How to Secure Nginx with Let's Encrypt On Ubuntu 20.04 / 18.04

Introduction

Any website that aspires to attract visitors needs to include SSL/TLS encryption for its domain. SSL/TLS certificates ensure a safe connection between your web server and browsers.

Let’s Encrypt is a free certificate authority that allows you to set up such protection. It is the simplest way to secure your Nginx server.

In this article, you will find the simplest way to secure your Nginx server by obtaining Let’s Encrypt certificates using the Certbot software. 

Prerequisites

• A system running Ubuntu 20.04 (or Ubuntu 18.04)
• Access to a terminal window/command line
• Sudo or root privileges on local/remote machines
• Nginx installed and set up
• A registered domain name
• A server block configured for that domain name

How to Secure Nginx with Let's Encrypt On Ubuntu 20.04

Step 1: Install Certbot

Certbot is an open-source software tool for automatically enabling HTTPS using Let’s Encrypt certificates.

The first step to securing Nginx with Let’s Encrypt is to install Certbot. To do so, start by opening a terminal window and updating the local repository:

sudo apt update

Then, download and install Certbot and its Nginx plugin by running:

sudo apt install certbot python3-certbot-nginx

Type y to confirm the installation and hit Enter.

Step 2: Check Nginx Configuration

As noted in the prerequisites, you should already have a registered domain and an Nginx server block for that domain. As an example, this article uses the domain example.com.

To check whether it is set up correctly, open the Nginx configuration file:

sudo nano /etc/nginx/sites-available/example.com

Then, locate the server_name directive and make sure it is set to your domain name. As you want to include the domain name with and without the www. prefix, the line should look similar to the one below:

server_name example.com www.example.com;

Step 3: Adjust Firewall to Allow HTTPS Traffic

The next step is to adjust the firewall to allow HTTPS traffic.

If you followed the Nginx installation guide, you already enabled your firewall to allow Nginx HTTP. As you are adding Let’s Encrypt certificates, you need to configure the firewall for encrypted traffic.

1. To ensure your firewall is active and allows HTTPS traffic, run the command:

sudo ufw status

The output should tell you UFW is active and give you a list of set rules. In the following example, it shows that the firewall allows Nginx HTTP traffic, but not HTTPS.

Nginx has three (3) profiles you can add as rules:

• Nginx HTTP (opens port 80)
• Nginx HTTPS (opens port 443 – encrypted traffic)
• Nginx Full (opens port 80 and 443)

2. To allow encrypted traffic, you can either add the Nginx HTTPS profile or use Nginx Full and delete the existing Nginx HTTP rule:

a) Allow Nginx HTTPS traffic by running the command:

sudo ufw allow 'Nginx HTTPS'

b) Remove Nginx HTTP and use Nginx Full instead with:

sudo ufw deny 'Nginx HTTP'

sudo ufw allow 'Nginx Full'

3. Verify you added a rule that allows HTTPS traffic by using the ufw status command.

Step 4: Obtain the SSL/TLS Certificate

Nginx’s plugin for Certbot reconfigures Nginx and reloads its configuration when needed. Therefore, the only thing you need to do is generate certificates with the NGINX plug‑in.

1. To do so, run the command:

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

2. The output asks you to configure your HTTPS settings. Enter your email address and agree to the terms of service to continue.

3. Once you configure HTTPS, Certbot completes generating the certificate and reloads Nginx with the new settings.

4. Finally, the output displays that you have successfully generated a certificate and specifies the location of the certificate on your server.

Step 5: Enable Automatic Certificate Renewal

Since Let’s Encrypt certificates expire every 90 days, Nginx recommends setting up and automatic renewal cron job.

1. First, open the crontab configuration file for the current user:

crontab -e

2. Add a cron job that runs the certbot command, which renews the certificate if it detects the certificate will expire within 30 days. Schedule it to run daily at a specified time (in this example, it does so at 05:00 a.m.):

0 5 * * * /usr/bin/certbot renew --quiet

The cron job should also include the --quiet attribute, as in the command above. This instructs certbot not to include any output after performing the task.

3. Once you added the cron job, save the changes, and exit the file.

Conclusion

If you followed the steps outlined in this article, you should have successfully secured your Nginx with Let’s Encrypt that will generate SSL/TLS certificates for your domain. In addition, you should have enabled Certbot to renew certificates automatically.