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实验环境：CentOS Linux release 7.3.1611 (Core)
内核版本：Linux version 3.10.0-514.el7.x86_64
Nginx 版本：Nginx-1.13.0
Let’s Encrypt 是一个免费的、自动化、开放的证书颁发机构。由 Mozilla、Cisco、Chrome、facebook、Akamai 等众多公司和机构发起的，其安全稳定及其可靠。具体信息可以去 letsencrypt 官方网站了解详情。
今天我们就充分利用 Lets Encrypt 让你的网站实现 https 加密。
官网：https://letsencrypt.org/
1. 安装 certbot 及源扩展包
$ yum install -y epel-release
Certbot 是 Let’s Encrypt 官方指定推荐的客户端。通过 Certbot，你可以自动化部署 Let’s Encrypt SSL 证书，以便为网站加上 HTTPS 加密支持。$ yum install certbot
$ certbot certonly
Saving debug log to /var/log/letsencrypt/letsencrypt.log
How would you like to authenticate with the ACME CA?
// 你是希望如何使用 ACME CA 进行身份验证？——————————————————————————-
1: Place files in webroot directory (webroot)
// 将文件放在 webroot 目录
2: Spin up a temporary webserver (standalone)
// 使用临时 Web 服务器（独立目录）-------------------------------------------------------------------------------
Select the appropriate number [1-2] then [enter] (press 'c' to cancel):1【选择 1 回车】Enter email address (used for urgent renewal and security notices) (Enter 'c' to
cancel):su@renwole.com【输入您的邮箱地址，用于紧急更新和安全通知】Starting new HTTPS connection (1): acme-v01.api.letsencrypt.org
-------------------------------------------------------------------------------
Please read the Terms of Service at
https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf. You must agree
in order to register with the ACME server at
https://acme-v01.api.letsencrypt.org/directory
-------------------------------------------------------------------------------
(A)gree/(C)ancel: A【选择 A 回车同意服务条款，C 为拒绝】-------------------------------------------------------------------------------
Would you be willing to share your email address with the Electronic Frontier
Foundation, a founding partner of the Let's Encrypt project and the non-profit
organization that develops Certbot? We'd like to send you email about EFF and
our work to encrypt the web, protect its users and defend digital rights.
-------------------------------------------------------------------------------
(Y)es/(N)o:Y【您是否愿意分享您的电子邮件地址，建议选择 Y 回车】Please enter in your domain name(s) (comma and/or space separated) (Enter 'c'
to cancel): blog.renwole.com【输入域名回车】Obtaining a new certificate
Performing the following challenges:
http-01 challenge for blog.renwole.com
Select the webroot for blog.renwole.com:
-------------------------------------------------------------------------------
1: Enter a new webroot
// 输入网站绝对路径
-------------------------------------------------------------------------------
Press 1 [enter] to confirm the selection (press 'c' to cancel):1【选择数字 1 回车】Input the webroot for blog.renwole.com: (Enter 'c' to cancel):/home/www/blog.renwole.com【输入网站所在绝对路径回车】Waiting for verification...
Waiting for verification...
Cleaning up challenges
Generating key (2048 bits): /etc/letsencrypt/keys/0001_key-certbot.pem
Creating CSR: /etc/letsencrypt/csr/0001_csr-certbot.pem
IMPORTANT NOTES:
- Congratulations! Your certificate and chain have been saved at
/etc/letsencrypt/live/blog.renwole.com/fullchain.pem. Your cert
will expire on 2017-08-09. 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:
恭喜! 您的 SSL 证书和密钥链接已保存，你的证书将于 2017-08-09 到期。注意：这里需要说明，在生成证书之前，你必须保证 nginx 443 端口是运行状态，否则会生成证书失败。
2. 自动续订
Certbot 可以配置为在证书过期之前自动更新证书。由于 Let’s Encrypt SSL 证书有效期时间为 90 天，所以建议您利用此功能。您可以通过运行以下命令来测试证书的自动续订：
$ sudo certbot --nginx certonly如果以上正常工作，你可以通过添加运行以下操作的 cron 或 systemd 定时任务安排自动更新：
certbot renew我们写一个自动执行脚本，建议每小时执行一次：
$ sudo crontab -e
添加以下内容：0 */6 * * * /usr/bin/certbot renew --quiet && /bin/systemctl restart nginx
保存并退出！通过命令查看是否添加成功：$ crontab -l
0 */6 * * * /usr/bin/certbot renew --quiet && /bin/systemctl restart nginx
重启 crontab
$ systemctl status crond.service
$ systemctl restart crond.service通过命令观察 crontab 是否执行：
$ tail -f /var/log/cron证书是否续订成功，可以通过以下命令管理查看证书信息：
$ certbot certificates更多 Certbot 命令请参阅官方文档 https://certbot.eff.org/docs/
3. 配置 nginx.conf
接下来修改 Nginx 配置文件，修改 sever 段，去掉相应注释，将生成的 SSL 证书填写到 ssl_certificate 后面，将生成的密钥填写到 ssl_certificate_key 后面，保存并重启 nginx 服务器即可。
# vi /usr/local/nginx/conf/nginx.conf
server {
listen 443 ssl;
ssl_certificate /etc/letsencrypt/live/blog.renwole.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/blog.renwole.com/privkey.pem;
# ssl_session_cache shared:SSL:1m;
ssl_session_timeout 5m;
# ssl_ciphers HIGH:!aNULL:!MD5;
ssl_prefer_server_ciphers on;
# location / {
# root html;
# index index.html index.htm;
# }
}使用谷歌浏览器访问 https://blog.renwole.com/ 可以看到绿色的安全小锁图标，说明网站已经 https 加密成功。
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