Greeter shows in secondary monitor mode when only one monitor

[Till Kamppeter]

I am on n Intel Core i5 quad-core PC with Intel's on-Chip graphics. Quantal and Raring worked perfectly on this machine. Last Friday (Oct 18, 2013) I have upgraded to Saucy and the upgrade went smoothly and the first boot also worked correctly. Then I stayed logged in during the whole weekend. I am not sure but it can be that during that time a smaller update happened, but I do not know which packages. Yesterday (Sunday) something crashed and I had to reboot.

Now after the boot LightDM did not come up again. X started and the standard background showed up, but instead of the login facility there was nothing but a white Ubuntu logo in the center. There was a short OSD notification that I am connected to the wired network. Then the system was hanging.

I could switch into text mode and operate in text mode. I could also SSH into the system from another machine.

Intext mode I have stopped the lightdm service, installed GDM and started the GDM service, which also hung before getting a login facility.

I can get a Unity desktop via

export COMPIZ_CONFIG_PROFILE=ubuntu
startx

on the text console.

I also cannot start a Saucy live system (USB stick). It comes to starting X and the standard background shows, with a top bar with accessibility and network indicator applets (which actually work), but the screen stays otherwise empty. The dialogs to enter language and keyboard layout do not appear and nothing happens.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: lightdm 1.8.2-0ubuntu1
ProcVersionSignature: Ubuntu 3.11.0-12.19-generic 3.11.3
Uname: Linux 3.11.0-12-generic x86_64
ApportVersion: 2.12.5-0ubuntu2
Architecture: amd64
Date: Mon Oct 21 22:10:23 2013
InstallationDate: Installed on 2012-07-27 (451 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha amd64 (20120724.2)
LightdmConfig:
 [SeatDefaults]
 user-session=ubuntu
 greeter-session=unity-greeter
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: lightdm
UpgradeStatus: Upgraded to saucy on 2013-10-17 (4 days ago)

[Robert Ancell (robert-ancell)]

By your description and logs:
- LightDM is running fine
- Unity Greeter is also running, but what you can see (the ubuntu logo in the middle) indicates that you are looking at a second monitor without the cursor inside it. There should be another output which shows the user list.
- Unity greeter is authenticating correctly (if you typed blindly it would probably log you into a session).
- Because neither LightDM, GDM or the live session work this indicates a common component problem which is likely to be X.org or your video drivers.

Reassigning to xorg.

[Till Kamppeter (till-kamppeter)]

There seems to be a ghost monitor (I have only one, with 1920x1080 resolution):

till@till:~$ xrandr
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 32767 x 32767
VGA1 connected (normal left inverted right x axis y axis)
   1024x768 60.0
   800x600 60.3 56.2
   848x480 60.0
   640x480 59.9
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 510mm x 287mm
   1920x1080 60.0*+ 59.9
   1680x1050 59.9
   1280x1024 60.0
   1280x960 60.0
   1280x720 60.0 59.9
   1024x768 60.0
   800x600 60.3
   720x576 50.0
   720x480 60.0 59.9
   640x480 60.0 59.9
   720x400 70.1
DP1 disconnected (normal left inverted right x axis y axis)
DP2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
till@till:~$

[Till Kamppeter (till-kamppeter)]

The mouse starts off on the ghost screen on to left of the real screen having the login facility there. I move it a longer distance to the right and it enters the real screen, making the login facility flipping into the real screen. Then I can actually log in.

The live session is unusable though, with the mouse I can spot the ghost screen on the left, but as I cannot work blindly with a mouse I cannot pull the windows into the visible screen.

[Till Kamppeter (till-kamppeter)]

Note that my PC has no VGA connector (only HDMI and DisplayPort), so there must be a bug in the X driver for the Intel GPUs.

[Chris Wilson (ickle)]

Your hw is falsely reporting a VGA connection. I see that you tried to disable it with video=VGA1:d, but since that should read video=VGA-1:d.

[Till Kamppeter (till-kamppeter)]

Sorry for the late reply.

That's it. "video=VGA-1:d" does the trick. Thank you very much.

[Till Kamppeter (till-kamppeter)]

Also there is no second ghost screen in the Displays part of the System Settings any more and xrandr gives the following (correct) output:

till@till:~$ xrandr
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 32767 x 32767
VGA1 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 510mm x 287mm
   1920x1080 60.0*+ 59.9
   1680x1050 59.9
   1280x1024 60.0
   1280x960 60.0
   1280x720 60.0 59.9
   1024x768 60.0
   800x600 60.3
   720x576 50.0
   720x480 60.0 59.9
   640x480 60.0 59.9
   720x400 70.1
DP1 disconnected (normal left inverted right x axis y axis)
DP2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
till@till:~$

[Chris Wilson (ickle)]

If you do get a chance to attach a drm.debug=6 dmesg without video=VGA-1:d, I can have a better idea as to whose fault it is.

[Till Kamppeter (till-kamppeter)]

Done, output of the "dmesg" command is attached.

[Chris Wilson (ickle)]

That device is expected to have a VGA header on the motherboard, so it would seem a manufacturing detect. (VGA link detection is all in hardware.)

[Till Kamppeter (till-kamppeter)]

You mean that the CPU with its on-chip GPU puts out a VGA signal through some of its pins and the motherboard does not correctly take care of it due to a hardware design bug?

[Chris Wilson (ickle)]

Yes, more often than not it is a short across a couple of pins.