Add Docker on Docker shim to docker-outside-of-docker

[felipecrs]

As an avid user of Docker on Docker (or as you call, Docker outside of Docker), I figured that not being able to handle volume mounts within the container is unnaceptable. That's why I built the Docker on Docker shim, which is a transparent shim that translates paths within the container to their correct counterparts on the host.

Apart from just devcontainer's needs, I built the tool for some business use cases as well. For example, to have it packed in a CI/CD pipeline to allow running workload within containers, or to have a tool that ships as a container but needs to spawn more containers within it, without the overhead of running a full Docker daemon and the --privileged flag.

I have been testing internally it for almost an year by now in production, and I believe it has matured enough to be shipped by this feature by default. It is also very well tested.

When useDockerOnDockerShimAsDocker is enabled, calling docker from within the container will actually call the shim. Otherwise, the shim is available as the dond command.

It is a big improvement for the feature, in my opinion.

Please let me know your thoughts.

TODOs

• Add tests for the feature

[samruddhikhandale]

Hi 👋

We appreciate your enthusiasm and contribution for adding docker-on-docker-shim to the first party Feature. However, as https://github.com/felipecrs/docker-on-docker-shim is hosted on a personal repository, I'm afraid we won't be able to accept this contribution. We rely on first party/official releases of tools/artifacts which are trusted by the community and are happy to add it to their dev container without second thoughts.

@felipecrs Have you thought of publishing it as new Feature which you could share with the community? The devcontainers/feature-starter repo has more guidance on self authoring them.

Once you've self authored and if you'd like to share it with the community, we'd recommend adding it to the index. It will make them visible in our supporting tools (like https://containers.dev/templates, Dev Containers Extension, GitHub Codespaces etc).

Feel free to ask any questions/queries along the way, feedbacks are welcome too!

Looping in @bamurtaugh (whose a PM on our team) to share her thoughts as well, thanks!

[felipecrs]

Hi @samruddhikhandale, super understand. I will try creating a devcontainer feature for it too. Thanks for the advice.