Single file volume mounted as directory in Docker

Question

Docker documentation says that it\'s possible to mount a single file into a Docker container:

The -v flag can also be used to mount a single file - in

Answer 1

I spent a bit fighting with and diagnosing this issue running docker on Windows. This could also effect people running on Mac OSX, so I add an answer here for people possibly having an issue in those environments as my search brought me to this place and to add an explanation of what appears to be happening in docker.

In Windows or Mac OSX your docker is actually running in a boot2docker VM and only the users directory is actually shared by default. On Windows, this user directory is shared as /c/Users/, however in the MinGW shell shipped with Docker Machine, the drive can be accessed as /C or /c, so this can drive you nuts if you forget the docker commands are actually running against the boot2docker VM and your file paths have to exist on the boot2docker VM and be specified in the manner that they exist there because what appears to be occurring in docker is that instead of giving a warning or error that the directory/file does not exist, docker silently creates the specified source as a directory in the boot2docker VM so there is no ready output to indicate that you are doing anything incorrectly.

So, as in the answer above, if your file is mounting as a directory, then check that you are providing an absolute path. For Windows and Mac OSX check that the absolute path that you are mounting exists in your boot2docker VM.