This page details the steps needed to get Knoppix running as a pure Debian system.
The following is a modified extract of an e-mail I sent to HantsLUG...
Knoppix, like Debian, uses its own packages and specific .debs, which are nothing to do with Debian at all. Because of this, the route into Debian is controlled from the file /etc/apt/sources.list . This lists the location of the repositories where all the packages are so that apt can access them. My version of /etc/apt/sources.list for my version of Knoppix relies heavily on the use of German mirrors which are unofficial to Debian.
The first step therefore, should be to move the current /etc/apt/sources.list file out of the way and re-create it with Debian-specific entries, thus:
1. mv /etc/apt/sources.list /etc/apt/sources.list.knoppix
2. Create a new /etc/apt/sources.list, and add something like:
deb http://mirror.ox.ac.uk/debian/ testing main
deb-src http://mirror.ox.ac.uk/debian/ testing main
Making sure you change 'testing' to something else if you want, say, 'unstable'.
Then all that is left to do is to is to update some core packages, before updating everything that was installed by Knoppix:
3. apt-get update 4. apt-get install apt-utils debconf dpkg 5. apt-get -u upgrade 6. apt-get -u dist-upgrade
You'll also want to remove the 'knoppix' user (possibly).