Gfilui

After upgrading to Ubuntu 18.04, my laptop has been unable to detect/use an external monitor attached via HDMI. Even when plugged in, the "detect displays" button within the default settings app doesn't do anything.

Here is the output from xrandr:

Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 16384 x 16384
eDP-1-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 194mm
 1920x1080 60.01*+ 60.01 59.97 59.96 59.93 
 1680x1050 59.95 59.88 
 1600x1024 60.17 
 1400x1050 59.98 
 1600x900 59.99 59.94 59.95 59.82 
 1280x1024 60.02 
 1440x900 59.89 
 1400x900 59.96 59.88 
 1280x960 60.00 
 1440x810 60.00 59.97 
 1368x768 59.88 59.85 
 1360x768 59.80 59.96 
 1280x800 59.99 59.97 59.81 59.91 
 1152x864 60.00 
 1280x720 60.00 59.99 59.86 59.74 
 1024x768 60.04 60.00 
 960x720 60.00 
 928x696 60.05 
 896x672 60.01 
 1024x576 59.95 59.96 59.90 59.82 
 960x600 59.93 60.00 
 960x540 59.96 59.99 59.63 59.82 
 800x600 60.00 60.32 56.25 
 840x525 60.01 59.88 
 864x486 59.92 59.57 
 800x512 60.17 
 700x525 59.98 
 800x450 59.95 59.82 
 640x512 60.02 
 720x450 59.89 
 700x450 59.96 59.88 
 640x480 60.00 59.94 
 720x405 59.51 58.99 
 684x384 59.88 59.85 
 680x384 59.80 59.96 
 640x400 59.88 59.98 
 576x432 60.06 
 640x360 59.86 59.83 59.84 59.32 
 512x384 60.00 
 512x288 60.00 59.92 
 480x270 59.63 59.82 
 400x300 60.32 56.34 
 432x243 59.92 59.57 
 320x240 60.05 
 360x202 59.51 59.13 
 320x180 59.84 59.32 
DP-1-1 disconnected (normal left inverted right x axis y axis)
HDMI-1-1 disconnected (normal left inverted right x axis y axis)

My main concern is the final line: HDMI-1-1 disconnected. There is a monitor plugged in and ready for use, and nothing I do seems to cause it to be detected.

I have an nvidia graphics card, and before the update I was using proprietary drivers. When the external display problem first arose, my initial attempt was to switch back to the open source Xorg drivers. However, upon reboot, Ubuntu displayed my driver settings as using a "manually installed driver", and won't let me change it:

Any recommendations?

I solved the problem installing lightdm and set it as the default display manager.

In the process, something changes because is starting to detect external displays again even if you go back to GDM3.

You can follow the instructions here on how to make these changes:

• sudo dpkg-reconfigure gdm


• select the display manager (LightDM, MDM, KDM, Slim, GDM) you want to use by default and hit enter


• restart your computer

Try this (change resolution, if 1920x1080 is not your resolution):

 xrandr --addmode HDMI-1-1 1920x1080
 xrandr --output HDMI-1-1 --mode 1920x1080

I connected my external monitor through VGA and went to Settings > Devices > Displays choose Mirror and then Apply. was asked if I wanted to keep this Setting choose Yes and everything connected. Simple and Beautiful.