Let's Encrypt 是当前最常用的免费 HTTPS 证书生成工具之一。该服务由非营利组织提供，致力于为全球范围内的网站提供便捷的自动化证书颁发服务。虽然 Let's Encrypt 证书的有效期只有90天，但是可以自动续期，这使得 Let's Encrypt 更加易于使用和部署。

Certbot 安装

在 Ubuntu/Debian 系统上安装 Certbot

apt update && apt install certbot -y

证书申请与续签

注意 *.uain.ccc 为你自己的域名，需要修改

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

填写信息

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Enter email address (used for urgent renewal and security notices)
 (Enter 'c' to cancel):  # 这里输入你的邮箱

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Please read the Terms of Service at
https://letsencrypt.org/documents/LE-SA-v1.4-April-3-2024.pdf. You must agree in
order to register with the ACME server. Do you agree?
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(Y)es/(N)o: Y    # 输入 Y

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Would you be willing, once your first certificate is successfully issued, 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 our work encrypting the web,
EFF news, campaigns, and ways to support digital freedom.
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(Y)es/(N)o: Y       # 输入 Y

Account registered.
Requesting a certificate for *.runoob.com

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Please deploy a DNS TXT record under the name:

xxxxxxx.uain.ccc. # 这里需要设置域名解析，需要到域名后台填写信息，参考下图

with the following value:

aIwqY00CZtziVwr-xxxxxxxxxxxxxx  # 这里是域名解析的内容，参考下图

Before continuing, verify the TXT record has been deployed. Depending on the DNS
provider, this may take some time, from a few seconds to multiple minutes. You can
check if it has finished deploying with aid of online tools, such as the Google
Admin Toolbox: https://toolbox.googleapps.com/apps/dig/#TXT/_acme-challenge.runoob.com.
Look for one or more bolded line(s) below the line ';ANSWER'. It should show the
value(s) you've just added.

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Press Enter to Continue  # 参考下图设置完域名解析后，按回车就可以生成了，记住一定要先解析设置完成后再回车，然后生成的证书信息如下：

Successfully received certificate.
Certificate is saved at: /etc/letsencrypt/live/uain.cc/fullchain.pem
Key is saved at:         /etc/letsencrypt/live/uain.cc/privkey.pem
This certificate expires on 2024-12-21.
These files will be updated when the certificate renews.

NEXT STEPS:
- This certificate will not be renewed automatically. Autorenewal of --manual certificates requires the use of an authentication hook script (--manual-auth-hook) but one was not provided. To renew this certificate, repeat this same certbot command before the certificate's expiry date.

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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
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Let's Encrypt 颁发的证书有效期为 90 天，可以使用以下命令进行续签证书:

certbot certonly --force-renewal --manual -d '*.uain.cc' \
--preferred-challenges dns \
--server https://acme-v02.api.letsencrypt.org/directory

执行以上续签命令后，就会让我们更新下 DNS 解析记录：

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Requesting a certificate for *.uain.cc

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Please deploy a DNS TXT record under the name:

_acme-challenge.uain.cc.

with the following value:

ckxo1wGXbP1CtNQ3ZRfvHxxxxxx          # 这里会显示你要更改的 DNS 解析记录值，设置好就可以完成更新了

Before continuing, verify the TXT record has been deployed. Depending on the DNS
provider, this may take some time, from a few seconds to multiple minutes. You can
check if it has finished deploying with aid of online tools, such as the Google
Admin Toolbox: https://toolbox.googleapps.com/apps/dig/#TXT/_acme-challenge.jysahre.com.
Look for one or more bolded line(s) below the line ';ANSWER'. It should show the
value(s) you've just added.

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