Introduction
Let’s Encrypt is a Certificate Authority (CA) that provides an easy way to obtain and install free TLS/SSL certificates, thereby enabling encrypted HTTPS on web servers. It simplifies the process by providing a software client, Certbot, that attempts to automate most (if not all) of the required steps. Currently, the entire process of obtaining and installing a certificate is fully automated on both Apache and Nginx.
In this tutorial, you will use Certbot to obtain a free SSL certificate for Nginx on Ubuntu 20.04 and set up your certificate to renew automatically.
This tutorial will use a separate Nginx server configuration file instead of the default file.
We recommend creating new Nginx server block files for each domain because it helps to avoid common mistakes and maintains the default files as a fallback configuration.
Prerequisites
To follow this tutorial, you will need:
- One Ubuntu 20.04 server set up by following this initial server setup for Ubuntu 20.04 tutorial, including a sudo-enabled non-root user and a firewall.
- A registered domain name. This tutorial will use
example.com throughout.
Both of the following DNS records set up for your server.
- An A record with
example.com pointing to your server’s public IP address. - A CNAME record with
www.example.com pointing to your server. - Nginx installed by following How To Install Nginx on Ubuntu 20.04. Be sure that you have a server block for your domain. This tutorial will use
/etc/nginx/sites-available/example.com as an example.
Step 1 — Installing Certbot
The first step to using Let’s Encrypt to obtain an SSL certificate is to install the Certbot software on your server.
Install Certbot and it’s Nginx plugin with
apt:
sudo apt install certbot python3-certbot-nginx
Certbot is now ready to use, but in order for it to automatically configure SSL for Nginx, we need to verify some of Nginx’s configuration.
Step 2 — Confirming Nginx’s Configuration
Certbot needs to be able to find the correct
server block in your Nginx configuration for it to be able to automatically configure SSL. Specifically, it does this by looking for a
server_name directive that matches the domain you request a certificate for.
If you followed the
server block set up step in the Nginx installation tutorial, you should have a server block for your domain at
/etc/nginx/sites-available/example.com with the
server_name directive already set appropriately.
To check, open the configuration file for your domain using
nano or your favorite text editor:
sudo nano /etc/nginx/sites-available/example.com
Find the existing
server_name line. It should look like this:
/etc/nginx/sites-available/example.com
...
server_name example.com www.example.com;
...
If it does, exit your editor and move on to the next step.
If it doesn’t, update it to match. Then save the file, quit your editor, and verify the syntax of your configuration edits:
sudo nginx -t
If you get an error, reopen the server block file and check for any typos or missing characters. Once your configuration file’s syntax is correct, reload Nginx to load the new configuration:
sudo systemctl reload nginx
Certbot can now find the correct
server block and update it automatically.
Next, let’s update the firewall to allow HTTPS traffic.
Step 3 — Allowing HTTPS Through the Firewall
If you have the
ufw firewall enabled, as recommended by the prerequisite guides, you’ll need to adjust the settings to allow for HTTPS traffic. Luckily, Nginx registers a few profiles with
ufw upon installation.
You can see the current setting by typing:
sudo ufw status
It will probably look like this, meaning that only HTTP traffic is allowed to the web server:
OutputStatus: active
To Action From
-- ------ ----
OpenSSH ALLOW Anywhere
Nginx HTTP ALLOW Anywhere
OpenSSH (v6) ALLOW Anywhere (v6)
Nginx HTTP (v6) ALLOW Anywhere (v6)
To additionally let in HTTPS traffic, allow the Nginx Full profile and delete the redundant Nginx HTTP profile allowance:
sudo ufw allow 'Nginx Full'
sudo ufw delete allow 'Nginx HTTP'
Your status should now look like this:
sudo ufw status
OutputStatus: active
To Action From
-- ------ ----
OpenSSH ALLOW Anywhere
Nginx Full ALLOW Anywhere
OpenSSH (v6) ALLOW Anywhere (v6)
Nginx Full (v6) ALLOW Anywhere (v6)
Next, let’s run Certbot and fetch our certificates.
Step 4 — Obtaining an SSL Certificate
Certbot provides a variety of ways to obtain SSL certificates through plugins. The Nginx plugin will take care of reconfiguring Nginx and reloading the config whenever necessary. To use this plugin, type the following:
sudo certbot --nginx -d example.com -d www.example.com
This runs
certbot with the
--nginx plugin, using
-d to specify the domain names we’d like the certificate to be valid for.
If this is your first time running
certbot, you will be prompted to enter an email address and agree to the terms of service. After doing so,
certbot will communicate with the Let’s Encrypt server, then run a challenge to verify that you control the domain you’re requesting a certificate for.
If that’s successful,
certbot will ask how you’d like to configure your HTTPS settings.
OutputPlease choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
1: No redirect - Make no further changes to the webserver configuration.
2: Redirect - Make all requests redirect to secure HTTPS access. Choose this for
new sites, or if you're confident your site works on HTTPS. You can undo this
change by editing your web server's configuration.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Select the appropriate number [1-2] then [enter] (press 'c' to cancel):
Select your choice then hit
ENTER. The configuration will be updated, and Nginx will reload to pick up the new settings.
certbot will wrap up with a message telling you the process was successful and where your certificates are stored:
OutputIMPORTANT NOTES:
- Congratulations! Your certificate and chain have been saved at:
/etc/letsencrypt/live/example.com/fullchain.pem
Your key file has been saved at:
/etc/letsencrypt/live/example.com/privkey.pem
Your cert will expire on 2020-08-18. To obtain a new or tweaked
version of this certificate in the future, simply run certbot again
with the "certonly" option. To non-interactively renew *all* of
your certificates, run "certbot renew"
- If you like Certbot, please consider supporting our work by:
Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate
Donating to EFF: https://eff.org/donate-le
Your certificates are downloaded, installed, and loaded. Try reloading your website using
https:// and notice your browser’s security indicator. It should indicate that the site is properly secured, usually with a lock icon. If you test your server using the
SSL Labs Server Test, it will get an
A grade.
Let’s finish by testing the renewal process.
Step 5 — Verifying Certbot Auto-Renewal
Let’s Encrypt’s certificates are only valid for ninety days. This is to encourage users to automate their certificate renewal process. The
certbot package we installed takes care of this for us by adding a systemd timer that will run twice a day and automatically renew any certificate that’s within thirty days of expiration.
You can query the status of the timer with
systemctl:
sudo systemctl status certbot.timer
Output● certbot.timer - Run certbot twice daily
Loaded: loaded (/lib/systemd/system/certbot.timer; enabled; vendor preset: enabled)
Active: active (waiting) since Mon 2020-05-04 20:04:36 UTC; 2 weeks 1 days ago
Trigger: Thu 2020-05-21 05:22:32 UTC; 9h left
Triggers: ● certbot.service
To test the renewal process, you can do a dry run with
certbot:
sudo certbot renew --dry-run
If you see no errors, you’re all set. When necessary, Certbot will renew your certificates and reload Nginx to pick up the changes. If the automated renewal process ever fails, Let’s Encrypt will send a message to the email you specified, warning you when your certificate is about to expire.
Conclusion
In this tutorial, you installed the Let’s Encrypt client
certbot, downloaded SSL certificates for your domain, configured Nginx to use these certificates, and set up automatic certificate renewal. If you have further questions about using Certbot,
the official documentation is a good place to start.
