步骤目录：
步骤一：将要申请 Let’s Encrypt SSL 的域名解析到要进行操作的服务器 IP 地址上
步骤二：安装 certbot
步骤三：使用 certbot 生成 Let’s Encrypt SSL 证书
步骤四：查看已经生成的 Let’s Encrypt SSL 证书
步骤五：延期 Let’s Encrypt SSL 证书
5.1 查看 Let’s Encrypt SSL 证书的延期策略
5.2 手动延期 Let’s Encrypt SSL 证书
5.3 自动延期 Let’s Encrypt SSL 证书
步骤六：Let’s Encrypt SSL 证书的生成限制
具体的操作步骤：
步骤一：将要申请 Let’s Encrypt SSL 的域名解析到要进行操作的服务器 IP 地址上
（步骤略）
步骤二：安装 certbot
# yum -y install certbot（补充：这里以在 Fedora 35 上安装 certbot 为例）
步骤三：使用 certbot 生成 Let’s Encrypt SSL 证书
# certbot certonly --email mingyu.zhu@eternalcenter.com -n --agree-tos --webroot -w /usr/share/nginx/html/ -d eternalcenter.com
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator webroot, Installer None
Requesting a certificate for eternalcenter.com
Performing the following challenges:
http-01 challenge for eternalcenter.com
Using the webroot path /usr/share/nginx/html for all unmatched domains.
Waiting for verification...
Cleaning up challenges
IMPORTANT NOTES:
- Congratulations! Your certificate and chain have been saved at:
/etc/letsencrypt/live/eternalcenter.com/fullchain.pem
Your key file has been saved at:
/etc/letsencrypt/live/eternalcenter.com/privkey.pem
Your certificate will expire on 2022-03-20. 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（
补充：这里以
1) 使用 mingyu.zhu@eternalcenter.com 邮箱
2) 以非交互式的方式
3) 通过给 /usr/share/nginx/html/ 网站目录里添加验证文件进行验证
4) 给 eternalcenter.com 域名
申请 Let’s Encrypt SSL 证书为例
）
步骤四：查看已经生成的 Let’s Encrypt SSL 证书
# certbot certificates
Saving debug log to /var/log/letsencrypt/letsencrypt.log
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Found the following certs:
Certificate Name: eternalcenter.com
Serial Number: 3e8cdb74a1abfbf3d535ec1c3f8cb3e4e4c
Key Type: RSA
Domains: eternalcenter.com
Expiry Date: 2022-03-20 13:48:48+00:00 (VALID: 89 days)
Certificate Path: /etc/letsencrypt/live/eternalcenter.com/fullchain.pem
Private Key Path: /etc/letsencrypt/live/eternalcenter.com/privkey.pem
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
（
补充：
1) /etc/letsencrypt/live/eternalcenter.com/fullchain.pem 是公钥
2) /etc/letsencrypt/live/eternalcenter.com/privkey.pem 是私钥
）
步骤五：延期 Let’s Encrypt SSL 证书
5.1 查看 Let’s Encrypt SSL 证书的延期策略
# cat /etc/letsencrypt/renewal/eternalcenter.com.conf
# renew_before_expiry = 30 days
version = 1.20.0
archive_dir = /etc/letsencrypt/archive/eternalcenter.com
cert = /etc/letsencrypt/live/eternalcenter.com/cert.pem
privkey = /etc/letsencrypt/live/eternalcenter.com/privkey.pem
chain = /etc/letsencrypt/live/eternalcenter.com/chain.pem
fullchain = /etc/letsencrypt/live/eternalcenter.com/fullchain.pem（补充：可以看出 Let’s Encrypt SSL 证书是在过期前 30 天才能更新）
5.2 手动延期 Let’s Encrypt SSL 证书
# /usr/bin/certbot renew（补充：这里以延期 Let’s Encrypt SSL 证书为例）
5.3 自动延期 Let’s Encrypt SSL 证书
# crontab -e添加以下内容：
......
0 0 */30 * * /usr/bin/certbot renew（补充：这里以每过 30 天的 0 时 0 分延期 Let’s Encrypt SSL 证书为例）
步骤六：Let’s Encrypt SSL 证书的生成限制
1) 一个域名申请次数不能超过 5 次/周
2) 允许申请失败次数不能超过 5 次/时
3) 属于同一个顶级域名的二级域名申请次数不能超过 20 次/周
4) 申请请求频率不能超过 20 次/秒
5) 一个 IP 地址创建用户个数不能超过 10 个/3 小时
6) 一个用户最多 pending 审核的数不能超过 300 个