Become superuser.
Using the editor of your choice, open the /etc/cron.d/at.deny file.
Add the names of users, one per line, who will be prevented from using at commands.
daemon bin smtp nuucp listen nobody noaccess username1 username2 username3 . . . |
Exit the file, saving your changes.
The following example shows an at.deny file that has been edited so that the users Smith and Jones may not access at.
$ cat at.deny daemon bin smtp nuucp listen nobody noaccess jones smith |