README.md

Creating and publishing a docker image to ghcr.io

1. Create a new repsitory container-demo and add a new file namend Dockerfile (without extension). Add the following content:

   FROM alpine
   CMD ["echo", "Hello World!"]

   If you want to test this locally, clone your repository and change directory to it. Build and run the image. The output is Hello World!:

   $ docker build -t container-demo .
   $ docker run --rm container-demo
   > Hello World!

2. Create a workflow file .github/workflows/release-container.yml with the following content and commit/push it to your repository:

   name: Publish Docker image
   
   on:
     release:
       types: [published]
   
   env:
     REGISTRY: ghcr.io
     IMAGE_NAME: ${{ github.repository }}
   
   jobs:
     build-and-push-image:
       runs-on: ubuntu-latest
       permissions:
         contents: read
         packages: write
   
       steps:
         - name: Checkout repository
           uses: actions/checkout@v2
   
         - name: Log in to the Container registry
           uses: docker/[email protected]
           with:
             registry: ${{ env.REGISTRY }}
             username: ${{ github.actor }}
             password: ${{ secrets.GITHUB_TOKEN }}
   
         - name: Extract metadata (tags, labels) for Docker
           id: meta
           uses: docker/[email protected]
           with:
             images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
   
         - name: Build and push Docker image
           uses: docker/[email protected]
           with:
             context: .
             push: true
             tags: ${{ steps.meta.outputs.tags }}
             labels: ${{ steps.meta.outputs.labels }}

3. The workflow gets triggered if you publish a new release. Navigate to Source and click on Create a new release:

   

4. Enter v1.0.0 as a tag and hit enter:

   

5. Enter a name for the release and publish it:

   

6. If the workflow has completed you can see the container-demo package under Code | Packages. Click on it to see details:

   

7. To test the image, pull it from the library and run it:

   $ docker pull ghcr.io/<github-user>/container-demo:latest
   $ docker run  --rm ghcr.io/<github-user>/container-demo:latest
   > Hello World!