Docker Slim GitHub Action

This GitHub Action helps you to minify your container image, making it smaller and more secure. With this Action, you can reduce the size of your container image by up to 30x (and even more for compiled languages) without compromising its functionality.

What does this Action do?

This GitHub Action uses slimtoolkit/slim to minimize your container image. slim is an open-source tool that removes unnecessary files and libraries from your image, resulting in a smaller and more secure container.

Slim uses static and dynamic analysis techniques to identify the components of your image that are not needed at runtime. It also removes debug symbols, unused files, and libraries that are not required by your application, reducing the size of your image.

See their README for more information about how Slim works.

Setup

To use this GitHub Action, you will need to have the docker/login-action or docker/build-push-action set up in your workflow as well. These actions will allow you to execute Docker commands needed for this action to run successfully.

Usage

Example

Create a workflow file in your repository and add these steps to your job:

      # Build the Docker image first
      - uses: docker/build-push-action@v4
        with:
          push: false
          tags: ${{ github.repository }}:latest

      # Slim it!
      - uses: kitabisa/docker-slim-action@v1
        env:
          DSLIM_HTTP_PROBE: false
        with:
          target: ${{ github.repository }}:latest
          tag: "slim"

      # Push to the registry
      - run: docker image push "${{ github.repository }}" --all-tags

In this example, it will minify ${{ github.repository }}:latest as target and will create a slimmed version of the target image with the slim tag from the input (${{ github.repository }}:slim) then push the images to the registry.

Inputs

The following input actions are supported:

[!CAUTION] Enabling the overwrite option will result in the replacement of the target image (original) with its slimmed version, regardless of the tag input.

[!IMPORTANT] Please note that when you disable HTTP probing (either by setting DSLIM_HTTP_PROBE_OFF to true or DSLIM_HTTP_PROBE to false), it will effectively modify the behavior of the continue mode (if the DSLIM_CONTINUE_AFTER value is undefined) by imposing a timeout of 1 second. This adjustment occurs because, by default, when HTTP probes are disabled, the Slim's behavior will switch to 'enter' mode — and there is no way to interact with the temporary container created by Slim within the GitHub Action runner.

Outputs

To view the report results generated by the Slim build command, you can access the report property (Object) of the steps outputs context. Here's an example of how to access it: ${{ steps.<id>.outputs.report }}.

      # Slim it!
      - uses: kitabisa/docker-slim-action@v1
        id: slim
        env:
          DSLIM_HTTP_PROBE: false
        with:
          target: ${{ github.repository }}:latest

      # Dump the report
      - run: echo "${REPORT}"
        env:
          REPORT: ${{ steps.slim.outputs.report }}

License

The associated scripts and documentation in this project are released under the MIT License.

Binary used in this project include third party materials.