lightdm does not start

[Thomas Schweikle]

lightdm tries to initialize screen output, fails, tries again, fails until the backlight electronics break, killing the monitor.

lightdm fails initializing screen. This turns on backlight, initializes graphics, then lightdm stops with an error message. systemd starts lightdm again. Lightdm tries to initialize graphics. This turns on backlight. Lightdm fails, exausts an error message, backlight turns off again. systemd starts lightdm, lightdm tries to initialize graphics. Turns on backlight. Exausts an error message. Backlight is turned off again. ...

After doing so more than twice a second backlight breaks. Electronics broke down.

Conclusion: at the moment Ubuntu 18.10 is capable of killing monitors by lightdm not able to initialize screens and breaking, then beeing restarted by systemd.

Since this can kill hardware it is a no go! It is a bad bad bad bad bad bad bad bad bad bad bad bad bad bad bug!

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: lightdm 1.28.0-0ubuntu1
ProcVersionSignature: Ubuntu 4.18.0-11.12-generic 4.18.12
Uname: Linux 4.18.0-11-generic x86_64
ApportVersion: 2.20.10-0ubuntu13.1
Architecture: amd64
Date: Sat Nov 3 17:03:19 2018
InstallationDate: Installed on 2011-10-19 (2571 days ago)
InstallationMedia: Xubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
SourcePackage: lightdm
UpgradeStatus: Upgraded to cosmic on 2018-11-03 (0 days ago)

[Thomas Schweikle (tps)]

Same problem: it does not matter if upgraded from 18.04 or installed new with 18.10. lightdm might not allways be capable initializing graphics leeding to some loop together with systemd turning on backlight, turning it off again, then restarting.

Backlight is turned on, then off about twice a second. After some time backlight electronics break down, killing the monitor.

[Thomas Schweikle (tps)]

This schouldn't happen. lightdm should only be started about 10 times, then disabled.

BTW: no errors are readable on screen. Logs only show lightdm restarted by systemd after terminatating. Errors can be seen by disabling lightdm, then starting it from commandline. But this isn't helpful either: "Could not initialize screen. Terminating."

[Thomas Schweikle (tps)]

This bug exists since 16.10 – we are at 18.10 now it is now two years with this monitor killing bug.