How to Secure Nginx with Let’s Encrypt SSL/TLS on Ubuntu

ByAkensai

Learning how to secure Nginx with Let’s Encrypt SSL/TLS on Ubuntu is one of the most important tasks for any server administrator. Running a website without HTTPS exposes your visitors to serious security risks. It also hurts your search engine rankings. Let’s Encrypt provides free, trusted SSL/TLS certificates that renew automatically. In this tutorial, you’ll install Certbot, obtain a certificate, configure Nginx, and set up auto-renewal. By the end, your site will serve traffic over HTTPS with a valid certificate.

Prerequisites to Secure Nginx with Let’s Encrypt SSL/TLS on Ubuntu

Before you start, make sure you have the following in place.

Required access and software:

  • A server running Ubuntu 20.04 or 22.04
  • Nginx installed and running
  • A registered domain name pointing to your server’s IP address
  • Root or sudo access to the server
  • Port 80 and 443 open in your firewall

Assumed knowledge: You should be comfortable using the Linux command line. Basic Nginx configuration knowledge helps. You don’t need to be an expert.

Estimated time: This tutorial takes about 20–30 minutes to complete.

Make sure your domain’s DNS A record points to your server before you begin. Let’s Encrypt validates your domain over HTTP. If the DNS isn’t set up correctly, certificate issuance will fail. You can verify your DNS propagation using a tool like whatsmydns.net before continuing.

Step-by-Step Guide to Secure Nginx with Let’s Encrypt SSL/TLS on Ubuntu

Another fascinating historical case is: How to Configure Tls 1.3 on Nginx with Modern Security Headers

Follow these steps carefully. Each one builds on the previous.

Step 1: Update your system packages

Start by updating your package list. This ensures you install the latest versions of all software.

sudo apt update
sudo apt upgrade -y

Step 2: Install Nginx (if not already installed)

If Nginx isn’t installed yet, run this command:

sudo apt install nginx -y
sudo systemctl enable nginx
sudo systemctl start nginx

Confirm Nginx is running with sudo systemctl status nginx. You should see “active (running)” in the output.

Step 3: Allow HTTP and HTTPS through the firewall

Ubuntu uses UFW as its default firewall. Open the required ports:

sudo ufw allow 'Nginx Full'
sudo ufw enable
sudo ufw status

The “Nginx Full” profile opens both port 80 and port 443. You need both for certificate validation and HTTPS traffic.

Step 4: Install Certbot and the Nginx plugin

Certbot is the official Let’s Encrypt client. Install it along with the Nginx plugin:

sudo apt install certbot python3-certbot-nginx -y

The Nginx plugin automates certificate installation. It modifies your Nginx config directly. This saves you from editing files manually.

Step 5: Obtain your SSL/TLS certificate

Run Certbot with the Nginx plugin. Replace yourdomain.com with your actual domain:

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

Certbot will ask for your email address. It also asks you to agree to the terms of service. Enter your email and follow the prompts. Certbot then contacts Let’s Encrypt, validates your domain, and installs the certificate.

You’ll also be asked whether to redirect HTTP to HTTPS. Choose option 2 to enable automatic redirection. This is the recommended choice.

Step 6: Verify your Nginx configuration

After Certbot runs, check your Nginx config for errors:

sudo nginx -t

You should see “syntax is ok” and “test is successful.” If you see errors, review the config file Certbot modified. It’s usually located at /etc/nginx/sites-available/yourdomain.com.

Reload Nginx to apply any changes:

sudo systemctl reload nginx

Step 7: Test HTTPS in your browser

Open your browser and navigate to https://yourdomain.com. You should see a padlock icon in the address bar. This confirms your certificate is active and working.

You can also test your SSL configuration using the SSL Labs Server Test. Aim for an A or A+ rating.

Step 8: Set up automatic certificate renewal

Let’s Encrypt certificates expire after 90 days. Certbot installs a systemd timer that handles renewal automatically. Verify it’s active:

sudo systemctl status certbot.timer

You should see “active (waiting)” in the output. You can also do a dry run to confirm renewal works:

sudo certbot renew --dry-run

If the dry run completes without errors, auto-renewal is working correctly. You don’t need to do anything else.

Troubleshooting Common Issues When Securing Nginx with SSL/TLS

Even with careful steps, things can go wrong. Here are the most common problems and how to fix them.

Error: “Domain not found” or “Connection refused”

This usually means your DNS isn’t pointing to your server yet. Wait for DNS propagation and try again. Use dig yourdomain.com to check what IP your domain resolves to.

Error: “Too many certificates already issued”

Let’s Encrypt limits certificate requests to 5 per domain per week. If you hit this limit, wait before trying again. Use the --staging flag during testing to avoid burning your quota:

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

Nginx fails to reload after Certbot

Run sudo nginx -t to find the exact error. Certbot sometimes adds duplicate directives if your config already had SSL settings. Open the config file and remove any duplicate listen 443 or ssl_certificate lines.

Certificate not renewing automatically

Check if the Certbot timer is enabled:

sudo systemctl enable certbot.timer
sudo systemctl start certbot.timer

Also check the renewal config at /etc/letsencrypt/renewal/yourdomain.com.conf. Make sure the authenticator is set to nginx.

Warning: Mixed content on your site

If your site loads over HTTPS but shows warnings, you likely have HTTP resources embedded in your pages. Update all internal links and asset URLs to use HTTPS. If you run WordPress, the Search Replace DB tool can help update URLs in the database.

Conclusion

You now know how to secure Nginx with Let’s Encrypt SSL/TLS on Ubuntu from start to finish. You installed Certbot, obtained a free certificate, configured HTTPS, and set up auto-renewal. Your server now encrypts all traffic between itself and your visitors. This protects user data and builds trust.

Keep your server updated regularly. Check your SSL rating periodically using SSL Labs. If you run WordPress on this server, consider also configuring HTTP/2 in Nginx for better performance. You can also explore setting up security headers like Strict-Transport-Security and X-Content-Type-Options to harden your setup further.

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