官方安装步骤:https://certbot.eff.org/lets-encrypt/centosrhel7-nginx
centos7如何安装snapd:https://snapcraft.io/docs/installing-snap-on-fedora
参考:https://blog.csdn.net/qq_37769323/article/details/104124108
如果centos的内核为:kernel 3.10.0-123.4.2.el7.x86_64 则会报错:error: system does not fully support snapd: cannot read the value of fs.may_detach_mounts kernel
parameter: open /proc/sys/fs/may_detach_mounts: no such file or directory
此情况请升级你的centos内核,参考:注意:升级内核之前必须先执行 yum update 更新所有的包,在参考https://linux.cn/article-8310-1.html方法,否则无法更新成功!【升级linux内核的方法参考:https://linux.cn/article-8310-1.html】
旧的安装方式【定时器自动更新都是使用命令certbot -q renew】:https://blog.csdn.net/weixin_43343144/article/details/108312285