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Revision 75 as of 2011-11-15 01:06:54
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Comment: mention debuild --prepend-path=/usr/lib/ccache
Revision 77 as of 2012-08-18 12:06:55
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apt-get build-dep linux-2.6 apt-get build-dep linux
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'''+++ 09-Oct-2011: NOTE: Current SVN trunk (linux-3.1-rcX): linux-tools package now contains linux-kbuild stuff. +++''' '''+++ 16-Nov-2011: NOTE: linux-kbuild stuff moved to linux-tools package with >=3.2-rcX. +++'''

Translation(s): English - Italiano

(!) ?Discussion

Building custom kernel packages

(this wiki page should be renamed/moved to better reflect the actual content)

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

Reasons to do this:

  1. Modifying the Debian configuration to change the preemption model.

  2. Modifying the Debian configuration to change the timer frequency.

  3. Add a patch fix.
  4. 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.

Caveat: ulimit -n problem

If patch series are silently(!) not applied, that may be because the total number of patches to apply is too high to work with the default “ulimit -n” value (usually 1024). This has been fixed in 2.6.32-26 in squeeze.

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. 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
  3. Look at the top of debian/changelog and think of an appropriate version number. You cannot dch yet, though. 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".

  4. 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.

  5. Put your patch into the debian/patches directory and create a new series file to match the Debian revision; assuming you are basing your work on the -1 package, you would create a file named 1+foo.1:

    cp ~/special-fix.patch debian/patches/bugfix/
    echo "+ bugfix/special-fix.patch" >> debian/patches/series/1+foo.1
  6. Optional : If it's not the first build attempt, and should you need to clean things in case of build failures :

    make -f debian/rules clean
  7. 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
  8. Now that the above error message has occured after the first “debian/rules clean”, dch will work because debian/control has been (re-)generated. (Note that, after editing debian/changelog, “debian/rules clean” must again be run because its hash changes.) Start a new stanza at the top of debian/changelog and use an appropriate version number. Ensure that the distribution is not set to the regular release names. Change it to something like UNRELEASED. You could do this with the dch tool from the devscripts package like so:

    dch --local +foo.
  9. Document the addition of this patch in the new stanza in debian/changelog.

  1. Make sure you have at least 40 GB of disk space free (version 2.6.32-17 took 30 GB).
  2. 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}

If you plan to do multiple rebuilds you might want to use ccache by adding the --prepend-path=/usr/lib/ccache option to the above debuild command.

Building only a single kernel variant

  1. Make sure you have at least 10 GB of disk space free (setup_amd64_none_amd64 took 7.3 GB in version 2.6.32-17).
  2. 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.

  3. Change the .config file, using e.g.

    make menuconfig
    cd ../../..
  4. 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 \


    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 this thread. Solution:

    fakeroot make -f debian/rules.gen binary-arch_i386_none_real
  5. 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


    rm debian/stamps/build_i386_none_686_plain

The story of linux-kbuild-2.6

+++ 16-Nov-2011: NOTE: linux-kbuild stuff moved to linux-tools package with >=3.2-rcX. +++

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

NOTE: The instructions which follow are implemented by the attached shell script - build-linux-kbuild.sh - edit it to suit your needs (e.g., change VERSION to your kernel version).

Checkout the source from SVN repository:

svn co svn://svn.debian.org/kernel/dists/trunk/linux-kbuild-2.6

Then, download 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-${VERSION}.tar.bz2

Now, you prepare the Debian package:

cd linux-kbuild-2.6
./debian/bin/genorig.py ../linux-${VERSION}.tar.bz2
cd ..
tar -xzf orig/linux-kbuild-2.6_${VERSION}.orig.tar.gz
cd linux-kbuild-2.6-${VERSION}
cp -a ../linux-kbuild-2.6/* ./

NOTE: Optionally, you have to change Debian-version in debian/changelog if $VERSION of Linux-kernel is higher, think of 2.6.35 (latest version in linux-kbuild-2.6 SVN-branch) is smaller than 2.6.36-rcX (version of tarball), otherwise the genorig.py line fails.

Finally, adjust the Debian version and add comments like "Non-maintainer upload" plus "New upstream version" via dch command. Last but not least, build the package itself after you installed eventually missing build-dependencies:

dch -i
make -f debian/rules clean
cp -av ../orig/linux-kbuild-2.6_${VERSION}.orig.tar.gz ../ <--- Necessary to get a diff file.
dpkg-buildpackage -us -uc (or debuild)

and you are done.