# do everything you need as root (maybe installing some dependencies)

# create a non-root user
RUN addgroup --gid 1001 appgroup
RUN useradd --create-home --gid 1001 --uid 1001 appuser

# set new workdir
WORKDIR /home/appuser

# activate non-root user
USER appuser

# copy new files with correct permissions
COPY --chown=appuser:appgroup app.py .

# set ownership, recursive, userid:groupid
chown -R 1001:1001 /data/myvolume

# full access to members of the group (read+write+execute)
chmod 775 /data/myvolume

# inherit group ownership
chmod g+s /data/myvolume

# Add your host user to the group allowing you to conveniently work with the directory from your host machine
adduser <your-username> 1001