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Erland
Asked: 2012-04-12 05:40:00 +0800 CST

How do I list connected displays using the command line?

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Is there a command that will list displays connected to the computer?

Specifically, I'm looking to find out how my external monitor is being detected by the system when connected by HDMI cable and what it's (not sure of the correct term here) hardware address is (eg. "CRT-0" or "DFP-1").

This is just a general question, but for reference, I'm using:

  • Asus UL30JT laptop - running Ubuntu 12.04 beta and 11.10
  • Asus PA238 23" monitor
  • HDMI 1.4 cable
  • Optimus graphics (Intel + nVidia GeForce 310M) - running with Bumblebee
multiple-monitors command-line hardware display monitor

2 Answers

  1. Try this:

    xrandr --query

    This lists the display names and detected available resolutions. You can also reconfigure your displays using xrandr.

    Note that this might not work if you're using the NVidia or ATI drivers; I'm not sure.

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  2. For most machines with the proprietary driver loaded, /usr/lib/nvidia-current/bin/nvidia-xconfig --query-gpu-info --nvidia-cfg-path=/usr/lib/nvidia-current works. Note that I said "with the proprietary driver loaded". For instance, it does not work if the driver is unloaded or nouveau is loaded. Therefore, when using Bumblebee, run optirun /usr/lib/nvidia-current/bin/nvidia-xconfig --query-gpu-info. The --nvidia-cfg-path part is not needed here as optirun sets the correct library path.

    See also the discussion on https://github.com/Bumblebee-Project/Bumblebee/issues/21

    /var/log/Xorg.0.log (where 0 is the display number) may also contain valuable information about available screens. For Optimus laptops, this log contains only details on the Intel screen, so replace 0 by 8 to find out the log from the X server started by Bumblebee.

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