xfs is a filesystem developed by SGI that the knoppix kernel supports, most stock kernels do not support it. Do a google for "linux xfs filesystem" for more info.

I have not run a current version of knoppix as an hd install, I only run knoppix and other live systems as live systems I don't install them to hd, so don't take this as an absolute but, in the past I when I had a knoppix hd install, I was not able to install a stock debian kernel (stable, testing, or unstable) onto my knoppix system, as the knoppix kernel is made to run in a live environment not as a "normal" installed system.

What I think you will have to do is get all of the necessary kernel source packages and patches and build your new kernel from source. Do some searching here on this forum and there should be a bunch of posts about building new kernels for knoppix.

Note: you can upgrade all of your packages except the kernel to sid (unstable) easily, by just commenting out the references in /etc/apt/sources.list to woody (or stable) and testing, just put a # (hash) in front of the lines that refer to the debian stable and testing repositories, then run apt-get update, and then apt-get dist-upgrade. NOTE: there may be problems when you do this upgrade, especially with packages such as KDE and you may need to manually fixing some dependency problems using:
dpkg --force-overwrite -i *fullpath-and-packagename-with-version.deb

ALSO NOTE: there is a chance that you may break your system doing this!

~rock