Compile a kernel

2007-05-13T21:41:28Z

Picobyte: /* Installing the kernel source */

== Requirements ==
Not all Linux [[distribution]]s come with all of the components needed to build a kernel. You'll need a C compiler, make, and system header files installed before you can begin to build the kernel. This document assumes you have them. You can test this with:
cc -v
make -v
ls /usr/src/linux

If you want to update your 2.4.x kernel to a 2.6.x, read [http://www.linux-sxs.org/upgrading/migration26.html THIS] and [http://thomer.com/linux/migrate-to-2.6.html that].

== Preparations ==

=== Obtaining the kernel source ===
To [[compiler|compile]] a kernel, you will need the kernel [[source]]. You can get it from [http://www.kernel.org kernel.org]. Your [[distribution]] may also already provide the kernel source, for instance on the cd or dvd. It is also possible to get the latest kernel development version [[using git]].

=== Installing the kernel source ===
You can install the kernel source by either installing the package that came with your distribution, or extracting the [[tarball]] you downloaded from kernel.org . You can remain user (don't need to be root) until mentioned.

It is recommended that you put new kernel sources in a subdirectory of your [[home directory]] for example:
[[mkdir]] -p /home/$user/src/kernel
[[cd]] /home/$user/src/kernel

Download the kernel sources (linux-x.x.x.tar.gz or linux-x.x.x.tar.bz2) in this directory.
for the remaining to work with this version we'll use a variable ''$KV'' (for kernel version). Replace x.x.x with the kernel version
KV=x.x.x

Extract the sources using one of:
[[tar]] -zxvf linux-$KV.tar.gz
tar -jxvf linux-$KV.tar.bz2

and enter the created subdirectory
cd linux-$KV

== Building the kernel ==
It is recommended that you do not build in your kernel source directory.

=== Preparing to build ===
Create another directory in your home directory:
mkdir -p /home/$user/build/kernel/$KV/

If this is not the first time you compile the kernel you'll have to clean up your build directory. You may want to backup the previous .config file, however:
[[cp]] /home/$user/build/kernel/.config /home/$user/kernel.config
[[make]] O=/home/$user/build/kernel/$KV/ mrproper

=== Obtaining a configuration ===
Do this to restore the previous configuration:
cp /home/$user/kernel.config /home/$user/build/kernel/$KV/.config

Otherwise, if compiling for the first time you may want to start with your distribution's .config You can obtain that from cd or do:
[[zcat]] /proc/config.gz > /home/$user/build/kernel/$KV/.config

If you're going to upgrade to a newer kernel, first do:
make O=/home/$user/build/kernel/$KV/ oldconfig

For ncurses GUI in the terminal
make O=/home/$user/build/kernel/$KV/ menuconfig

;Notes: Most options are about specifying whether you want a feature [*] compiled into the kernel image, [M] compiled as a module, or [ ] not compiled at all. Do not compile your hard drive and file system type as a module - these must be compiled in the kernel [*], e.g. " [*] ReiserFS".
:Here you to specify an enormous number of features. It is advisable to skim through all the sections to get a feel for the different things you can do. The kernel configuration is one LINUX program that offers lots of help--select < Help > on any feature. The raw help file is /usr/src/linux/Documentation/Configure.help can also be worth reading. See also [[configuring linux kernel]].
:When you're done with the config, click exit and save current configuration. Your file is now known as .config .

=== Extra cleaning for old kernels ===
------->SKIP SECTION IF DOING A 2.6.x KERNEL<------
Respectively 1. ensures dependancies such as include files are in place and 2. clean your sources so they compile correctly:
make O=/home/$user/build/kernel/$KV/ dep
make O=/home/$user/build/kernel/$KV/ clean

=== compiling kernel and modules ===
make the kernel image (compile and creates compressed image of kernel). This may take a while...
make O=/home/$user/build/kernel/$KV/

make the modules
make O=/home/$user/build/kernel/$KV/ modules

== installation ==
for the remainder you need to be root:
su

To install the newly compiled modules to <tt>/lib/modules/$KV/</tt>:
make O=/home/$user/build/kernel/$KV/ modules_install

