All resolution options except 1024x768 gone after upgrade to Ubuntu 20.04.2 LTS

I got prompted an update (20.04.2 LTS from 20.04.1 LTS) this morning, installed it and rebooted. Now, the only resolution available on my 4K monitor is 1024x768. I have a nvidia 3090 card, run the monitor via DisplayPort.

Running xrandr shows me the following:

xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1024 x 768, current 1024 x 768, maximum 1024 x 768
default connected primary 1024x768+0+0 0mm x 0mm 1024x768 76.00* 

My current (activated) driver is nvidia-driver-460 (proprietary, tested). I tried switching to the nouveau driver without luck, so reverted back. I also tried adding a new resolution using xrandr without luck.

I also noticed that running the command nvidia-smi no longer works:

NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver. Make sure that the latest NVIDIA driver is installed and running.

Any advice or suggestions?

EDIT: Another Base update in "Software Updater" was available today, 24h later, that come with some nvidia updates. After a restart, this solved the issue and I'm able to change the resolution back to 4k.

Showing today's update in /var/log/apt/history.log:

Start-Date: 2021-03-17 11:16:25
Commandline: aptdaemon role='role-commit-packages' sender=':1.171'
Upgrade: linux-modules-nvidia-460-5.8.0-45-generic:amd64 (5.8.0-45.51~20.04.1, 5.8.0-45.51~20.04.1+1)
End-Date: 2021-03-17 11:16:37

4 Answers

You probably got bit by the same kernel upgrade I was bit by this morning.

Check /var/log/apt/history.log and you'll probably see something of the form

Commandline: apt -y full-upgrade
Requested-By: spl (1000)
Install: linux-image-5.8.0-45-generic:amd64 (5.8.0-45.51, automatic), linux-headers-5.8.0-45:amd64 (5.8.0-45.51, automatic), linux-modules-extra-5.8.0-45-generic:amd64 (5.8.0-45.51, automatic), linux-headers-5.8.0-45-generic:amd64 (5.8.0-45.51, automatic), linux-modules-5.8.0-45-generic:amd64 (5.8.0-45.51, automatic), linux-modules-nvidia-460-5.8.0-45-generic:amd64 (5.8.0-45.51, automatic)
Upgrade: linux-headers-generic:amd64 (5.8.0.44.49, 5.8.0.45.50), linux-libc-dev:amd64 (5.8.0-44.50, 5.8.0-45.51), linux-modules-nvidia-460-generic-hwe-20.04-edge:amd64 (5.8.0-44.50, 5.8.0-45.51), linux-image-generic:amd64 (5.8.0.44.49, 5.8.0.45.50), libglib2.0-dev-bin:amd64 (2.66.1-2ubuntu0.1, 2.66.1-2ubuntu0.2), libglib2.0-bin:amd64 (2.66.1-2ubuntu0.1, 2.66.1-2ubuntu0.2), libglib2.0-dev:amd64 (2.66.1-2ubuntu0.1, 2.66.1-2ubuntu0.2), libglib2.0-doc:amd64 (2.66.1-2ubuntu0.1, 2.66.1-2ubuntu0.2), libglib2.0-data:amd64 (2.66.1-2ubuntu0.1, 2.66.1-2ubuntu0.2), linux-generic:amd64 (5.8.0.44.49, 5.8.0.45.50), libglib2.0-0:amd64 (2.66.1-2ubuntu0.1, 2.66.1-2ubuntu0.2), libglib2.0-0:i386 (2.66.1-2ubuntu0.1, 2.66.1-2ubuntu0.2)
End-Date: 2021-03-16 05:52:21

I backed those changes out as follows:

/usr/bin/sudo apt remove linux-headers-5.8.0-45:amd64
/usr/bin/sudo apt remove linux-modules-extra-5.8.0-45-generic:amd64
/usr/bin/sudo apt remove linux-headers-5.8.0-45-generic:amd64
/usr/bin/sudo apt remove linux-modules-5.8.0-45-generic:amd64
/usr/bin/sudo apt remove linux-modules-nvidia-460-5.8.0-45-generic:amd64
/usr/bin/sudo apt install linux-image-5.8.0-43-generic:amd64
/usr/bin/sudo apt install linux-modules-extra-5.8.0-43-generic:amd64
/usr/bin/sudo apt install linux-headers-5.8.0-43:amd64
/usr/bin/sudo apt install linux-headers-5.8.0-43-generic:amd64
/usr/bin/sudo apt install linux-modules-5.8.0-43-generic:amd64
/usr/bin/sudo apt install linux-modules-nvidia-460-5.8.0-43-generic:amd64

which reverted me to the previous kernel. I then sacrificed a goat, took a great big slug of coffee, crossed my fingers and rebooted.

All returned to whatever passes for normal.

Your mileage may vary.

Note: You'll get some scary warnings about deleting a running kernel. Hence the sacrificial goat.

I can confirm a similar issue. My computer reverted to 640x480, I was able to get this to 1024x768 but updating Grub.

It seems to be the "failed to get the size of gamma output" that is the issue.

I have tried to use CVT and xrandr to manually add a new resolution but this just results in the "failed to get gamma" output again.

Another Base update in "Software Updater" was available today, 24h later, that come with some nvidia updates. After a restart, this solved the issue and I'm able to change the resolution back to 4k.

Showing today's update in /var/log/apt/history.log:

Start-Date: 2021-03-17 11:16:25
Commandline: aptdaemon role='role-commit-packages' sender=':1.171'
Upgrade: linux-modules-nvidia-460-5.8.0-45-generic:amd64 (5.8.0-45.51~20.04.1, 5.8.0-45.51~20.04.1+1)
End-Date: 2021-03-17 11:16:37

I have found a solution for me here

Running the following commands in Terminal fixed this for me this morning

sudo apt install nvidia-settings

sudo ubuntu-drivers autoinstall

sudo reboot