The screen Lock is corrupt. It is not possible to unlock the screen anymore. Instead a message is displayed that on a text-terminal ‘loginctl unlock-session’ should be entered. This unlocks the screen, but is not quite convenient. I think it came with the last update (kernel and nvidia driver) but I’m not shure.
KDE 5.8.3 on Intel i7
Is this a known bug?
Thanks, Tobias
Not really a “known bug”.
But it can happen if updates get installed in the running session that change the whole system underneath, or your OpenGL support gets broken (which can probably happen if you update the nvidia driver in a running session).
That’s the reason why GNOME nowadays prefers to do so-called “off-line updates” (but they actually do so because GNOME crashes anyway if e.g. the X server gets updated AFAIK), i.e. the updates get installed when you shutdown the system or reboot it.
But personally I would be against introducing that in KDE, I have to say.
So, is this reproducable after you logout/login or reboot?
If not, I do not really see a problem here…
It is all part of Lennart Poettering’s diabolical scheme to control the universe 
I had that happen to me (once) on 42.1 (after which I rebooted). I have not seen any repeat on 42.1 or 42.2.
thanks Lennart 
Yes it is. It is permanent. I felt back with snapper to a state before the last updates and screenlock was O.K. Then made the updates again and screenlock is corrupted again. Next i will try the snapper rollback and make the upates without the nvidia driver.
Well, I don’t think it’s Lennart Poettering’s fault if KDE/Plasma’s screenlocker is broken/fails to start on your system… 
Yes it is. It is permanent. I felt back with snapper to a state before the last updates and screenlock was O.K. Then made the updates again and screenlock is corrupted again. Next i will try the snapper rollback and make the upates without the nvidia driver.
Have you tried to reinstall the nvidia driver after the updates?
Have you tried booting the previous kernel?
I suppose you are using the nvidia driver from the repo?
The screenlocker’s greeter uses QML, which requires working OpenGL support.
Though OTOH, if that was broken completely, Plasma (or even SDDM) wouldn’t start either…
What happens if you run the greeter manually?
/usr/lib64/libexec/kscreenlocker_greet --testing
(as user of course)
Do you get any error message in the Konsole?
Wolfi, I think I have a mess here. kscreenlocker_greet --testing gives
QStandardPaths: wrong ownership on runtime directory /run/user/1000, 1000 instead of 0
Locked at 1481835837
KCrash: Application 'kscreenlocker_greet' crashing...
Speicherzugriffsfehler (Speicherabzug geschrieben)
In dmesg I find
13.398126] NVRM: Your system is not currently configured to drive a VGA console
13.398128] NVRM: on the primary VGA device. The NVIDIA Linux graphics driver
13.398129] NVRM: requires the use of a text-mode VGA console. Use of other console
13.398129] NVRM: drivers including, but not limited to, vesafb, may result in
13.398130] NVRM: corruption and stability problems, and is not supported.
Also I can see, that opengl is not running. glxgears doesn’t work.
Two days ago I had an old harddisk attached as second disk with absolut identical partitions then my current ssd. I fear that something got mixed up. May be I should reinstall from scratch.
QStandardPaths: wrong ownership on runtime directory /run/user/1000, 1000 instead of 0
Locked at 1481835837
KCrash: Application 'kscreenlocker_greet' crashing...
Speicherzugriffsfehler (Speicherabzug geschrieben)
Argh, that was root. As user ‘kscreenlocker_greet’ yields
file:///usr/share/plasma/look-and-feel/org.openSUSE.desktop/contents/components/Battery.qml:39:18: Unable to assign [undefined] to int
The X11 connection broke (error 1). Did the X11 server die?
KCrash: Application 'kscreenlocker_greet' crashing...
Speicherzugriffsfehler (Speicherabzug geschrieben)
Actually, I heard that Tim Cook snuck in and released a bug into there, somewhere. Seems Linux offspring Android has been upsetting the Apple-cart.
Before I reinstall Leap 42.2, is there something I can do to fix opengl? I think the broken opengl is the cause of the trouble.
I didn’t reinstall since I noticed that for other users the openGL problems did not come up. So - brute force - I deleted the .config directory of my user. It seems up to now, that the graphics is stable now. So I don’t know the root cause, somewhere buried in the kde config files. (Reinstall wouldn’t have helped, if thats true)