~ $ uname -a
FreeBSD scorpio.seibercom.net 11.1-RELEASE-p4 FreeBSD 11.1-RELEASE-p4 #0: Tue Nov 14 06:12:40 UTC 2017 email@example.com:/usr/obj/usr/src/sys/GENERIC amd64
~ $ freebsd-version
I have been using the p5-certbot port without a problem until recently. It is being run via cron: /usr/local/bin/certbot -q renew --pre-hook "service dovecot stop" --post-hook "service dovecot start". Until recently that worked fine. Now I have started receiving this error message: "Another instance of Certbot is already running." Try as I might, I cannot find another instance of "certbot" running.
Apparently, the only way to correct the problem is to reboot the system. This only works until after the cron command has run one time, after which the problem resurfaces.
I have confirmed that at least one other user is experiencing this problem. He stated that the problem does not occur if the command is only run via the command line. He believes that certbot is waiting on the post-hook command, but only when it was ran from cron. I have not confirmed this, however.