[SOLVED] Second Monitor disappeared in Kubuntu 22.10

[relief.melone]

I am currently having an issue with my second monior on Kubuntu. I don't know if this is relevant but its an ultrawide monitor (5120x1440). Everything was working well and fine up until this morning now my behaviour is this.

• xrandr -q does not show the second monitor
• lspci | grep VGA shows both the integrated and dedicated Graphics Card
• The prompt to choose how to use the second monitor (extend to left, right etc.) shows up repeatedly but selecting does not change anything
• it seems like in the display configuration for a quarter of a second the preferences for a second monitor show up but dissapear right again
• Windows (I have a dual boot system) shows now issues

Now I have been using Linux for a while now on the server side but am still pretty new to the graphical user interface. So I have difficulties choosing what information/logs might be helpful here and where to find them but I'd be happy to supply any additional information if needed.

[claydoh]

xrandr -q does not show the second monitor

and

Windows (I have a dual boot system) shows now issues

A bad/loose connection on the monitor (or at the computer end), or a bad cable, is the first place to look. The monitor does not seem to be detected by the OS, if xrandr doesn't show any info about it.
Can you swap cable between monitors, and see if the disappearing screen is now the other one?

lspci | grep VGA shows both the integrated and dedicated Graphics Card

And what does this show, specifically?

• The prompt to choose how to use the second monitor (extend to left, right etc.) shows up repeatedly but selecting does not change anything
• it seems like in the display configuration for a quarter of a second the preferences for a second monitor show up but dissapear right again

These also seem to add to the thought that there is a poor connection somewhere.

[relief.melone]

Originally posted by relief.melone View Post
xrandr -q does not show the second monitor
and

a lot of topics I came across while looking into issues with secondary monitors still showed both monitors but they also had no image. However I wanted to rule out problems that are the root cause to those issues.

I can definately rule out the cable. I tried HDMI and the DisplayPort as well as different cables. I am also on windows at the moment on the same machine and the monitor works flawlessly.

Other people that had issues also reported that their dedicated graphics card did not show and their secondary monitor worked again after the resolved that issue. However that also does not seem to be the underlying problem here.

I also came across a post where someone maybe had the same issue as I do now after the last updates (unfortunately I cannot find the link in my history right now but I will try to dig it up again). The post was also relatively fresh (<2 weeks).

What I find irritating is that I get prompted to choose the monitors behaviour but the display configuration window changes right back to 1 monitor (which also made me think of a bad cable first).

Are there any good places to look in terms of log files that might shed a little light on the problem.

[claydoh]

Sooooooo...

lspci | grep VGA shows both the integrated and dedicated Graphics Card

^^^^^^^^^^Show us what hardware you have, for starters......
maybe there was a driver update (nvidia) that went south?

xrandr -q does not show the second monitor

What does it show, exactly? what does running it without -q show?
Or xrandr --listmonitors?


Some basic info can help decide what to look for, or where to look.

[relief.melone]

yep. it was the driver update indeed. Also a reinstallation of the current driver did not work. However after downgrading to nvidia-drivers-515 everything worked again. Didn't think of the drivers at first. Just out of curiousity to get the "chain of events".

The drivers act at the kernel level then -> X11 -> KDE? So if the drivers have an issue there's nothing for the display server to talk to right?

xrandr --listmonitors

also just showed the laptop monitor. Now it shows both again.

xrandr -q

showed just the native interface. Now shows all the display ports and hdmi again as well.

Thanks for the help. Very happy beeing able to read this thread without having to rotate the head 60 degrees again

[claydoh]

But.....post the output anyway, particularly just plain old xrandr and your lspci hardware info (or make and model of your GPU)
Looking for hard readable data

Things appearing and disappearing still smells like an intermittent hardware problem to me.

[relief.melone]

here you go (of course the output of the working instance now)

xrandr --listmonitors

Monitors: 2
0: +*DP-0.2 5120/1x1440/1+0+0 DP-0.2
1: +eDP-1-1 1920/344x1080/194+5120+0 eDP-1-1
​

lscpi | grep VGA

00:02.0 VGA compatible controller: Intel Corporation CometLake-H GT2 [UHD Graphics] (rev 05)
01:00.0 VGA compatible controller: NVIDIA Corporation GA104M [GeForce RTX 3070 Mobile / Max-Q] (rev a1)