Ubuntu server 12.04 apt-get update 不能正常使用

使用命令后出现以下错误：

root@ubuntu:~# apt-get update

Err http://mirrors.oschina.net raring Release.gpg

Temporary failure resolving 'mirrors.oschina.net'

Err http://mirrors.oschina.net raring-security Release.gpg

Temporary failure resolving 'mirrors.oschina.net'

Err http://mirrors.oschina.net raring-updates Release.gpg

Temporary failure resolving 'mirrors.oschina.net'

Err http://mirrors.oschina.net raring-proposed Release.gpg

Temporary failure resolving 'mirrors.oschina.net'

Err http://mirrors.oschina.net raring-backports Release.gpg

Temporary failure resolving 'mirrors.oschina.net'

Reading package lists... Done

W: Failed to fetch http://mirrors.oschina.net/ubuntu/dists/raring/Release.gpg Temporary failure resolving 'mirrors.oschina.net'

W: Failed to fetch http://mirrors.oschina.net/ubuntu/dists/raring-security/Release.gpg Temporary failure resolving 'mirrors.oschina.net'

W: Failed to fetch http://mirrors.oschina.net/ubuntu/dists/raring-updates/Release.gpg Temporary failure resolving 'mirrors.oschina.net'

W: Failed to fetch http://mirrors.oschina.net/ubuntu/dists/raring-proposed/Release.gpg Temporary failure resolving 'mirrors.oschina.net'

W: Failed to fetch http://mirrors.oschina.net/ubuntu/dists/raring-backports/Release.gpg Temporary failure resolving 'mirrors.oschina.net'

W: Some index files failed to download. They have been ignored, or old ones used instead.

折磨了许久后，设置 dns 后成功解决了此问题：

202.96.154.8 是深圳的 dns 服务器，之前设置的是 192.168.1.1 ，能够 ping 外网的ip，就是采用 apt-get update 不能正常使用。

重启网络服务：

/etc/init.d/networking restart

执行 apt-get update 成功：