For some people, the command you gave would fail because they can't bind port 80 because apache or nginx is already listening there. And they might not be able to stop it and restart it. That's not the case if you're only running an SMTP listener, but it would be if you're already running an HTTP listener.
(I wrote the original version of standalone in certbot, but I'm just trying to stand up for the people who complain that something is complicated in their use case.)
I had a few issues debugging the callbacks fired for letsencrypt-auto (i.e. how --post-hook and --renew-hook) works.
Almost hit the limit before I got it working
You can use the --test-cert or --dry-run flags for this purpose. The former just makes the client use the staging server (which has higher rate limits), while the latter uses the staging server to simulate renewal, stopping short of actually storing the staging certificates (in other words: ideal for testing renewal in production).
Even if you're not allowing it to directly mess with apache2 or nginx configuration files and want to run it in standalone mode. For example to get a certificate for my 'test' environment public facing smtpd:
sudo ./certbot-auto certonly -v --standalone --standalone-supported-challenges http-01 -d mail.mydomainname.us
The results:
- Congratulations! Your certificate and chain have been saved at /etc/letsencrypt/live/mail.mydomainname.us/fullchain.pem. Your cert will expire on 2016-08-17. To obtain a new version of the certificate in the future, simply run Certbot again. - If you lose your account credentials, you can recover through e-mails sent to [email protected]. - Your account credentials have been saved in your Certbot configuration directory at /etc/letsencrypt. You should make a secure backup of this folder now. This configuration directory will also contain certificates and private keys obtained by Certbot so making regular backups of this folder is ideal.
Now we have three files, the certificate itself, the certificate itself and the full chain, and the private key:
/etc/letsencrypt/live/mail.mydomainname.us# ls -alh total 8.0K drwxr-xr-x 2 root root 4.0K May 19 14:36 . drwx------ 3 root root 4.0K May 19 14:36 .. lrwxrwxrwx 1 root root 42 May 19 14:36 cert.pem -> ../../archive/mail.mydomainname.us/cert1.pem lrwxrwxrwx 1 root root 43 May 19 14:36 chain.pem -> ../../archive/mail.mydomainname.us/chain1.pem lrwxrwxrwx 1 root root 47 May 19 14:36 fullchain.pem -> ../../archive/mail.mydomainname.us/fullchain1.pem lrwxrwxrwx 1 root root 45 May 19 14:36 privkey.pem -> ../../archive/mail.mydomainname.us/privkey1.pem