How to Pull GCR Images from a GCE Instance through GitHub Actions: A Step-by-Step Guide

Are you tired of manually pulling GCR images from your GCE instances? Do you want to automate this process and make your life easier? Look no further! In this article, we’ll show you how to use GitHub Actions to pull GCR images from a GCE instance with ease.

What You’ll Need

To get started, you’ll need the following:

• A GCE instance with a GCR repository configured
• A GitHub repository with a GitHub Actions workflow file
• A basic understanding of GitHub Actions and YAML syntax

Step 1: Create a GCR Service Account and Generate a Key File

To authenticate with your GCR repository, you’ll need to create a service account and generate a key file. Follow these steps:

1. Go to the Google Cloud Console and navigate to the IAM & Admin page
2. Click on “Service accounts” and then click on “Create service account”
3. Choose “Furnish a new private key” and select “JSON” as the key type
4. Save the generated key file to a secure location

Keep the key file safe, as it contains sensitive information about your GCR repository.

Step 2: Create a GitHub Actions Workflow File

Create a new file in your GitHub repository’s `.github/workflows` directory called `pull-gcr-image.yml`. This file will contain the instructions for GitHub Actions to follow.

name: Pull GCR Image

on:
  push:
    branches:
      - main

jobs:
  pull-image:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v2

      - name: Authenticate with GCR
        uses: google-github-actions/login@v1
        with:
          credentials: ${{ secrets.GCR_SA_KEY }}

      - name: Pull GCR image
        run: |
          docker pull gcr.io/[PROJECT-ID]/[IMAGE-NAME]:[TAG]
          docker tag gcr.io/[PROJECT-ID]/[IMAGE-NAME]:[TAG] [NEW-IMAGE-NAME]:[NEW-TAG]

      - name: Push image to Docker Hub
        uses: docker/login-action@v1
        with:
          username: ${{ secrets.DOCKER_USERNAME }}
          password: ${{ secrets.DOCKER_PASSWORD }}

      - name: Push image
        run: |
          docker push [NEW-IMAGE-NAME]:[NEW-TAG]

Let’s break down what each step does:

• The `checkout` step retrieves the code in your repository.
• The `Authenticate with GCR` step uses the `google-github-actions/login` action to authenticate with your GCR repository using the service account key file.
• The `Pull GCR image` step pulls the GCR image using the `docker pull` command.
• The `Push image to Docker Hub` step logs in to Docker Hub using the `docker/login-action` action.
• The `Push image` step pushes the pulled image to Docker Hub using the `docker push` command.

Step 3: Store Your GCR Service Account Key File and Docker Credentials as Secrets

To keep your credentials secure, you’ll need to store them as secrets in your GitHub repository. Follow these steps:

1. Go to your GitHub repository’s settings page and click on “Actions” in the left-hand menu
2. Click on “Secrets” and then click on “New secret”
3. Enter `GCR_SA_KEY` as the name and paste the contents of your GCR service account key file as the value
4. Click “Add secret” to save the secret
5. Repeat the process for your Docker credentials, using `DOCKER_USERNAME` and `DOCKER_PASSWORD` as the names

By storing your credentials as secrets, you can keep them secure and avoid hardcoding them in your workflow file.

Step 4: Trigger the GitHub Actions Workflow

To trigger the workflow, simply push changes to your `main` branch. You can do this by making a small change to a file, such as adding a newline character, and then committing and pushing the changes.

Once the workflow is triggered, GitHub Actions will pull the GCR image, authenticate with your GCR repository, and push the image to Docker Hub.

Troubleshooting Common Issues

If you encounter any issues during the workflow, here are some troubleshooting tips:

Error	Solution
Error authenticating with GCR	Check that your service account key file is correct and that you’ve stored it as a secret in your GitHub repository.
Error pulling GCR image	Check that your GCR repository is configured correctly and that you’ve entered the correct image name and tag in your workflow file.
Error pushing image to Docker Hub	Check that your Docker credentials are correct and that you’ve stored them as secrets in your GitHub repository.

By following these steps and troubleshooting common issues, you should be able to successfully pull GCR images from a GCE instance using GitHub Actions.

Conclusion

In this article, we’ve shown you how to use GitHub Actions to pull GCR images from a GCE instance. By automating this process, you can save time and reduce the risk of errors. Remember to keep your credentials secure by storing them as secrets in your GitHub repository.

With this workflow in place, you can focus on more important tasks and let GitHub Actions handle the heavy lifting.

Happy automating!

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