How do I attach to intermediate docker container when building with buildkit

Question

I recently heard about Buildkit and have been trying to use it with Docker.

I'm using DOCKER_BUILDKIT=1 docker build . -t experimental to build my Dockerfile.

My Dockerfile doesn't build properly because of some missing dependant packages.

What I want to do is to attach to the last working intermediate container and fix the problem with say, apt tools.

When building without Buildkit, this would have been possible with the hash values of intermediate containers from the terminal output.

However, the output from Buildkit is not providing me such values. So, is there any way for me to access them?

Thanks in advance.

Answer 1

I think it is not possible at the moment see buildkit/issue#1472.

But BuildKit still caches all layers so you could use a work around.

• Inspecting the image before the failing RUN command, comment out the failing and all subsequent RUN commands. Rerun docker build and then do docker run to inspect the image.

• Inspecting the image after the failing RUN command, add || true at the end of your RUN command to force the command to succeed. Rerun docker build and then do docker run to inspect the image.