How To Compile A Kernel - The Debian (Sarge) Way
Author: Falko Timme
Each distribution has some specific tools to build a custom kernel from the sources. This article is about compiling a kernel on Debian Sarge systems. It describes how to build a custom kernel using the latest unmodified kernel sources from www.kernel.org (vanilla kernel) so that you are independent from the kernels supplied by your distribution. It also shows how to patch the kernel sources if you need features that are not in there.
I have tested this on Debian Sarge in VMware Server.
I want to say first that this is not the only way of setting up such a system. There are many ways of achieving this goal but this is the way I take. I do not issue any guarantee that this will work for you!
1 Preliminary Note
The goal of this tutorial is to build a kernel .deb package that can be installed on the system, and that you can share with others and install on other Debian Sarge systems which is a big advantage compared to the "traditional" way where you don't end up with a .deb package.
2 Install Required Packages For Kernel Compilation
First we update our package database:
Then we install all needed packages like this:
apt-get install kernel-package libncurses5-dev fakeroot wget bzip2 build-essential udev
Please note that we have just installed udev which replaces the old (deprecated) devfs in new kernels. The default Debian Sarge kernel (2.6.8) still uses devfs which isn't available anymore in new kernels.
3 Download The Kernel Sources
Next we download our desired kernel to /usr/src. Go to www.kernel.org and select the kernel you want to install, e.g. linux-22.214.171.124.tar.bz2 (you can find all 2.6 kernels here: http://www.kernel.org/pub/linux/kernel/v2.6/). Then you can download it to /usr/src like this:
Then we unpack the kernel sources and create a symlink linux to the kernel sources directory:
tar xjf linux-126.96.36.199.tar.bz2
ln -s linux-188.8.131.52 linux
4 Apply Patches To The Kernel Sources (Optional)
Sometimes you need drivers for hardware that isn't supported by the new kernel by default, or you need support for virtualization techniques or some other bleeding-edge technology that hasn't made it to the kernel yet. In all these cases you have to patch the kernel sources (provided there is a patch available...).
Now let's assume you have downloaded the needed patch (I call it patch.bz2 in this example) to /usr/src. This is how you apply it to your kernel sources (you must still be in the /usr/src/linux directory):
bzip2 -dc /usr/src/patch.bz2 | patch -p1 --dry-run
bzip2 -dc /usr/src/patch.bz2 | patch -p1
The first command is just a test, it does nothing to your sources. If it doesn't show errors, you can run the second command which actually applies the patch. Don't do it if the first command shows errors!
If your patches are compressed with gzip (.gz) instead of bzip2 (.bz2), then you patch your kernel as follows:
gunzip -c /usr/src/patch.gz | patch -p1 --dry-run
gunzip -c /usr/src/patch.gz | patch -p1
You can also apply kernel prepatches to your kernel sources. For example, if you need a feature that is available only in kernel 2.6.19-rc6, but the full sources haven't been released yet for this kernel. Instead, a patch-2.6.19-rc6.bz2 is available. You can apply that patch to the 2.6.18 kernel sources, but not to kernel 184.108.40.206 or 220.127.116.11 or 18.104.22.168, etc. This is explained on http://kernel.org/patchtypes/pre.html:
Prepatches are the equivalent to alpha releases for Linux; they live in the testing directories in the archives. They should be applied using the patch(1) utility to the source code of the previous full release with a 3-part version number (for example, the 2.6.12-rc4 prepatch should be applied to the 2.6.11 kernel sources, not, for example, 22.214.171.124.)
So if you want to compile a 2.6.19-rc6 kernel, you must download the 2.6.18 kernel sources (http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.18.tar.bz2) in step 3 instead of kernel 126.96.36.199!
This is how you apply the 2.6.19-rc6 patch to kernel 2.6.18:
bzip2 -dc /usr/src/patch-2.6.19-rc6.bz2 | patch -p1 --dry-run
bzip2 -dc /usr/src/patch-2.6.19-rc6.bz2 | patch -p1
5 Configure The Kernel
It's a good idea to use the configuration of your current working kernel as a basis for your new kernel. Therefore we copy the existing configuration to /usr/src/linux:
make clean && make mrproper
cp /boot/config-`uname -r` ./.config
Then we run
which brings up the kernel configuration menu. Go to Load an Alternate Configuration File and choose .config (which contains the configuration of your current working kernel) as the configuration file:
Then browse through the kernel configuration menu and make your choices. Make sure you specify a kernel version identification string under General Setup ---> () Local version - append to kernel release. I use -default1 so our kernel .deb package will be named linux-188.8.131.52-default1_184.108.40.206-default1_i386.deb. Please make sure that the string contains a digit (e.g. 1, 2, ...) because otherwise the kernel build process will result in an error.
Please note: After you have installed linux-220.127.116.11-default1_18.104.22.168-default1_i386.deb and decide to compile another 22.214.171.124 kernel .deb package, it is important to use a different version string, e.g. -default2, -default3, etc., because otherwise you can't install your new kernel because dpkg complains that linux-126.96.36.199-default1_188.8.131.52-default1_i386.deb is already installed!
Next make sure you enable the Fusion MPT device drivers under Device Drivers --> Fusion MPT device support. I don't know if this is necessary on all platforms; at least it is on mine (Debian Sarge on a VMware Server) because otherwise you'll get this error message when you boot your new kernel:
/bin/cat: /sys/block/sda/dev: No such file or directory
which results in a kernel panic.
Then browse through the rest of the kernel configuration menu and make your choices. When you are finished and select Exit, answer the following question (Do you wish to save your new kernel configuration?) with Yes: