certbot と Let's encrypt で証明書を取得

certbotのインストール

sudo apt install certbot

証明書の取得

sudo certbot certonly -d <ドメイン名>

証明書の場所

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at:
   /etc/letsencrypt/live/<ドメイン名>/fullchain.pem
   Your key file has been saved at:
   /etc/letsencrypt/live/<ドメイン名>/privkey.pem
   Your cert will expire on 2020-01-20. 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

証明書は/etc/letsencrypt/live/<ドメイン名>/fullchain.pem、秘密鍵は/etc/letsencrypt/live/<ドメイン名>/privkey.pem