When learning about and using docker you will often hear a number of frequently used terms. It is important to understand them and them and their definitions. We” attempt to simplify these terms and minimize and ambiguity to help you learn and understand docker faster.
A Docker Image is a collection of all the files that make up a software application. An image is a combination of a file system and parameters. Any Docker Image originates from a base image which then additional libraries and functionality are added too.
Every time you
Commit a docker image, you create a new layer on the Docker image, but the original layer image and each pre-existing layer remains unchanged. Therefore
images can be thought of a
Every Image has a
unique ID, which is represented using a 64 HEX digit randon number. By default, the docker images sub command will only show 12 Hex digits.
An image could contain any libraries, files and Operating systems i.e. a docker image could contain the Ubuntu Operating System, nginx, php, WordPress and your sites theme and files installed on it.
Docker provides a simple way for building new images or updating existing ones. You can also download and use Docker images that other people have already created. Docker Images are the building blocks of the Docker containers.
A Docker Layer could represent either read-only or read-write images. However, the top layer of a container stack is always the read-write layer, which hosts the Docker container
A Docker Container is an instance of a Docker image that is run using the
docker run command. The basic purpose of Docker is to run containers.
start a container, a reference is made to an image using the
unique id. Docker pulls the required image and its parent image, and will contine to pull all the parent images until it reaches the base image.
Docker containers are easily deployed to any device, any VM or even on the cloud, because they are so lightweight. It is due to this that containers enable easy scalability.
A Docker Registry is a place where Docker Images can be stored and publicly accessed by the community, enabling anyone to create and compose applications without risks. Docker Hub and Docker Cloud are public registries that anyone can use, and Docker is configured to look for images on Docker Hub by default
All stored images go through multiple validations, verifications and refinements the quality of images will be very high.
The Registry is a stateless, highly scalable server side application that stores and distribute Docker images. The Registry is open-source, under the permissive Apache license.
You can even run your own private registry. If you use Docker Datacenter (DDC), it includes Docker Trusted Registry (DTR).
A Docker Repository is a namespace that is used fro storing a docker image. You can create either public or private Docker Repositories and store all the images your organisation creates.
We have created a public repository on Docker Hub, threenine repository, and all the docker images we create are available to download and use.
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