centos已經不能安裝Certbot, 須改用snapd安裝
請先安裝 snapd https://kafeiou.pw/2021/02/17/3008/
sudo yum remove certbot sudo yum install httpd mod_ssl setsebool -P httpd_can_network_connect true sudo snap install --classic certbot sudo ln -s /snap/bin/certbot /usr/bin/certbot
