I launched the upgrade process to 17.10 when asked for it (on 17.04).
My screen was locked (and off) during the download of the packages but it flashed by waking sometimes (I was in the dark so I noticed that).
Then an hour later, I wanted to see how the upgrade went but I couldn't login anymore. My password was refused (but I could login without problem on a console Ctrl-Alt-F1) so I guess something was wrong with lightDM ?
So I rebooted, and now the boot process fails with Failed to start Login service
which is not related to lightDM anymore but systemd-logind.service
.
Edit: systemd-logind log shows that:
Failed to add match for JobRemoved: Connection timed out
Failed to fully start daemon: Connectin timed out
systemd-logind.service: Main process exited, code=exited, status=1/FAILURE
Stopped Login Service.
systemd-logind.service: Unit entered failed state.
systemd-logind.serivce: Failed with result 'exit-code'.
I can't find much about this on the net