setting an invalid greeter makes lightdm say that you are in low graphics mode

Bug #971891 reported by Matt Fischer on 2012-04-02
This bug affects 12 people
Affects Status Importance Assigned to Milestone
Light Display Manager
lightdm (Ubuntu)

Bug Description

In the process of experimenting with a new greeter, I mistyped the greeter name. When I did this and restarted lightdm, lightdm throws up a screen saying I'm in low graphics mode "Your screen, graphics card, and input device settings could not be detected correctly". At this point, none of the options provided works. I double checked my lightdm conf file and caught the error, but this is a confusing and incorrect message in this specific case.

See screen cap attached.

To repro, edit lightdm.conf and set "greeter-session=fred" or anything that's not a valid session name.

I'm running lightdm 1.1.9-0ubuntu1

Matt Fischer (mfisch) wrote :
Robert Ancell (robert-ancell) wrote :

Matt, you keep finding all the bugs we like to pretend don't exist :)

Yeah, we need a way of providing some information to failsafe X as to why lightdm didn't start. The solution to this will probably have to be failsafe X scanning the log files for some known regexps and using those to suggest to the user why the problem existed.

Changed in lightdm:
status: New → Triaged
importance: Undecided → Low
Matt Fischer (mfisch) wrote :

Couldn't lightdm check for the existence of the requested greeter and just bail when it's not present?

Robert Ancell (robert-ancell) wrote :

That's what it's done; failsafe X is started when lightdm exits with an error. It's the catch all for when you can't get a normal graphical display up.

Daniel (hackie) wrote :

In my case, the bad greeter-session setting appeared after removing unity. I also think the greeters themselves should do something like update-alternatives when they get uninstalled.
But more important is a better error message.

Bryce Harrington (bryce) wrote :

Yeah, parsing the lightdm logs is doable. Mind attaching an example log?

Also provide detailed steps to reproduce.

Bonus points if you can suggest a good wording for an error message.

Changed in xdiagnose:
status: New → Incomplete
Matt Fischer (mfisch) wrote :

Repro steps are in the original description:

"To repro, edit lightdm.conf and set "greeter-session=fred" or anything that's not a valid session name."

Logs are attached.

Matt Fischer (mfisch) wrote :
Mathias Dietrich (theghost) wrote :

If you installed and removed lightdm-kde-greeter and you want to go back to Unity's lightdm try:

    sudo dpkg-reconfigure unity-greeter
    sudo dpkg-reconfigure lightdm

and select lightdm and reboot.

Nathan Hartley (treestryder) wrote :

This happened to me while I was trying to remove that darned Guest Login option from the logon screen. Do you think I could argue, that the Guest Login triggered a denial of service attach against my PC and thus needs to be removed from the default install?

Thanks for this bug report. I had gone a long time without rebooting, when I finally applied updates and went to bed the night before I found the error. I never would have put the cause and effect together otherwise.

Matt Fischer (mfisch) wrote :

@Nathan: You could use /usr/lib/lightdm/lightdm-set-defaults next time, it's a safer way to change options.

piotr zimoch (ebytyes) on 2013-05-22
Changed in lightdm:
status: Triaged → New
status: New → Incomplete
status: Incomplete → Opinion
status: Opinion → Invalid
status: Invalid → Confirmed
status: Confirmed → In Progress
status: In Progress → Fix Committed
status: Fix Committed → Fix Released
Changed in xdiagnose:
status: Incomplete → New
status: New → Incomplete
status: Incomplete → Invalid
status: Invalid → In Progress
status: In Progress → Fix Committed
status: Fix Committed → Fix Released
Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in lightdm (Ubuntu):
status: New → Confirmed
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