I have a few Dockerfiles right now.
One is for Cassandra 3.5, and it is FROM cassandra:3.5
I also have a Dockerfile for Kafka, but t is quite a
Docker doesn't do merges of the images, but there isn't anything stopping you combining the dockerfiles if available, and rolling into them into a fat image which you'd need to build. There's times where this makes sense, however, as for running multiple processes in a container most Docker dogma will point to this as less desirable especially with microservice architecture (however rules are there to be broken right?)