HOW TO : Compile Linux Kernel 2.6

This is the start point, if you want to play around with your customized kernel. Compiling custom kernel has its own advantages and disadvantages. Compiling kernel needs to understand few things and then just type couple of commands. This step by step howto covers compiling Linux kernel version 2.6.xx under Debian GNU Linux. However, instructions remains the same for any other distribution except for apt-get command.

Step # 1 Get Latest Linux kernel code

Visit http://kernel.org/ and download the latest source code. File name would be linux-x.y.z.tar.bz2, where x.y.z is actual version number. For example file linux-2.6.38.5.tar.bz2 represents 2.6.38.5 kernel version. Use wget command to download kernel source code:
$ cd /tmp
$ wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-x.y.z.tar.bz2

Note: Replace x.y.z with actual version number. USE sudo before the commands, if you are not the root / admin

Step # 2 Extract tar (.tar.bz3) file

Type the following command:
# sudo tar -xjvf linux-2.6.38.5.tar.bz2 -C /usr/src
# cd /usr/src

Step # 3 Configure kernel

Before you configure kernel make sure you have development tools (gcc compilers and related tools) are installed on your system. If gcc compiler and tools are not installed then use apt-get command under Debian Linux to install development tools.
# sudo apt-get install gcc

Now you can start kernel configuration by typing any one of the command:

• $ make menuconfig - Text based color menus, radiolists & dialogs. This option also useful on remote server if you wanna compile kernel remotely.
• $ make xconfig - X windows (Qt) based configuration tool, works best under KDE desktop
• $ make gconfig - X windows (Gtk) based configuration tool, works best under Gnome Dekstop.

For example make menuconfig command launches following screen:
$ sudo make menuconfig

You have to select different options as per your need. Each configuration option has HELP button associated with it so select help button to get help.

Step # 4 Compile kernel

Start compiling to create a compressed kernel image, enter:
$ sudo makeStart compiling to kernel modules:
$ sudo make modules

Install kernel modules (become a root user, use su command):
$ su -
# sudo make modules_install


Step # 5 Install kernel

So far we have compiled kernel and installed kernel modules. It is time to install kernel itself.
# sudo make install

It will install three files into /boot directory as well as modification to your kernel grub configuration file:

• System.map-2.6.38.5
• config-2.6.38.5
• vmlinuz-2.6.38.5

Step # 6: Create an initrd image

Type the following command at a shell prompt:
# cd /boot
# sudo mkinitramfs -o initrd.img-2.6.38.5 2.6.38.5

initrd images contains device driver which needed to load rest of the operating system later on. Not all computer requires initrd, but it is safe to create one.

Step # 7 Modify Grub configuration file - /boot/grub/menu.lst

Open file using vi:
# vi /boot/grub/menu.lst

title           Debian GNU/Linux, kernel 2.6.38.5 Default root            (hd0,0) kernel          /boot/vmlinuz root=/dev/hdb1 ro initrd          /boot/initrd.img-2.6.38.5 savedefault boot

Remember to setup correct root=/dev/hdXX device. Save and close the file. If you think editing and writing all lines by hand is too much for you, try out update-grub command to update the lines for each kernel in /boot/grub/menu.lst file. Just type the command:
# update-grub
Simple. Isn't?

Step # 8 : Reboot computer and boot into your new kernel

Just issue reboot command:
# reboot

Step # 9 : Check your new kernel version

Just issue the command:
# uname -a

Linux sudipto 2.6.38.5 #33-Ubuntu SMP Sun Sep 19 20:34:50 UTC 2010 i686_64 GNU/Linux

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