Docker Desktop Architecture

This is a diagram of the Docker desktop application. On the left hand side is the client application which is the thing that we will be interacting with. In the client application there is are number of elements:

The Docker CLI: Whenever you are going to the command line and typing Docker run or Docker pull you are interfacing with that Docker CLI.

The Docker GUI: There is also a graphical user interface which is useful for browsing the images we have on your system. You can also do things like configure how much CPU and memory and disk space the docker application has access to.

Docker credential Helper: Registry is a place where we can store we can push images to and pull images from and in order to have a private registry you need some way to log in. So the docker credential helper is a mechanism to help store the necessary credentials to do the authentication for that.

Extensions: Extensions are a relatively new feature of Docker that are third-party pieces of software that plug into the client and provide additional functionalities to the user.

When you install Docker desktop on your system it also creates a Linux virtual machine. For Mac OS Docker uses a hypervisor and installs a Linux virtual machine and then within that virtual machine it sets up two things – it sets up the server host application and that is known as the docker Daemon or Docker D that exposes the Docker API. When someone executes a command from the command line that command gets passed to the Docker Daemon which is listening via that Docker API and then it executes whatever the command is specifying within that server host application.

Then there is an optional Kubernetes cluster that gets configured and installed within that virtual machine. This can be a nice to have if you are developing for Kubernetes. You can leverage that cluster directly without having to install and configure a separate cluster.

And then finally we have Registry, it is a place to store container images and share those container images with a team or with the world or with wherever you are deploying your containers to. For example, Docker Hub. Docker Daemon when it needs to get an image that it is not building locally, it will go to some registry like Docker Hub and pull that image into the host environment.

In this article we are going to do a technology deep dive and start understanding the foundational Linux kernel features that software like Docker is using to make the containers work and provide those isolated environments that we all use. then towards the end of this section, we’ll also take a look at the docker system architecture.