slock - simple screen locker
The most simple screen locker utility available for X.
Requirements
Installation
Edit config.mk to match your local setup (slock is installed into the /usr/local namespace by default).
In order to build and install slock execute
sudo make clean install
Running slock
Standard
slock
Lock X by displaying a black screen and waiting for your input.
Spy Mode
slock -s
Lock X whereas your screen looks unlocked. If a mouse button is hit the screen becomes black and a snapshot of the unwanted user is taken and rendered. In order to use this spy mode you need to have fswebcam installed.
Exit slock
Just enter your password.