Creating Wildcard SSL Certificates with Certbot

The process varies slightly depending on which DNS verification provider you use. For this guide we will focus on Cloudflare but if you use another DNS provider like GCore, your certbot generation may require a few extra flags like --rsa-key-size 2048.

Creating DNS API Token

Cloudflare’s API Tokens provide restricted access controls for specific domains and operations, and are therefore the recommended authentication option.

The Token needed by Certbot requires Zone:DNS:Edit permissions for only the zones you need certificates for.

Then add the token to a config file:

/root/cloudflare.ini

# Cloudflare API token used by Certbot
dns_cloudflare_api_token = YOUR_CLOUDFLARE_API_TOKEN

Install Required Dependencies

apt install -y certbot python3-certbot-nginx python3-pip
pip3 install certbot-dns-cloudflare

Generate Certificate

certbot certonly \
  --dns-cloudflare \
  --dns-cloudflare-credentials /root/cloudflare.ini \
  --dns-cloudflare-propagation-seconds 60 \
  -d example.com \
  -d *.example.com

Automatic Renewal

Install crontab:

apt install cron

Create a crontab rule for the automatic renewal:

(crontab -l ; echo "0 23 * * * certbot renew --quiet --deploy-hook \"systemctl restart nginx\"")| crontab -

Lets Encrypt Google Trust Services