ECR Replication for Beginners: Simplify Your Container Workflow

The ability to replicate container images between AWS ECR (Elastic Container Registry) accounts is a powerful tool for disaster recovery, streamlined multi-account management, and efficient cross-region deployments. Amazon ECR supports both cross-region and cross-account replication, making it easier to distribute and maintain your Docker images.

This guide will walk you through the step-by-step process of configuring AWS ECR replication between multiple accounts.

Pre-requisites

1. AWS CLI installed and configured.
2. AWS IAM roles with sufficient permissions. (e.g., AmazonEC2ContainerRegistryFullAccess).
3. Source and destination AWS accounts.
4. Source and destination repositories in ECR.

Considerations Before Proceeding

• New Images Only: Only content pushed to a repository after configuring replication will be replicated. Existing images will not be automatically copied.
• IAM Role Creation: An IAM role with appropriate permissions will be created during the process.
• Destination Account Permissions: Registry permissions must be configured in the destination account to allow replication from the source.
• Policy Changes: Changing permission policies mid-replication might affect ongoing replications.
• Destination Limit: A private registry is limited to 25 unique destinations across all replication rules

Steps

Step 1: Enable Replication at the source Account

In the source AWS account, navigate to the Amazon ECR console. Under “Private registry settings,” enable cross-account replication.

Step 2: Configure Registry Permissions Policy in the Destination Account

In the destination AWS account, you need to grant permission for the source account to replicate images.

1. Open the Amazon ECR console.
2. Navigate to “Registry Permissions” and create a new permissions policy.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "AllowCrossAccountReplication",
      "Effect": "Allow",
      "Principal": {
        "AWS": "Source_Account_ID"
      },
      "Action": [
        "ecr:ReplicateImage"
      ]
    }
  ]
}

Replace "Source_Account_ID" with the actual AWS account ID of the source account.

Step 3: Configure ECR Replication in Source Account

Go back to the source account to configure the ECR replication rule.

• Return to the Amazon ECR console in the source account.
• Under the desired registry, navigate to “Replication.
• “Create a new replication rule, specifying the destination region and account.
• (Optional) You can filter which repositories to replicate using a repository prefix.

You can also filter which repositories to replicate using a repository prefix.

aws ecr put-replication-configuration --region us-west-2 --replication-configuration file://replication-configuration.json

Step 4: Test Replication

After setting up the replication, push a new Docker image to the source repository to verify that the image replicates to the destination account.

docker push <source_repo_url>:<tag>

Monitor the replication status in the ECR console in the destination account. Successful replication usually takes less than 30 minutes.

Post-Configuration Actions

• Clean Up: Manually delete unnecessary replicated images and repositories.
• Additional Settings: Configure repository settings like tag immutability and image scanning in the destination account, as these are not replicated by default.

Conclusion

By following this guide, you’ve successfully configured cross-account ECR replication. This setup enhances your container workflow by enabling:

• Disaster Recovery: Maintain copies of your images in multiple regions for resilience.
• Multi-Account Management: Simplify image distribution and management across your AWS organization.
• Global Deployments: Easily replicate images to different regions for faster and more reliable deployments.