Install SSL Certificate in Debian 12, 11 and 10

This guide shows you how to install and configure Let's Encrypt SSL certificates on your Debian web server using Certbot.

Prerequisites

• Apache or Nginx web server installed
• Domain name pointing to your server's IP address
• Port 80 and 443 open in your firewall

Step 1: Install Certbot

Debian 12 or 11

sudo apt update
sudo apt install python3-certbot-apache

For Nginx instead of Apache

sudo apt install python3-certbot-nginx

Debian 10

sudo apt update
sudo apt install certbot python3-certbot-apache

Step 2: Obtain SSL Certificate

For Apache

sudo certbot --apache -d yourdomain.com -d www.yourdomain.com

For Nginx

sudo certbot --nginx -d yourdomain.com -d www.yourdomain.com

Follow the interactive prompts:

• Enter your email address for renewal notifications
• Agree to the Terms of Service
• Choose whether to redirect HTTP to HTTPS (recommended: Yes)

Step 3: Verify Installation

Test your SSL certificate:

sudo certbot certificates

Visit your website with https:// to confirm it's working.

Step 4: Configure Auto-Renewal

Certbot automatically sets up renewal. Test the renewal process:

sudo certbot renew --dry-run

Check the renewal timer status:

sudo systemctl status certbot.timer

Troubleshooting

Certificate Not Renewing Automatically

Manual renewal:

sudo certbot renew

Check renewal logs:

sudo tail -f /var/log/letsencrypt/letsencrypt.log

Port 80 Not Accessible

Ensure your firewall allows HTTP and HTTPS:

sudo ufw allow 'Apache Full'

Or for Nginx:

sudo ufw allow 'Nginx Full'

Domain Not Resolving

Verify DNS settings:

dig yourdomain.com +short

Additional Resources

• Check your SSL rating: https://www.ssllabs.com/ssltest/
• Let's Encrypt documentation: https://letsencrypt.org/docs/