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.
Best Answer
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
B) Set KWIN variables.
I hope the above steps help others get rid of the login hang and screen tearing problems.