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= Building custom kernel packages =
(this wiki page should be renamed/moved to better reflect the actual content)
#language en
||<tablestyle="width: 100%;" style="border: 0px hidden">~-[[DebianWiki/EditorGuide#translation|Translation(s)]]: English - [[it/HowToRebuildAnOfficialDebianKernelPackage|Italiano]]-~||<style="text-align: right;border: 0px hidden"> (!) [[/Discussion|Discussion]]||
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This page is about rebuilding an official Debian kernel package with custom changes. There is the Kernel Handbook about this: http://kernel-handbook.alioth.debian.org/ (which explains how to "Rebuild an official Debian linux kernel package", hopefully : http://kernel-handbook.alioth.debian.org/ch-common-tasks.html ch 4.2 : "Rebuilding an official Debian kernel package").

We are following section 4.2: '''Rebuilding an official Debian kernel package'''

<<Anchor(reasons)>> '''Reasons to do this:'''

 1. Modifying the Debian configuration to change the '''preemption model'''.
 1. Modifying the Debian configuration to change the '''timer frequency'''.
 1. Modifying the Debian configuration to change to '''Pata'''.
 1. Add a patch fix.
 1. Add your favorite patchset.
What you'll get is exactly the kernel that Debian releases but with those added changes. The new packages will not step on the official kernel images' toes.

== Add a patch to linux-2.6 and build new kernel packages ==
 1. Create the directory where you will build the kernel package as a normal user and make sure you have all necessary packages installed: {{{
apt-get install fakeroot build-essential devscripts
apt-get build-dep linux-2.6

 1. Get the package source. For this to work, you need to have {{{deb-src}}} lines for the official archive in {{{/etc/apt/sources.list}}}: {{{
apt-get source linux-2.6
cd linux-2.6-*
 Now you are in the tree that holds the source and all changes Debian made to it. As an alternative, you could get a kernel tarball, e.g. from buildserver (see DebianKernel), unpack it, and get the latest Debian patches + config settings: {{{
tar xzf linux-2.6_2.6.24~rc6.orig.tar.gz
cd linux-2.6-*
svn export svn://svn.debian.org/svn/kernel/dists/trunk/linux-2.6/debian

 1. Start a new stanza at the top of {{{debian/changelog}}} and use an appropriate version number. If you are adding a single patch "foo", you might want to append "+foo.1". If you are adding multiple patches for your company or yourself, use "+somename.1". You could do this with the {{{dch}}} tool from the {{{devscripts}}} package like so: {{{
dch --local +foo.

 1. Append the same string to the {{{abi.abiname}}} field in {{{debian/config/defines}}} to ensure that your custom kernel package name doesn't bite with the official ones. In our case, we're now creating {{{linux-image-2.6.xx-y+foo.1-zzz}}}.

 1. Put your patch into the {{{debian/patches}}} directory and add it to the series file (assuming {{{debian/patches/series/1}}} is the latest file in there): {{{
cp ~/special-fix.patch debian/patches/bugfix/
echo "+ bugfix/special-fix.patch" >> debian/patches/series/1+foo.1
 Now check that your patchset still applies and fix any conflicts:

Note: on the first run, the target fails. Make sure you run it twice.
This target is made to fail intentionally, to make sure
that it is NEVER run during the automated build. Please
ignore the following error, the debian/control file has
been generated SUCCESSFULLY.

make -f debian/rules source-all

 1. Document the addition of this patch in the new stanza in {{{debian/changelog}}}.

=== Building all kernel-related packages ===
 1. Assuming you want to build '''all''' kernel-related packages, build with the appropriate {{{DEBIAN_KERNEL_JOBS}}} parameter (the number of processors you can use for the build): {{{
~/src/linux-2.6-2.6.24~rc6$ debuild -e DEBIAN_KERNEL_JOBS=${NR_CPUS}

=== Building only a single kernel variant ===
 1. Prepare the rules file for the one build you want to make: {{{
fakeroot make -f debian/rules.gen setup_i386_none_k7
 This presumes you are only interested in building a k7 AMD processor image! If you were interested in a 686 processor image do: {{{
fakeroot make -f debian/rules.gen setup_i386_none_686
 This will build a tree in the {{{debian/build/build_i386_none_k7}}} or {{{debian/build/build_i386_none_686}}} directory. Go to that directory.

 1. Change the {{{.config}}} file, using e.g. {{{
make menuconfig
cd ../../..

 1. Compile the kernel and generate the kernel packages. Replace {{{$NR_CPUS}}} with the number of CPUs of the build machine (keeping it all on the same line) and run either: {{{
fakeroot make -f debian/rules.gen binary-arch_i386_none_k7 binary-indep \
}}} ''or'' {{{
fakeroot make -f debian/rules.gen binary-arch_i386_none_686 binary-indep \
 On a 2.0GHz CPU the compile will take 1 hour and 20 minutes and 8 package files will be generated, e.g.: {{{
 '''Problem''': In this case, {{{linux-headers-2.6.24-1+foo.1-common}}} will be missing. One needs to invoke the {{{binary-arch_i386}}} target, which will yield all feature sets (Xen, VServer) and flavours to be generated, and obviously takes a lot longer. See [[http://lists.debian.org/debian-kernel/2008/04/msg00190.html|this thread]].

 1. If you apply further changes to the source package and need to rebuild the binary packages without rebuilding each and every binary objects, you can remove the build stamp before running the above mentioned building command. {{{
rm debian/stamps/build_i386_none_k7_plain
}}} ''or'' {{{
rm debian/stamps/build_i386_none_686_plain

== The story of linux-kbuild-2.6 ==
The {{{linux-headers-*}}} packages created with the above method depend on {{{linux-kbuild-*}}}, which is a '''not''' built from the {{{linux-2.6}}} source package, but from {{{linux-kbuild-2.6}}}.

Often, when a new kernel comes around, {{{linux-kbuild-2.6.xx}}} isn't yet available in the archive, so you either have to build it yourself, or wait.

=== How to build linux-kbuild-2.6 yourself ===
Fetch the sources from SVN: {{{
svn co svn://svn.debian.org/kernel/dists/trunk/linux-kbuild-2.6
Then, fetch the vanilla kernel tarball (important: the 2.6.x version, no 2.6.x.y version): {{{
wget http://ftp.de.kernel.org/pub/linux/kernel/v2.6/linux-2.6.27.tar.bz2
Now, you can prepare the package: {{{
cd linux-kbuild-2.6
./debian/bin/genorig.py ../linux-2.6.27.tar.bz2
cd ..
tar xzf orig/linux-kbuild-2.6_2.6.27.orig.tar.gz
cd linux-kbuild-2.6-2.6.27/
cp -a ../linux-kbuild-2.6/* ./
dch -i
Now adjust the version, and add a comment like "New upstream version" or something, and build the package itself, after you installed eventually missing build-dependencies: {{{
make -f debian/rules clean
dpkg-buildpackage -us -uc
and you are done.
See the Kernel Handbook section [[https://kernel-team.pages.debian.net/kernel-handbook/ch-common-tasks.html#s-common-official|Rebuilding official Debian kernel packages]].

Translation(s): English - Italiano

(!) ?Discussion

See the Kernel Handbook section Rebuilding official Debian kernel packages.