You should get a guest account from
(for instance your laptop if you are a guest) You should register your computer at the Rechenzentrum (www.uni-regensburg.de/rechenzentrum/index.html), currently (Nov 2014) this can be done here: register.uni-regensburg.de. Important note: If you want to register your computer outside of our faculty (e.g. from biology), please choose "Kursrechneroption", further information is available from register.uni-regensburg.de/dhcpreginfo.html.
The Rechenzentrum offers a so-called "SMS-Passwortservice" (short message service for mobile phones) in case you lost your password. Further information is available from www.uni-regensburg.de/rechenzentrum/rz-account/rz-passwort-aendern/passwort-reset-einrichten/index.html.
In case of problems send an email to math.linux"at"mailman.uni-regensburg.de, or ask the secretary of your host.