我安装了 Ubuntu 12.04，然后将我的机器升级到 14.04。升级后，我的有线互联网停止工作了。
输出如下ipconfig：
root@vyaw:/# ifconfig -a
eth0 Link encap:Ethernet HWaddr 34:e6:d7:5a:a5:db
inet6 addr: fe80::36e6:d7ff:fe5a:a5db/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:106158 errors:0 dropped:3 overruns:0 frame:0
TX packets:1772 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:7393113 (7.3 MB) TX bytes:362147 (362.1 KB)
Interrupt:20 Memory:f7c00000-f7c20000
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:7274 errors:0 dropped:0 overruns:0 frame:0
TX packets:7274 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:949502 (949.5 KB) TX bytes:949502 (949.5 KB)
wlan0 Link encap:Ethernet HWaddr 80:00:0b:96:e5:2e
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:95306 errors:0 dropped:0 overruns:0 frame:0
TX packets:95730 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:93910858 (93.9 MB) TX bytes:17695478 (17.6 MB)
我们在这里可以看到，IP 地址尚未分配。
请帮忙