I recently compiled the new 2.6.23.1 Linux kernel under Slackware 12.0. It was a pretty straight forward process so I’ve decided to do a small write-up on it for people who are thinking about, or wanting to compile a custom kernel, but are unclear about the process. Compiling your first kernel can be an intimidating task, but can serve as a valuable learning experience. Hopefully, the following article can serve as a quick introduction on the basic steps of kernel compilation.

Make a directory to work in:

$mkdir ~/linux
$cd ~/linux

Grab the kernel and its matching .sign file. (If you want to compile the most up-to-date kernel be sure to check here for the status of stable, snapshot, etc. kernels)

linux-2.6.23.1.tar.gz
linux-2.6.23.1.tar.gz.sign

After downloading the kernel source and the .sign file, verify the kernel’s authenticity. For more info on the verification process and the 0×517D0F0E key, visit www.kernel.org/signature.html

$gpg --keyserver wwwkeys.pgp.net --recv-keys 0x517D0F0E

Once you have kernel.org’s key, Verify the kernel source.

$gpg --verify linux-2.6.23.1.tar.gz.sign linux-2.6.23.1.tar.gz

Unpack it.

$tar -xvzf linux-2.6.23.1

Check to see everything looks ok before proceeding.

$ls
linux-2.6.23.1.tar.gz
linux-2.6.23.1/
$cd linux-2.6.23.1

There are several ways of creating a config file. For the sake of simplicity, grab the .config file from here (Slackware ftp). (At the time of this writing, 2007-10-18, Slackware’s ‘current’ kernel is 2.6.23.1)

$mv config .config

Note: use the smp config file if you’re using an smp set-up.

If you have some changes to make to the config file:

$make menuconfig

Ready? Ok.

$make

No errors? Once the kernel is done compiling, drop into a root shell and begin the install process.

#make modules_install

Double check the kernel version you just compiled.

#make kernelversion
2.6.23.1

Now copy the kernel image and System.map file into the boot directory. Notice the version you append to the end of bzImage and System.map match the ‘make kernelversion’ output.

#cp arch/i386/boot/bzImage /boot/bzImage-2.6.23.1
#cp System.map /boot/System.map-2.6.23.1

Create an initrd file to be sure your filesystem(s), especially your root filesystem, will be mounted on boot-up. There is a detailed explanaiton of what an initrd file is and why you need one, located in /boot/README.initrd. It will also hint as to what parameters you need to give mkinitrd in order for it to correctly generate an initrd file for your system. I’m using an IDE drive (I know it’s ancient) with the ‘/’ (root) partition residing in /dev/hda3 using the ext3 filesystem.

#cd /boot
#mkinitrd -c -k 2.6.23.1 -m ext3 -f ext3 -r /dev/hda3

Now edit your /etc/lilo.conf file to make sure you can boot into your new kernel.

#vi lilo.conf

Add these lines to the end of your lilo.conf file (substitue the respective entries to match your system setup)

image=/boot/bzImage-2.6.23.1
initrd=/boot/initrd.gz
root=/dev/hda3
label=2.6.23.1
read-only

Once that’s done, run lilo to work with your new config file.

#/sbin/lilo
#shutdown -r now

The moment of truth. Once your system reboots, select your new kernel…

Did it work? Once you’re using your new kernel, create a new rc.modules file in the /etc/rc.d/ directory for your new modules to be used.


#cd /etc/rc.d/
#cp rc.modules-2.6.21.5 rc.modules-2.6.23.1
#rm /etc/rc.d/rc.modules
#ln -s rc.modules-2.6.23.1 rc.modules


This was a very quick introduction into compiling a kernel under Slackware. There are a wide range of options you can enable/disable in your .config file, other ways you could have gone about compiling, etc. which would have gone beyond the scope of this document. My intent on writing this article was to show you a somewhat generalized idea of the compilation process for those of you who are curious about it.

Questions and comments are always welcome (and encouraged).

Cosa troviamo nel nuovo 2.6.23?

Abbiamo il CFS (Complete Fair Scheduler). Questo nuovo scheduler permette prestazioni migliori. C’è stato molto rumore a proposito, anche perché Con Kolivas (il creatore del set di patches -ck per migliorare le prestazioni) ha detto che se non fossero state incluse le sue patches nella main-line del kernel linux, lui non avrebbe più lavorato a questo progetto. E così è stato: Kolivas ha finito di mantenere il suo set di patch.

E’ stato incluso un nuovo sistema di virtualizzazione chiamato lguest. Anche una parte di xen è stata inserita.

Molte bugfixes, nuovi drivers, e… una cosa che è passata in secondo piano è il fatto che non si ha più bisogno di usare il fastidioso demone per le schede wifi Centrino. Inoltre nel 2.6.24 avremo il driver per le Centrino direttamente incluso nel kernel ^_^

Links:

http://dgrossato.blogspot.com/2007/10/rilasciato-il-kernel-linux-2623-la.html
http://kernelnewbies.org/Linux_2_6_23
http://kerneltrap.org/2.6.23

Ya ha sido liberada la versión 2.6.23 del núcleo Linux. Para una explicación en cristiano de los cambios, conviene echar un vistazo en kernelnewbies.

A destacar el nuevo planificador de procesos CFS (Completely Fair Scheduler), el nuevo sistema read-ahead, la implementación real en el núcleo de la llamada al sistema fallocate() (hasta ahora emulada vía glibc), la integración de mejoras en la virtualización para Xen y lguest, la supuesta carga automática de los módulos acpi por parte de udev (mentira cochina, precisamente no me funcionaba powernowd porque no cargaba el módulo acpi_cpufreq)… en fin, que mejor leer la lista completa.

¿A qué esperáis? ¡Vamos, a darle alimento a vuestros gcc!

master@blingdenstone:~$ uname -a
Linux blingdenstone 2.6.23 #1 PREEMPT Wed Oct 10 01:02:03 CEST 2007 i686 GNU/Linux
master@blingdenstone:~$