If the Ubuntu Server installer has set your server to use DHCP, you will want to change it to a static IP address so that people can actually use it.
Let’s open up the /etc/network/interfaces file. I’m going to use nano, but you can choose a different editor
sudo nano /etc/network/interfaces
For the primary interface, which is usually eth0, you will see these lines:
iface eth0 inet dhcp
As you can see, it’s using DHCP right now. We are going to change dhcp to static, and then there are a number of options that should be added below it. Obviously you’d customize this to your network.
iface eth0 inet static
Now we’ll just need to restart the networking components:
sudo /etc/init.d/networking restart