Mouse and keyboard not working on login 16.04

[Skal1]

Hello all,
I recently tried to install the proprietary nvidia drivers. Before I was using the nouveau driver which was working well for office etc. I used the driver manager to switch to the proprietary one (version 384). After the successful installation and a reboot the driver appeared to have been installed properly. However I noticed some display errors. Overall it looked fine but there were strange artifacts on mouseover (eg in the launcher or on the buttons on windows). So I tried a newer driver version from a PPA using:

sudo add-apt-repository ppa:graphics-drivers
sudo apt-get update
sudo apt-get nvidia-390

That too seemed to work and after a reboot the nvidia x-settings claimed I was using the new driver version. However the annoying display errors were still present so I decided to revert back to the nouveau driver for now. That is where the current problem starts. I reselected nouveau in the driver manager and issued a reboot.

After that reboot I can not login anymore because neither my mouse nor keyboard are working. Booting seems to work fine but once I arrive at the login screen the mouse and keyboard are just dead. The screens not frozen (I can see the cursor blinking) and navigating the BIOS and GRUB works.

So far I have figured out how to use GRUB to boot into recovery mode. First I tried getting rid of all the nvidia stuff

sudo apt-get remove --purge nvidia-*

Purging worked. The problem still exists.

Does anyone have any suggestions what to try next?

Im using 16.04 on my E570 ThinkPad which has a GeForce GTX 950M.

[GreyGeek]

Reinstall the NVidia driver from the repository. 390 works.

1) On the login screen, instead of loging in use Ctrl+Alt+F2 to switch to a terminal.
2) Log into the terminal with your name and password.
Issue
3) sudo systemctl restart sddm
and enter your password.
That will take you back to the login screen.
4) Log in with your password and your plasma desktop should appear without any mouse artifacts.

Repeat steps 1 through 4 each time you boot up.

I'm not sure what the cause of the bug is but it seems to be related to an interaction between NVidia and sddm on some systems, mine included. That restart of sddm works for me and takes only a few seconds at boot up.

[Skal1]

Hello GreyGeek,
thank you for your reply. At least Im not the only one with this problem.

In the meantime I have tried some more things that have made it both better and worse.

I reinstalled the xserver and the nouveau driver to make sure it was properly activated

sudo apt-get install --reinstall xserver-xorg
sudo apt-get install --reinstall xserver-xorg-video-nouveau

After that the mouse and keyboard issue was fixed. I can now enter my credentials into the login screen.

However, after entering my credentials I just see a black screen. As if the login is accepted but something is not running properly (dm, X, ?) so I see nothing. I tried restarting sddm as you suggested both before logging in and after but it doesn't make a difference.

The second thing I did try was installing the nvidia drivers again. I installed 384 as that seemed to work before (ignoring the artifacts).

sudo apt-get install nvidia-384

That produces the same result, it just looks a bit different. Instead of showing a black screen I continue to see the login screen with a greyed out text field. Restarting sddm also doesnt change anything.

For both drivers I verified that they're being used with lshw. My credentials are fine, I can use them to log into a console without a problem.

Im fine with using nouveau for now as that didn't produce any problems at all. I can still experiment with nvidia drivers later but first I'd like to fix this login issue.

Does anyone have a suggestion what I could try next? To me it seems like it could just be a borked config or something but I don't know where to look.

[GreyGeek]

The 390 NVidia is what you should. The black screen means that either root owns your -/.Xauthority file or your plasma desktop didn’t start
First, delete the .Xauthority file, then log in. At the login screen use Ctrl+Alt+F2 to get a terminal. Then “sudo rm /Home/youracctname/.Xauthority”
Then reboot

If that doesn’t work then restart the plasma desktop.

[jlittle]

Does anyone have a suggestion what I could try next? To me it seems like it could just be a borked config or something...

A reinstall might be the least costly in time, assuming your data is backed up, depending on how long it will take you get back to a system the way you like it. Too often I've plugged away at problems and wasted so much time.

[Skal1]

GreyGeeks suggestion was spot on. I deleted Xauthority and everything turned out fine. And I have no mouse artifacts on 390 so that is well, too.

@jlittle, I did consider reinstalling but I had a feeling the solution would be simple.

Thank you guys!