How can I restrict an user, to access the internet, or just use gaim at a certain interval every day ?

A bit of a hack could be to run a cron-job as root to change the permissions on gaim. One job to a-x and another to a+x when you want to allow it again. I don't think it's particularly elegant, however, and there is probably a better way of doing so.

Apologies for not being too useful,
- Piete.

Wouldn't it just keep running cause the x is only checked when you start the program?

edit I'd do it with a cronjob which blocks and unblocks the ports gaim uses with IPtables. Can't help you with the code for it though.

Or a crontab that changes the permissions and also runs "killall gaim"

I suggest configuring iptables to block Gaim's ports at regular intervals. Chmodding would do the trick, but it can be circumvented quite easily. If you want to keep your small children (or your wife/husband out of Gaim for a while, chmodding could be enough, however.

I think you should also install anacron, because otherwise, if the system is down during the time when the chmodding/iptabling should take place, it doesn't. It's only a matter of time when users realize this.

Anacron handles cron jobs that have been skipped due to downtime.

chmod-ing did the trick... but now I want something else. I want to allow a total amount of 3 hours of gaim usage per user , how can I do that ?