Set a static IP in Ubuntu

sudo pico /etc/network/interfaces

auto lo eth0
iface lo inet loopback
iface eth0 inet static
address xxx.xxx.xxx.xxx(enter your ip here)
netmask xxx.xxx.xxx.xxx
network xxx.xxx.xxx.0
broadcast xxx.xxx.xxx.255
gateway xxx.xxx.xxx.xxx(enter gateway ip here)

sudo pico /etc/resolv.conf

# Generated by NetworkManager
nameserver xxx.xxx.xxx.xxx(enter your dns server ip)
nameserver xxx.xxx.xxx.xxx(enter your alt dns server ip)

sudo /etc/init.d/networking restart