Docker Slim

Status:

A Docker image containing Docker Slim for use with CI & CD pipelines.

Installing Docker Slim is noted as a series of commands which xan be run as part of your pipeline. However, to save resources, time and a point of failure (if the machine at the time cannot execute the curl command) we thought it efficient to have it packaged ready to go.

Usage

This image is designed to be used as the base image for a job within a CI/CD pipeline.

We only have experience with Gitlab and Github, so PRs with examples for other tools would be appreciated.

Gitlab

It is worth running docker-slim locally to ensure you get the parameters you need, some useful ones i've found:

• --http-probe="false" combined with --continue-after="1" is handy if your docker image doesn't expose ports
• --include-path="/usr/local/bin/docker-slim" - makes sure your custom scripts or files & folders are definitely included

slim:image:build:
  # Use the image with built-in docker slim
  image: ghcr.io/liquidlight/docker-slim:1.40.11
  # Specify input and output names
  variables:
    IMAGE_NAME: "$CI_REGISTRY_IMAGE:$CI_COMMIT_BRANCH"
    SLIM_IMAGE_NAME: "$IMAGE_NAME-slim"
  # Login to the registry
  before_script:
    # Login to our registry
    - echo "$CI_REGISTRY_PASSWORD" | docker login $CI_REGISTRY --username $CI_REGISTRY_USER --password-stdin
  script:
    # Ensure that the fat image is cached locally
    - docker pull $IMAGE_NAME
    # Note regarding parameters: "--target" is the input, "--tag" is the output
    - >
      docker-slim build
      --target="$IMAGE_NAME"
      --tag="$SLIM_IMAGE_NAME"

    # Push the slimmer image
    - docker push $SLIM_IMAGE_NAME

Github

Note: We haven't properly worked out how to use our image on Github Actions, so for now, the Docker Slim GitHub Action is available.

There is an example in this very repository.

- name: Make a Slim image
  uses: kitabisa/docker-slim-action@v1
  env:
    DSLIM_HTTP_PROBE: false
  with:
    target: ${{ env.IMAGE_NAME }}
    tag: "${{ env.DOCKER_SLIM_VERSION }}-slim"

  # Push to the registry
  - run: docker push ${{ env.IMAGE_NAME }}-slim