1. Install certbot
apt-get install certbot
2. Obtain certificate only
certbot -d <domainname> --manual --preferred-challenges dns certonly
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3. Besure to add _acme-challenge and it’s value on DNS management
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4. The certificate and key files will be saved at following location. Please move it to appropriate location if changes have been made.
Certificate is saved at: /etc/letsencrypt/live/<domain name>/fullchain.pem
Key is saved at: /etc/letsencrypt/live/<domain name>/privkey.pem
*Certificate can be renamed to *.crt, Key can be renamed to *.key.