I upgraded to dapper and everything is working great,
But when I choose my older kernel (2.6.12) from the grub menu,
I get a kernel panic:

[4294667.940000] Kernel Panic - not syncing: VFS:unable to mount root fs on unknown block(0,0)

[4294667.940000]


I need my previous kernel to work as I have software that relies on it.

Does anybody know why the upgrade to dapper would cause my previous kernel to break??

Thanks.

Go to /boot and see if your old kernel is there or not.

My gut feeling is that Ubuntu (like Debian) installs a metapackage like linux-image-686 that keeps track of the stock kernels. So when you dist-upgraded, it updated linux-image-686 to the newest kernel in the repositories, 2.6.15. Just glancing at the package repositories for dapper, it seems like there's nothing less than a 2.6.15 kernel in there at all.

You might have to rebuild it yourself or recompile your programs against the new kernel. Or maybe pin your repositories to breezy and reinstall the kernel. I've personally never had much luck with apt-pinning as it always wants to install really change my Debian Sarge install...

It probably didn't break the old kernel, the upgrade probably revised (borked) your grub.conf (menu.lst) file. Post the contents of referenced file.

Ok, so I think I've figured out the problem.

I tried to reproduce the error on a test machine I have.
I noticed in the grub menu.lst that the kernel that I was having problems with didn't
have the following line:

initrd /boot/initrd.img....

So I took that line out of the the grub menu.lst on my test machine and I pretty much got the
same error.

My problem is that initrd.img-... for the kernel I need to get back running isn't in the /boot
directory. I don't know what happened to it.

Does anybody know how I would get the initrd.img-whatever back, either reproducing it or rebuilding it?

Thanks.