Allow to easily configure the containerd snapshotter with dind

[victornoel]

Hi,

I am using docker:25-dind in my Gitlab CI pipeline to build images (following this guide: https://docs.gitlab.com/ee/ci/docker/using_docker_build.html#use-docker-in-docker) and it is not possible in this situation to add or modify files from dind.

I would like to be able to use this feature: https://docs.docker.com/storage/containerd/#enable-containerd-image-store-on-docker-engine but there is no option for dockerd to enable the feature.

For now, I found a workaround by setting the environment variable TEST_INTEGRATION_USE_SNAPSHOTTER, which is originally how the moby project enable the feature when running their integration test 🙃 I would like instead to have an official way of doing that, either by improving the dind image, or if you tell me it's not possible, I will create an issue in the moby repository.

[tianon]

I totally agree: https://github.com/tianon/dockerfiles/blob/d3347e43ce001c98954b38fef5d894cc77742842/docker-master/Dockerfile.containerd 😭
(for my personal tianon/docker-master images, I maintain a whole second Dockerfile just to enable the containerd snapshotter correctly 😅)

@thaJeztah do you know if there's already an open issue for enabling "features" via flags to dockerd? 👀