use Ubuntu 12.04 root USER

1.

#sudo -s

2.

#vim /etc/lightdm/lightdm.conf

3.

ADD:

greeter-show-manual-login=true  

allow-guest=false

LIKE THIS:

[SeatDefaults]
greeter-session=unity-greeter
user-session=ubuntu
greeter-show-manual-login=true 
allow-guest=false   

4.

#sudo passwd root

5.

RESTART UBUNTU, OK!