Ubuntu Linux Configure DNS Name Server IP Address ( DNS Client )

Type the following command, enter:
sudo gedit /etc/resolv.conf

Append your ISP name server or free fast dns nameservers IP address as follows:
nameserver 208.67.222.222
nameserver 208.67.220.220
nameserver 202.51.5.52


or
Use Google DNS


8.8.8.8
8.8.4.4