[otrs] Instructions on How To Upgrade OTRS from 2.0 to 2.2 in Linux

Hello, everyone! I've searched all through the Web for instructions regarding the OTRS upgrade in a Linux environment. I was unsuccessful, though. Could anyone tell me where is this information to be found? My OTRS is currently installed on a Debian System, and was setup with a debian package. Any help is appreciated. Best wishes, Harry