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