Quote Originally Posted by RoyalMail
So after I've isntalled knoppix to HD, and looked around a bit, I see that the standard (stable) Debian version is Woody (3.something - now a year old) and the upcoming version is Sarge (AKA 'unstable') and there's a further version in the pipeline called Sid.

My LILO boot screen screams 'Sid' at me so I suppose a lot of the packages are from the development stream of Debian, rather than the stable stream.
Haven't checked but could be that just lilo and some other packages are from Sid aka unstable. Sarge is testing soon to be next stable. http://www.nl.debian.org/releases/

If I want to move to a particular release of Debian (for stability reasons), which apt-get commands do I issue? And do I have to make changes in the apt/sources.list file to ensure I don't upgrade to something more bleeding edge? I don't like the idea of just running apt-get update and then apt-get upgrade; who knows what I'll be left with.
What's wrong with bleeding edge? I'm running kanotix BH5 based on Sid without any trouble.
<asbestos suit> If you run a production server that's another story while you shouldn't be running Knoppix anyway </asbestos suit>.
Besides, as stated here...: http://www.nl.debian.org/releases/testing/ ..testing isn't getting any security updates for now. And if you're considering downgrading to stable (Woody) you might as well install Debian directly.