Access control files at allow or deny
/etc/at.allow file has list of user who can use the at command and perform schedule task
/etc/at.deny file has list of user who can not use the at command and do not perform the schedule task
It the two files are not present then root user got access to at command.
If empty /etc/at.deny then all user are permitted for using at command
[root@studentwebsite ~]# vim /etc/at.deny
I add user2 into the at.deny file
so user2 he does not have privliage to use the at command.
[root@studentwebsite ~]# su user2
[user2@studentwebsite root]$ at 10:00
then it display message like that
You do not have permission to use at command.