Another good link on the basics of [http://www.ahinc.com/linux101/permission.htm linux permissions].
=== CRON Tester ===
[http://cron.schlitt.info/ CRON Tester] will show you what your CRON definition equates too in time and frequency.
For example, <code>0 2 * * *</code> equates to ''2AM daily''.