Laptop screen blank after login when external monitor is not connected

Posted by Ramon Suarez on Ask Ubuntu See other posts from Ask Ubuntu or by Ramon Suarez
Published on 2012-06-09T20:30:47Z Indexed on 2012/09/30 9:48 UTC
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Ubuntu does not switch back automatically to only monitor present when booting after disconnecting external monitor.

Here's a video showing what happens. I get to the login window and everything looks ok, then I type my password, the desktop image shows up and... everything goes blank. It does not happen when I just login as a guest.

When possible I work with my laptop connected to an external screen via the VGA port. The problem comes when I boot the computer without that secondary screen connected:

  • The login screen comes out ok.
  • After login the screen goes black, but I can hear the login sound.
  • If I hit ctr + alt + backwards-delete and login again sometimes it is fixed, but not all.
  • If I log in as a different user everything is OK. Then I log in as my user and sometimes it works.

To have a screen I have to plug a monitor. Although I have turned on the laptop display with that monitor on, if I reboot it goes blank again after login, even if I turn off the external monitor before turning off the computer.

I've managed to get my screen back with my username after going into recovery mode, but only sometimes. Failsafe would not load after second screen asking me what I wanted to do (no mouse to click nor keyboard working).

My computer is a LDLC Aurore BB1-i5 -8 -S1.

Which is the configuration file that keeps the information about the monitors using Displays under lightgdm and where is it? I guess if I could edit it I may have a chance :)

One of the things I tried following a solution in another post was removing my monitors.xml file, but it does not work and I don't know how to create a good one that I could use now.

When doing DISPLAY=:0 xrandrI get:

Screen 0: minimum 320 x 200, current 320 x 200, maximum 8192 x 8192 LVDS1 connected (normal left inverted right x axis y axis) 1366x768 60.0 + 1360x768 59.8 60.0
1024x768 60.0
800x600 60.3 56.2
640x480 59.9
VGA1 disconnected (normal left inverted right x axis y axis) HDMI1 disconnected (normal left inverted right x axis y axis) DP1 disconnected (normal left inverted right x axis y axis)

This is the full dmesg after activating sudo xdiagnoseas Bryce sugested. (If you tell me the relevant parts I will paste them here)

When conecting the external monitor, only the external will work, although I can see using Displays that the computer thinks that both are working.

I've asked the question in Launchpad but have it keeps on expiring without any feedback. In my opinion Ubuntu should be able to detect automatically that there is no external monitor present and switch to the laptop monitor.

There's a similar question here, but it does not apply to my case External monitor set as primary even when disconnected from laptop

Update: For clarification, the problem happens only with my user and once I log in. I even get to see the screensaver for about a second, and then it goes blank. Tried Bryce's example (see his answer below), but it did not work. This is the info I get from tty1 with Display=:0 xrandr: – Ramon Suarez Jul 9 at 16:36

Screen 0: minimum 320 x 200, current 320 x 200, maximum 8192 x 8192 LVDS1 connected (normal left inverted right x axis y axis) 1366x768 60.0 + 1360x768 59.8 60.0 1024x768 60.0 800x600 60.3 56.2 640x480 59.9 VGA1 disconnected (normal left inverted right x axis y axis) HDMI1 disconnected (normal left inverted right x axis y axis) DP1 disconnected (normal left inverted right x axis y axis)

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