Enable GNOME3 Screensaver Idle Activation
To activate the screensaver in the GNOME3 desktop after a period of inactivity,
the 'idle-activation-enabled' setting must be set under an appropriate
configuration file(s) in the '/etc/dconf/db/local.d' directory
and locked in '/etc/dconf/db/local.d/locks' directory to prevent user modification.
After the settings have been set, run 'dconf update'.