Let's Encrypt でワイルドカード対応のSSL証明書を取得するための手順

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

$ sudo certbot certonly --manual \
    --preferred-challenges dns-01 \
    --server https://acme-v02.api.letsencrypt.org/directory \
    -m youremail@example.com \
    -d example.com \
    -d *.example.com

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator manual, Installer None

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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
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(A)gree/(C)ancel: A

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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 our work
encrypting the web, EFF news, campaigns, and ways to support digital freedom.
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(Y)es/(N)o: N

Obtaining a new certificate
Performing the following challenges:
dns-01 challenge for example.com
dns-01 challenge for example.com

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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?
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(Y)es/(N)o:Y

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

KiejN-Skifje8-slejntONRwW9ko3ijJAopoie21KAI

Before continuing, verify the record is deployed.
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Press Enter to Continue

$ dig -t txt @your.dns.ne.jp _acme-challenge.example.com +short
"KiejN-Skifje8-slejntONRwW9ko3ijJAopoie21KAI"

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

KiejN-Skifje8-slejntONRwW9ko3ijJAopoie21KAI

Before continuing, verify the record is deployed.
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Press Enter to Continue

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

Skiskeije8-AsiejN8-skKsoNeuNntONRwW9ko31KAI

Before continuing, verify the record is deployed.
(This must be set up in addition to the previous challenges; do not remove,
replace, or undo the previous challenge tasks yet. Note that you might be
asked to create multiple distinct TXT records with the same name. This is
permitted by DNS standards.)

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Press Enter to Continue

$ dig -t txt @your.dns.ne.jp _acme-challenge.example.com +short
"KiejN-Skifje8-slejntONRwW9ko3ijJAopoie21KAI"
"Skiskeije8-AsiejN8-skKsoNeuNntONRwW9ko31KAI"

Waiting for verification...
Cleaning up challenges

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/example.com/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/example.com/privkey.pem
   Your cert will expire on 2019-11-27. 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

server {
  listen 443 ssl;
  server_name  *.example.com;
  ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
  ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

(...省略...)

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