share images between host and child docker

Question

I read this article http://blog.docker.io/2013/09/docker-can-now-run-within-docker/ and I want to share images between my "host" docker and "child" docker. But when I run

sudo docker run -v /var/lib/docker:/var/lib/docker -privileged -t -i jpetazzo/dind

I can't connect to "child" docker from dind container.

     root@5a0cbdc2b7df:/# docker version
     Client version: 0.8.1
     Go version (client): go1.2
     Git commit (client): a1598d1
     2014/03/13 18:37:49 Can't connect to docker daemon. Is 'docker -d' running on this host?

How can I share my local images between host and child docker?

Answer 1

You shouldn't do that! Docker assumes that it has exclusive access to /var/lib/docker, and if you (or another Docker instance) meddles with this directory, it could have unexpected results.

There are multiple solutions, depending on what you want to achieve.

• If you want to be able to run Docker commands from within a container, but don't need a separate daemon, then you can share the Docker control socket with this container, e.g.:

  docker run -v /var/run/docker.sock:/var/run/docker.sock \
             -v /usr/bin/docker:/usr/bin/docker \
             -t -i ubuntu bash
  

• If you really want to run a different Docker daemon (e.g. because you're hacking on Docker and/or want to run a different version), but want to access the same images, maybe you could run a private registry in a container, and use that registry to easily share images between Docker-in-the-Host and Docker-in-the-Container.

Don't hesitate to give more details about your use-case so we can tell you the most appropriate solution!