Webmin

Webmin is a modern web control panel that allows you to administer your Linux server through a browser-based interface. With Webmin, you can manage user accounts, configure DNS settings, and change settings for common packages on the fly.

The Webmin Dashboard - Dark Mode

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Installation

First, update your server’s package index if you’ve not done so recently:

sudo apt update

Then you need to add the Webmin repository so that you can install and update Webmin using your package manager. In order for your system to trust this new repository, first you’ll download Webmin’s PGP key and then convert it to a format that apt can use to verify files:

curl -fsSL https://download.webmin.com/jcameron-key.asc | sudo gpg --dearmor -o /usr/share/keyrings/webmin.gpg

This downloaded key is the same key that was used by the creator of Webmin to sign the package, and you will use this key to verify the package’s authenticity. In order to convert the .asc file to a workable .gpg file, the gpg --dearmor command is necessary.

Next you will add this repository to your /etc/apt/sources.list file, while referencing your newly converted file you just acquired in the previous step.

Open the file in your preferred editor. Here, you’ll use nano:

sudo nano /etc/apt/sources.list

Then add this line to the bottom of the file to add the new repository:

deb [signed-by=/usr/share/keyrings/webmin.gpg] http://download.webmin.com/download/repository sarge contrib

Save the file and exit the editor. If you had used nano to edit, you can exit by pressing CTRL+X, Y, then ENTER.

Next, update the list of packages again in order to include the now-trusted Webmin repository:

sudo apt update

Then install Webmin:

sudo apt install webmin

Once the installation finishes, you’ll be presented with the following output:

Output
. . .
Webmin install complete. You can now login to
https://your_server:10000 as root with your
root password, or as any user who can use sudo.

If you have installed and enabled the Ubuntu firewall (ufw), you will need to run the following command in order to allow Webmin through the firewall: 

sudo ufw allow 10000

Adding a Valid Certificate with Let’s Encrypt

Although I use a reverse proxy to manage my internal websites; with valid certificates for each site including Webmin, you can use a separate certificate with Webmin directly. The following tutorial from Digital Ocean outlines that process.

Webmin is already configured to use HTTPS, but it uses a self-signed, untrusted certificate. Let’s replace it with a valid certificate from Let’s Encrypt.

Navigate to https://your_domain:10000 in your web browser, replacing 'your_domain' with the domain name pointing to the domain name of your Webmin server or you can use your server’s IP address.

Note: When logging in for the first time, you will see an “Invalid SSL” warning. This warning may say something different depending on your browser, but the reason for it is that the server has generated a self-signed certificate. Allow the exception and proceed to your domain so you can replace the self-signed certificate with one from Let’s Encrypt.

You’ll be presented with a login screen. Sign in with the non-root user you created while fulfilling the prerequisites for this tutorial.

Once you log in, the first screen you will see is the Webmin dashboard. Before you can apply a valid certificate, you have to set the server’s hostname. Look for the System hostname field and click on the link to the right, as shown in the following figure:

This will take you to the Hostname and DNS Client page. Locate the Hostname field, and enter your Fully-Qualified Domain Name into the field. Then click the Save button at the bottom of the page to apply the setting.

After you’ve set your hostname, click on the Webmin dropdown menu in the left-hand navigation bar, and then click on Webmin Configuration.

From the Webmin Configuration page, select SSL Encryption from the list of icons, and then click on the Let’s Encrypt tab. You’ll see a screen like the following figure:

On this page, you’ll tell Webmin how to obtain and renew your certificate. Let’s Encrypt certificates expire after 3 months, but you can instruct Webmin to automatically attempt to renew the Let’s Encrypt certificate every month. Let’s Encrypt looks for a verification file on the server, so you’ll configure Webmin to place the verification file inside the folder /var/www/your_domain, which is the folder that the Apache web server you configured in the prerequisites uses. Follow these steps to set up your certificate:

1. Fill in Hostnames for certificate with your FQDN.
2. For Website root directory for validation file, select the Other Directory button and enter your website’s document root. Assuming you followed the prerequisite Apache tutorial this will be /var/www/your_domain.
3. For Months between automatic renewal section, deselect the Only renew manually option by typing 1 into the input box, and select the radio button to the left of the input box.

Click the Request Certificate button. After a few seconds, you will see a confirmation screen.

To use the new certificate, click the Return to Webmin configuration button on the confirmation screen. From that page, scroll down and click the Restart Webmin button. Wait around 30 seconds, and then reload the page and log in again. Your browser should now indicate that the certificate is valid.