the cron script lives in /bin/cron and FIRST edits the Cron Table and NEXT, it reloads the cron daemon (crond) to save then refresh it.
LINUX COMMAND LINE FUNCTION ONLY
1. takes a database backup every hour and on the first minute.
2. warns with "SYSTEM BEING SHUT DOWN IN 5 MINUTES" message sent to everyone, 5 minutes prior to 3.
3. reboot the system at 03:00 GMT+11 hrs. (Daylight Savings Time) every night.