In order to print from Ε wing labs with a Linux laptop you have to install CUPS (ready and packaged for most Linux flavours) and change the Server setting in the client.conf CUPS file (usually in the /etc/cups directory). The setting is 

Server prserver.csd.uoc.gr

Restart cupsd and add printers from the Administration (or Printers) Tab.

General info:

1. Add new printer, choose Network printer (or Internet Protocol Printing or IPP). CUPS servername is prserver.csd.uoc.gr (or prserver.csd.uoc.gr/ipp - prserver.csd.uoc.gr:631/ipp)
2. Choose Find Queue or continue adding printers.
3. You can add the printers by their name:

laser108 (Ε108): ipp://prserver.csd.uoc.gr/printers/laser108 
laser105 single page (Ε105): ipp://prserver.csd.uoc.gr/printers/laser105-s
laser105 double page (Ε105): ipp://prserver.csd.uoc.gr:631/printers/laser105

Models and URI: 
laser108 (Ε108): HP LaserJet 4200 / URI socket://10.150.2.15 
laser105 (Ε105): HP LaserJet4300n / URI socket://10.150.2.14

At the URL http://prserver.csd.uoc.gr:631/printers you can browse the names of installed printers.