Environment:
Ubuntu desktop 20.04.5 LTS
Issue:
Failed to start Light Display Manager, then can't successfully boot desktop system
Logs:
...
[ OK ] Started Hostname Service.
Starting Light Display Manager...
[FAILED] Failed to start Light Display Manager.
See 'systemctl status lightdm.service' for details.
[2022/11/29 20:31:13] (base) zyx@Opt-7080:~$ sudo systemctl status lightdm.service
[2022/11/29 20:31:15] ● lightdm.service - Light Display Manager
[2022/11/29 20:31:15] Loaded: loaded (/lib/systemd/system/lightdm.service; indirect; vendor preset: enabled)
[2022/11/29 20:31:15] Active: failed (Result: exit-code) since Tue 2022-11-29 20:25:40 CST; 3min ago
[2022/11/29 20:31:15] Docs: man:lightdm(1)
[2022/11/29 20:31:15] Process: 1345 ExecStartPre=/bin/sh -c [ "