Lock screen has nno widget to enter password

[Chen Levy]

After today upgrade of:

Start-Date: 2018-09-04 12:06:31
Commandline: packagekit role='update-packages'
Upgrade:
  libgpgmepp6:amd64 (1.10.0-1ubuntu1, 1.10.0-1ubuntu2),
  libpackagekit-glib2-18:amd64 (1.1.9-1ubuntu2, 1.1.9-1ubuntu2.18.04.1),
  libgpgme11:amd64 (1.10.0-1ubuntu1, 1.10.0-1ubuntu2),
  console-setup-linux:amd64 (1.178ubuntu2.6, 1.178ubuntu2.7),
  console-setup:amd64 (1.178ubuntu2.6, 1.178ubuntu2.7),
  packagekit-tools:amd64 (1.1.9-1ubuntu2, 1.1.9-1ubuntu2.18.04.1),
  packagekit:amd64 (1.1.9-1ubuntu2, 1.1.9-1ubuntu2.18.04.1),
  keyboard-configuration:amd64 (1.178ubuntu2.6, 1.178ubuntu2.7),
  gir1.2-packagekitglib-1.0:amd64 (1.1.9-1ubuntu2, 1.1.9-1ubuntu2.18.04.1),
  libqgpgme7:amd64 (1.10.0-1ubuntu1, 1.10.0-1ubuntu2)

when I lock my screen with Ctrl-Alt-L I get the lock screen background image and nothing more.
I am unable to unlock the GUI.

I can go to a different virtual terminal with Ctrl+Alt+F2, but to get back to the GUI I need to reboot the host.

I have a dual monitor setup with one monitor rotated at 90 degrees.
When I disconnect the rotated screen, I do get to see the password field and the unlock button, but I can't interact not with the keyboard nor with the mouse, and I am forced to reboot then too.

As a work around I disabled the automatic locking of the screen, but this is not a secure solution.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: plasma-desktop 4:5.12.6-0ubuntu0.1
ProcVersionSignature: Ubuntu 4.15.0-33.36-generic 4.15.18
Uname: Linux 4.15.0-33-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
CurrentDesktop: KDE
Date: Tue Sep 4 15:18:02 2018
InstallationDate: Installed on 2018-03-20 (167 days ago)
InstallationMedia: Kubuntu 17.10 "Artful Aardvark" - Release amd64 (20180105.2)
SourcePackage: plasma-desktop
UpgradeStatus: Upgraded to bionic on 2018-04-29 (128 days ago)

[Chen Levy (ubuntu-com-chenlevy)]

I was able to reproduce this behavior with running manually /usr/lib/x86_64-linux-gnu/libexec/kscreenlocker_greet

Oddly enough the first time I ran it I did got the password prompt and was able to unlock it and return to my desktop.

Running it again reproduced the reported issue, i.e. no password widget and thus no way to unlock it.
Killing kscreenlocker_greet from an other VT, didn't fix the issue, rather background became black, and only the mouse pointer was moving around.

[Chen Levy (ubuntu-com-chenlevy)]

Update: sending sigint to the kscreenlock_greet made it trhow a message on screen that instructed me to run `loginctl unlock-session 3` which did unlocked the my screen.

[Chen Levy (ubuntu-com-chenlevy)]

Update: a better workaround is running from VT2 `pkill -sigint screenlocker`, which make the password widget visible, and the screen unlock-able.

[Chen Levy (ubuntu-com-chenlevy)]

Update: a better workaround is running from VT2 `pkill -sigint screenlocker`, which make the password widget visible, and the screen unlock-able.

I created a new user on the system, that use dosn't exhibit this issue

[Chen Levy (ubuntu-com-chenlevy)]

To resolve my issue, I created a new user, moved my ~/.kde/ ~/.config/ and ~/.cache/ out of the way, copied over the ~newuser/.kde/ and ~/newuser/.config/, and reconfigured the desktop by hand.

I don't yet know what was the root cause of this issue, and I am willing to hand over my bad configuration file(s), to help resolve this issue. Just ping me at ubuntu.com(at)chenlevy.com.

[Scarlett Gately Moore (scarlettmoore)]

This bug is very old, if it is still an issue please update the bug with information from a supported release.