I can't seem to log in on Ubuntu 16.04.4 with lightdm, even though authentication is successful. I am able to use the console just fine, but I need to be able to use graphical browsers from time to time.

This is an excerpt of my /var/log/lightdm/lightdm.log:

[+3.56s] DEBUG: Session pid=8307: Got 1 message(s) from PAM
[+3.56s] DEBUG: Prompt greeter with 1 message(s)
[+10.81s] DEBUG: Continue authentication
[+10.83s] DEBUG: Session pid=8307: Authentication complete with return value 0: Success
[+10.83s] DEBUG: User x authorized
[+10.83s] DEBUG: Greeter requests session unity8-mir
[+10.83s] DEBUG: Using VT 8
[+10.83s] DEBUG: DisplayServer: Logging to /var/log/lightdm/unity-system-compositor.log
[+10.83s] DEBUG: Launching process 8311: /usr/sbin/unity-suystem-compositor.sleep --file '/run/mir_socket' --from-dm-fd 12 --to-dm-fd 21 --vt 8
[+10.83s] DEBUG: DisplayServer: Waiting for system compositor for 60s
[+10.97s] DEBUG: DisplayServer: Compositor closed communication channel
[+10.97s] DEBUG: Process 8311 exited with return value 0

For some reason, the compositor is closing the communication channel. Other users can log in to the graphical interface.

Has anyone encountered similar issues? It's not that lightdm redirects. Nor does it hang the computer, although sudo service lightdm restart from an alternate console lets me repeat the error every time.

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