====== Fedora Kernel Building Information ======

Current Version at time of writing: **Fedora 12**

New Info:

[[http://fedoraproject.org/wiki/Building_a_custom_kernel]] (info for fedora > 8)

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Old Info:

[[http://www.mjmwired.net/]]

[[http://www.mjmwired.net/resources/mjm-fedora-fc5.html#kernelsrc]]

<tab>the above links shows how to download the fedora kernel source

[[http://www.howtoforge.com/kernel_compilation_fedora]]

<tab>the above link explains how to build a fedora rpm kernel

[[http://fedoraproject.org/wiki/Docs/CustomKernel]]

<note warning>
Fedora is using a system frequency of 1000Hz now, which sometimes causes problems when the Fedora server is being run as a virtual server (the client system).  The clock gets all out of whack.

I've been able to compile a custom kernel with a frequency of 100Hz to solve this problem. (([[linux:server:fedoravm]]))
</note>


===== Preparation =====


==== Download Kernel Source ====

Obtaining Kernel Source through 'yum'

There are yum utilities which will download the LATEST kernel source.

You only have to install yum-utils once:

<code bash>[root@maltsweb kernel-source]# yum install yum-utils</code>

Download the new kernel source:

<code bash>[root@maltsweb kernel-source]# yumdownloader --source kernel --enablerepo core-source --enablerepo updates-source</code>

==== Install the Kernel Source ====

Install the SRC.RPM file and Prepare source

Install the kernel.src.rpm that you chose to install in the previous steps.

Install:
<code bash>[root@maltsweb kernel-source]# rpm -Uvh kernel-2.6.15-1.1955_FC5.src.rpm
   1:kernel                 ########################################### [100%]</code>


==== Prep the Source ====

Install any dependencies that our kernel build might have: <code># yum-builddep kernel</code>


Set it up:

First we need to "brand" our custom kernel:

<code bash>[root@maltsweb kernel-source]# vi /usr/src/redhat/SPECS/kernel-2.6.spec</code>

And change:

<code diff>
- #% define dist .XX
+ %define dist .www
</code>

<note note>Make sure you remove the space after the ''%''</note>

And finally run:

<code bash>[root@maltsweb kernel-source]# rpmbuild -bp --target=$(uname -m)  /usr/src/redhat/SPECS/kernel-2.6.spec</code>

<note warning>rpmbuild: -bp = build prep (it extracts and patches the kernel, preparing it for building, but does **NOT** build the kernel)</note>

===== Customize your kernel =====

This is when you prepare patches, new configs, etc.



==== Configure the Kernel ====

<code bash>cd SOURCES/*
make menuconfig</code>


===== Build the Kernel RPM =====

Build the RPM: <code># cd SPECS/
# rpmbuild -bb --target=$(uname -m) --with firmware --without debug --without debuginfo --without devel kernel.spec</code>

Install the RPM:<code bash>cd RPMS/i386
rpm -ivh kernel-2.6.20www1.2316-2.i386.rpm</code>



===== Old Notes =====


==== mkinitrd ====

<code bash>mkinitrd /boot/initrd-2.6.20-www1.2316-2.img 2.6.20-www1.2316</code>



==== Edit grub ====

<code bash>vi /boot/grub/menu.lst</code>

<code>#title Fedora Core (2.6.20-1.2316.fc5smp)
#       root (hd0,0)
#       kernel /vmlinuz-2.6.20-1.2316.fc5smp ro root=/dev/VolGroup00/LogVol00 rhgb quiet
#       initrd /initrd-2.6.20-1.2316.fc5smp.img

title Fedora Core (2.6.20-www1.2316)
        root (hd0,0)
        kernel /vmlinuz-2.6.20-www1.2316 ro root=/dev/VolGroup00/LogVol00 rhgb quiet
        initrd /initrd-2.6.20-www1.2316-2.img
</code>

==== Removing old Kernels ====

Reboot using the new kernel (and leave the old one installed just incase).

Run the following to verify that the new kernel is loaded:

<code bash>[john@maltsweb ~]$ uname -r
2.6.20-www1.2316
</code>

\\ 
Now, view the currently installed kernels:

<code bash>[root@maltsweb john]# rpm -q kernel
kernel-2.6.20www1-1
kernel-2.6.20www1.2316-2
</code>

select the kernel you wish to remove (kernel-2.6.20www1-1 in this case, since the other kernel looks similar to the currently running kernel) and remove it:

<code bash>[root@maltsweb john]# rpm -e --nodeps kernel-2.6.20www1-1
[root@maltsweb john]#
</code>


==== Removing old source files/making space for the build ====

You should probably remove the source of your previous kernel build prior to building the new kernel.

<code bash>[root@maltsweb ~]# cd /usr/src/redhat/BUILD/
[root@maltsweb BUILD]# ls
kernel-2.6.20  kernel-2.6.20www1.2316
[root@maltsweb BUILD]# ls -l
total 16
drwxr-xr-x  5 root root 4096 May 15 18:33 kernel-2.6.20
drwxr-xr-x 21 root root 4096 May 15 18:25 kernel-2.6.20www1.2316
[root@maltsweb BUILD]# uname -r
2.6.20-www1.2316
[root@maltsweb BUILD]#
</code>

The above shows that I currently have the kernel-2.6.20 source code, and a custom build for kernel-2.6.20www1.2316, which matches the currently running kernel.  So when I upgrade my kernel, before I start I can remove the custom kernel directory:

<code bash>[root@maltsweb BUILD]# rm -Rf kernel-2.6.20www1.2316/
[root@maltsweb BUILD]#
</code>

This should clear up enough space to build a new kernel.

== 

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{{tag>:linux :linux:server :linux:fedora}}