How to unlock screen from script in KDE Plasma 5?

Question

I use pam_usb and want to lock/unlock computer when USB stick is removed/inserted. For locking I use qdbus org.freedesktop.ScreenSaver /ScreenSaver Lock and it works perfectly. For unlocking I've tried a series of commands I've found (most of them are aggregated here), but they don't work. Specifically, if we exclude those with KDE 4 syntax, they fall into 2 categories: those using qdbus (relevant path here, several variations exists) /MainApplication quit which hang my Xorg completely, and those using killall against screenlocker process, but the process just restarts instantly after that!

So, my question is: how to unlock KDE5 screen locked with its standard locker programmatically?

Answer 1

Not really my answer, but it might be useful to someone else too.
It comes from https://forum.kde.org/viewtopic.php?f=289&t=130691#p350000 and it works on latest archlinux with kde 5.7

loginctl lock-session
loginctl unlock-session

Answer 2

On modern KDE Plasma the command is apparently:

qdbus --system org.freedesktop.ConsoleKit /org/freedesktop/ConsoleKit/$session Unlock

The session name can be obtained from

qdbus --literal --system org.freedesktop.ConsoleKit /org/freedesktop/ConsoleKit/Manager \
org.freedesktop.ConsoleKit.Manager.GetSessions | sed 's/^.*\(Session[0-9]*\).*$/\1/'

Beware, as there can be multiple sessions! There are several GetSession* functions for varying use cases though.

The problem is, that all these functions of course require root!

I don’t know how how loginctl would circumvent this, but it suggests it is possible. Otherwise maybe you can use sudo and allow a script that does this to be run without entering a password.

Answer 3

The screen locker is broken and unlocking is not possible anymore. In order to unlock switch to a virtual terminal (e.g. Ctrl+Alt+F2), log in and execute the command: loginctl unlock-sessions Afterwards switch back to the running session (Ctrl+Alt+F7).

The above message appears sometimes on my laptop running Gentoo Stable with Plasma 5, OpenRC and ConsoleKit. The following script I launch from TTY1 successfully unlocks the X11 session on TTY7:

fitzcarraldo@clevow230ss ~ $ cat unlockKDEsession.sh
#!/bin/bash

# Screen locker broken in KDE with ConsoleKit
# See https://forums.gentoo.org/viewtopic-t-1046566.html
# and https://forums.gentoo.org/viewtopic-t-1054134.html

# Find which session is locked
session=Session$(ck-list-sessions | grep -B10 "x11-display = ':0" | grep -o -P '(?<=Session).*(?=:)')

# Create Bash script to unlock session
echo "#!/bin/bash" > /unlock.sh
echo "su -c 'dbus-send --system --print-reply --dest=\"org.freedesktop.ConsoleKit\" /org/freedesktop/ConsoleKit/$session org.freedesktop.ConsoleKit.Session.Unlock'" >> /unlock.sh
chmod +x /unlock.sh

# Run Bash script in another TTY
openvt -s -w /unlock.sh