The best way to limit user logins is using Pluggable Authentication Modules (PAM). Red Hat 8.0 should come with PAM enabled by default. Check in the /etc/security directory for a file called limits.conf that should provide the functionality you require. The limits.conf file is well-documented and you can also view the PAM man page using the command: man pam. Your Red Hat documentation should also discuss how PAM is implemented on your version of Red Hat.
This was first published in February 2006