docker-compose in docker-compose: Share network

Question

I am aware of sharing the docker socket by adding this volume /var/run/docker.sock:/var/run/docker.sock to the docker-compose file as proposed by Using Docker-in-Docker for your CI or testing environment?

I created this simple example/experiment setup to make it possible to start docker-compose in a docker-compose container, without sharing everything.

docker-compose.yml

services:
  manager:
    build:
      context: ./manager
    privileged: true

  ngnix:
    image: nginx:latest

manager/Dockerfile

FROM nginx:latest

RUN apt-get -y update 
  && apt-get install -y iputils-ping docker-compose

RUN mkdir /app
WORKDIR /app

COPY . ./

ENTRYPOINT ["/app/entrypoint.sh"]

CMD ["ping", "www.google.com"]

manager/entrypoint.sh

#!/bin/sh

set -e
service docker start
exec "$@"

manager/docker-compose.yml

services:
  foobar:
    image: ruby:latest

Possible command now would be: docker-compose up -d; docker-compose exec manager docker-compose run foobar /bin/bash

For now, I did not manage to share the docker-compose network between the host and the one on the manager. This, off course, is how docker is intended to work per design. Therefore after executing the command above executing ping ngnix from the foobar container will not work.

My question is: how can I make this work?

I tried adding network: hostto the manager/docker-compose.yml in different ways but that did not work, or I was too stupid to do it correct.

Answer 1

As David Maze points out possibly the only solution is to share the socket. More reading information on that here:

• Using Docker-in-Docker for your CI or testing environment?
• Docker in Docker?