docker run -it -v /private/etc/passwd:/etc/passwd alpine sh
(not recommended for any actual use obviously)
Is there a particular case in which this failed for you? We'd appreciate a bug report on https://github.com/docker/for-mac/issues (or from the Docker for Mac GUI, just click on "Diagnose and Feedback") so we can chase down whatever issue you're having.
Yes, this use case, it happens on Windows and on Mac as well.
C:\Program Files\Docker\Docker\Resources\bin\docker.exe: Error response from daemon: oci runtime error: rootfs_linux.go:53: mounting "/var/lib/docker/aufs/mn
t/90d24356afdeb7b9ddad4b3b6903be92063151c33bf34f3d63ede464437060c6/cryptoservice/broker-config.yml" to rootfs "/var/lib/docker/aufs/mnt/90d24356afdeb7b9ddad4
b3b6903be92063151c33bf34f3d63ede464437060c6" caused "not a directory".
(I'm mounting broker-config.yml and that file is already present in the container. Most recent Docker for Win beta in this case, but getting the same on non-beta Docker for Mac.)
The error message specifically says "not a directory" and afaik you can't mount single files, only directories. I at least have never even thought of trying to mount individual files since the bind mounting functionality in Docker seems to always and everywhere have been described in a way that suggests that it's for mounting directories, not individual files.
