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After upgrading from kubuntu 15.10 to 16.04, the login screen hangs right after typing the (correct) password and pressing enter. The controls like the text field are disabled and brightness slightly dimmed, then nothing else happens.

By switching to a text console with Ctrl+Alt+F1 and back to X with Ctrl+Alt+F7 I can get into the logged in session, so it seems the screen is just not being updated during login where normally the progress bar is shown.

This doesn't happen always, but most of the time.

It is running on a Lenovo L420 with Intel integrated graphics. Running in VirtualBox on another PC, this does not happen.

Is this a known issue or bug? I wasn't able to find any posts or reports about it.

Torsten Römer
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3 Answers3

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Recently I encountered this problem with kubuntu 16.04 SDDM login screen hangs. The issue occurred after I installed kubuntu 16.04 on an Intel i7-7700k with Intel 630 HD graphics and then updated to the latest packages.

I was able to login using the workaround of using Ctrl+Alt+F1 to get to a text console and then Ctrl+Alt+F7 to get back to X and the logged in session.

I stumbled upon a fix to the login hang while I was working to get rid of a screen tearing problem. The fix involves changing the compositor rendering backend from XRender to OpenGL.

More specifically to address the hang on login and problem with screen tearing I did the following:

FIX SCREEN TEARING AND LOGIN HANGING

A) Start K -> Settings -> System Settings

     Under Hardware section
     Double-click Display and Monitor
       Choose Compositor on LHS
         Enable compositor on startup:  Checked               # was checked
         Rendering backend:             OpenGL 3.1            # was XRender
         OpenGL interface:              GLX
         Tearing prevention ("vsync"):  Full screen repaints  # was Automatic
          Ignore message "Full screen repaints" can cause performance problems.
       Click Apply

REFERENCES:

Bug 321589 - Automatic VSync strategy causes tearing
https://bugs.kde.org/show_bug.cgi?id=321589

Screen Tearing on Kubuntu 16.04 with Intel Drivers?
https://askubuntu.com/questions/764302/screen-tearing-on-kubuntu-16-04-with-intel-drivers

B) Set KWIN variables.

Edit /etc/environment and add the top and bottom line:

__GL_YIELD="USLEEP"
#KWIN_TRIPLE_BUFFER=0
KWIN_USE_BUFFER_AGE=0

REFERENCES:

https://community.kde.org/KWin/Environment_Variables
https://askubuntu.com/questions/764302/screen-tearing-on-kubuntu-16-04-with-intel-drivers/774788

Listed as also working with NVidia.

I hope the above steps help others get rid of the login hang and screen tearing problems.

Curtis Gedak
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3

Check the ownership of the .Xauthority file in your home directory. If it is owned by root delete it, or take ownership. See for instance Ownership of .Xauthority transferred to root for more information.

Community
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KiekerJan
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0

Finaly it started to work for me. There is a problem in a user configuration files. I have installed nodm for some time, started X as a root, created new account, and switched few times between the users. Make sure you have OpenGl 3.1 selected as a default renderer.

zxka555
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