参考:
https://letsencrypt.org/zh-cn/getting-started/
https://www.cnblogs.com/stulzq/p/8628163.html
yum -y install yum-utils
yum-config-manager --enable rhui-REGION-rhel-server-extras rhui-REGION-rhel-server-optional
yum install certbot python2-certbot-apache
certbot certonly -d 你的域名 -d *.你的域名 --manual --preferred-challenges dns
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