下载letsencrypt

git clone https://github.com/letsencrypt/letsencrypt.git

进入letsencrypt

cd letsencrypt

生成证书

 ./certbot-auto --help all
 ./letsencrypt-auto certonly --standalone

查看证书过期时间

openssl x509 -in server.crt -noout -dates

网页题目：letscript证书生成以及查询证书过期时间
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