Standard Kernels with Ubuntu / Debian

[Myatu]

I've seen a couple threads that ask if its possible to use the standard kernel - one that can load kernel modules - instead of OVH's kernels. With Ubuntu and Debian this is an easy task, that does not require compiling:

Step 1: ensure your server has the GRUB-2 boot loader.

Most newer servers from OVH do, as do all VPS/Cloud installations. You can have a quick look to see if the file /etc/default/grub exists, or whether this command give a valid output:

# update-grub -v
grub-mkconfig (GRUB) 1.99~rc1-13ubuntu3

Step 2: install a kernel

First make sure you have the most recent data from the repositories:

apt-get update

And check what kernels are available to you with:

apt-cache search linux-image

An example output:

# apt-cache search linux-image
linux-image-2.6.38-8-generic - Linux kernel image for version 2.6.38 on x86/x86_64
linux-image-2.6.38-8-generic-pae - Linux kernel image for version 2.6.38 on x86
linux-image-2.6.38-8-virtual - Linux kernel image for version 2.6.38 on x86/x86_64
linux-image-generic - Generic Linux kernel image
linux-image-generic-pae - Generic Linux kernel image
linux-image-server - Linux kernel image on Server Equipment.
linux-image-virtual - Linux kernel image for virtual machines
linux-image-2.6.32-25-generic-pae - Linux kernel image for version 2.6.32 on x86
linux-image-2.6.32-31-generic-pae - Linux kernel image for version 2.6.32 on x86
linux-image-2.6.32-29-generic-pae - Linux kernel image for version 2.6.32 on x86

The kernels that do not have a specific version, such as linux-image-generic, are meta packages that automatically select the most recent kernel.

The "generic" kernels are best suitable for desktop systems, "servers" for, well, servers, and so on.

Once you have decided on a kernel, install it with:

apt-get install linux-image-[your selection]

Step 3: Load a kernel

Debian and Ubuntu should already have issued a update-grub command when it installed the kernel you've selected in step 2. But it will not yet be loaded, reason being is that you don't see the "boot screen" of the server (except in vKVM mode or the ipKVM option) and so can't make a selection during boot time.

First determine the order the kernels are listed by GRUB, which can easily be done with fgrep or cat | grep:

# fgrep menuentry /boot/grub/grub.cfg 
menuentry "Ubuntu 10.10, OVH kernel 2.6.38.2-xxxx-grs-ipv6-64" {
menuentry 'Ubuntu, with Linux 2.6.38-8-server' --class ubuntu --class gnu-linux --class gnu --class os {
menuentry 'Ubuntu, with Linux 2.6.38-8-server (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os {

The text between the quotes will give you an idea what's-what. Do keep in mind you need to start counting from zero, so the first entry is 0, the second is 1, etc.

Now you need to edit the file /etc/default/grub and change the the GRUB_DEFAULT=0 entry according to which boot option/kernel you wish to use.

So using the previous sample output, we want to load "Ubuntu, with Linux 2.6.38-8-server", and therefore need to change the zero (0) to a one (1) in /etc/default/grub:

GRUB_DEFAULT=1

Now re-update the GRUB configuration (and this is important) with:

update-grub

Now reboot your server and cross your fingers. Once the server is back up, you can verify the correct kernel has loaded with uname, ie:

# uname -a
Linux my-super-duper-server 2.6.38-8-server #42-Ubuntu SMP Mon Apr 11 03:49:04 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

[jonlewi5]

Seems to have worked perfectly!
Cheers myatu

[Myatu]

Good stuff I was updating an OVH server with a standard kernel when I saw your post, so good timing!

[jonlewi5]

haha it really was, managed to vmware server to half install, still failing but i know its something im doing an its too late to be messing with it

[Iray]

Myatu .. Thanks dude! You need some man love... *Hug*

I'll try this out once I get my new shiny server. Hopefully this is a step by step process for us fellow noobs.

[jonlewi5]

I can confirm this works perfectly, got vmware setup and working alongside GNS3,

thanks very very much myatu!

[Winit]

Thank you Myatu.

[nodokodo]

Just an FYI, but you do NOT have to (and really shouldn't) edit /etc/default/grub.

Instead cd in to /etc/grub.d and if you ls you will see a bunch of scripts prefixed by numbers; the numbers are the boot ordering—change these numbers and you alter the order.

For example, on my Ubuntu 11.04, the OVH kernel is prefixed 06 (to slip in ahead of 10):

-rwxr-xr-x 1 root root 6658 2011-04-21 14:31 00_header
-rwxr-xr-x 1 root root 5522 2011-04-21 14:19 05_debian_theme
-rwxr-xr-x 1 root root  959 2010-10-11 12:31 06_OVHkernel
-rwxr-xr-x 1 root root 6304 2011-04-21 14:31 10_linux
-rwxr-xr-x 1 root root 5233 2011-04-21 14:31 20_linux_xen
-rwxr-xr-x 1 root root 7119 2011-04-21 14:31 30_os-prober
-rwxr-xr-x 1 root root  214 2011-04-21 14:31 40_custom
-rwxr-xr-x 1 root root   95 2011-04-21 14:31 41_custom
-rw-r--r-- 1 root root  483 2011-04-21 14:31 README

I altered that to 25 (to slip it in after the other kernels):

-rwxr-xr-x 1 root root 6658 2011-04-21 14:31 00_header
-rwxr-xr-x 1 root root 5522 2011-04-21 14:19 05_debian_theme
-rwxr-xr-x 1 root root 6304 2011-04-21 14:31 10_linux
-rwxr-xr-x 1 root root 5233 2011-04-21 14:31 20_linux_xen
-rwxr-xr-x 1 root root  959 2010-10-11 12:31 25_OVHkernel
-rwxr-xr-x 1 root root 7119 2011-04-21 14:31 30_os-prober
-rwxr-xr-x 1 root root  214 2011-04-21 14:31 40_custom
-rwxr-xr-x 1 root root   95 2011-04-21 14:31 41_custom
-rw-r--r-- 1 root root  483 2011-04-21 14:31 README

Run:

update-grub

and the default becomes 10_linux (whatever kernel you've just installed after following Myatu).

I'm pretty positive you can just remove it (06_OVHkernel) altogether, but if it aint broke… redundancy never killed anyone (well maybe a few coal miners but that's another story). HTH

[mrchrister]

thanks so much for the explination, this is sooo much easier then self compiling

I used your instructions on 2 ovh servers now, works flawlessly!

[Phixion]

Can anyone tell me the benefits of doing this?