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How-to: Access the Docker Daemon in a Codefresh build

Use case

The general and most common uses-cases that require access to the Docker Daemon are covered by Codefresh-provided native steps:

But there are still cases when you need direct access to the Docker Daemon in your steps, for example:

  • As part of your test-step you need to dynamically create new containers (e.g.: Testcontainers library)
  • You need to run a composition and dynamically add to that composition a new container you'll create
  • You need to send specific flags to your docker-build process

For all those cases (and any others), you're still able to access the Docker Daemon on a step of your build, by providing the correct configuration (and under certain circumstances).

Solution

There are two main options to access the Docker Daemon in a pipeline step:

  • In a freestyle step: using an image with Docker installed, and mounting the required volumes (the Docker socket). In Hybrid REs, these volumes are already mounted. You don't need to specify anything else.
  • In a composition step: same as with the freestyle option, you'll need to use an image with Docker installed in one of the composition-services. Also, you'll need to mount the corresponding volumes to that composition-service

In the following sections, we'll provide details on how to use each of the options described above.

Accessing the Docker Daemon in a freestyle step

The following snippet shows a step using this approach:

  docker_daemon_access:
    image: docker
    commands:
      - docker version
      - docker ps
      - docker run alpine ping 8.8.8.8 -c 4      
      - docker build -t your/image -f yourDockerfile .

Note 1: By default, and for security reasons, the Docker Daemon is not exposed to freestyle steps running on our SaaS environments. In other words, this approach cannot be used in our SaaS Runtime Environments.

Note 2: There's still a way to use this approach in a RE hosted by Codefresh. For this option, you'll need a dedicated Runtime Environment.

Note 3: This approach is usable by default in Hybrid REs (i.e.: Codefresh Runner REs). Since the REs is running in your infrastructure, access to the Docker Daemon in a freestyle step is enabled by default

Accessing the Docker Daemon in a composition step

The following snippet shows a step using this approach:

  docker_daemon_access:
    title: composition style step
    type: composition
    composition:
      version: '2'
      services:
        docker_compose:
          image: docker/compose
          command: sh -c "docker-compose --version"
          volumes: # Volumes required to run DIND and to mount your Repository
            - /var/run/docker.sock:/var/run/docker.sock
            - /var/lib/docker:/var/lib/docker
            - ${{CF_VOLUME_NAME}}:/codefresh/volume
    composition_candidates:
      test_service:
        image: docker
        command: docker ps
        volumes: # Volumes required to run DIND and to mount your Repository
          - /var/run/docker.sock:/var/run/docker.sock
          - /var/lib/docker:/var/lib/docker
          - ${{CF_VOLUME_NAME}}:/codefresh/volume

Note 1: This approach can be used in any kind of Runtime Environment: SaaS, Hybrid and on-prem

A similar implementation can be achieved using Service Containers:

  docker_daemon_access_serv_cont:
    image: alpine
    commands:
      - echo testing
    services:
      composition:
        my_service:
          image: docker
          command: docker ps
          volumes: # Volumes required to run DIND and to mount your Repository
            - /var/run/docker.sock:/var/run/docker.sock
            - /var/lib/docker:/var/lib/docker
            - ${{CF_VOLUME_NAME}}:/codefresh/volume

Notes

As mentioned at the beginning of this article, Codefresh covers the general cases where access to the Docker Daemon is required (building a Docker image, pushing a Docker image, etc). For all these common cases we encourage you to keep using our native steps. Since they'll provide different levels of optimization (e.g.: Codefresh-cache mechanism), also their usage is directly related to the level of traceability you will get (e.g.: the images you build in Codefresh using our docker-build step will be reflected in the images view and other dashboards we provide).

This way of directly accessing the Docker Dameon should be exclusively used for very specific use-cases.

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