static ip

/etc/network/interfaces

change

auto eth0
iface eth0 inet dhcp

or  auto lo
iface lo inet loopback



to

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:

sudo /etc/init.d/networking restart