If you are using ubuntu 14.04, you may find you can not setting dns on your /etc/resolv.conf
This is because ubuntu using resolvconf to manage the dns setting, every times system boot, resolvconf will regenerate resolv.conf file.
But there always have way to do this.
put your nameserver list in
nameserver 18.104.22.168nameserver 22.214.171.124
this command tell resolvconf to regenerate the resolve file