Changing a Linux kernel

Red Squirrel · 12-30-2014, 04:18 PM

I have a server through OVH and I just learned the hard way (after fully configuring and putting it live, thus too late to do anything drastic) that they use a custom kernel that has no support for kernel modules. I need kernel modules so I can play around with KVM/Qemu and try to get a VM going for a game server.

I read this which shows how to change it back:

http://change_ovh_kernel.onlinephpfunctions.com/

Is it really that simple? What about having to install kernel headers and messing around with compiling stuff and all that? I figured it would be more complicated. Am I missing anything?

In my grub.conf I have two entries and one is pointing to the normal kernel. Is it really as easy as removing the other entry?

Also is there a way to apply the new kernel without rebooting? I don't want to risk the machine not coming back, I have no physical access.

Teufel · 12-30-2014, 04:54 PM

Just do not remove your old kernel/initramfs, as well as grub.conf entry. If something will go wrong you can boot with old kernel and fix things.
Regarding kernel modules, they are located under /lib/modules directory and seperated by kernel versions, so they cannot be messed.

Code:

ls -l /lib/modules
total 8
drwxr-xr-x 4 root root 4096 dec 20 22:16 3.16.5-gentoo
drwxr-xr-x 4 root root 4096 dec 29 21:21 3.17.7-gentoo

every kernel has it's own modules set, for me it is 3.16.5 and 3.17.7 kernels.

I suspect the same for kernel headers, but not sure.
There are two paths where kernel headers might be located. The first is aforementioned /lib/modules/<kernel-version>/build/include/. And the second is /usr/src/linux-<version>/include.
You may check these locations for headers presence