Access control Files at.allow and at.deny | Task Automation at |Who can Schedule Task in Linux

By through /etc/at.allow and /etc/at.deny file we can restricted and allow the user to access or perform at command. And these can done only by through root privliage.
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
Example
[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.

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