By now everyone should have an SSL enabled website thanks to the Let’s Encrypt project which provides free SSL certificates that are good for three months at a time. If you don’t, check out their site and generate your free SSL certificate. The main problem with a three month SSL certificate is remembering to renew it before it expires. Fortunately Let’s Encrypt provides an application called Certbot that does automatic certificate renewal. The instructions were simple. Set up a daily cronjob that calls certbot and it will automatically renew your SSL certificate when it reaches the thirty day expiration period. No problem, I set up the following:
0 0 * * * certbot renew --quiet --no-self-upgrade
Because certbot does not renew the certificate until it reaches the thirty day threshold, there was no easy way to test it. Fortunately I stuck a reminder on my calendar to check. Sixty days later I opened my website, clicked the padlock and checked the certificate expiration date. It still had the same expiration date, ie it didn’t get renewed. Puzzled I ran the command manually:
# certbot renew --quiet --no-self-upgrade #
That seemed to work fine. I checked the certificate’s expiration date and it was now ninety days into the future. There was nothing obvious in the logs so I did a Google search. I found a lot of other people reporting the same issue. It wasn’t until I saw this post that I understood the issue. The crontab had a PATH that did not include the location of certbot. When I downloaded certbot, I installed it in /usr/local/bin. By default, my crontab’s PATH did not include /usr/local/bin. There were a few ways to fix this.
- Update the crontab to contain the complete path to the certbot application:
0 0 * * * /usr/local/bin/certbot renew --quiet --no-self-upgrade
- Update the PATH variable to include the missing PATH location. If no PATH is defined in the crontab, simply add the following at the top:
- Move the certbot application to a common location like /usr/bin
If you were struggling to figure out why your Let’s Encrypt SSL certificate was not renewing automatically with certbot, I hope you found this page before spending a lot of time debugging.