USAGE.md

Usage

Here you can find verbose examples of configuring the action to do what you want.

Changing error level

In many cases, the hadolint "warning" error level can be seen as somewhat verbose. You can manage this by changing the error level, which tells CI to fail or pass depending on what output is given by hadolint. Passing -1 will only generate output but never fail CI which can be useful if you chain actions as dependencies.

name: Lint
on: pull_request

jobs:
  hadolint:
    runs-on: ubuntu-22.04
    name: Hadolint
    steps:
      - uses: actions/checkout@v4
      - uses: jbergstroem/hadolint-gh-action@v1
    with:
      # ignore warnings (but still fail on errors) from hadolint
      error_level: 1

Run on certain Dockerfiles

By default, hadolint only looks for a Dockerfile in the same directory you would invoke it from - most often the root of your repository.

Depending on what your you case, you can tailor either when the action should run or what files you want to pass to it.

Only run if there are changes to a Dockerfile

If you want to control when you want hadolint to fire, you can tell github actions when it should run by using the on directive; specifically paths or ignore-paths.

In this example, the job will only run if there is a change to Dockerfile in the commits found in said PR:

name: Lint
on:
  pull_request:
    paths:
      - "./Dockerfile"

jobs:
  hadolint:
    runs-on: ubuntu-22.04
    name: Hadolint
    steps:
      - uses: actions/checkout@v4
      - uses: jbergstroem/hadolint-gh-action@v1

A similar path pattern could be looking for changes in any Dockerfile:

name: Lint
on:
  pull_request:
    paths:
      - "**/Dockerfile"
# job goes here

Pass multiple Dockerfiles to process

As found in the parameters, you can pass multiple files for processing:

name: Lint
on: pull_request

jobs:
  hadolint:
    runs-on: ubuntu-22.04
    name: Hadolint"
    steps:
      - uses: actions/checkout@v4
      - uses: jbergstroem/hadolint-gh-action@v1
    with:
      dockerfile: "Dockerfile path/to/my/other/Dockerfile"

Only pass Dockerfiles that are changed in the PR

In certain use-cases – for instance when you have a monorepo with a lot of Dockerfiles; you may only want to pass the files that are changed in the PR. This would make processing faster.

To achieve this, you first need to find what files are changed and extract the relevant files as a separate step in your job. Thankfully, there's already an action for that.

name: Lint
on: pull_request

jobs:
  hadolint:
    runs-on: ubuntu-22.04
    name: Hadolint
    steps:
      - uses: actions/checkout@v4
      - name: Get changed files
        id: changed-files
        uses: tj-actions/changed-files@v42
        with:
          # Pass what names/filters you want to catch
          files: |
            **/Dockerfile
          separator: " "
      # Only run if expected files are changed and pass these as input
      - uses: jbergstroem/hadolint-gh-action@v1
        if: steps.changed-files.outputs.any_changed == 'true'
        with:
          dockerfile: "${{ steps.changed-files.outputs.other_changed_files }}"