at(5) -- Linux man page
NAMEat.allow, at.deny - determine who can submit jobs via at or batch
DESCRIPTIONThe /etc/at.allow and /etc/at.deny files determine which user can submit commands for later execution via at(1) or batch(1).
The format of the files is a list of usernames, one on each line. Whitespace is not permitted.
The superuser may always use at.
If the file /etc/at.allow exists, only usernames mentioned in it are allowed to use at.
SEE ALSOat(1), atrun(1), cron(8), crontab(1), atd(8).