Running GUI Apps on a Docker Container

Containerization and the GUI

Before we launch GUI on docker, let's understand how GUI works on any system. What provides a display interface or a graphical interface between the system and the user is a client/server windowing system known as the X Window System, and sometimes X11 or even X.

It is a dedicated terminal that displays the windows and handles input devices such as keyboards, mice, and touchscreens. The clients are applications.

To run GUI apps on Docker we need to use X11 of our host.

Running GUI Containers on docker in 5 easy steps

Step 1: Install Docker

To be able to launch a container you need to first have Docker installed. On your host OS (preferably Linux) get Docker installed and then move on to the next step.

Orientation and setup

Step 2: Pull an image

Download a container image of your choice from Docker Hub. In this blog I am using CentOS image.

To pull the image from Docker Hub type

docker pull centos

docker images

This command will show you the images you have in your local system.

Step 3: Create the container

Method 1:

Launch a container using docker run command

docker run -dit --name centos_gui --env=’Display’ --net=host centos:latest

Here, the run subcommand is used to launch the container, -i to make it interactive, -t to get the terminal, and -d to daemonize it. We use --env to set the environment variable DISPLAY and --net to connect the container to the host network.

Method 2:

Set the DISPLAY environment variable on the host OS with your network:

set-variable -name DISPLAY -value YOUR-IP:0.0

And then finally launch the container using

docker run -dit --env=DISPLAY=$DISPLAY

Here we have manually set the environment variable.

docker ps

This command shows running containers

Step 4: Install GUI application inside the container

Attach the container to go inside the container’s terminal. To do so, type:

docker attach centos_gui

Now you are inside the container’s terminal.

Next, install a GUI application using a package manager. In our case since we have CentOS, we will be using the yum command.

yum install firefox

Step 5: Running the application

As we have already specified the DISPLAY environment variable while launching the container, now all we have to do is just run the app normally.

firefox

In a while, the GUI of the app will show up something like this.

We have successfully launched firefox GUI over a docker container!

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