Get root access:
sudo su

To backup:
tar cvpzf backup.tgz --exclude=/proc --exclude=/lost+found --exclude=/backup.tgz --exclude=/mnt --exclude=/sys /

To restore:
tar xvpfz backup.tgz -C /

Source: http://ubuntuforums.org/showthread.php?t=35087

To backup on an other mount:
tar cvpzf /mnt/data/backup.tgz --exclude=/proc --exclude=/lost+found --exclude=/mnt --exclude=/sys /