Aug 19, 2011
tom

What day/time does a weekly cron start on?

Question

I had a look though the cron man but didn’t find anything that helped :(

Anyone know?

Answer

I’m giving an alternative answer here even though Trevor is correct.

The cron @weekly keyword does exactly as he mentioned. However, most distributions use run-parts to run their own scheduled crontab files (on an hourly, daily, weekly and monthly basis) which do not make use of cron’s keywords.

e.g. Ubuntu has an /etc/cron.weekly which contains a separate file for each crnojob.

This is generally defined in /etc/crontab

Ubuntu’s karmic 9.10 release has the following in /etc/crontab

17 *    * * *   root    cd / && run-parts --report /etc/cron.hourly
25 6    * * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
47 6    * * 7   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
52 6    1 * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )

So the weekly crontab in Ubuntu is run at 6.47am on Sunday

Note: when looking for manpages for crontab implementations, you want to use man 5 crontab instead of just man crontab. The latter will only give you the syntax for the crontab command. The former gives you crontab implementation details.

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