Hey! I have an ubuntu server (So I tested it and it works this way), install mono in your linux computer (something like apt-get mono-runtime in ubuntu. I do not know exactly the package name)
after that build your server with monodevelop and upload it to your server, do not worry about the .exe extension, the executable is a native mono executable, it will work on linux. Then to run it write "mono yourserver.exe" and it will run just fine..
I read that linux does not support async sockets etc... would be nice if Aren could tell us if linux is full supported !