[SOLVED WITH A HACK]
sudo apt-get remove gnome-screensaver
Do not worry, there are no other package which depends on gnome-screensave, so you can safely remove it.
But obviously, a consumer would never have found that solution. Why is gnome-screensaver installed and enabled when running a Unity based OS?
When a resume from suspend, half the time I have gnome-screensaver that ask me to login over the Unity lock screen. Not only this requires me to login twice, but the gnome-screensaver does not permit anybody else but the last user to login.
This bug is annoying since I share my laptop with members of my family. Now whenever a member of my family resume the computer and gnome-screensaver show up, that member cannot switch to his/her account. I have to be there and available to enter my password.
I mentioned this bug in Ubuntu forums to no vail. I did not find it on Launchpad and have not yet had the time to report it. I have cleared all settings from my home account, so it should not be caused by an old setting.
I am not the only user reporting this problem, however some have found a reason and solution which does not apply to my case.
I tried the following to no vail:
- gsettings set org.gnome.desktop.screensaver lock-enabled false
- gsettings set org.gnome.desktop.lockdown disable-lock-screen 'true'
Talking about screensaver, if one perform a search in the dash for 'screensaver', nothing is returned. You have to guess for "lock", but I believe that the dash should redirect 'screensaver' to 'lock' or better, explain that 'lock' is where one goes for setting up the 'screensaver'. Yes, there is no actual screensaver in Unity; one can only blank and/or lock the screen. But the term is still used by many normal consumers to refer to the blanking and locking of the screen.
I did install KDE plasma, but I doubt that this is the source of the problem. I I have no solution and not workaround.