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:

enter image description here

Any recommendations?

  • What do you call open source Xorg driver ? is it the nouveau driver ? – solsTiCe May 8 '18 at 22:07
  • Yes. Sorry for not being specific. – PullJosh May 8 '18 at 22:40
  • 1
    This problem seemingly fixed itself. For any future readers experiencing the same issue: I launched an i3 session (as opposed to gnome) and then rebooted and the problem was solved. I don't expect that the two things are correlated, but if you're really stuck, it could be worth a shot. – PullJosh May 8 '18 at 23:27
  • 4
    For me, no "detect displays" button in displays settings. :( – angelcervera May 13 '18 at 10:32
  • 1
    @angelcervera's answer solved it for me. For reference, here are two very detailed threads outlining some other potential solutions: devtalk.nvidia.com/default/topic/1035768/linux/…, devtalk.nvidia.com/default/topic/1032482/… – dskrvk Sep 13 '18 at 1:36

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
  • This worked for my MSI GS65 on Ubuntu 18.04. I also have to sudo prime-select nvidia and restart my computer -- doesn't work unless nvidia drivers are being used, it seems. – Russell Richie Sep 2 '18 at 20:08
  • Although it seems that, contra angelcervera's post, if I switch back to gdm3, the problem reappears.... – Russell Richie Sep 3 '18 at 17:08
  • In addition to this answer I renamed my xorg.conf, though don't know if that actually had any effect in the end. – dskrvk Sep 13 '18 at 1:38
  • Choosing lightdm instead of gdm3 worked for me on Ubuntu 18.04 after the latest updates introduced the problem... – Kopfgeldjaeger Nov 27 '18 at 20:24
  • Wow! Good catch. It worked when I changed to LightDM. Ubuntu 18.04 here. – Lupus Jan 9 at 9:05

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

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

My external monitor plugged into my Lenovo L380 HDMI stopped working on Ubuntu 18.04. I succeeded to fix this issue by opening the BIOS setup and changing the display priority option from the USB Type-C to the HDMI.


The top solution did not work for me on my Acer laptop, which suddenly stopped showing HDMI-1 as an output in xrandr this morning. I tried changing to the noveau drivers in case that helped, but it didn't.
I read on a different site that sometimes the OEM laptop Nvidia cards can "get confused whether cable is connected or not", which I had assumed was just tech-support appeasing someone. But, for giggles, I tried unplugging the HDMI cable, plugging in the VGA cable, rebooting, and plugging the HDMI cable back in. For some reason, that worked.

This is probably an extension of "Just Learning"'s solution, the important part of which is probably the "through VGA" part.


I solved it by purging, then reinstalling the nvidia drivers

sudo apt-get purge 'nvidia*'
sudo add-apt-repository ppa:graphics-drivers
sudo apt-get update

Then using the Software & Updates tool's Additional Drivers tab and installing the latest nvidia drivers


I did not have this problem on Ubuntu 18.04 with NVIDIA GeForce GTX 1050 Mobile and GeForce GTX 1050. But after upgrading my kernel to 4.19 my external monitor was not detected anymore. Reverting back to the standard 4.15 kernel made the problem disappear.


Solved for me by updating to recommended Nvidea card drivers how-to.
To install all recommended Drivers:
sudo ubuntu-drivers autoinstall


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.

  • 1
    Unfortunately, the default settings app was the very first thing I tried. That being said, perhaps someone else will find this advice useful! (My problem has been solved, by the way, although I'm not entirely sure how...) – PullJosh May 22 '18 at 20:56

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