Just downloaded kernel 2.6.12.3 and what-do-you-know, I actually managed to complied the thing. Before proceeding I'd like to back up my current kernel (something recommended by the instructions anyway). Which files do I copy? I don't want to miss any.

I'm using debian sarge with the stock kernel (2.4.27-2). I boot using grub with a dual boot setup with windows 98 on the other partition.

The /boot/grub/menu.lst entry for debian looks like this:

title Debian GNU/Linux, kernel 2.4.27-2-386
root (hd0,1)
savedefault
kernel /boot/vmlinuz-2.4.27-2-386 root=/dev/hda2 ro
initrd /boot/initrd.img-2.4.27-2-386

-Gareth C

PS: Is it possible to set up grub to boot from different kernels? For example, adding a entry for the new kernel and keeping the old entry?

Not sure about when you compile a new kernel, but if you install one through apt-get it creates a new entry and at boot you can choose the one you want to use.

I have 2.4.27, 2.6.10, and 2.6.11-7-k7 to choose from.

After compiling and installing a newer kernel version, I don't really backup my old kernel, instead I keep the image and the modules until I make sure the new one works as I want it to.
Anyway, the files you may want to backup is /boot/vmlinuz-version, /boot/System.map-version, /boot/initrd-version (if case) and the modules found at /lib/modules/version, where version is something like 2.4.27-2.
Of course, after you install the modules (make modules_install), copy the new vmlinuz and the new System.map to /boot, edit menu.lst to look something like:This way you keep both kernels. Once you think you don't need the old kernel, remove the old files from /boot and the corresponding directory in /lib/modules.

On a side note, you could compile your new kernel without the need of an initrd.

I've located the files, I'll back them up (I'm paranoid, this is my first attempt at this) then try out the new kernel. Thanks for the help.

-Gareth C

You're welcome. Come back and let us know how it worked.

It's worked (though I had slight problem getting the initrc.img file to work). I'm typing this on a kernel 2.6 box. Thanks.

-Gareth C

Great, glad to hear that! Now you can test for a while the new kernel to see if everything works as it should (sound/video/network card, printer, other peripherals) then delete the old kernel and the corresponding modules as they may take up some space and considering future kernel updates you won't want to waste your harddisk space.
Also, it's a good thing to keep a backup of the .config file you used to compile the current kernel, so you can use it for future versions (the compiling options don't change dramatically from version to version).
Anyways, good job.