For a long time in 14.04.1 LTS I see gnome-screensaver lock screen instead of unity-greeter (or which one is the latest and greatest?). I've already tried to
dpkg-reconfigure lightdm and
dpkr-reconfigure unity-greeter. It doesn't help. And there's no lockscreen selection dropdown in CCSM's Unity plugin preferences (but I've faced screenshots with it on
webupd8). Simple uninstalling of
gnome-screensaver also didn't work. How can I enable/revert back unity lock screen?
dm-tool switch-to-greeter or
dm-tool lock also work both and after successful screen unlock I see
gnome-screensaver unlock screen, so I'm unlocking screen twice.