src https://community.letsencrypt.org/t/how-to-automatically-renew-certificates/4393/4
@monthly letsencrypt-auto --config /etc/letsencrypt/cli.ini -d www.yourdomain.com certonly && service nginx restart
/etc/letsencrypt/cli.ini
authenticator = webroot
webroot-path = /var/www/
renew-by-default
agree-tos
email = [email protected]