Quote Originally Posted by wolfi323 View Post
But you would have to grant that dummy user access to your X session with "xhost".
Sorry, actually this is _not_necessary.

One easy way to create an icon on the desktop (in KDE) would be:
- Right-click on the folderview and select "Create New"->"Link to Program..." in the context menu
- If you want to, change the icon's label and icon on the "General" tab
- Switch to the "Application" tab and enter "/usr/bin/xlock" into the "Command:" field
- Click on "Advanced Options", activate "Run as a different user" and enter the name of your dummy user into the "Username:" field below
- Click "OK"

You should now have an icon on your desktop (in the folderview plasmoid), that would lock your screen requiring your dummy user's password to unlock it.
You can of course also drag it out of the folderview to anywhere else on your desktop, it will be changed to a plasmoid then which you can freely position anywhere you like (you could even put it into the panel).
The only drawback is, you have to enter the dummy user's password already for _locking_ the screen. I have no idea how this could be workarounded (making /usr/bin/xlock owned by the dummy user and setting the setuid bit _doesn't_ work, I already tried that ).