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JJD
Asked: 2020-10-22 10:15:05 +0800 CST

How to let Ubuntu 20.04.1 recognize an unknown display to adjust its resolution?

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I recently updated from Ubuntu 18.04.4 to 20.04.1 on a Lenovo T400 2765. When I connected an external Fujitsu Siemens P19-1A monitor via VGA it is shown as "Unknown Display" in Settings > Displays. This was not the case in Ubuntu 18.04.4.

Screenshot of Settings > Displays

Also, the native resolution (1280x1024) is not available.

Here is what xrandr tells about the monitors:

$ xrandr --listmonitors
Monitors: 2
 0: +XWAYLAND0 1440/300x900/190+0+768  XWAYLAND0
 1: +XWAYLAND1 1024/271x768/203+0+0  XWAYLAND1

...

$ xrandr
Screen 0: minimum 16 x 16, current 1440 x 1668, maximum 32767 x 32767
XWAYLAND0 connected 1440x900+0+768 (normal left inverted right x axis y axis) 300mm x 190mm
   1440x900      60.03*+
XWAYLAND1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768      59.92*+

There is no additional drivers installed:

Screenshot of Software & Updates > Additional Drivers

How can I make Ubuntu recognize the monitor? Is there a driver in Ubuntu 18.04.4 which I have to manually install?

I found this very good article on how to add a custom resolution but I would prefer to let Ubuntu recognize the actual monitor (brand/model) as before.

Related

multiple-monitors drivers display gpu-driver 20.04

1 Answers

  1. Follow these steps:

    1. Locate monitors.xml, usually in /home/username/.config/monitors.xml.

    2. Then find the name of unknown display inside <connector>DP-1</connector>.

    3. Open GRUB using nano:

      sudo nano /etc/default/grub

      or, if you prefer a GUI application such as gedit:

      gksudo gedit /etc/default/grub

    4. Change the line starting with GRUB_CMDLINE_LINUX= to include the name of the unknown display you found in step 2 as follows:

      GRUB_CMDLINE_LINUX="video=DP-1:d"

    5. Save the changes in nano by Ctrl+O and Enter and close the editor by Ctrl+X and Enter (if you used a GUI editor just save as usually and close the editor).

    6. Update GRUB:

      sudo update-grub
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