Re: Linux noob looking for help setting up gaming server
If you already have the Server up and running probably your best bet for getting the games served up is to look into the relevant Game Forums or Google "[Game] server Linux install".
The trick might be finding the install files for "Old Games". Of Course, check the Repos.
Generally, the limitation is how many players you can have at once based on CPU and RAM. Each game should have that sort of info in the SysReqs. I don't believe game servers really require too much disk space.
You also may want to look into a Dynamic DNS host to get yourself a Domain that can be updated to your (I assume) Home based DHCP IP your ISP gives you. That way you can play against friends from beyond the LAN and they were free for what you seem to have in mind last I checked.
I've got a machine setup to run ETQW (all of the "ET"s should have plenty of documentation for Linux servers.) and I run a Murmer/Mumble Com server as well.
I separate the different servers out into the different TTY Terminals to run as much or little as desired. (I think that would address your "Multiboot" comment)
I like to keep a GUI on my server for when I don't want to have to think or just edit a Conf File like I would on any other computer but you'll definitely want to do as TheFu said and take the few minutes to learn the CLI commands as that is all you'd want to use to run your DynDNS update, start/stop Com Server & Game Server.
12.04 64 bit
AMD Phenom 9600 2.3GHz /4GB DDR2 1066 / Gigabyte MA790FX-DS5 /Gecube ATI HD3850