Log what is happening during Image build


I have already post a request some weeks ago that handels a problem with the initialization from a solr image and a additonaly executed copy command.

FROM solr:7.7.2
COPY /extensions /opt/solr/server/solr/mycores
RUN ["bash", "-c", "precreate-core MyCore"] # executed only once during image build
ENTRYPOINT ["bash", "-c", "exec solr -f"] # executed every time the container starts

Well, I still have a problem. If I take a look at the container using its cli, I see that the core “MyCore” is created, but the extensions are not copied.
Is it possible to activate a log, what is happening during the execution of the above DockerFile instructions?

Thanks and regards,