I run Ubuntu 12.04 on an old iMac G3. Since the GUI is too resource heavy I have disabled the display manager (lightdm) and am currently running the computer in console mode. How do I establish a mobile broadband connection from the command line?

When I connect the modem it shows up as ttyUSB0 in the Network Manager device list:

$ nmcli dev

DEVICE     TYPE              STATE        

ttyUSB0    gsm               disconnected    

eth0       802-3-ethernet    unavailable

I have also copied a working connection configuration file from another computer to
/etc/NetworkManager/system-connections/Com Hem Default 1. Still, when I try to connect I get an "unknown connection" error:

$ nmcli con up id "Com Hem Default 1"

Error: Unknown connection: Com Hem Default 1.

Any clues?