You should install either xscreensaver or gnome-screensaver. In both cases you can install the -data, -data-extra -gl and -gl-extra packages. Ubuntu comes with gnome-screensaver by default, so unless you have special needs I would recommend to keep it.
You should install either xscreensaver or gnome-screensaver. In both cases you can install the -data, -data-extra -gl and -gl-extra packages. Ubuntu comes with gnome-screensaver by default, so unless you have special needs I would recommend to keep it.