System
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configuration+ menu) to the root of the overlay. You can even specify
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multiple overlays, space-separated. If you specify a relative path,
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it will be relative to the root of the Buildroot tree. Hidden
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directories of version control systems, like +.git+, +.svn+, +.hg+,
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etc., files called +.empty+ and files ending in +~+ are excluded from
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the copy.
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+
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As shown in xref:customize-dir-structure[], the recommended path for
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this overlay is +board/<company>/<boardname>/rootfs-overlay+.
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Post-build scripts (+BR2_ROOTFS_POST_BUILD_SCRIPT+)::
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+
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Post-build scripts are shell scripts called 'after' Buildroot builds
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all the selected software, but 'before' the rootfs images are
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assembled. To enable this feature, specify a space-separated list of
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post-build scripts in config option +BR2_ROOTFS_POST_BUILD_SCRIPT+ (in
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the +System configuration+ menu). If you specify a relative path, it
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will be relative to the root of the Buildroot tree.
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+
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Using post-build scripts, you can remove or modify any file in your
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target filesystem. You should, however, use this feature with care.
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Whenever you find that a certain package generates wrong or unneeded
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files, you should fix that package rather than work around it with some
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post-build cleanup scripts.
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+
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As shown in xref:customize-dir-structure[], the recommended path for
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this script is +board/<company>/<boardname>/post_build.sh+.
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+
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The post-build scripts are run with the main Buildroot tree as current
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working directory. The path to the target filesystem is passed as the
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first argument to each script. If the config option
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+BR2_ROOTFS_POST_SCRIPT_ARGS+ is not empty, these arguments will be
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passed to the script too. All the scripts will be passed the exact
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same set of arguments, it is not possible to pass different sets of
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arguments to each script.
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+
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In addition, you may also use these environment variables:
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- +BR2_CONFIG+: the path to the Buildroot .config file
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- +HOST_DIR+, +STAGING_DIR+, +TARGET_DIR+: see
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xref:generic-package-reference[]
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- +BUILD_DIR+: the directory where packages are extracted and built
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- +BINARIES_DIR+: the place where all binary files (aka images) are
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stored
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- +BASE_DIR+: the base output directory
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Below two more methods of customizing the target filesystem are
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described, but they are not recommended.
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Direct modification of the target filesystem::
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+
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For temporary modifications, you can modify the target filesystem
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directly and rebuild the image. The target filesystem is available
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under +output/target/+. After making your changes, run +make+ to
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rebuild the target filesystem image.
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+
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This method allows you to do anything to the target filesystem, but if
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you need to clean your Buildroot tree using +make clean+, these
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changes will be lost. Such cleaning is necessary in several cases,
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refer to xref:full-rebuild[] for details. This solution is therefore
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only useful for quick tests: _changes do not survive the +make clean+
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command_. Once you have validated your changes, you should make sure
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that they will persist after a +make clean+, using a root filesystem
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overlay or a post-build script.
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Custom target skeleton (+BR2_ROOTFS_SKELETON_CUSTOM+)::
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+
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The root filesystem image is created from a target skeleton, on top of
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which all packages install their files. The skeleton is copied to the
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target directory +output/target+ before any package is built and
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installed. The default target skeleton provides the standard Unix
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filesystem layout and some basic init scripts and configuration files.
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+
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If the default skeleton (available under +system/skeleton+) does not
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match your needs, you would typically use a root filesystem overlay or
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post-build script to adapt it. However, if the default skeleton is
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entirely different than what you need, using a custom skeleton may be
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more suitable.
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+
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To enable this feature, enable config option
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+BR2_ROOTFS_SKELETON_CUSTOM+ and set +BR2_ROOTFS_SKELETON_CUSTOM_PATH+
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to the path of your custom skeleton. Both options are available in the
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+System configuration+ menu. If you specify a relative path, it will
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be relative to the root of the Buildroot tree.
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+
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This method is not recommended because it duplicates the entire
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skeleton, which prevents taking advantage of the fixes or improvements
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brought to the default skeleton in later Buildroot releases.
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include::customize-device-permission-tables.txt[]
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