利用Certbot全自動安裝Let's Encrypt安全證書，實現全站加密

Certbot使用的官方文檔，能夠選擇系統，切換對應的使用方法，我選擇的是Ubuntu16.04+Nginx

一、安裝Cerbot

$ sudo apt-get update
$ sudo apt-get install software-properties-common
$ sudo add-apt-repository ppa:certbot/certbot
$ sudo apt-get update
$ sudo apt-get install python-certbot-nginx

安裝過程當中，若出現 W: GPG error: http://ppa.launchpad.net/ondrej/php/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 4F4EA0AAE5267A6C 錯誤，可以使用 sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 4F4EA0AAE5267A6C 解決，注意後面的key要替換爲提示錯誤中的PUBKEY

二、申請證書

sudo certbot --nginx --nginx-server-root /etc/nginx/ -d xxx.j2do.com

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator nginx, Installer nginx
Enter email address (used for urgent renewal and security notices) (Enter 'c' to
cancel): xxxxx@126.com
Starting new HTTPS connection (1): acme-v01.api.letsencrypt.org

-------------------------------------------------------------------------------
Please read the Terms of Service at
https://letsencrypt.org/documents/LE-SA-v1.2-November-15-2017.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

-------------------------------------------------------------------------------
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: N
Obtaining a new certificate
Performing the following challenges:
http-01 challenge for ddy.j2do.com
nginx: [warn] conflicting server name "" on 0.0.0.0:80, ignored
nginx: [warn] conflicting server name "" on [::]:80, ignored
Waiting for verification...
Cleaning up challenges
nginx: [warn] conflicting server name "" on 0.0.0.0:80, ignored
nginx: [warn] conflicting server name "" on [::]:80, ignored
Deploying Certificate to VirtualHost /etc/nginx/sites-enabled/ddy
nginx: [warn] conflicting server name "" on 0.0.0.0:80, ignored
nginx: [warn] conflicting server name "" on [::]:80, ignored

Please choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access.
-------------------------------------------------------------------------------
1: No redirect - Make no further changes to the webserver configuration.
2: Redirect - Make all requests redirect to secure HTTPS access. Choose this for
new sites, or if you're confident your site works on HTTPS. You can undo this
change by editing your web server's configuration.
-------------------------------------------------------------------------------
Select the appropriate number [1-2] then [enter] (press 'c' to cancel): 1

-------------------------------------------------------------------------------
Congratulations! You have successfully enabled https://ddy.j2do.com

You should test your configuration at:
https://www.ssllabs.com/ssltest/analyze.html?d=ddy.j2do.com
-------------------------------------------------------------------------------

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/xxx.j2do.com/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/xxx.j2do.com/privkey.pem
   Your cert will expire on 2018-09-16. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot again
   with the "certonly" option. To non-interactively renew *all* of
   your certificates, run "certbot renew"
 - Your account credentials have been saved in your Certbot
   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 Certbot so
   making regular backups of this folder is ideal.
 - 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

第一項必須是選擇贊成（A)，第二項無所謂，是將記得郵件地址添加到EFF郵件列表中，發送一些郵件給你，能夠選擇否（N)，這時候證書會自動生成，並根據你的域名，去查找nginx配置，自動修改nginx配置支持https，最後詢問你，是否要將http的請求所有重置到https上，配置完成後告訴你一些信息，證書存放在 /etc/letsencrypt位置

三、重啓nignx便可

sudo service nginx restart

四、Let's Encrypt推薦使用ACME v2證書，此證書支持通配符，使證書更容易管理，稍後補充申請方法

五、自動定時申請更新證書

不管如何要記得更新證書這個事情仍是很麻煩，那麼certbot提供了一個自動爲全部證書從新申請的命令，並且它是智能的，只申請七天內到期的證書

#設置crontab命令
0 2 * * * certbot renew