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Building a Docker image and pushing it to multiple registries—like Docker Hub, GitLab Container Registry, or GitHub Container Registry (GHCR)—is a common requirement for modern CI/CD pipelines. In this guide, we’ll focus on how to build and push an image to GHCR using GitHub Actions.

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What Is GitHub Container Registry?

GitHub Container Registry (ghcr.io) is part of GitHub Packages. It allows you to store and manage both Docker and OCI images, either publicly or privately.
The image shows a GitHub Actions workflow page for a repository named "solar-system" by the user "sidd-harth-7," displaying a list of recent workflow runs with their statuses and timestamps.
Key Features:
FeatureDescription
Namespaceghcr.io
Image FormatsDocker images, OCI artifacts
VisibilityPublic or private
IntegrationTight integration with GitHub Actions and GitHub Packages API
Click Packages → Container registry in your repo sidebar to explore existing images:
The image shows a GitHub documentation page about GitHub Packages, detailing its features and usage for hosting and managing software packages. The sidebar includes links to various package registries and related topics.

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Authenticating to GHCR

You can authenticate using:
  • A GitHub Personal Access Token (PAT) scoped for read:packages and write:packages.
  • The automatically generated GITHUB_TOKEN in Actions workflows (requires explicit packages: write permission).
The image shows a GitHub documentation page about authenticating to the container registry, detailing the use of personal access tokens and GitHub Actions workflows. The page includes a navigation menu on the left and a list of related topics on the right.

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Using a PAT Locally

export CR_PAT=YOUR_PERSONAL_ACCESS_TOKEN
echo "$CR_PAT" | docker login ghcr.io -u YOUR_USERNAME --password-stdin
# Login Succeeded
docker push ghcr.io/YOUR_USERNAME/IMAGE_NAME:latest
You can push multiple tags: 
docker push ghcr.io/YOUR_USERNAME/IMAGE_NAME:latest
docker push ghcr.io/YOUR_USERNAME/IMAGE_NAME:2.5
For automation, store your PAT as a GitHub Secret (e.g., GHCR_PAT) and reference it in workflows.

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Updating Your GitHub Actions Workflow

We’ll extend our CI workflow to:
  1. Build the Docker image.
  2. Run a quick container test.
  3. Authenticate and push to Docker Hub and GHCR.
Add or update the Containerization job in .github/workflows/workflow.yml: 
jobs:
  unit-testing: ...
  code-coverage: ...

  docker:
    name: Containerization
    needs: [unit-testing, code-coverage]
    runs-on: ubuntu-latest
    permissions:
      packages: write    # Grant write access to GHCR
      contents: read

    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Login to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ vars.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_PASSWORD }}

      - name: Login to GHCR
        uses: docker/login-action@v2
        with:
          registry: ghcr.io
          username: ${{ github.repository_owner }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Build image for tests
        uses: docker/build-push-action@v4
        with:
          context: .
          push: false
          tags: ${{ vars.DOCKERHUB_USERNAME }}/solar-system:${{ github.sha }}

      - name: Test container locally
        run: |
          docker run --rm -d -p 3000:3000 \
            -e MONGO_URI=$MONGO_URI \
            -e MONGO_USERNAME=$MONGO_USERNAME \
            -e MONGO_PASSWORD=$MONGO_PASSWORD \
            ${{ vars.DOCKERHUB_USERNAME }}/solar-system:${{ github.sha }}
          sleep 5
          wget -qO- http://localhost:3000/live | grep "live"

      - name: Push to Docker Hub & GHCR
        uses: docker/build-push-action@v4
        with:
          context: .
          push: true
          tags: |
            ${{ vars.DOCKERHUB_USERNAME }}/solar-system:${{ github.sha }}
            ghcr.io/${{ github.repository_owner }}/solar-system:${{ github.sha }}

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Workflow in Action

When the workflow triggers, you’ll see Unit Testing and Code Coverage complete before Containerization runs:
The image shows a GitHub Actions workflow in progress, with unit testing and code coverage jobs completed, and containerization currently running.

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Troubleshooting: Permissions Error

If you omit permissions: packages: write, the push to GHCR will fail:
The image shows a GitHub Actions workflow interface with a failed "Containerization" job, specifically at the "Container Registry Push" step. Other steps like "Unit Testing" and "Code Coverage" are marked as successful.
Error message: 
#12 ERROR: denied: installation not allowed to Create organization package
By default, GITHUB_TOKEN only has read access to packages. You must explicitly set write permissions.
Refer to GitHub’s token permissions documentation:
The image shows a GitHub Docs page detailing permissions for the GITHUB_TOKEN, with a table listing different actions and their access levels. The sidebar includes navigation links related to GitHub Actions.
After updating the workflow, pushes succeed:
The image shows a GitHub Actions workflow interface with a focus on the "Containerization" job, displaying steps and logs related to setting up the job and permissions.

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Verifying the Failure Case

In earlier runs (without write access), you can inspect the setup logs for clues:
The image shows a GitHub Actions workflow interface with a failed "Containerization" job, displaying logs and details of the setup process.

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Using Your Published Image

Once the workflow finishes:
  1. Navigate to Packages → Container registry in your repository.
  2. You’ll see your Docker image listed under GHCR.
Pull your published image: 
docker pull ghcr.io/${{ github.repository_owner }}/solar-system:${{ github.sha }}
Use it as a base image in another Dockerfile: 
FROM ghcr.io/${{ github.repository_owner }}/solar-system:${{ github.sha }}
Congratulations! You’ve successfully built, tested, and pushed Docker images to both Docker Hub and GitHub Container Registry in a single GitHub Actions workflow.

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