Ubuntu

Nameserver Address Nameserver Addresses represent the IP addresses of Domain Name Service (DNS) systems, which resolve network hostnames into IP addresses. There are three levels of Nameserver Addresses, which may be specified in order of precedence: The Primary Nameserver, the Secondary Nameserver, and the Tertiary Nameserver. In order for your system to be able to resolve network hostnames into their corresponding IP addresses, you must specify valid Nameserver Addresses which you are authorized to use in your system's TCP/IP configuration. In many cases these addresses can and will be provided by your network service provider, but many free and publicly accessible Nameservers are available for use, such as the Level3 (Verizon) servers with IP addresses from 4.2.2.1 to 4.2.2.6.

Tip: The IP address, Netmask, Network Address, Broadcast Address, and Gateway Address are typically specified via the appropriate directives in the file /etc/network/interfaces. The Nameserver Addresses are typically specified via nameserver directives in the file /etc/resolv.conf. For more information, view the system manual page for interfaces or resolv.conf respectively, with the following commands typed at a terminal prompt:

Access the system manual page for interfaces with the following command:

 man interfaces 

Access the system manual page for resolv.conf with the following command:

 man resolv.conf