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I have a peculiar problem. For some reason as the clock struck midnight on February 1st, cron is now running certbot every minute trying to renew a certificate.

When running sudo crontab -l I get the following output, which I can't really understand the syntax of;

* * */89 * * sudo certbot renew

I personally can get my head around what that /89 is supposed to mean.

Anyone seen anything like this before with certbot? If I check the /etc/cron.d/certbot file, it's just there as it should be, running twice a day.

Stuggi
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    That's weird. What's even weirder is having a crontab for certbot in the first place. Are you using some unusual distro that doesn't have systemd? On most systems certbot renew is called from a systemd timer, not from crontab, and there should not be a crontab entry at all. – Michael Hampton Jan 31 '21 at 23:15
  • Bog standard Debian 10, only exotic part is that certbot isn't running against Let's Encrypt but another CA, so I only really need it to run once a month or so as the certificates are 1 year in length. My current working theory is that the crontab entry was done manually by the guy that set it up, and a typo made it into the file, but that doesn't explain how it 10 months later stated running every minute instead of instantly. – Stuggi Jan 31 '21 at 23:24
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    Well, it does specify to run every minute, but only on the 89th day...of a field that only goes from 1-31. And yes, Debian has the aforementioned systemd timer, so that should be enabled and started and this crontab entry deleted. Problem solved. – Michael Hampton Jan 31 '21 at 23:27
  • Has that implementation changed at some point or has certbot always used systemd timers? This server was originally installed in 2016, so it's been upgrade a couple of times? – Stuggi Jan 31 '21 at 23:28
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    certbot has only been in Debian since stretch, and it did have the timer then; before that certbot would have had to be manually installed. – Michael Hampton Jan 31 '21 at 23:30

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