SSL certificates are used within web servers to encrypt the traffic between the server and client, providing extra layer of security for users accessing your applications. Let’s Encrypt provides an easy way to obtain and install trusted certificates free of cost.
Prerequisites
- One Ubuntu 17.10 server with a non-root sudo user
- Apache web server installed with one or more domain names properly configured
If you are done with above prerequisites, you are ready to begin by log into your server using sudo-enabled user account.
Install the Let’s Encrypt Client
The first step to using Let's Encrypt to obtain an SSL certificate is to install the certbot software on your server. The Certbot developers maintain their own Ubuntu software repository with up-to-date versions of the software. Because Certbot is in such active development it's worth using this repository to install a newer Certbot than provided by Ubuntu.
sudo add-apt-repository ppa:certbot/certbot
You'll need to press ENTER to accept. Afterwards, update the package list to pick up the new repository's package information:
sudo apt-get update
And finally, install Certbot from the new repository with apt-get:
sudo apt-get install python-certbot-apache
The certbot Let's Encrypt client is now ready to use.
Set Up the SSL Certificate
Generating the SSL Certificate for Apache using the certbot Let’s Encrypt client is pretty straightforward. The client will automatically obtain and install a new SSL certificate that is valid for the domains provided as parameters.To execute the interactive installation and obtain a certificate that covers only a single domain, run the certbot command with:
sudo certbot --apache -d yourdomain.com
If you want to install a single certificate that is valid for multiple domains or subdomains, you can pass them as additional parameters to the command. The first domain name in the list of parameters will be the base domain used by Let’s Encrypt to create the certificate, and for that reason we recommend that you pass the bare top-level domain name as first in the list, followed by any additional subdomains or aliases:
For this example, the base domain will be yourdomain.com.
You will be prompted to provide an email address for lost key recovery and notices, and you will be need to agree to the Let's Encrypt terms of service. You'll then be asked to choose between enabling both http and https access or force all requests to redirect to https.
When the installation is finished, you should be able to find the generated certificate files at /etc/letsencrypt/live. You can verify the status of your SSL certificate with the following link (don’t forget to replace yourdomain.com with your base domain):
https://www.ssllabs.com/ssltest/analyze.html?d=yourdomain.com&latest
You should now be able to access your website using a https prefix.
Verify Certbot Auto-Renewal
Let’s Encrypt certificates only last for 90 days. However, the certbot package we installed takes care of this for us by running certbot renew twice a day via a systemd timer. On non-systemd distributions this functionality is provided by a cron script placed in /etc/cron.d. The task runs twice daily and will renew any certificate that's within thirty days of expiration.
sudo certbot renew --dry-run
If you see no errors, you're all set. When necessary, Certbot will renew your certificates and reload Apache 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.