Change IP address on Ubuntu Server

If Your Ubuntu System has set to use DHCP, you will want to change it to a static IP address

sudo vi /etc/network/interfaces

If you are using DHCP for your primary network card which is usually eth0, you will see the following lines

auto eth0
iface eth0 inet dhcp

To change to static address change the dhcp to static as shown below

auto eth0
iface eth0 inet static
address 192.168.1.100
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255
gateway 192.168.1.1

Restart the neworking service using the following command

sudo /etc/init.d/networking restart