Cron settings explained

If you ever wondered what the numbers in crontabs are, here’s an explanation.

# Example of job definition:
# .---------------- minute (0 - 59)
# |  .------------- hour (0 - 23)
# |  |  .---------- day of month (1 - 31)
# |  |  |  .------- month (1 - 12) OR jan,feb,mar,apr ...
# |  |  |  |  .---- day of week (0 - 6) (Sunday=0 or 7) OR
# |  |  |  |  |     sun,mon,tue,wed,thu,fri,sat
# |  |  |  |  |
# *  *  *  *  * user-name command to be executed
17 *	* * *	root    cd / && run-parts --report /etc/cron.hourly

This is the syntax for files in /etc/cron.*, not for the command “crontab”.

The user-based crontab has the same syntax, but the user name is omitted. That’s important difference between the files in “/etc/cron.*” and the “crontab” command.

You can copy the text above in your crontab so you will have a reference every time you edit it.