The at.allow and at.deny files
The at and batch commands use the files /usr/lib/cron/at.allow
and /usr/lib/cron/at.deny
to restrict usage. If the at.allow
file exists, only users listed in the file are allowed to use at and batch. If the file does not exist, at.deny
is checked to see if the user is explicitly denied permission. If
neither of the files exists, only the root user is permitted
to use the commands.