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I've tried searching for answers but haven't come up with anything useful.

I installed Ubuntu about a month ago on my desktop computer. It has worked great initially, but just the other day my main monitor has now stopped being detected completely. I've read about the monitor maybe being deactivated or such, but I can't find it anywhere.

I've tried unplugging it and plugging it in again after restarting and that didn't work. I've tried installing ARandR but it doesn't detect my other monitor.

I dual boot my computer with Windows and it has no problem detecting my monitor as normal, which is really strange. I didn't do anything in particular before I got this problem, like install an update or such, so it's strange that it just suddenly stopped working.

Pleas help! I use Ubuntu for school and I think it works better than Windows for what I'm doing. It sucks that things just stop working for apparently no reason.

Edit: Output from xrandr --listmonitors: xrandr: Failed to get size of gamma for output default Monitors: 1 0: +*default 1920/508x1080/286+0+0 default

Edit: RESOLVED

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  • 1
    Open a terminal CTRL+ALT+T and type this command: xrandr --listmonitors Please post the output.
    – koni_raid
    Sep 25, 2020 at 13:12
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    xrandr: Failed to get size of gamma for output default Monitors: 1 0: +*default 1920/508x1080/286+0+0 default
    – Gaennil
    Sep 25, 2020 at 13:18
  • So only one Monitor is shown! Cable should not be the problem, as it works with Win, correct? What type of Monitor? Which Graphic card? What type of Desktop PC? See also this post: askubuntu.com/questions/1105332/…
    – koni_raid
    Sep 25, 2020 at 13:27
  • When I run lspci | grep VGA it says: 01:00.0 VGA compatible controller: NVIDIA Corporation GK104 [GeForce GTX 760 OEM] (rev a1). My monitor has a few years on its back but it worked fine just a few days ago. It's an LG Flatron E2441. My computer is quite old (it's an Acer Predator from at least 5 years back if not more) but I haven't had any major issues with it. And yes, it works fine with Windows so the cable is not the problem.
    – Gaennil
    Sep 25, 2020 at 13:34
  • my HDMI cable somehow got fried ... unplugging it from my monitor and taking a close look revealed a scorched mangle of pins ... evidently its not a good idea to simply unplug the HDMI cable without first unplugging the power to the monitor even though I have been just pulling the HDMI cable out of my laptop for years ... luckily my 4k monitor has a second HDMI jack where it runs OK using a new cable
    – Scott Stensland
    Oct 3, 2021 at 14:47

6 Answers 6

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I had a similar issue like this. I downloaded and selected the proprietary drivers I needed in software&updates->additional drivers, and did a couple of restarts. You can check which driver you need with:

ubuntu-drivers devices

Select the right one and restart. It should resolve itself. If that doesn't work try this:

sudo apt-get purge 'nvidia*'
sudo add-apt-repository ppa:graphics-drivers
sudo apt-get update
sudo ubuntu-drivers autoinstall
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  • How do I know which proprietary drivers I need? Currently it says "Using NVIDIA driver metapackage from nvidia-driver-450 (proprietary, tested)".
    – Gaennil
    Sep 25, 2020 at 13:37
  • Check edit above.
    – Mike Rawding
    Sep 25, 2020 at 14:19
  • 2
    Thank you! Typing "ubuntu-drivers devices" listed a bunch of different proprietaries, but after I switched to another one it works just like before. I swear I had the same one selected when everything got messed up as well, but I'm not sure. It worked at least, so I'm glad!
    – Gaennil
    Sep 25, 2020 at 17:52
  • 1
    Wow - this saved me, thanks!
    – someuser
    Mar 23, 2022 at 5:11
  • 1
    Top! Worked for me the second part with purge and autoinstall .. many thanks!
    – Mutatos
    May 23, 2022 at 13:47
5

Uninstalling intel drivers was what actually did the trick for me:

sudo apt-get purge xserver-xorg-video-intel
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5
  • I have tried what Mike Rawding mentioned above. I also tried your solution After typing every command and reboot. It works again :D
    – Redplane
    Apr 13, 2021 at 13:35
  • Before uninstalling this, my nvidia settings only had the nvidia-profile (performance, on-demand, and intel) available. Second monitor was detected when using on-demand profile). After uninstalling, all my nvidia settings are back to normal, and second monitor is detected and working in performance mode yet again. Thanks!
    – Martin Hansen
    Sep 17, 2021 at 7:37
  • i ofc mean intel settings. Second time around, this fix didnt work.
    – Martin Hansen
    Sep 21, 2021 at 5:58
  • This worked well on my early 2010 MacBook Pro (13in) (it has a Nvidia GeForce 320 built in.) External Display stopped working after the NVidia driver was installed. Thank you Yuri.
    – ocodo
    May 31, 2022 at 13:37
  • Worked for me too!
    – Mike Lawrence
    Oct 6, 2022 at 16:06
0

If nothing else works: probably it is a specific issue that I had here, with my old M6700 laptop, but I could solve this problem by using an old VGA cable instead of HDMI.

The monitor was not identified with the HDMI, but is identified immediately with VGA.

Regarding the advantages of HDMI over VGA - regarding the picture I get - it looks the same... I don't use audio from the screen, so no worries there.

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0

I run a Thinkpad Extreme Gen 2 on Ubunutu 20.04 (Windows 10 Dual Boot). The notebook is Windows native. I rebooted with Windows and my external monitor was detected, then I have shut the computer down and reboot with Ubuntu, then the monitor was detected.

Note: The exact same pattern came up 1 year ago on Ubuntu 19 with the Intel Network drivers, that's how I got the idea.

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In my case it helped removing the *-nvidia.rules under /lib/udev/rules.d and rebooting

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I would suggest you to simply go to software & update, go to additional drivers and then degrade your driver version. Example Using NVIDIA driver metapackage from nvidia-driver-515 TO Using NVIDIA driver metapackage from nvidia-driver-470-SERVER

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  • exceptionally bad advice. Anyone reading this should try UPGRADING their devices before reverting -- that's all I had to do to get my monitor back.
    – Derek Adair
    Dec 23, 2023 at 13:37

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