Xscreensaver is a package providing an OpenGL accelerated screensaver for the X.org display server. Screensavers in general are not required nor make sense for LCD monitors, however if using one or more CRT monitors, a screensaver can prove beneficial.
Installation on Ubuntu can be done as follows.
Install the screensaver daemon and the screensavers themselves by running:
# apt-get install xscreensaver xscreensaver-gl-extra xscreensaver-data-extra
Several configuration changes are required for Xscreensaver to work correctly.
Remove gnome-screensaver by running:
# apt-get remove gnome-screensaver
gnome-screensaver interferes with the startup of Xscreensaver.
Add the Xscreensaver daemon to auto start at login.
Run "Startup Applictions" and add a new entry with the following command:
Customize the daemon by running "Screensaver" and editing preferences with the GUI.