So I have acquired a Debian virtual machine on a Xen cluster to play around with. I want to use it to eventually get into trying to see if I can make some interesting websites using Ruby on Rails with metaprogramming. I have worked in a *nix environment plenty of times but rarely have I had to actually maintain the machine. So I thought playing with a VM would be a great way to start it off.

The odd part is unlike installing Debian right onto a machine where certain installation options are available, I have to use the image provided by the Xen cluster, of which I have none of the details. I don't even know if it is Etch or Lenny! I have been trying to go through tutorials but my main problem is a lot of them assume you are starting from scratch while I really don't know what I already have, and so I've been getting conflicts. So I guess my questions boil down to this...

How do I get my VM to a similar to state to that of a fresh installation?
How do I properly configure my sources file? (Keep getting public key and package not found errors for the Debian secure repository server, and my college hosts a package mirror that I would like to keep in there.)
(Once the first two questions are answered) What other things should I keep in mind and set up other than Apache2, MySQL (or SQLite), SVN, Ruby and Rails?

In all likelihood the VM base install is pretty similar to a clean install.

and remove the packages you don't want with a command like (be very careful what you pull):

You can find out what distribution you're running by catting out /etc/debian_version. Version 4 is etch, version 5 is lenny.

You need to setup your /etc/apt/sources.list, try something like... (you can put your colleges mirror in place of the debian repositories... but keep in mind for security it'll likely lag a bit behind and they may not mirror ~everything~. Also make sure your distribution name is right-- i do NOT recommend using 'stable' 'unstable' 'testing' 'oldstable' as your distribution name as sometimes this can make a simple upgrade break things horribly. If you're using etch you should be able to use this by opening the file in vi and doing :s/lenny/etch/g :wq)

(I'll note backports stuff will not be considered for install by default even with it added to the sources list.)

Then do:
This will update your sources, update your keyrings (or install them if necessary), and then upgrade you to the current release specified.

That really about covers it, don't have any services running and listening on ports you don't absolutely need. Might wanna toss php5 on there for completeness sake, any other scripting languages you want to use either system or web level. Maybe basic smtp.

Keep the system updated and upgraded.