Black screen with mouse pointer after login

[dominik]

Hello everybody,

I am new to this forum but I am using Kubuntu now for a few years. Nevertheless, if the problem with kubuntu goes into more technical depth I am really a newbie... So far I never had problems with Linux I couldn't solve by using google. This time it appears to be different

First of all I am currently running Kubuntu 18.04 for more than six month now and haven't had real issues so far. My computer has a Nvidia graphics card (GeForce GTX 1050Ti) installed and an i7.

Today I was trying to get an old printer running when the power supply broke down for a bit. So my computer as well lost power and switched off. I was not installing any updates at that time! When I rebooted the machine it showed the login as usual and for a few seconds my normal desktop wallpaper. But then the screen went black and only the mouse pointer is shown, which is responsive btw. Then I opened the terminal with ctrl + alt + F2 (using f1 doesn't work...)

startkde

results in "$DISPLAY is not set or cannot connect to the X server."

fgrep '(EE)' /var/log/Xorg.0.log

returns two lines:

Unable to add conservative default mode "nvidia-auto-select"
Unable to add "nvidia-auto-select" mode to ModePool

So far I haven't found a solution which worked using google. I tried to rename the folders "kde", ".config", ".local" in my home directory but that didn't help either.

I read that the nvidia driver could be of a problem but I am not sure how to reinstall the driver properly from the command line and without breaking something else. My current nvidia driver is 390.77.

I hope that I posted my problem in the correct channel - if not please give me a hint on where to move it!

Does anybody know what the problem is or how I could find the problem. I really would like to get around a fresh installation of Kubuntu.

Thanks a lot!
Cheers Dominik

[bradleypariah]

Perhaps try entering

sudo nvidia-xconfig

, then reboot.

If that doesn't work, look for /etc/X11/xorg.conf, and edit it

sudo vi /etc/X11/xorg.conf

look for Section "Monitor"
Add something to the last line above EndSection

If you know your monitor is a 60Hz monitor, add the line

VertRefresh 60.0 - 60.0

If you know you have a 120Hz monitor, then add

VertRefresh 120.0 - 120.0

So the section would look like

Section "Monitor"
Identifier "Configured Monitor"
HorizSync 31.5 - 90.0
VertRefresh 60.0 - 60.0
EndSection

[dominik]

Thanks bradleypariah
I tried the

sudo nvidia-xonfig

it returned basically that the file /etc/X11/xorg.conf didn't exist and that it created a new one. Additionally it displayed that some package would be missing. Unfortunately I couldn't see the message anymore after I looked at the .conf file. After the restart nothing changed. Same behaviour as before!

Then I tried to modify the xorg.conf as you suggested and it basically didn't change, as well.

Thank you very much for input. Unfortunately it did not help. Do you maybe have some more ideas what I could try?

Cheers
Dominik

[claydoh]

If you still have a working mouse cursor, try hitting alt-f2 to open Krunner. If it opens, type 'plasmashell' to see if that brings up the desktop. Plasma itself may have crashed and just needs a restart. You can manual run applications using krunner as well.

You don't need an xorg.conf file, nvidia creates one to store any settings made in nvidia-settings. Having a mouse cursor (and presumably the gui login screen) and not a Vt at login leads me to think it is not an xorg/nvidia specific problem at all.


The errors you note in your first post are because running the startkde command does not set up all the environment variables needed -- such as the display. using the startx command after moving to Vt2 (ctrl-alt-f2) instead would start a second desktop instance , but likely having the same black screen you already have on Vt1.

Deleting or moving configs is good, but you probably have to do so while Plasma is not running at all - not even the black screen.

It is also slightly possible that the power loss corrupted multiple things in multiple places.

[dominik]

Thanks everyone so far, for your input! I really appreciate it. Sorry for the late reply but life is more than a computer

@claydoh: Thank you for the hint with the krunner I didn't stumble across this one so far. In short krunner is responsive and I can start applications from there. Tested it with Firefox and that works.
However, run plasmashell did not work :/ The wallpaper appear for a few seconds and then turned black again Unfortunately no change there.

Now I will try to run startx and see what happens. I think I tried it once before I started this thread and as you assumed the result was similar to vt1.

How would you suggest to move the configs without starting plasma? I tried to start kubuntu in the recovery mode but somehow I only see a black screen...

Update:
I just ran startx in vt2 and it worked. Plasma started and I have the normal interface again. I will now restart the machine and see if the behaviour changed.

Update2:
After the restart everything started fine again. That's really good news. But somehow a bit unsatisfying to not know the exact reason
Another thing which comes to my mind is: When I started firefox I deleted via the cups interface all open jobs for the printer I tried to install and removed the printer within cups. Do you think this could be the reason for the system to - apparently - going back to normal?

[Snowhog]

Nope. Almost certainly, plasma itself 'crashed'. Running startx as claydoh suggested was the 'solution' to your problem. Simple as that.