I’m using Let’s Encrypt as Certificate Authority on this and many other sites. I like it, as it allows me to automate certificate creation and renewals, however I also have some monitoring making sure everything works as expected. I recently got a few alerts as some certificates weren’t renewed as expected. I figured nothing had changed on the server setup and there was renewal happening for a few days, I started looking into it and found the issue why the renewal was failing, so here’s the story.
One of Linux five star things is the cronjobs. They allow you to automatically run stuf (scripts, applications, etc.) at quite specific times. The crontab is the place controlling when the stuff is run and you can list the crontab using the commaand crontab -l for the current user. If you want to edit the crontab, just use the command crontab -e and it launches the crontab in the default editor (set EDITOR env variable to change the editor used).