1.网上解决方案
https://askubuntu.com/questions/1043337/is-there-to-make-the-login-screen-appear-on-the-external-display-in-18-04
问题:在nvidia独显电脑上不生效
2.实际解决方法
1.配置好主副屏
2.打开nvidia-settings
3.在X Server Display Configuration
中选择Save X Configuration File
4.重启,OK