In the process of upgrading my 2.4.20 kernel to 2.6.2, I made the bzImage for 2.6.2 and copied it to the /boot directory. Then I configured lilo.conf to boot to this image and ran lilo to finalize the changes. During my first boot of the new kernel, I recieved the following error:

UDF-fs: No partition found (1)
Kernel Panic: Unable to mount root fs on hda2

I failed to make a boot disk, and have not been successful in attempting to access the system by booting the old kernel from the boot prompt of my Slackware 9 installation cd, but I would prefer to keep my data and settings if possible.

Thank you for any help you may offer.

1. Boot from a live CD like Knoppix, open a root console, then mount the partition hosting / on your harddrive (eg. mount -t reiserfs /dev/hda2 /mnt/hda2)

2. Change root to your mounted harddrive partition eg. chroot /mnt/hda2

3. After chroot, edit /etc/lilo.conf and either restore your old kernel or add a new boot option to boot into your old kernel. When recompiling, you should always add your new kernel as a non-default boot option in lilo.conf; NEVER delete your old kernel image or remove your old kernel from lilo.conf.

4. While staying in chroot, run lilo.

5. Exit chroot (just type 'exit'), and reboot.

Regarding the error in booting from your new 2.6 kernel: you probably failed to compile support for ReiserFS, the default filesystem for Slackware (or support for whatever filesystem you use). So, when you boot the new kernel, it can't mount your /boot partition and panics.

Just compile ReiserFS (or ext3 or XFS, etc) directly into the kernel. If you compile it as a module instead, you will have to muck around with mkinitrd afterward, which personally I've never been able to do successfully. Fortunately, Slackware by default does not use an initrd image to boot.