1. 安装CertBot

$ sudo yum install certbot python2-certbot-nginx

参考官方网址：https://certbot.eff.org/lets-encrypt/centosrhel7-nginx

2. 手动模式

2.1 输入命令：

$ certbot certonly --preferred-challenges dns --manual  -d *.cncaq.com --server https://acme-v02.api.letsencrypt.org/directory

参数说明：

--preferred-challenges dns: 认证方式选择DNS, 泛域名支持DNS
--manual: 手动模式, 这里为了简单就使用手动认证了, 下面会说自动模式的使用.
-d *.cncaq.com: 就是要申请的泛域名了
--server https://acme-v02.api.letsencrypt.org/directory: 泛域名证书是新功能, 如果要使用就得加上这个参数

如果出现下列错误：

ImportError: cannot import name UnrewindableBodyError
pkg_resources.DistributionNotFound: The 'urllib3<1.23,>=1.21.1' distribution was not found and is required by requests
ImportError: 'pyOpenSSL' module missing required functionality. Try upgrading to v0.14 or newer.

则需要执行下列命令(参考https://github.com/certbot/certbot/issues/5534)：

pip install --upgrade --force-reinstall 'requests==2.6.0'

2.2 敲下回车：

-------------------------------------------------------------------------------
NOTE: The IP of this machine will be publicly logged as having requested this
certificate. If you're running certbot in manual mode on a machine that is not
your server, please ensure you're okay with that.

Are you OK with your IP being logged?
-------------------------------------------------------------------------------
(Y)es/(N)o: y

2.3 再敲下y：

-------------------------------------------------------------------------------
Please deploy a DNS TXT record under the name
_acme-challenge.cncaq.com with the following value:

W2Z_PT1RQX8usavprZ1ly43Je2ayst3ShIBxpgicdEA

Before continuing, verify the record is deployed.
-------------------------------------------------------------------------------

2.4 在阿里云控制台的域名解析服务中添加一个泛解析：

2.5 按下回车

Waiting for verification...
Cleaning up challenges

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/cncaq.com/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/cncaq.com/privkey.pem
   Your cert will expire on 2020-07-16. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot
   again. To non-interactively renew *all* of your certificates, run
   "certbot renew"
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le

https://www.jianshu.com/p/1eb7060c5ede
https://blog.csdn.net/wc810267705/article/details/79917688
https://www.jianshu.com/p/43e74cddba45
https://www.jianshu.com/p/2c1de124d994

CentOS下通过CertBot申请泛域名ssl证书

1. 安装CertBot

2. 手动模式

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