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首先我们要安装git
apt-get update
apt-get -y install git
然后，检出Let's Encrypt的客户端源码
git clone https://github.com/letsencrypt/letsencrypt
这样，我们就成功的下载了Let's Encrypt的客户端
关闭nginx后进入Let's Encrypt目录
cd letsencrypt
运行Standalone插件
./letsencrypt-auto certonly --standalone
在你运行插件后，Let's Encrypt会进入初始化阶段，这时，你要输入一些信息，用于生成证书
多个域名用空格分割
如果你看到这样的文字，就说明生成了
IMPORTANT NOTES:
- Congratulations! Your certificate and chain have been saved at
/etc/letsencrypt/live/example.com/fullchain.pem. Your
cert will expire on 2016-03-19. To obtain a new version of the
certificate in the future, simply run Let's Encrypt again.
- Your account credentials have been saved in your Let's Encrypt
configuration directory at /etc/letsencrypt. You should make a
secure backup of this folder now. This configuration directory will
also contain certificates and private keys obtained by Let's
Encrypt so making regular backups of this folder is ideal.
- If like Let's Encrypt, please consider supporting our work by:
Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate
Donating to EFF: https://eff.org/donate-le
这段文字提示了证书的存放位置和过期日期
我的存放位置是 /etc/letsencrypt/live/example.com/fullchain.pem 在2016年3月19日过期
我们配置Nginx证书时的证书文件和密钥文件都在那个目录下。其中fullchain.pem包含了网站证书和根证书链
配置Nginx
修改我们的虚拟主机配置文件，在listen后面把80改成443，并加SSL，然后在下面加入我们的证书和密钥地址。
listen 443 ssl;
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_prefer_server_ciphers on;
ssl_ciphers AES256+EECDH:AES256+EDH:!aNULL;
然后保存，退出，重启Nginx即可！
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