TLDR; Is it possible to physically turn off a built in display for a laptop so a docking station could utilise all available display outs.

I am struggling to physically turn-off a laptops built in display for Ubuntu 20.04. Due to the built in display always being available, when I attempt to connect more than a total of 3 [internal or external] monitors to my Dell Docking Station WD19 Thunderbolt in Settings > Screen Display I receive the error (in the windows title bar):

Changes Cannot be Applied
This could be due to hardware limitations

It is worth noting that the documentation for the docking station states:

NOTE: : Linux operating system is unable to physically turn-off built-in display, the external display numbers will be one less than the display numbers listed in above tables.

Additional Info:

  • Graphics card: NVIDIA GeForce GTX 1650 4GB GDDR5
  • Graphics driver: NVIDIA Corporation: TU117M [GeForce GTX 1650 Mobile / Max-Q] - Using NVIDIA driver metapackage from nvidia-driver-440
  • Some laptops have a key or fn combo to either disable the main display, or toggle which display is main, did you look for this functionality?
    – justus95
    Jun 21 '20 at 18:32
  • @justus95 yeah I did look, toggling doesnt remove the laptop screen as an available option, only prevents it from being used (it is still listed under monitors in the settings) Jun 21 '20 at 21:04

You can by using the preferences command for X server (http://systembash.com/content/how-to-turn-off-your-monitor-via-command-line-in-ubuntu/)

  • To turn off the monitor $ xset dpms force off

  • To turn on the monitor $ xset dpms force on Well if you press any key, the monitor will wake up, so to turn the screen off without turning it on use the below command:

    sleep 3; xset dpms force off

To determine the display you can use the command

'$ xrandr'

You can even run xrandr --output <DISPLAY_NAME> --brightness 0 to manually turn off display for a selected monitor.

NOTE: Once You $ sleep 3; xset dpms force off, you won't be able to turn on the display by clicking or pressing any key, then you've to blindly enter the code or use secondary display.

  • Thanks for the response, I'll give this a shot tonight and get back Jun 21 '20 at 21:05
  • Sorry that took soo long. I tested using xrandr as well as xset but using this only turns off the display, not remove it as an available monitor. The laptop monitor, even with the lid closed, is still listed :/ thanks though Jun 24 '20 at 15:32
  • [I forgot to actually state that I am] Still unable to connect to an additional display (I'm assuming due to the monitor still being listed). Jun 24 '20 at 15:42
  • Well here ends by thinking, I don't think so I have any idea after that, so probably I should start digging in for other methods. Jun 25 '20 at 16:04

Assuming that Dell actually has an interest in solving this admitted problem, (Linux operating system is unable to physically turn-off built-in display, the external display numbers will be one less than the display numbers listed in above tables.) it would likely be resolved via a firmware update to the device in question.

  • Thanks for the response, Ill give this a shot and get back to you. Jun 24 '20 at 16:12
  • 1
    No dice unfortunately, I'm thinking its outside of their hands and is more on the user to configure their system in a way that utilises all available monitor ports Jun 24 '20 at 18:26
  • @MiroslavGlamuzina Were you able to configure your system in a way that utilizes all available monitor ports on your Dell Docking Station WD19 Thunderbolt? I notice that there still doesn't appear to be a firmware update on Dells site (although it appears that they've expanded the commentary on what doesn't work if my memory serves)
    – Elder Geek
    Jul 30 '20 at 17:18
  • had no luck getting that fourth screen to work. I ended up setting up a Chromecast for it. The Chromecast solved most of my problems (when casting as desktop + application window), as my primary use for that monitor is media. Aug 2 '20 at 15:03

You could try mirroring your laptop's screen on one of the external monitors - How can I mirror one of the screens in a 3-monitor setup?

The answer I linked to suggests running the xrandr command to find the names of the available displays, and then

xrandr --output SCREEN1 --output SCREEN2 --output SCREEN3 --output SCREEN4 --same-as SCREEN1

Replacing "SCREEN#" with the names of the displays (assuming that SCREEN1 is your laptop display).

  • Thanks for the answer, but mirroring isn't what I'm looking for :/ Jul 2 '20 at 23:01
  • If you cannot live without disconnecting the screen, then just open up the laptop and yank the display cable. Maybe that's not a great solution every time you sit down, but at least then you could see if you are even able to connect another display if the laptop's display isn't there, or if the presence of the laptop display is hard-coded into the GPU. I suspect the latter, in which case mirroring seems like the only practical solution to the actual problem you're having, even if it doesn't satisfy the specific step you want to take to get there.
    – odd135
    Jul 3 '20 at 0:38

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