Recently I encountered this problem and discovered a solution. I posted my solution at:
kubuntu 16.04 SDDM login screen hangs https://askubuntu.com/questions/765364/kubuntu-16-04-sddm-login-screen-hangs/874972#874972 For completeness sake, I will also repost the solution here. ---------- 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. ** Bug watch added: KDE Bug Tracking System #321589 https://bugs.kde.org/show_bug.cgi?id=321589 -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1623969 Title: Cannot log in to kubuntu after update (Intel graphics + ksshaskpass) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1623969/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp
