Docker registry – trying to simplify concept and bit details

Hi All,

Greetings for the day 🙂 LIFE IS BEAUTIFUL 🙂

Background : Since exploring Docker / Kubernetes, recently got an assignment to create Private registry and push our docker images to our private registry

Before discussing private registry and how to create it, here I will discuss first what is Docker Registry? Types of Docker Registry ? and few more details

What is Docker Registry ?

• A Docker registry is the storage for our docker image
  • As we discussed in previous articles as well – Docker Image is nothing but read-only template which contains set of instructions for creating container which runs on Docker platform
• These images within registries are available either public – can be downloaded by anyone OR private – restricted access to users
• Registry is nothing but instance of registry image and runs within Docker
• We interact with registry using Push and Pull commands
• Its the service which hosts and distributes Docker images
• We could host Docker registries either in cloud or on-premises
• The Registry is stateless
• The Registry is open-source
• We could have either Public Registry OR Private Registry
• Some example of public Docker registries are
  • Googles container registry (GCR)
    • It supports only private registries
    • It supports automated image build via GitHub
  • Amazon’s Elastic Container Registry (ECR)
    • It supports only private registries
    • It doesn’t support automated image building
  • Azure Container Registry (ACR)
    • It supports only private registries
    • It does not provide automated image building
• We can create our private registry deriving from Official registry image – registry version 2 – we will discuss this in next article

Prerequisites :

• Docker must be installed to have Docker registry

What is Docker Hub?

• Docker Hub is official cloud based repository for Docker images
• This is default registry
• This registry is ready when we install Docker
• The Registry is compatible with Docker engine version 1.6.0 or higher.
• Docker Hub registry is free to use
• We have very good articles on Docker installation
  • On Windows : Docker : Installation on Windows – resolving error – WSL2 Installation is incomplete.
  • On Linux / Ubuntu : Docker – Introduction to Containers and Docker – part 2 – Creating first Docker program – our first container with detailed steps
• Docker Hub supports the integration with Github – we will discuss how this happen in upcoming articles
• It hosts around 8,836,465 images and 170+ official images

Interacting with Registry : (Here using default registry – Docker Hub)

• Pushing our Docker image to registry :
  • We have very good article on pushing our image to Docker Hub, please have a look once – Docker : How to push docker image to docker hub – resolving error – “denied: requested access to the resource is denied”

docker push username(dockerid)/imagename

Example:
docker push prashamsabadra/knowledgejunction:latest

here please note - "prashamsabadra" is my docker id / username

• Pulling image from registry :

docker pull <image name>

Example : 
docker pull ubuntu => downloads locally image ubuntu

We have very good series of Docker / Kubernetes, trying to simplifying the concepts, please have a look once – https://knowledge-junction.in/category/containerization/

Thanks for reading 🙂 If you think its useful, kindly please like and share 🙂

HAVE A GREAT TIME AHEAD 🙂