Docker 101

What is Docker?

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According to wikipedia Docker is a set of platform as a service (PaaS) products that use OS-level virtualization to deliver software in packages called containers. Just like we can manage our application, docker enables us to manage the application infrastructure as well.

Why Docker?

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While we try to run an existing code base, we often have to troubleshoot environment issues. This could be dependency issue, module installation problem or environment mis-match.

Docker, in its core is trying to fix these problems. Docker is trying to make it super easy and really straight-forward for anyone to run any code-base or software in any pc, desktop or even server.

In a nutshell

Docker make it really easy to install and run software without worrying about setup and dependencies.

Docker Ecosystem

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Dockers ecosystem contains

• Docker Client
• Docker Server
• Docker Machine
• Docker Image
• Docker Hub
• Docker Compose

Docker Image : Single file with all the dependencies and config required to run a program.

Docker Container : Instance of the Docker Image.

Docker Hub : Repository of free public Docker Images, can be downloaded to local machine to use.

Docker Client :

• Took the command from the user
• Do the pre-processing
• Pass it to the Docker Server
• Docker Server do the heavy processing

An Docker Example :

Assuming you have already installed docker in your system, let's run,

docker run hello-world

• It imply to run an container from the image hello-world
• This hello-world is a tiny little program, whose sole purpose is to print Hello from Docker!
• Docker Server check the local image cache. If it is not exist in the local image cache it goes to Docker Hub and download the image.
• Finally the Docker Server run the image as container or image instance.
• If we run the same command again and the image is already in the cache, It does not download it from the Docker Hub.