i3lock software package provides improved screen locker, you can install in your Ubuntu 14.04 LTS (Trusty Tahr) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install i3lock
i3lock is installed in your system.
Make ensure the i3lock package were installed using the commands given below,
$ sudo dpkg-query -l | grep i3lock *
You will get with i3lock package name, version, architecture and description in a table
| Distro | Ubuntu 14 04 lts trusty tahr |
| Section | X Window System software |
| Package | i3lock |
| Version | 2.5-1 |
| Description | improved screen locker |
| Sub Section | x11 |