Webmin is an open-source, web-based server administration panel that provides a graphical interface for managing Linux systems. It supports modules for user management, disk quotas, firewall configuration, package updates, and service monitoring, eliminating the need to manually edit configuration files for routine tasks.

This article explains how to install Webmin on an Ubuntu 26.04 server, secure the control panel with a trusted SSL certificate, and configure firewall rules to allow access to the Webmin interface.

Prerequisites

Before you begin, you need to:

• Have access to an Ubuntu 26.04 server instance as a non-root user with sudo privileges.
• Have a subdomain A record pointing to the server's public IP address. For example, webmin.example.com.

Install Webmin

Webmin is not included in the default Ubuntu 26.04 APT repositories. The official Webmin repository setup script adds the package source to APT, allowing installation through the standard package manager.

1. Update the APT package index.

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   $ sudo apt update
   

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2. Download the Webmin repository setup script.

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   $ curl -o webmin-setup-repo.sh https://raw.githubusercontent.com/webmin/webmin/master/webmin-setup-repo.sh
   

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3. Run the script to add the Webmin repository.

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   $ sudo bash webmin-setup-repo.sh
   

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4. Install Webmin with all recommended packages.

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   $ sudo apt install --install-recommends webmin -y
   

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5. Verify that the Webmin service is active and running.

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   $ sudo systemctl status webmin
   

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   The output should display active (running), confirming that the Webmin server daemon is operational.

Set Up Firewall Rules

Uncomplicated Firewall (UFW) is active by default on Ubuntu 26.04. Webmin listens on port 10000 by default. The following steps open the required ports for Webmin access, HTTPS traffic, and HTTP for certificate validation.

1. Allow HTTP traffic on port 80 for SSL certificate validation.

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   $ sudo ufw allow 80/tcp
   

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2. Allow HTTPS traffic on port 443.

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   $ sudo ufw allow 443/tcp
   

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3. Allow connections on the Webmin port 10000.

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   $ sudo ufw allow 10000/tcp
   

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4. Verify the active firewall rules.

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   $ sudo ufw status
   

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   Verify that ports 80, 443, and 10000 are listed as ALLOW in the output.

Secure Webmin

Webmin uses HTTPS by default with a self-signed certificate. Replacing it with a trusted Let's Encrypt certificate eliminates browser security warnings and encrypts all traffic to the control panel. The following steps generate a certificate, merge it into the format Webmin expects, and update the configuration.

1. Install the Certbot Let's Encrypt client.

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   $ sudo apt install certbot -y
   

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2. Generate an SSL certificate for your Webmin domain. Replace webmin.example.com with your actual domain.

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   $ sudo certbot certonly --standalone -d webmin.example.com --agree-tos
   

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   Follow the on-screen prompts to complete the certificate generation.

3. Merge the SSL certificate and private key into a single .pem file that Webmin can use. Replace webmin.example.com with your actual domain.

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   $ sudo cat /etc/letsencrypt/live/webmin.example.com/fullchain.pem /etc/letsencrypt/live/webmin.example.com/privkey.pem | sudo tee /etc/webmin/webmin.pem > /dev/null
   

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4. Open the main Webmin configuration file using a text editor such as Nano.

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   $ sudo nano /etc/webmin/miniserv.conf
   

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5. Find the keyfile directive and update its value to point to the new certificate file.

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   keyfile=/etc/webmin/webmin.pem
   

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   Save and close the file.

6. Restart Webmin to apply the SSL configuration.

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   $ sudo systemctl restart webmin
   

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Access Webmin

The Webmin control panel is accessible through a web browser on port 10000 using HTTPS. Any system user with login privileges can access the interface, but only users with sudo privileges can perform administrative tasks.

1. Open a web browser and navigate to your Webmin domain on port 10000. Replace webmin.example.com with your actual domain.

   https://webmin.example.com:10000

2. Enter your system username and password, then click Sign In to access the Webmin dashboard.

3. The dashboard displays system information including CPU usage, memory consumption, disk space, running processes, and network statistics.

4. Expand System in the navigation menu and select Software Package Updates to view and install available package updates.

5. Select Tools and click File Manager to browse and manage files on the server.

6. Select Tools and click Terminal to open a command-line session directly from the Webmin interface.

Conclusion

You have installed Webmin on an Ubuntu 26.04 server and secured the control panel with a trusted Let's Encrypt SSL certificate. Webmin provides a graphical interface for managing users, services, packages, and system configurations without direct command-line access. For more information, refer to the official Webmin documentation.