Log in as root

 1,编辑/etc/lightdm/lightdm.conf：
gedit  /etc/lightdm/lightdm.conf

[Seat:*]
autologin-guest=false
autologin-user=root
autologin-user-timeout=0
greeter-session=lightdm-gtk-greeter

2,编辑/root/.profile文件，增加tty -s &&：
gedit /root/.profile 

if [ "$BASH" ]; then
  if [ -f ~/.bashrc ]; then
    . ~/.bashrc
  fi
fi

tty -s && mesg n || true

3. reboot