I am new to Docker and using the Cloud/Hub infrastructure connected to GitHub for automated builds. I found that after following the online documentation for Dockerfiles, and setting up multi stage builds, that COPY --chown is not supported in Docker Cloud.
On further investigation, Docker Cloud is running a version of docker three or four releases older than the one I downloaded to my Mac (even when I select “Edge” in the Docker Cloud options) so is missing this feature. As a consequence my images are much larger because I need to run a manual chown command after the copy which creates a useless additional layer.
I attempted to address this by then squashing the image of the final build stage using a custom build hook and running “docker build … --squash .” but then I find that the engine running in Docker Cloud does not have the so-called experimental feature of --squash enabled.
I would be grateful to know when these features (or a general upgrade) will be delivered to Docker Cloud. I would like to become a paying customer once things are working smoothly.