If the base image Dockerfile has a VOUME /var/lib directive, then an image derived from the base image cannot do a RUN mkdir -p /var/lib/somedir

The mkdir command has no effect. I think it is convenient to have the base image export a VOLUME and the derived images can create their own structure without having to explicitly calling their own VOLUME.

As-is, the base image must not issue the VOLUME /var/lib or the derived images won't be able to create a directory in /var/lib