View Source: CronNotes - Waikato Linux Users Group

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Scheduling under Linux is provided by cron(8).

crontab -e as a user will edit the users crontab entry (which is hidden somewhere in /var/spool/cron.) You need to get the format right - read crontab(5) for the format of the entry.

The cron.d/cron.daily etc seem to vary slightly between distros. The basic guts of them are, put a script in /etc/cron.daily and the cron daemon will run it once a day (at whatever time it runs that job - 3am or whenever 'midnight' maintenance is scheduled.)

These files are just normal shell scripts - no cron control info needed.

same for /etc/cron.{hourly,weekly,monthly}

/etc/cron.d has single-file crontab entries - these are crontab entries, so read crontab(5) again ;). EG:

 # /etc/cron.d/exim: crontab fragment for exim

 # Run queue every 15 minutes
 08,23,38,53 * * * *     mail   if [[ -x /usr/sbin/exim -a -f /etc/exim/exim.conf ]; then /usr/sbin/exim -q ; fi

Every 15 minutes (8 past the hour, 23 past the hour etc) on every hour, every day, etc etc, as user mail, run the command 'if [[] ... fi'

The if magic is a sanity check - to check that its possible to run exim and there is an exim.conf file, before bothering to do anything else.

/etc/crontab also has entries - the ones in my debian system tell cron to, every day, week, month, run the entries in /etc/cron.{daily,weekly,monthly},
respectively.

In short, the easiest thing for you to do, if you want your script run daily, is to drop it in /etc/cron.daily. if it needs custom runtimes, put
them in /etc/cron.d/ in a crontab file.

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Version 1, saved on Monday, September 23, 2002 6:21:41 pm by CraigBox

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