Compiling a kernel

This is an example how to compile a Linux kernel. It has been tested for SUSE Linux 10.2 and kernel 2.6.21, but should work same or similar for every combination.

Check prerequesites

• Make sure you have a compiler installed

yast -i gcc

Get the code

• Download the kernel from ftp.kernel.org

wget ftp://ftp.kernel.org/pub/linux/kernel/v2.6/linux-2.6.21.tar.bz2

• unpack the kernel

bunzip linux-2.6.21.tar.bz2

• unpack the kernel for the second time

tar xvf linux-2.6.21.tar

Build it

• configure the kernel

cd linux-2.6.21
make oldconfig

• answer some un-understandable questions

The sense of the step make oldconfig is to tell the kernel its configuration, e.g. which parts should be built as a module, which parts should not be built at all and the name of your special build. oldconfig takes over the settings from the running kernel that you can check with zcat /proc/config.gz. The settings for the new kernel are stored in the file .config. E.g. a line CONFIG_LOCALVERSION="-thorsten" in .config would tell kernel 2.6.27 to call himself 2.6.27-thorsten.

• compile the kernel, note: on a two-CPU VMWare virtual machine with 2.4 GHz, this lasted 19m28.605s

make -j4

• compile the drivers

make -j4 modules

Install it

• install the drivers

make modules_install

• install the kernel

cp arch/x86_64/boot/bzImage /boot/vmlinuz-2.6.21

This will install the kernel for the x86_64 architecture.

• prepare the initial ramdisk

cp System.map /boot
mkinitrd

This will build an initial ramdisk for all kernels contained in /boot.

• add an entry to the bootloader. Let's take grub's /boot/grub/menu.lst:

title 2.6.21-selfcompiled
   root (hd0,0)
   kernel /boot/vmlinuz-2.6.21 root=/dev/sda1
   initrd /boot/initrd-2.6.21