batch commands work well if you just want to execute a single task at a later date, but they are less useful if you want to run a task frequently. Instead, the
cron daemon exists for running tasks repeatedly based on system (and user) requests. The
cron daemon has a similar permissions system to
at: Users listed in the
cron.deny file are not allowed to use
cron, and users listed in the
cron.allow file are. An empty
cron.deny file—the default—means everyone can set jobs. An empty
cron.allow file means that no one (except root) can set jobs.
There are two types of jobs: system jobs and user jobs. Only root can edit system jobs, whereas any user whose name appears in
cron.allow or does not appear in ...