I actually have a problem with a Dockerfile from https://github.com/asciimoo/searx (commit 6a158ca2d2c5fdec597f1025c58fad90a57312dc). There the code
COPY requirements.txt .
creates a “Not a directory” error with my btrfs based docker system. The developer of this tool has no problems with overlay filesystem. Are there known differences between btrfs, aufs, or overlay?