Docker in Docker setup with VSCode Dev Containers: How to access running docker containers on the host machine

Question

I am using VSCode dev containers as a golang development environment using the default golang image. I added the following snippet to the Dockerfile to download the Docker CLI:

# Add Docker
RUN apt-get update \
    && apt-get -y install --no-install-recommends \
    apt-transport-https \
    ca-certificates \
    curl \
    gnupg2 \
    software-properties-common \
   && curl -fsSL https://download.docker.com/linux/debian/gpg | sudo apt-key add - \
   && add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/debian $(lsb_release -cs) stable" \
   && apt-get update \
   && apt-get -y install --no-install-recommends docker-ce \
   # Clean up
   && apt-get autoremove -y \
   && apt-get clean -y \
   && rm -rf /var/lib/apt/lists/*

# Symlink docker socket
RUN ln -s "/var/run/docker-host.sock" "/var/run/docker.sock"

And added the following mount to the mounts in the devcontainer.json:

"mounts": ["source=/var/run/docker.sock,target=/var/run/docker-host.sock,type=bind"]

This does allow me to access the Docker Daemon running on my local machine. However if I spin up a postgres container:

docker run -e POSTGRES_USER=user -e POSTGRES_PASSWORD=password -p 5432:5432 -d postgres:9

I can connect to it from my local machine but not from inside the Dev Container. Is there any way to specify the networking option when spinning up a Dev Container (e.g. allow host networking or create a shared network)? Or is there another way I can connect to another running docker container from inside my Dev Container?

Michigan · Accepted Answer · 2023-03-04 00:10:43Z

6

If you prefer to remain in the docker-from-docker approach, different from the alternative solution called docker-in-docker proposed by wanheda, you can connect the dev container to your host ports.

Assuming that you preserve your host's docker socket mount:

"mounts": ["source=/var/run/docker.sock,target=/var/run/docker-host.sock,type=bind"]

you can add this line to your .devcontainer/devcontainer.json file:

"runArgs": ["--add-host=host.docker.internal:host-gateway"]

In this way, you give the dev container a way to reach your host's address by just using the host name host.docker.internal

I suggest you to read this article, because docker-from-docker has the advantage of lower overhead but it has also some bind mounting limitations.

Use Docker or Kubernetes from a container

answered Mar 4, 2023 at 0:10

Michigan

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Jethro · Accepted Answer · 2024-10-31 12:29:59Z

6

You can add the following line to your .devcontainer.json and it will set it up for you:

    // Allow the devcontainer to run host docker commands, see https://github.com/devcontainers/templates/tree/main/src/docker-outside-of-docker
    "features": {
        "ghcr.io/devcontainers/features/docker-outside-of-docker:1": {}
    }

This uses "Devcontainer Features", which add common language/tool/CLI to a development container. You will have the docker CLI installed, and it will point to the existing docker daemon on your host.

answered Oct 31, 2024 at 12:29

Jethro

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wanheda · Accepted Answer · 2020-08-15 21:03:59Z

2

This answer is only good if you are able to run the other container within your Dev Container.

You can setup your Dev Container with docker-in-docker. This way you can run docker containers within your Dev Container (and thus the networking will work). The Dockerfile would look like this. There's a medium article that explains this well.

    FROM docker:19.03.12-dind-rootless@sha256:7606255ca83a7f516fae1b78299b79774f1f798ba9fc792a7231e7b0967ddb05
    USER root

    # Change this with your dependencies, note that this uses alpine apk
    RUN apk add git bash curl make vim go

    USER rootless
    ENV DOCKER_HOST=unix:///var/run/user/1000/docker.sock

answered Aug 15, 2020 at 21:03

wanheda

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1 Comment

gkephorus Over a year ago

Remark about the required changes to .devcontainers/devcontainer.json: Update (2021-03-04): as of 20.10.x, --experimental is no longer required (moby/moby#40759) (See Add experimental "rootless" dind variant)

doublethink13 · Accepted Answer · 2022-11-01 16:20:51Z

0

Assuming I understood you problem correctly, you want to:

Use docker CLI in you devcontainer
Devcontainer is actually using the host's docker socket
Devcontainer spins up a Postgres container
Devcontainer should be able to communicate with the Postgres container directly

Assuming a default setup, both your devcontainer container and your Postgres container should live in the same network. If they do, the devcontainer can communicate with Postgres using the Postgres container's IP:port. You can use docker inspect command to find that out.

answered Nov 1, 2022 at 16:20

doublethink13

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