vi /etc/lightdm/lightdm.conf
[SeatDefaults]
greeter-session=unity-greeter
user-session=ubuntu
greeter-show-manual-login=true #手工輸入登陸系統的使用者名和密碼
allow-guest=false #不允許guest登入
sudo apt-get install gnome-session-fallback
user-session=ubuntu ---> user-session=gnome-classic
![sudo apt-get update 出錯 Updating from such a repository can‘t be done securely, and is therefore[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)