Copy Images from Container Registry

In the dynamic realm of containerized applications, managing and distributing container images is a pivotal task. Container registries play a crucial role in storing and organizing these images, ensuring seamless deployment across various environments. This article delves into the process of copying images from a container registry, providing insights and step-by-step instructions to streamline this operation.

Understanding the Basics:

Before we embark on the journey of copying images, let's grasp the fundamentals. Container registries act as repositories for storing Docker images, allowing for efficient version control and distribution. Popular container registries include Docker Hub, Google Container Registry (GCR), and Amazon Elastic Container Registry (ECR).

Commands at a Glance:

To copy images from a container registry, several commands come into play. Familiarizing yourself with these commands is essential for a smooth process. The core command often involves pulling an image from the source registry and pushing it to the destination registry.

docker pull source-registry/image:tag
docker tag source-registry/image:tag destination-registry/image:tag
docker push destination-registry/image:tag

Step-by-Step Instructions:

Now, let's break down the process into manageable steps.

Step 1: Authenticate with Source Registry:

Before pulling an image from the source registry, ensure proper authentication. This step varies depending on the registry, but commonly involves using the docker login command.

docker login source-registry

Step 2: Pull the Image:

Use the docker pull command to fetch the desired image from the source registry.

docker pull source-registry/image:tag

Step 3: Tag the Image:

Assign a new tag to the pulled image to reflect the destination registry.

docker tag source-registry/image:tag destination-registry/image:tag

Step 4: Authenticate with Destination Registry:

Similar to the source registry, ensure proper authentication with the destination registry.

docker login destination-registry

Step 5: Push the Image:

Finally, use the docker push command to upload the tagged image to the destination registry.

docker push destination-registry/image:tag

More Examples:

Let's explore a scenario involving Google Container Registry (GCR) and Amazon Elastic Container Registry (ECR).

Example 1: Copying from GCR to ECR:

# Authenticate with GCR
docker login -u _json_key -p "$(cat gcr-key.json)" https://gcr.io

# Pull the image from GCR
docker pull gcr.io/source-project/image:tag

# Tag the image for ECR
docker tag gcr.io/source-project/image:tag destination-registry/image:tag

# Authenticate with ECR
aws ecr get-login-password --region region | docker login --username AWS --password-stdin destination-registry

# Push the image to ECR
docker push destination-registry/image:tag

Example 2: Copying within Docker Hub:

# Authenticate with Docker Hub
docker login

# Pull the image from Docker Hub
docker pull username/source-image:tag

# Tag the image for a different user on Docker Hub
docker tag username/source-image:tag new-username/destination-image:tag

# Authenticate with Docker Hub using the new user
docker login

# Push the tagged image to Docker Hub with the new user
docker push new-username/destination-image:tag