Is there a command that i can issue in Ubuntu to see explicitly if my ethernet controller supports gigabit ethernet?
As root, run
ethtool eth0 if eth0 is the NIC in question. You'll get an output like:
Settings for eth0: Supported ports: [ TP ] Supported link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Half 1000baseT/Full Supports auto-negotiation: Yes Advertised link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Half 1000baseT/Full Advertised auto-negotiation: Yes Speed: 1000Mb/s Duplex: Full Port: Twisted Pair PHYAD: 1 Transceiver: internal Auto-negotiation: on Supports Wake-on: g Wake-on: g Current message level: 0x000000ff (255) Link detected: yes
Should be all the info you need.
lspci should show it like "blah blah Gigabit 10/100/1000 blah blah controller". Like that. :)