update: 2018-08-20
已支持泛域名申请：https://certbot.eff.org/
Trying to get a wildcard certificate? Please use the dropdown menus below to get instructions specific to your system, and read those instructions carefully.
$ sudo apt-get update
$ sudo apt-get install software-properties-common
$ sudo add-apt-repository ppa:certbot/certbot
$ sudo apt-get update
$ sudo apt-get install python-certbot-nginx
$ service nginx stop
$ certbot certonly --standalone --email your@email.com -d yourdomain.com
安装参考：[https://www.cnblogs.com/SzeCheng/p/8075799.html](https://www.cnblogs.com/SzeCheng/p/8075799.html)
证书三个月需要续签一次，使用crontab每个月检查一次，自动续期
0 0 1 * * certbot renew -q --pre-hook "service nginx stop" --post-hook "service nginx start"
