Quote Originally Posted by alexv
Knoppix 2.4.20-xfs kernel works but debian's 2.4.20-686 does not - says it can't mount root filesystem. I use reiserfs on both /boot and / partitions. Does anybody know exact differences between Knoppix kernel and Debian kernel, please?
The biggest difference is that the knoppix .config file (in /usr/src/linux) includes support for many modules (including reiserfs). I suggest copying that .config file and building a new kernel with your changes.

Also, knoppix uses an initrd image to hold many modules before the root system is even mounted.