Red Hat® Linux® 7 Unleashed

Scheduling Tasks with cron and at Jobs

Red Hat Linux comes with several utilities that manage the rudiments of job scheduling. at schedules a process for later execution, and cron (or crontab—it has a couple of interfaces, and different engineers use both these names) periodically launches a process. Lastly, for systems that don't stay up all the time there's anacron.

The crond daemon is started by the crond script under the /etc/rc.d/init.d directory when you boot Red Hat Linux. This daemon checks your system's /etc/crontab file and /var/spool/cron directory every minute, looking for assigned tasks at assigned times. As a system administrator, you'll schedule system tasks in /etc/crontab. This file initially contains four entries:

 001 01 * ...