Migrating my Docker images to the GitHub Container Registry

Now that my look simple, but, I named each of the workflows after the folder where the Dockerfile is hosted within my repo, this meant that I could use the `${{ github.workflow }}` variable within the job definitions so I didn't have to hardcode anything outside of the following:

```bash frame="terminal" title="Github Action"
``` yaml
on:
  push:
    branches: master
    paths:
      - '!**'
      - 'ab/**'

This section defines when the workflow should be triggered, here I am doing it whenever the main branch is pushed to — but only if any of the files in the `ab` folder changes. To do this I am using two paths, the first `!**` tells the workflow to ignore all changes to everything apart from the include folder which is defined as `ab/**`, unfortunately I can't use the `${{ github.workflow }}` here as at this point in the workflow the it hasn't been started so I can use variables meaning I have to hardcode the path.

Moving on to the actual build, there is a single job called `login-build-and-push`, as you may have guessed - this does all of the work:

```bash frame="terminal" title="Github Action"
``` yaml
jobs:
  login-build-and-push:
    runs-on: ubuntu-latest

The first step is common to all workflows and checks out the repo:

```bash frame="terminal" title="Github Action"
``` yaml
      -
        name: Checkout
        uses: actions/checkout@v2

The next step does the setup of Docker Buildx using the [action provided by Docker](https://github.com/docker/setup-buildx-action) themselves:

```bash frame="terminal" title="Github Action"
``` yaml
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v1
        with:
          driver-opts: image=moby/buildkit:master

“Docker Buildx” you might be thinking to yourself, what's that? This is a Docker CLI plugin which extends the build functionality of Docker using BuildKit, it introduces the following features:

- Full BuildKit capabilities with container driver
- Multiple builder instance support
- Multi-node builds for cross-platform images
- Compose build support
- High-level build constructs (bake)
- In-container driver support (both Docker and Kubernetes)

The reason why I am using it as I want to tag each image twice, once with `latest` and also once with the build date and time. There is a known issue where you will receive an **Unexpected status: 401 Unauthorized** error if you try and push more than one tag which we are doing in step #5.

In the next step I am getting the current date and time, then setting it as an output variable so I can use it on step #5:

```bash frame="terminal" title="Github Action"
``` yaml
      -
        name: Get current date
        id: date
        run: echo "::set-output name=date::$(date +'%Y%m%d%H%M')"

Now we are at the point where we are ready to login to the GitHub Container Registry service:

```bash frame="terminal" title="Github Action"
``` yaml
      -
        name: Login to the GitHub Container Registry
        uses: docker/login-action@v1
        with:
          registry: ghcr.io
          username: ${{ github.repository_owner }}
          password: ${{ secrets.GHCR_TOKEN }}

As you can see, I am logging to `ghcr.io`, which is the registry URL, as me using the `${{ github.repository_owner }}` variable. The password is a Personal Access Token (PAT) which has the following permissions:

- delete:packages
- read:packages
- write:packages
- repo

The token is then stored in an encrypted secret called `GHCR_TOKEN`. For details on how to create a PAT click [here](https://docs.github.com/en/free-pro-team@latest/github/authenticating-to-github/creating-a-personal-access-token) and for more encrypted secrets see [here](https://docs.github.com/en/free-pro-team@latest/actions/reference/encrypted-secrets).

Now that I am logged in I can build and push my the two tagged images using step #5:

```bash frame="terminal" title="Github Action"
``` yaml
      -
        name: Build and push image
        id: docker_build
        uses: docker/build-push-action@v2
        with:
          push: true
          context: ./${{ github.workflow }}/
          file: ./${{ github.workflow }}/Dockerfile
          tags: |
            ghcr.io/${{ github.repository_owner }}/${{ github.workflow }}:latest
            ghcr.io/${{ github.repository_owner }}/${{ github.workflow }}:${{ steps.date.outputs.date }}

This is where the `${{ github.workflow }}` variable comes into play, here I am using to define both the working directory (`context`) and also the path to the Dockerfile (`file`) as well as in combination with the `${{ github.repository_owner }}` variable to generate the two tags I want to push.

Once pushed, the final step runs and this just outputs some images on the image which has just been pushed:

```bash frame="terminal" title="Github Action"
``` yaml
      -
        name: Image digest
        run: echo ${{ steps.docker_build.outputs.digest }}

After checking in the changes it triggered the build as expected and you see the output below:

<Img src="/assets/2020-09-27-migrating-my-docker-images-to-the-github-container-registry/images/01.png" alt="graphical user interface, text" />

Once pushed I was able to run Apache Bench by running the following commands:

```bash frame="terminal" title="Docker"
``` bash
docker run --link=web ghcr.io/russmckendrick/ab ab -k -n 10000 -c 16 http://web/

Running the containers

<Img src="/assets/2020-09-27-migrating-my-docker-images-to-the-github-container-registry/images/02.png" alt="text" />

I then repeated this process for the rest of my images, you can find the full repo at [https://github.com/russmckendrick/docker/](https://github.com/russmckendrick/docker/) with the workflow files at [https://github.com/russmckendrick/docker/tree/master/.github/workflows](https://github.com/russmckendrick/docker/tree/master/.github/workflows) and finally, the resulting images are at [https://github.com/russmckendrick?tab=packages](https://github.com/russmckendrick?tab=packages).

For more details on the changes to Docker Hub see the following blog posts:

- [https://www.docker.com/blog/scaling-dockers-business-to-serve-millions-more-developers-storage/](https://www.docker.com/blog/scaling-dockers-business-to-serve-millions-more-developers-storage/)
- [https://www.docker.com/blog/scaling-docker-to-serve-millions-more-developers-network-egress/](https://www.docker.com/blog/scaling-docker-to-serve-millions-more-developers-network-egress/)

The announcement for GitHub Container Registry is at:

- [https://github.blog/2020-09-01-introducing-github-container-registry/](https://github.blog/2020-09-01-introducing-github-container-registry/)

Finally, Mastering Docker — Fourth Edition:

<Img src="/assets/2020-09-27-migrating-my-docker-images-to-the-github-container-registry/images/03.png" alt="diagram" />

This is available from [Packt Publishing](https://www.packtpub.com/product/mastering-docker-fourth-edition/9781839216572).