i've seen some answers that says edit the /etc/network/interfaces http://www.sudo-juice.com/how-to-set-a-static-ip-in-ubuntu-the-proper-way/#gather-info
auto lo iface lo inet loopback
iface eth0 inet static address 192.168.0.101 gateway 192.168.0.1 netmask 255.255.255.0
Restart your networking services
Finally, restart your networking services to put your new settings into effect.
Type/copy the following:
sudo service network-manager restart sudo service networking restart sudo service resolvconf restart This should restart your network interfaces and services. Use ifconfig to confirm your new static IP
i have succeded to change the interfaces but the ip does not change !!