From : http://www.cyberciti.biz/faq/automatically-log-out-linux-bash-user/
Q . We have a few users who frequently forget to log out and I'd like to force them or automatically log out a user in case of inactivity detected. How do I force user to be logged out automatically?
A. BASH provides TMOUT variable. It is necessary for security reasons to have an inactive user logged out after a period of inactivity from Linux / UNIX ssh / telnet session. This can be accomplished by setting an environment variable TMOUT.
Add the TMOUT variable to your /etc/bashrc file: # vi /etc/bashrc Set TMOUT to 300 seconds (5 minuets): TMOUT=300 Save an close the file. Above config would automatically logout users after 300 seconds of inactivity. Please note that this hack only works with run level 2, 3 i.e. it will not work with GUI sessions.
