network

For up interface on boot and DHCP configuring you need edit /etc/network/interfaces

auto eth0
iface eth0 inet dhcp

For static configuration

auto eth0
iface eth0 inet static
address 192.168.1.254
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255
gateway 192.168.1.1

After editing conf files you need restart network service

sudo /etc/init.d/networking restart