Docker on Windows10 home - inside docker container connect to the docker engine

Question

When creating a Jenkins Docker container, it is very useful to able to connect to the Docker daemon. In that way, I can start docker commands inside the Jenkins container.

For example, after starting the Jenkins Docker container, I would like to 'docker exec -it container-id bash' and start 'docker ps'.

On Linux you can use bind-mounts on /var/run/docker.sock. On Windows this seems not possible. The solution is by using 'named pipes'. So, in my docker-compose.yml file I tried to create a named pipe.

version: '2'
services:
  jenkins:
    image: jenkins-docker
    build:
      context: ./
      dockerfile: Dockerfile_docker
    ports:
      - "8080:8080"
      - "50000:50000"
    networks:
      - jenkins
    volumes:
      - jenkins_home:/var/jenkins_home
      - \\.\pipe\docker_engine:\\.\pipe\docker_engine
      # - /var/run/docker.sock:/var/run/docker.sock
      # - /path/to/postgresql/data:/var/run/postgresql/data
      # - etc.

Starting docker-compose with this file, I get the following error:

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

How can I setup the docker-compose file so that I can use the docker.sock (or Docker) inside the started container?

On Linux you can use something like volumes: /var/run/docker.sock:/var/run/docker.sock. This does not work in a Windows environment. When you add this folder (/var) to Oracle VM Virtualbox, it won't get any IP forever. And on many posts

Windows10 not use mobylinux vm? You setup your own virtual machine as host in virtualbox? — atline
It looks that installing an linux /ubuntu VM is the best solution. I will start experimenting with it. — tm1701

Paul Rey Paul Rey · Accepted Answer · 2018-09-07T08:11:21

You can expose the daemon on tcp://localhost:2375 without TLS in the settings. This way you can configure Jenkins to use the Docker API instead of the socket. I encourage you to read this article by Nick Janetakis about "Understanding how the Docker Daemon and the Docker CLI work together".

And then there are several Docker plugins for Jenkins that allows this connection:

Also, you can find additional information in the Docker plugin documentation on wiki.jenkins.io:

def dockerCloudParameters = [
  connectTimeout:   3,
  containerCapStr:  '4',
  credentialsId:    '',
  dockerHostname:   '',
  name:             'docker.local',
  readTimeout:      60,
  serverUrl:        'unix:///var/run/docker.sock', // <-- Replace here by the tcp address
  version:          ''
]

EDIT 1:

I don't know if it is useful, but the Docker Daemon on Windows is located to C:\ProgramData\docker according to the Docker Daemon configuration doc.

EDIT 2:

You need to say explicitly the container to use the host network because you want to expose both Jenkins and Docker API. Following this documentation, you only have to add --network=host (or network_mode: 'host' in docker-compose) to your container/service. For further information, you can read this article to understand what is the purpose of this network mode.

Docker on Windows10 home - inside docker container connect to the docker engine

2 Answers