What is Docker Registry?

A Docker registry is a system for storing and distributing Docker images with specific names. There may be several versions of the same image, each with its own set of tags. A Docker registry is separated into Docker repositories, each of which holds all image modifications. The registry may be used by Docker users to fetch images locally and to push new images to the registry (given adequate access permissions when applicable). The registry is a server-side application that stores and distributes Docker images. It is stateless and extremely scalable. 

Docker is a container platform that facilitates the developers to packages an application with all its dependencies into a single package. It helps in building, shipping and running the containers across the platforms that supports docker without any dependency issues.

Docker Image is a light weight executable software template that contains all the dependencies such as software, libraries, runtime. These can be built from the dockerfile which specifies the configuration and steps required to create the image.

Docker Image Registry is repository for storing and sharing Docker Image. It acs as a centralized location for the developers to upload and download the images. It comes with popular registries include Dockerhub where many pre-built images exists.

DockerHub is a cloud-based repository that is provided by docker, that allows the users to store and share docker images. It act as a central hub for the developers in finding the pre-built image for various software applications.

Docker login is command used in the command line interface that is used for authentication of users with Dockerhub or any other docker registries. On executing the docker login command it prompts with asking dockerhub account username and password allowing them to access the private repositories and push or pull the images securely. Try on using the following command for authentication of dockerhub account.

docker login

Docker Distribution is an open source project that facilities with features for DockerHub and Docker registries. It provides the backend infrastructure storing and distribution docker images. It helps in ensuring the efficient and reliable delivery of container images to users worldwide.

Authentication of Dockerhub involves in securely verifying the identity of users who can access the platform. It typically requires users to provides credentials suc has username and password or token authentication. On authenticates the users with Dockerhub for ensuring only authorized individuals to pull, push or modify the stored images in the repository.

1. Our images can be stored in the Docker registry.
2. We can automate the development.
3. With the help of a private docker registry, we can secure our image.

• DockerHub
• Amazon Elastic Container Registry (ECR)
• Google Container Registry (GCR)
• Azure Container Registry (ACR)

The above-mentioned docker registries are the most commonly used docker registries.

1. Starting your registry:

docker run -d -p 5000:5000 --restart=always --name registry registry:2

It instructs Docker to start a registry named registry:2 in detached mode with the name registry. Map the registry’s port 5000 to a local port 5000 and restart it immediately if it dies.

2. Pulling some images from the hub:

docker pull ubuntu:latest

It says docker to pull Ubuntu latest.

3. Tagging that image and point to your registry:

docker image tag ubuntu:latest localhost:5000/gfg-image

4. Pushing the image:

docker push localhost:5000/gfg-image

5. Pulling that image back:

docker pull localhost:5000/gfg-image

6. Stop the registry:

docker container stop registry

7. Stop the registry and remove the data:

docker container stop registry && docker container rm -v registry

A Docker registry is an excellent way to supplement and integrate your CI/CD pipelines. Whenever there is a new commit in your source code or version control system, the CI workflow is triggered which then deploys the image to your registry if the CI workflow completion was successful. A signal from the Registry would then initiate a staging environment deployment or alert other systems to the availability of a new image.

So essentially we can say:

1. Docker Registry aids in development automation. The docker registry allows you to automate building, testing, and deployment. Docker registry may be used to create faster CI/CD pipelines, which helps to reduce build and deployment time.
2. Docker Registry is useful if you want complete control over where your images are kept. A private Docker registry can be used. You gain total control over your applications by doing so. In addition to controlling who may access your Docker images, you can determine who can view them.
3. Docker Registry can provide you with information about any issue you may encounter. You may also completely rely on it for container deployment and access it at any moment.

• Docker Registry provides a storage and distribution platform for Docker images.
• Users can upload their Docker images to the registry, and these images can be tagged with a version number and a name.
• Other users can then search for and download these images from the registry.
• Docker Registry can be self-hosted or used as a cloud-based service.

• Docker Registry is important because it makes it easy to share and distribute Docker images.
• It simplifies the process of managing and deploying Docker containers, which can save time and resources.
• Docker Registry is a key component of the Docker ecosystem and is widely used by developers and organizations of all sizes.

Following are some of the alternatives of Docker Registry: 

1. Docker Hub provides users with a free hosted Registry with capabilities of automated build and organization of accounts. 
2. A few other alternates for Docker Registry are: 
   • JFrog Bintray i.e a cloud platform that provides services for managing, deploying, and promoting your applications.
   • GitLab Container Registry, which is a private and highly secure repository for storing docker images.  

What is the Docker image registry?

It is centralized repository for storing and sharing docker images.

What is the difference between Docker Registry and Docker Image?

Docker registry stores the docker images while the docker image is a template for creating images.

Where are Docker Images stored in Registry?

Docker images are stored in the repositories with the tag name inside the docker registry such as Dockerhub or others.

How to create Docker Image Registry?

Sign in into Container Registry such as Dockerhub, quay.io registry, Amazon ECR, GCR etc.. it help provide you the registry inside that create repositories and store them.

How to get list of images on Docker Registry v2?

For listing the images on Docker Registry V2, you can use the DockerAPI or CLI commands such as docker search <image_name>, the command looks as follows:

docker search <image_name>