Run docker with bind-mount pointing to non-existent host folder: Where is the data?

Question

I run a docker image with a bind-mount pointing to a non-existing host directory. The docker image then created data into that volume, wherever it may be. The data is accessible on every docker run.

If I then create that missing host directory and re-run the container, the new host folder is used, creating new data. When I remove it again, the old data shows up again.

I have done docker volume prune and have nothing coming up with docker volume ls.

When I remove the host directory again, then also remove the container and the image, then re-run the docker container, I can see the image getting re-downloaded, but then the old data is still there.

How do I identify the location of the old data and interact with it?

(This is on MacOS)

Answer 1

I have been using Linux and since Docker volume caches the data, it is merely persistent until you remove it manually. In RHEL8, /var/lib/docker/volumes/, this is where all the volume mounts are stored. You can check if the same directory exists in MacOS. I haven't use Mac but I hope this helps.