By Kathleen Juell, Erika Heidi, and Mark Drake
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 Apache on Debian 10 and set up your certificate to renew automatically.
This tutorial will use a separate Apache virtual host file instead of the default configuration file. We recommend creating new Apache virtual host files for each domain because it helps to avoid common mistakes and maintains the default files as a fallback configuration.
To follow this tutorial, you will need:
One Debian 10 server set up by following this initial server setup for Debian 10 tutorial, including a non-root user with
sudo privileges and a firewall.
A fully registered domain name. This tutorial will use your_domain as an example throughout. You can purchase a domain name on Namecheap, get one for free on Freenom, or use the domain registrar of your choice.
Both of the following DNS records set up for your server. To set these up, you can follow these instructions for adding domains and then these instructions for creating DNS records.
your_domainpointing to your server’s public IP address.
www.your_domainpointing to your server’s public IP address.
Apache installed by following How To Install Apache on Debian 10. Be sure that you have a virtual host file set up for your domain. This tutorial will use
/etc/apache2/sites-available/your_domain.conf as an example.
The first step to using Let’s Encrypt to obtain an SSL certificate is to install the Certbot software on your server.
Note: Currently, Certbot is not available from the Debian software repositories by default, but it’s possible to configure the
buster-backports repository in your
/etc/apt/sources.list file to allow you to install a backport of the Certbot software with APT.
Backports, however, are recompiled packages from Debian’s testing and unstable repositories that have been recompiled to run in a stable Debian distribution. These packages are not tested regularly, and may not always be up to date. Accordingly, the Certbot backport will install version 0.31 while the current version as of this writing is 1.09. One notable difference between these versions of Certbot is that the default settings for version 0.31 will enable TLS v1.0 and TLS v1.1, two security protocols that have been deprecated in most major web browsers, and enabling these protocols can present a security vulnerability. While it’s possible to change this default, doing so can break the automatic updates that make Certbot so useful.
Until a more recent version of Certbot is available from the Debian APT repositories, this tutorial will follow the Certbot documentation’s recommendation of installing version 1.09 with snappy, a package manager developed for Linux systems that installs packages in a format referred to as snaps.
To install Certbot as a snap on Debian, you must first have
snapd installed on your server.
snapd is a daemon required to install, use, and manage snaps. Installing the
snapd package will also install the
snap command on your server.
snapd, update your local package index if you’ve not done so recently:
- sudo apt update
Then install the
- sudo apt install snapd
After running this command, you’ll be prompted to confirm that you want to install
snapd and its dependencies. Do so by pressing
Y and then
Next, use the
snap command to install the
core snap. This will install some dependencies on your server that are needed for any snap you install, including the Certbot snap:
- sudo snap install core
Then refresh the
core snap. Doing so will ensure that you have the latest versions of
snapd and its dependencies installed:
- sudo snap refresh core
Following that, you can install the
certbot snap with the following command.
Note that snaps can be installed under one of three confinement levels which provide varying degrees of isolation from your system. For example, most snaps are installed under the
--strict confinement level by default which prevents these programs from accessing your system’s files or network. Because Certbot must be allowed to edit certain configuration files in order to correctly set up certificates, this command includes the
--classic option. This confinement level allows any snaps installed under it the same access to system resources as traditional packages:
- sudo snap install --classic certbot
This installation process will install the
certbot executable in the
/snap/bin/ directory. Create a symbolic link to this file in the
/usr/bin/ directory to ensure that you can run the
certbot command anywhere on your system:
- sudo ln -s /snap/bin/certbot /usr/bin/certbot
Certbot is now ready to use, but in order for it to configure SSL for Apache, we need to verify that Apache has been configured correctly.
Certbot needs to be able to find the correct virtual host in your Apache configuration for it to automatically configure SSL. Specifically, it does this by looking for a
ServerName directive that matches the domain you request a certificate for.
If you followed the virtual host setup step in the Apache installation tutorial, you should have a
VirtualHost block for your domain at
/etc/apache2/sites-available/your_domain.conf with the
ServerName directive already set appropriately.
To check, open the virtual host file for your domain using
nano or your favorite text editor:
- sudo nano /etc/apache2/sites-available/your_domain.conf
Find the existing
ServerName line. It should look like this, with your own domain name instead of
... ServerName your_domain; ...
