Hi
I am using ubuntu linux. I have created a new account for my nephew (for his college assignments). How can I make this account that I can only be loggedin during 6PM and 9PM, except these timings, this (new) account cannot be logged in?
Regards

This link should solve all your needs http://askubuntu.com/questions/68918...computing-time
There are also some other links on LQ itself so give the search function a try.

Thanks. timekpr solved the problem.
Another question arises, if the user is already logged in then after the expiry time, the session would logged out automatically or is there any other way to force user to logout after expiry of time?

Dunno. While skimming the link I read something about a warning when overextending the login period or before that happens. But if it was with timkpr or someother mentioned tool I don't know.
Check out the config file of timekpr and see if it got some options for kinda like that.

While you were writing your answer, I have found a way and that is to create a cron job with following:
0 21 * * * /sbin/shutdown -h now

This for sure gets the server down but there might be occasion where the login period should be extended maybe cause all it takes are five minutes more to finish something. Right now this is not possible.

Maybe first see if someone is still logged in using who or w command. Then send a message to those users and check again in 5-10minutes then issue a second warning and after 2 minutes shutdown for sure.

Something like this. Checking if a user is logged in might go in a function maybe.
Sending the message has to be evaluated again. On command line shutdown will take care of telling the user about going down. Dunno what about a GUI. Guess that depends on the window manager in use but most recent ones have some kind of notification ability.

Dunno ... might be better just to stand right behind him and bellow, "Time's up! Get off of my computer!"

This is a problem I have considered. There are some GUI notification popups available, but I haven't found one that will stay visible on top when the user is busily using the keyboard or mouse, as might happen when he is playing a video game. The notification either gets buried when the user clicks on another window, or it dismisses itself when it receives keyboard or mouse clicks that were intended for the user's application.

One option in the gnome environment is to put a notification applet on the gnome panel. Then it would remain visible until the user clicks on gnome panel to dismiss it. It could even show the remaining time like a countdown timer, and change color when it reaches a critical level like 5 minutes remaining. I had hoped to develop such a gnome-panel applet, it doesn't look difficult, but I got distracted with other work. Does anyone know of a gnome-panel notification applet that's already available?

I used the following method:
I told my nephew that "the computer will shutdown automatically at 9PM, so save your work before that"