Docker - Exposing container directories to host directories without obscuring original contents

Question

I am still relatively new to Docker, so I haven't quite figured out all the nuances yet, so forgive me if this has already been resolved elsewhere.

I would like to share files between the container and the host.
So far I have been using volumes, and mounting a specific host directory to a container directory - but this presents an issue in that, if the host directory is messed around with, these changes are also present in the container.

Another problem I am experiencing is that if the host directory is empty, and is mounted to a pre-existing directory on the container, then the contents of the directory are made invisible. I do understand that this behaviour is consistent with mounting, so I know this is not technically an issue.

But I wonder if it would be possible to set up a volume, or an alternative solution, that:

• firstly cannot be edited on the host side,
• and secondly allows for the host directory contents to be merged with the container's directory?

Answer 1

I wonder if it would be possible to set up a volume, or an alternative solution, that

firstly cannot be edited on the host side,

That would be a data volume container (with docker create on an image with a VOLUME directive)

and secondly allows for the host directory contents to be merged with the container's directory?

Not that I know of. You would have to do some kind of copy on startup.