=== Move kernel and related files ===
Remove the following links:
rm -rf /boot/System.map
rm -rf /boot/vmlinuz

Then copy the newly created kernel and system.map to /boot
cp /home/$user/build/kernel/$KV/arch/i386/boot/bzImage /boot/vmlinuz-$KV
cp /home/$user/build/kernel/$KV/System.map /boot/System.map-$KV

Make the new links:
ln -s /boot/vmlinuz-$KV /boot/vmlinuz
ln -s /boot/System.map-$KV /boot/System.map

Next, if present, remove existing initrd.img file:
rm -rf /boot/initrd-$KV.img

And create the new one:
/sbin/mkinitrd /boot/initrd-$KV.img $KV

===Install a boot manager===
Use The Steps That Pertain To You 
*if you use [[grub]] then edit <tt>grub.conf</tt>
*if you use [[lilo]] then edit <tt>lilo.conf</tt>
:remember to leave the entry to your old kernel image just in case, so modify what is in the config originally to point to the old image and make a new entry for you new image you just made...

====GRUB====
Note today most distros now use menu.lst, so if you can't find grub or lilo, then you know what to look for.
title New Kernel :D
kernel /vmlinuz-$KV ro root=LABEL initrd /initrd-$KV.img
;Note:Look at the previous parameters in the grub.conf file and note what "root=" and use what is existing.

Exit and save grub.conf, and if you want (is not mandatory) type
/sbin/grub-install
reboot

====Lilo====
Append to your config to ''/etc/lilo.config'':
ROOTDEV=`mount -l | grep " \/ " | cut -d" " -f1`
cat << EOF >> /etc/lilo.conf
image = /boot/vmlinuz-$KV
label = vml-$KV
root = $ROOTDEV
read-only
EOF

install this lilo.conf (if listed, resolve errors before rebooting!):
/sbin/lilo

===Propietary nvidia module===
For some it is required to install proprietary modules. This can be done after booting, see [[NVIDIA graphics drivers]], or directly from the kernel directory after installation of the kernel if you're upgrading to a newer kernel version, by running as root:

/path/to/NVIDIA-Linux-*-pkg1.run -a --kernel-name="`grep -o "2\..\.[0-9]*.*$" .config`" \
--no-x-check --no-runlevel-check --kernel-module-only -s;

==instructions on how to apply patches to your kernel==

[http://www.linuxhq.com/patch-howto.html read this] or look below ...

This step comes after untarring your kernel source. When you download the patch, place it in the folder where you untarred your new kernel. Then type:
patch -E -p1 < sound_patch
Purely an example and you would type whatever the file name is in replace of sound_patch.

Regarding having alternative boot options, this is no problem. The stuff above that I tell you to add to your lilo or grub file above could just be appended to the file, and you could just add ".old" to the title of your original kernel name for you will know the difference. Whether it's grub or lilo, add "read-only" to the end of the original entries in the lilo.conf, or grub.conf, file.

=== Special notes for Debian Users ===
[[Debian]] has some utilities to make your life a little easier. The kernel-package set of utilities allows to to create your own kernel package. For most users, this just means that your kernel shows up like all other debian packages. However, if you have multiple machines running the same kernel, it allows an easy way to install it on all of them. So let's get started.

First, make sure you have the kernel-package tools. You can install them with the command
apt-get install kernel-package

The initial steps are the same
[[make]] clean
make menuconfig (or xconfig etc...).
Once your kernel is configured, type
[[make-kpkg]] kernel_image
and it will make your kernel.

Assuming the compile was successful, it will create a .deb in /usr/src which you can then install by typing
[[dpkg]] -i kernel-package-filename
follow the instructions and [[reboot]].

You can also create a custom kernel name (to avoid overwriting other kernels you have made) by typing something like:
make-kpkg kernel_image --revision=custom.1

This is just a quick review of the commands you need, for more information check out this [http://newbiedoc.sourceforge.net/tutorials/kernel-pkg/index-kernel-pkg.html guide] to compiling using the kernel package program.

[[Category:Kernel]]
[[Category:Example]]