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I'm on 19.04 on a laptop with an nvidia 1070 GTX. I have an external monitor connected via mini display port that was working perfectly.

I've been rebooting a few times to encrypt some partitions (home and swap) on both Ubuntu and Windows 10 (bitlocker) that is in dual boot on a separate ssd.

After this, with no apparent reason, the external monitor stopped working.

The weird thing is that it works perfectly during the login screen where I can see it as extended and I can even move my mouse cursor over it, but right after I login it just goes into energy saving mode. If I log out the external monitor works again only in the login screen.

What happened?

The nvidia driver I'm using is the official one in performance mode.

blisterine
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2 Answers2

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I had a similar issue which was solved by this. Apparently prime-select writes to a certain config file which can mess up external displays.

Open the file with any files editor:

sudo nano /lib/modprobe.d/nvidia-kms.conf

and comment out the nvidia-drm modeset option

# This file was generated by nvidia-prime
# Set value to 0 to disable modesetting
# options nvidia-drm modeset=1

You can find more information about it here. Essentially nvidia-drm provides anti-tearing solution, however it does this in a semi-convoluted way.

Thomas B.
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  • Hi, thanks for the reply. Unfortunately I've seen that post already and I've tried this solution. I'm trying again right now but with no luck. I've commented out the line in the nvidia file, it looks like I'm using the nvidia card now but still it doesn't detect the external monitor. Shall I try modeset=0 instead of commenting out? – blisterine Apr 24 '19 at 21:30
  • edit: I've tried modeset=0 but still no external monitor. Isn't it weird that it works on the login screen, though? What does this behaviour imply? – blisterine Apr 24 '19 at 21:42
  • I have verified that the Nvidia GPU is actually in use, I can even play games on it, it's just the mDP that doesn't connect to the external monitor right after login. The infuriating part, again, is that I can perfectly seeing the external monitor working during the login screen. – blisterine Apr 26 '19 at 19:36
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After trying all of the above solutions, while I was testing the card and trying to understand its behaviour I did this:

  • in the nvidia X server settings (the actual GUI), in PRIME profiles, I switched to Intel (power saving mode) and log out when prompted.

  • I then re-logged in and again I switched back to NVIDIA performance mode in PRIME Profiles.

  • I then logged out when prompted and after I re-logged in the external monitor got connected.

It looks like the nvidia PRIME Profile switcher has an inconsistent behaviour.

blisterine
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