dcind (Docker-Compose-in-Docker) For Concourse

Alpine based image that lets you run Docker inside a Concourse task. Task must have privileged: true for Docker to start.

Release Pipeline

Usage

Use it in a task config:

image_resource:
  type: registry-image
  source:
    repository: taylorsilva/dcind

Pull it in as a resource to use as a task image:

resoures:
- name: dcind
  icon: docker
  type: registry-image
  source:
    repository: taylorsilva/dcind
    tag: latest

jobs:
...
  - get: dcind
  - task: doing-things
    image: dcind
    privileged: true

Run it locally on your machine:

$ docker run -it --privileged taylorsilva/dcind
Starting Docker...
waiting for docker to come up...
bash-5.1#

Tags

The Docker version is used to tag releases of the image. A new image is published everyday to ensure OS packages are up to date.

There are three kinds of tags being published, two rolling and one static.

Rolling Tags:

• latest: points to the latest image pushed which contains the latest versions of Docker and Docker-Compose
• DOCKER_VERSION: This tag is the docker version (e.g. 20.10.6) and is republished daily. Only the latest version of docker is republished. Older versions will become stale.

Static Tag:

• DOCKER_VERSION-YYYYmmdd: This tag is the docker version plus the date it was published. If you want to stay on a specific version of Docker + Docker-Compose then sticking to a particular daily build will meet your needs.

Example

Here is an example of a Concourse job that uses taylorsilva/dcind image to run a bunch of containers in a task, and then runs the integration test suite. You can find a full version of this example in the example directory.

Note that docker-lib.sh has bash dependencies, so it is important to use bash in your task.

- name: integration
  plan:
  - aggregate:
    - get: code
      params: {depth: 1}
      passed: [unit-tests]
      trigger: true
    - get: redis #a registry-image resource
      params:
        format: oci
    - get: busybox #a registry-image resource
      params:
        format: oci
  - task: Run integration tests
    privileged: true
    config:
      platform: linux
      image_resource:
        type: docker-image
        source:
          repository: amidos/dcind
      inputs:
      - name: code
      - name: redis
      - name: busybox
      run:
        path: bash
        args:
        - -cex
        - |
          source /docker-lib.sh
          start_docker

          # Strictly speaking, preloading of Docker images is not required.
          # However, you might want to do this for a couple of reasons:
          # - If the image comes from a private repository, it is much easier to let Concourse pull it,
          #   and then pass it through to the task.
          # - When the image is passed to the task, Concourse can often get the image from its cache.
          docker load -i redis/image
          docker tag "$(cat redis/image-id)" "$(cat redis/repository):$(cat redis/tag)"

          docker load -i busybox/image
          docker tag "$(cat busybox/image-id)" "$(cat busybox/repository):$(cat busybox/tag)"

          # This is just to visually check in the log that images have been loaded successfully
          docker images

          # Run the container with tests and its dependencies.
          docker-compose -f code/example/integration.yml run tests

          # Cleanup.
          # Not sure if this is required.
          # It's quite possible that Concourse is smart enough to clean up the Docker mess itself.
          docker volume rm $(docker volume ls -q)