Bom. Então você não tem servidores de nomes DNS. Adicione estas duas linhas ao /etc/resolv.conf :
nameserver 8.8.8.8
nameserver 8.8.4.4
e isso deve funcionar.
Eu não tenho acesso à internet com fio no Ubuntu 14.04, embora seja detectado, meu computador conectado ao mesmo roteador tem.
$ ifconfig
eth0 Link encap:Ethernet HWaddr 4c:72:b9:7e:b5:61
inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::4e72:b9ff:fe7e:b561/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:93 errors:0 dropped:0 overruns:0 frame:0
TX packets:705 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:18292 (18.2 KB) TX bytes:76277 (76.2 KB)
Interrupt:17
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:701 errors:0 dropped:0 overruns:0 frame:0
TX packets:701 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:54442 (54.4 KB) TX bytes:54442 (54.4 KB)
wlan0 Link encap:Ethernet HWaddr 08:3e:8e:5f:56:1e
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
Tags linux ubuntu wired-networking