Configuration accès Internet Ubuntu 14.04

sudo vim /etc/network/interfaces

DHCP

# Loopback
#
auto lo
iface lo inet loopback

# network card
auto eth0
iface eth0 inet dhcp

Static

# Loopback
#
auto lo
iface lo inet loopback

# network card
#
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

Restart networking.

sudo /etc/init.d/networking restart

Source :
http://askubuntu.com/questions/22663/how-to-bring-up-network-on-boot-up-when-networkmanager-is-uninstalled