Every computer is uniquely identified by an IP address, but these are inconvenient, and it's much easier to refer to them by name. The Domain Name System is a network's white pages, but instead of looking up somebody's name in order to get their telephone number, you can look up a domain name (e.g. awasu.com) and get its corresponding IP address (e.g. 72.249.26.4).

Installing and configuring the DNS server

We need to install a DNS server on our gateway, so that computers on the internal network can do domain name lookups^[1]For example, if you open http://awasu.com in a browser, the browser needs to know the IP address of that web site so that it can get the web page..

First, we need to install the DNS server:

sudo apt-get install bind9

We can also install some useful tools that let us do DNS lookups from the command line (e.g. dig and nsupdate):

sudo apt-get install dnsutils

Now, computers on my internal network will have their DNS lookups done by the DNS server running on our gateway^[2]This happens because they were told to do this when they received their IP address, via the domain-name-servers option..

However, the gateway DNS server itself needs to do DNS lookups, and this is configured in /etc/resolv.conf. In the case of my home network, I get given the address of a DNS server when I connect via wifi, but you might want to use something else e.g. 8.8.8.8, if you want to use Google's DNS servers.