申请let's enscrypt通配符证书

certbot的版本为0.22或以上。

使用本机certbot：

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

使用docker：

docker run --rm -it \
-v /data/nginx/conf.d/letsencrypt:/etc/letsencrypt certbot/certbot \
-v /var/log/letsencrypt:/var/log/letsencrypt \
certonly -d *.domain.com \
--manual --preferred-challenges dns \
--server https://acme-v02.api.letsencrypt.org/directory

其中*.domain.com为申请的域名，参数--server在0.22版本为必填（参考）

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator manual, Installer None
Enter email address (used for urgent renewal and security notices) (Enter 'c' to
cancel): 你的邮箱

-----------------------------------------------------------------------------
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-v02.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 encryot the web,  protect its users and defend digital rights.
-------------------------------------------------------------------------------
(Y)es/(N)o: n
Obtaining a new certificate
Performing the following challenges:
dns-01 challenge for domain.com

-------------------------------------------------------------------------------
NOTE: The IP of this machine will be publicly logged as having requested this
certificate. If you're running certbot in manual mode on a machine that is not
your server, please ensure you're okay with that.

Are you OK with your IP being logged?
-------------------------------------------------------------------------------
(Y)es/(N)o: y

-------------------------------------------------------------------------------
Please deploy a DNS TXT record under the name
_acme-challenge.domain.com with the following value:

--tYXBwA9rHS6C_RnYiQVl72CXP1xOuAMhojZSwWTDg

Before continuing, verify the record is deployed.
-------------------------------------------------------------------------------
Press Enter to Continue
Waiting for verification...
Cleaning up challenges

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/domain.com/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/domain.com/privkey.pem
   Your cert will expire on 2018-06-15. 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"
 - 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

certbot的提示非常友好，按提示操作即可。