Docker Tagging: Docker Hub vs. AWS ECR vs. Nexus Private Registry¶

When tagging and pushing images, the repository naming conventions vary depending on the registry. Let's explore how Docker Hub, Amazon Elastic Container Registry (ECR), and a Nexus Private Registry handle tagging and pushing images.

1. Tagging for Docker Hub¶

Docker Hub follows a simple repository naming pattern:

<DockerHub_Username>/<Repository_Name>:<Tag>

For example, let's say we have a local image named my-app:latest. We can tag it for Docker Hub under the user mibtisam:

docker tag my-app:latest mibtisam/my-app:v1

Now, we can push this image to Docker Hub:

docker push mibtisam/my-app:v1

2. Tagging for AWS Elastic Container Registry (ECR)¶

AWS ECR requires the repository name to include the AWS account ID, AWS region, and ECR domain:

<AWS_Account_ID>.dkr.ecr.<Region>.amazonaws.com/<Repository_Name>:<Tag>

Example:¶

Authenticate Docker with AWS ECR:

aws ecr get-login-password --region us-east-1 | docker login --username AWS --password-stdin 123456789012.dkr.ecr.us-east-1.amazonaws.com

Tag the image for AWS ECR:

docker tag my-app:latest 123456789012.dkr.ecr.us-east-1.amazonaws.com/my-ecr-repo:v1

Push & Pull the image to AWS ECR:

docker push 123456789012.dkr.ecr.us-east-1.amazonaws.com/my-ecr-repo:v1
docker pull 123456789012.dkr.ecr.us-east-1.amazonaws.com/my-ecr-repo:v1

3. Tagging for Nexus Private Registry¶

A private Nexus repository is often hosted within an organization’s infrastructure. The repository URL follows the format:

<Registry_IP>:<Port>/<Repository_Name>:<Tag>

For example, if our Nexus Private Registry is hosted at https://154.65.3.12:5000, we can tag our image as follows:

docker tag my-app:latest 154.65.3.12:5000/my-private-repo:v1

Steps to Push the Image to Nexus¶

Login to Nexus Private Registry:

docker login 154.65.3.12:5000

Push the tagged image to Nexus:

docker push 154.65.3.12:5000/my-private-repo:v1

Comparison of Docker Image Tagging¶

Each registry has its own unique structure, and tagging the image correctly ensures a successful push. Docker Hub is the easiest to use, while AWS ECR and Nexus require additional authentication.