After being unsure for a while of what to look for in the Certbot / Letsencrypt log that is pertinent, as in useful to look for under normal circumstances, I finally had a renewal fail and figured it out. The string “(failure)” will appear if a renewal fails, and will be on the same line as the name of the cert.
In my web development career, I have countless times needed to look at Apache logs to figure out or find out about problems with sites, monitor activity, or for various other purposes. I’ve used command line tools to help with this, often looking for strings and counting occurrences. Since I recently needed to create a command string to count unique IP’s connected to a given string in the logs, I thought I’d post about it and a few related useful commands.