Introduction

Webmin is a web-based system administration tool for Unix-like systems. It provides an easy alternative to command line system administration and can be used to manage various aspects of a system, such as users and services, through the use of the provided Webmin modules. If you want to manage your own server but you are uncomfortable with the command line, Webmin is a good tool to help you get started.
This tutorial covers the installation of Webmin with SSL using apt-get on Ubuntu 14.04.

Prerequisites

To install Webmin, you will need to have access to a user with root privileges. It is recommended that you set up a non-root user with sudo access by following steps 1-3 of this link: Initial Server Setup with Ubuntu 14.04. This user will also be used to login to the Webmin interface, and Webmin will use the credentials to administer your server.
Note that you are required to use password-based authentication enabled to log in to your server via Webmin.

Log in Via SSH

Log in to your server as the new user that you created (or root) via SSH (substitute your user name and server IP address here):

ssh new_user@server_IP_address

Answer the password prompt to complete the login process.
Let’s get started with the Webmin installation!

Install Webmin

To install Webmin via apt-get, you must first add the Webmin repository to your sources.list file.
On your server, open the sources.list file in your favorite text editor. We will use nano in this tutorial:

sudo nano /etc/apt/sources.list

If you are prompted for a “[sudo] password”, enter your user’s password.
Now press Ctrl-W then Ctrl-V to navigate to the end of the file, then add the following lines to the file:

deb http://download.webmin.com/download/repository sarge contrib
deb http://webmin.mirror.somersettechsolutions.co.uk/repository sarge contrib

When you are finished editing, save the file by pressing Ctrl-X, then y, RETURN.
Now add the Webmin GPG key to apt, so the source repository you added will be trusted. This command will do that:

wget -q http://www.webmin.com/jcameron-key.asc -O- | sudo apt-key add -

Before installing Webmin, you must update apt-get’s package lists:

sudo apt-get update

Now run this apt-get command to install Webmin:

sudo apt-get install webmin

Enter y to confirm the installation.
After the installation is complete, the Webmin service will start automatically.

Log in to Webmin

In a web browser, access your server’s Webmin login page via its public IP address (the same IP address you used to login via SSH) on port 10000. By default, Webmin will start with SSL/TLS enabled, so you will need to use HTTPS to connect to it.
Open this URL in your web browser (substitute the IP address):

https://server_IP_address:10000

You will be prompted with a warning that says your server’s SSL certificate is not trusted. This is because Webmin automatically generates and installs an SSL certificate upon installation, and this SSL certificate was not issued by a certificate authority that is trusted by your computer. Although your computer cannot verify the validity of the certificate, you know that you are, in fact, accessing your own server. It is fine to proceed.
Instruct your web browser to trust the certificate. If you are using Chrome, for example, click the Advanced link, then click the Proceed to server_IP_address (unsafe) link. If you are using Firefox, click I Understand the Risks, then the Add Exception… button, then the Confirm Security Exception button.
At this point, you will see the Webmin login screen:

Enter the same login credentials that you used to log in to your server via SSH. This user must have root privileges via sudo.
Congratulations! You have successfully installed Webmin, and it is ready to be used. Remember that, because you are using a privileged user to access Webmin, the Webmin application has full access to your server—keep your login credentials secure!

Using Webmin

When you first log into Webmin, you will be taken to the System Information page, which will show you an overview of your system’s resources and other miscellaneous information. This view also shows you any Webmin updates that are available.

On the left side, you will see the navigation menu, which you can use to access the various Webmin modules and manage your server. The navigation menu is organized into categories, and each category has its own set of modules. The Webmin category is special because contains modules that are used to configure the Webmin application, while the other categories are used to perform various system administration tasks.
Take some time to explore the modules that are available, to familiarize yourself with Webmin.

Example: Create a New User

A basic system administration task that you can perform with Webmin is user management. We will show you how to create a new user with the Users and Groups module.
Expand the System category in the navigation menu, then click on Users and Groups.
Then click the Create a new user. link.

Enter the Username and any other settings you want to assign to the new user, then click the Create button.
The user will be created on the server, with the specified settings.
The Users and Groups module can also be used to perform other user management tasks, such as deleting and disabling users and groups.

Example: Install Apache

Webmin comes with a large variety of modules that manage different software packages. We will demonstrate how to install a web server using the the Apache Webserver module, as an example.
In the navigation menu, click Un-used Modules to expand the category, and then click Apache Webserver.
If you do not have Apache installed on your server, the module will notify you and provide you with a way to install Apache.
Use the Click here link (in the last sentence) to install Apache via apt-get through Webmin.
After the Apache installation is complete, your server will be running the default Apache server.
The Apache Webserver module will be moved to the Servers category, and you may use it to manage the configuration of your Apache server.

Conclusion

Now that you have Webmin installed on your Ubuntu server, you should be able to use it to perform basic system administration tasks.
Good luck!