Przemysław: edit /etc/network/interfaces (e.g. with 'sudo pico /etc/network/interfaces'), and remove everything BUT the first lines: auto lo iface lo inet loopback
Then you can add the interface using System->Preferences->Network Connections
Przemysław: edit /etc/network/ interfaces (e.g. with 'sudo pico /etc/network/ interfaces' ), and remove everything BUT the first lines:
auto lo
iface lo inet loopback
Then you can add the interface using System- >Preferences- >Network Connections