mirror of
https://git.busybox.net/buildroot.git
synced 2024-12-13 15:23:27 +08:00
32cec3be97
by using this standard extension `adoc`, these files are rendered on gitlab & github Signed-off-by: Francois Perrad <francois.perrad@gadz.org> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
122 lines
5.0 KiB
Plaintext
122 lines
5.0 KiB
Plaintext
// -*- mode:doc; -*-
|
|
// vim: set syntax=asciidoc:
|
|
|
|
==== Using Buildroot during development
|
|
|
|
The normal operation of Buildroot is to download a tarball, extract
|
|
it, configure, compile and install the software component found inside
|
|
this tarball. The source code is extracted in
|
|
+output/build/<package>-<version>+, which is a temporary directory:
|
|
whenever +make clean+ is used, this directory is entirely removed, and
|
|
re-created at the next +make+ invocation. Even when a Git or
|
|
Subversion repository is used as the input for the package source
|
|
code, Buildroot creates a tarball out of it, and then behaves as it
|
|
normally does with tarballs.
|
|
|
|
This behavior is well-suited when Buildroot is used mainly as an
|
|
integration tool, to build and integrate all the components of an
|
|
embedded Linux system. However, if one uses Buildroot during the
|
|
development of certain components of the system, this behavior is not
|
|
very convenient: one would instead like to make a small change to the
|
|
source code of one package, and be able to quickly rebuild the system
|
|
with Buildroot.
|
|
|
|
Making changes directly in +output/build/<package>-<version>+ is not
|
|
an appropriate solution, because this directory is removed on +make
|
|
clean+.
|
|
|
|
Therefore, Buildroot provides a specific mechanism for this use case:
|
|
the +<pkg>_OVERRIDE_SRCDIR+ mechanism. Buildroot reads an _override_
|
|
file, which allows the user to tell Buildroot the location of the
|
|
source for certain packages.
|
|
|
|
The default location of the override file is +$(CONFIG_DIR)/local.mk+,
|
|
as defined by the +BR2_PACKAGE_OVERRIDE_FILE+ configuration option.
|
|
+$(CONFIG_DIR)+ is the location of the Buildroot +.config+ file, so
|
|
+local.mk+ by default lives side-by-side with the +.config+ file,
|
|
which means:
|
|
|
|
* In the top-level Buildroot source directory for in-tree builds
|
|
(i.e., when +O=+ is not used)
|
|
* In the out-of-tree directory for out-of-tree builds (i.e., when
|
|
+O=+ is used)
|
|
|
|
If a different location than these defaults is required, it can be
|
|
specified through the +BR2_PACKAGE_OVERRIDE_FILE+ configuration
|
|
option.
|
|
|
|
In this _override_ file, Buildroot expects to find lines of the form:
|
|
|
|
------------------
|
|
<pkg1>_OVERRIDE_SRCDIR = /path/to/pkg1/sources
|
|
<pkg2>_OVERRIDE_SRCDIR = /path/to/pkg2/sources
|
|
------------------
|
|
|
|
For example:
|
|
|
|
------------------
|
|
LINUX_OVERRIDE_SRCDIR = /home/bob/linux/
|
|
BUSYBOX_OVERRIDE_SRCDIR = /home/bob/busybox/
|
|
------------------
|
|
|
|
When Buildroot finds that for a given package, an
|
|
+<pkg>_OVERRIDE_SRCDIR+ has been defined, it will no longer attempt to
|
|
download, extract and patch the package. Instead, it will directly use
|
|
the source code available in the specified directory and +make clean+
|
|
will not touch this directory. This allows to point Buildroot to your
|
|
own directories, that can be managed by Git, Subversion, or any other
|
|
version control system. To achieve this, Buildroot will use _rsync_ to
|
|
copy the source code of the component from the specified
|
|
+<pkg>_OVERRIDE_SRCDIR+ to +output/build/<package>-custom/+.
|
|
|
|
This mechanism is best used in conjunction with the +make
|
|
<pkg>-rebuild+ and +make <pkg>-reconfigure+ targets. A +make
|
|
<pkg>-rebuild all+ sequence will _rsync_ the source code from
|
|
+<pkg>_OVERRIDE_SRCDIR+ to +output/build/<package>-custom+ (thanks to
|
|
_rsync_, only the modified files are copied), and restart the build
|
|
process of just this package.
|
|
|
|
In the example of the +linux+ package above, the developer can then
|
|
make a source code change in +/home/bob/linux+ and then run:
|
|
|
|
-----------------------
|
|
make linux-rebuild all
|
|
-----------------------
|
|
|
|
and in a matter of seconds gets the updated Linux kernel image in
|
|
+output/images+. Similarly, a change can be made to the BusyBox source
|
|
code in +/home/bob/busybox+, and after:
|
|
|
|
-----------------------
|
|
make busybox-rebuild all
|
|
-----------------------
|
|
|
|
the root filesystem image in +output/images+ contains the updated
|
|
BusyBox.
|
|
|
|
Source trees for big projects often contain hundreds or thousands of
|
|
files which are not needed for building, but will slow down the process
|
|
of copying the sources with _rsync_. Optionally, it is possible define
|
|
+<pkg>_OVERRIDE_SRCDIR_RSYNC_EXCLUSIONS+ to skip syncing certain files
|
|
from the source tree. For example, when working on the +webkitgtk+
|
|
package, the following will exclude the tests and in-tree builds from
|
|
a local WebKit source tree:
|
|
|
|
------------------
|
|
WEBKITGTK_OVERRIDE_SRCDIR = /home/bob/WebKit
|
|
WEBKITGTK_OVERRIDE_SRCDIR_RSYNC_EXCLUSIONS = \
|
|
--exclude JSTests --exclude ManualTests --exclude PerformanceTests \
|
|
--exclude WebDriverTests --exclude WebKitBuild --exclude WebKitLibraries \
|
|
--exclude WebKit.xcworkspace --exclude Websites --exclude Examples
|
|
------------------
|
|
|
|
By default, Buildroot skips syncing of VCS artifacts (e.g., the *.git* and
|
|
*.svn* directories). Some packages prefer to have these VCS directories
|
|
available during build, for example for automatically determining a precise
|
|
commit reference for version information. To undo this built-in filtering at a
|
|
cost of a slower speed, add these directories back:
|
|
|
|
------------------
|
|
LINUX_OVERRIDE_SRCDIR_RSYNC_EXCLUSIONS = --include .git
|
|
------------------
|