Is docker build --check used to validate Dockerfiles and check for warnings?

[johnthagen]

I'd like to ensure that my Dockerfile does not have any warnings and that it's validated in CI. If I use a simple job such as:

  container:
    runs-on: ubuntu-24.04
    steps:
      - name: Build Container Image
        uses: docker/build-push-action@v6
        with:
          push: false

Will this fail if docker build --check fails? I don't see any documentation in the README about if lint warnings are checked. I think the documentation could be improved here.

If they aren't checked, I'd propose a new

        with:
          checked: true

flag so that users can lint their Dockerfiles using this action in CI.

References

• https://docs.docker.com/reference/build-checks/
• https://docs.docker.com/build/checks/

[mschoettle]

You can use the input call and pass check to it.

https://github.com/docker/build-push-action?tab=readme-ov-file#inputs

[johnthagen]

@mschoettle So would this look like:

  container:
    runs-on: ubuntu-24.04
    steps:
      - name: Lint Dockerfile
        uses: docker/build-push-action@v6
        with:
          call: check

If I want to check and then actually build the container, would the most concise way of expressing this be the following? (i.e., I need to duplicate and have two separate docker/build-push-action@v6 steps?

  container:
    runs-on: ubuntu-24.04
    steps:
      - name: Lint Dockerfile
        uses: docker/build-push-action@v6
        with:
          call: check
    steps:
      - name: Build Container Image
        uses: docker/build-push-action@v6
        with:
          push: false

[crazy-max]

We have docs for using Build checks in GHA: https://docs.docker.com/build/ci/github-actions/checks/

[mschoettle]

I created #1361 to add this to the README in the examples section.

[johnthagen]

Perfect, yes I was going to recommend adding it to the README for greater visibility. Thanks.