If it doesn’t already, update the
ServerName directive to point to your domain name. Then save the file and quit your editor. If you used
nano, do so by pressing
CTRL + X,
Next, verify the syntax of your configuration edits:
- sudo apache2ctl configtest
If there aren’t any syntax errors, you will see this in your output:
Output. . . Syntax OK
If you get an error, reopen the virtual host file and check for any typos or missing characters. Once your configuration file’s syntax is correct, reload Apache to load the new configuration:
- sudo systemctl reload apache2
Certbot can now find the correct
VirtualHost block and update it.
Next, let’s update the firewall to allow HTTPS traffic.
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, when installed on Debian,
ufw comes packaged with a few profiles that help to simplify the process of changing firewall rules for HTTP and HTTPS traffic.
You can see the current setting by typing:
- sudo ufw status
If you followed the Step 2 of our guide on How to Install Apache on Debian 10, the output of this command will look like this, showing that only HTTP traffic is allowed to the web server:
OutputStatus: active To Action From -- ------ ---- OpenSSH ALLOW Anywhere WWW ALLOW Anywhere OpenSSH (v6) ALLOW Anywhere (v6) WWW (v6) ALLOW Anywhere (v6)
To additionally let in HTTPS traffic, allow the “WWW Full” profile and delete the redundant “WWW” profile allowance:
- sudo ufw allow 'WWW Full'
- sudo ufw delete allow 'WWW'
Your status should now look like this:
- sudo ufw status
OutputStatus: active To Action From -- ------ ---- OpenSSH ALLOW Anywhere WWW Full ALLOW Anywhere OpenSSH (v6) ALLOW Anywhere (v6) WWW Full (v6) ALLOW Anywhere (v6)
Next, let’s run Certbot and fetch our certificates.
Certbot provides a variety of ways to obtain SSL certificates through plugins. The Apache plugin will take care of reconfiguring Apache and reloading the config whenever necessary. To use this plugin, type the following:
- sudo certbot --apache -d your_domain -d www.your_domain
certbot with the
--apache plugin, using
-d to specify the names for which you’d like the certificate to be valid.
If this is your first time running
certbot, you will be prompted to enter an email address and agree to the terms of service. Additionally, it will ask if you’re willing to share your email address with the Electronic Frontier Foundation, a nonprofit organization that advocates for digital rights and is also the maker of Certbot. Feel free to enter
Y to share your email address or
N to decline.
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, the configuration will be updated automatically and Apache 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:
Output. . . IMPORTANT NOTES: - Congratulations! Your certificate and chain have been saved at: /etc/letsencrypt/live/your_domain/fullchain.pem Your key file has been saved at: /etc/letsencrypt/live/your_domain/privkey.pem Your cert will expire on 2021-01-20. 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" - Your account credentials have been saved in your Certbot configuration directory at /etc/letsencrypt. You should make a secure backup of this folder now. This configuration directory will also contain certificates and private keys obtained by Certbot so making regular backups of this folder is ideal. - 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 green 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.
Let’s Encrypt 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 renew script to
/etc/cron.d. This script runs twice a day and will automatically renew any certificate that’s within thirty days of expiration.
To test the renewal process, you can do a dry run with
- 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.
In this tutorial, you installed the Let’s Encrypt client
certbot, downloaded SSL certificates for your domain, configured Apache to use these certificates, and set up automatic certificate renewal. If you have further questions about using Certbot, their documentation is a good place to start.
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I love you guys, thank you for these tutorials it’s been a huge help.
Thanks a lot for this very helpful tutorial. However, the SSL Labs Server Test is reporting grade B, because TLS 1.0 and 1.1 are still enabled. So it would be very useful to add an additional step to show how these old TLS protocols can be disabled. I used to change /etc/letsencrypt/options-ssl-apache.conf and replace the appropriate statement with “SSLProtocol ALL -SSLv2 -SSLv3 -TLSv1 -TLSv1.1”. But it’s written in this file that you should prevent from any manual changes in it to provide future security updates. Honestly, I don’t know if Certbot itself would offer options to disable some protocols. Thanks for your support.
Thank you for this tutorial. I’m checking over what I do on Debian 11 setup and can report that I’ve had success installing certbot for nginx directly from the Debian repositories with this command:
This installs version 1.12.0