echo '[SeatDefaults]' | sudo tee /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf
 echo 'greeter-session=unity-greeter' | sudo tee -a /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf
 sudo chmod +x /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf