Forcing a user to logout

Dear my friends... Please teach me which command line in the console which I can use to display which users are being logged in. They login through NIS. And please tell me which command line that I can use to kick the user out (forcing logout). If they login through NIS. If I login into a machine as a root with ssh (ssh -l root 192.168.23.1), can I force with command line the users which login locally to be log out? Thank you very much. __________________________________ Do you Yahoo!? SBC Yahoo! - Internet access at a great low price. http://promo.yahoo.com/sbc/