How to enable buildx when using DinD?

[rolandjitsu]

I'm trying to implement a CI pipeline using Docker in Docker on Gitlab. And so far it seem to work, but I was wondering if there's a way to enable the buildx command for the child docker containers.

I can run docker buildx on the host, but the child docker containers don't seem to have this.

Do I need to manually download the buildx binary? If I do, where should it actually go as there's no home dir to move it to?

NOTE: I'm using the official docker image.

[tonistiigi]

If I do, where should it actually go as there's no home dir to move it to?

wdym? if you run the docker image as root then home dir is /root

[rolandjitsu]

@tonistiigi I'm not sure how Gitlab runs the image. But I'm going to try to download and install buildx into root and see if that works.

Tried the following:

image: docker:19.03.13-beta2
stage: build
variables:
  DOCKER_DRIVER: overlay2
  DOCKER_TLS_CERTDIR: "/certs"
  BUILDX_VERSION: v0.4.1
services:
  - name: docker:19.03.13-beta2-dind  
    command: ["--experimental"]
before_script:
  - apk add curl
  - mkdir -p /root/.docker/cli-plugins
  - curl -sSLo /root/.docker/cli-plugins/buildx https://github.com/docker/buildx/releases/download/$BUILDX_VERSION/buildx-$BUILDX_VERSION.linux-amd64
  - chmod +x /root/.docker/cli-plugins/buildx
  - docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
  - docker info
script:
  - docker buildx

But the buildx CLI cmd is still not available.

Eventually, after going through the README, I replaced buildx -> docker-buildx and that seems to work.

So for others stumbling into the same issue, the following should work:

image: docker:19.03.13-beta2
stage: build
variables:
  DOCKER_DRIVER: overlay2
  DOCKER_TLS_CERTDIR: "/certs"
  BUILDX_VERSION: v0.4.1
services:
  - name: docker:19.03.13-beta2-dind  
    command: ["--experimental"]
before_script:
  - apk add curl
  - mkdir -p ~/.docker/cli-plugins
  - curl -sSLo ~/.docker/cli-plugins/docker-buildx https://github.com/docker/buildx/releases/download/$BUILDX_VERSION/buildx-$BUILDX_VERSION.linux-amd64
  - chmod +x ~/.docker/cli-plugins/docker-buildx
  - docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
  - docker info
script:
  - docker buildx

[maniator]

This is one of the reasons I created a fork of the official docker image with one that has buildx built in https://hub.docker.com/r/maniator/dind-buildx

[tonistiigi]

Buildx is available in main docker image now

 docker run -it --rm --entrypoint=docker docker buildx --help