cron every hour question.

EDIT>>> found this. Does everyone get these 17th minute of the hour cron entries.

"That's easy, the 17th minute one is just cron.hourly firing off. Even if it's empty (I just realized this), cron will still log in /var/log/auth.log even if there was nothing to do, because it still did fire off."

I was looking in auth.log and noticed that cron has been doing something every hour but when I look at etc/cron/hourly there is nothing but a placeholder.

I installed cron-apt to do daily updates which runs as expected once per day.

Any ideas what is happening?

edit. in /etc/cron.d there is just 2 files .placeholder and cron-apt (which says to run once per day)

nothing in /var/spool/cron/crontabs

in /etc/cron.daily , there is listed












I did install exim but nothing else .

3 Replies

On most Linux systems (including Ubuntu), cron uses run-parts to kick off hourly, daily, weekly, and monthly scripts. It simply looks at the directory it's given (/etc/cron.hourly in this case) and runs any* scripts in there. You can simply view these scripts to see what they do.

*Well, it won't run scripts that have anything other than letters, digits, underscores, or hyphens in their names.

There actually is nothing in the hourly directory nor anything that should run every hour in any other of the directories I mentioned.

Was the explanation that I found which I posted in my edit a reasonable explanation. i.e cron is checking if there are any hourly jobs to do at 17mins past the hour?

cron knows nothing about /etc/cron.hourly/ (or anything else); all it knows is that it needs to run run-parts every hour. And that's what it's doing. So yup, completely reasonable.


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