gnome-screensaver software package provides GNOME screen saver and locker, you can install in your Ubuntu 12.04 LTS (Precise Pangolin) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gnome-screensaver
gnome-screensaver is installed in your system.
Make ensure the gnome-screensaver package were installed using the commands given below,
$ sudo dpkg-query -l | grep gnome-screensaver *
You will get with gnome-screensaver package name, version, architecture and description in a table
| Distro | Ubuntu 12 04 lts precise pangolin |
| Section | GNOME |
| Package | gnome-screensaver |
| Version | 3.4.1-0ubuntu1 |
| Description | GNOME screen saver and locker |
| Sub Section | GNOME |