Docker Basic Terminologies

Before going deeply into Docker first we need to know about some basic terminologies which we use in dockers frequently.

Docker Overview :
Docker is a container management tool, by using docker we can wrap/compress huge environments into small docker images, not only environment we can wrap source-codes, applications, environments into docker images.
Docker is a lite weight tool which is worked based on os-level virtualization which is known as containerization.

Docker Terminologies:

Docker CLI: This is the utility we use when we run any docker commands e.g. docker run (docker container run), 'docker images', 'docker ps' etc. It allows us to run these commands which a human can easily understand.

Docker Engine/ Demon: This is the part which does rest of the magic and knows how to talk to the kernel, makes the system calls to create, operate and manage containers, which we as users of Docker don’t have to worry about.

Docker machine: Docker Machine is a tool that lets you install Docker Engine on virtual hosts, and manage the hosts with docker-machine commands. You can use Machine to create Docker hosts on your local Mac or Windows box, on your company network, in your data center, or on cloud providers like Azure, AWS, or Digital Ocean.
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Until recently Docker didn't run on native Mac or Windows OS, so another tool was created, Docker-Machine, which creates a virtual machine (using yet another tool, e.g. Oracle VirtualBox), runs Docker on that VM, and helps coordinate between the host OS and the Docker VM.

• If you want to use docker in your system kernel version should be >=3.10
• Communication between docker client and docker engine happens over REST API. Docker engine runs on port 2376 by default.

Docker Image: In Docker land, there are images and there are containers. The two are closely related, but distinct. A Docker Image is the template (application plus required binaries and libraries) needed to build a running Docker Container (the running instance of that image)
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Simply Docker image is a file which is consists of binary files/root level file system.
Every image will have a unique image id.

Docker Container: Docker container is a running instance of a docker image.
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Containers are ready applications created from docker images. Every container will have a unique container id. You can run ‘n’ number of containers from a single image(Based on your machine load).

Docker Hub: Docker Hub is a cloud storage of all docker images. In docker hub, we can get all docker images
official docker hub URL https://hub.docker.com/


Docker registry: Docker registry is also a docker image when you run docker registry it will create repository locally. You can push your customized images into your local repository, and you can push your images from the registry without using the internet.