As a user of the official apache/nifi Docker image, I would like to be able to easily pass in the ports I want NiFi to start on. This is particularly important since the 1.5.0 release, where remapping ports outside the container cause NiFi to throw a security error.
This will be particularly useful in NiFI-1.5.0 and newer, where users are often running multiple instances of the same version in order to test Flow Versioning and other new features around the NiFi-Registry project.
This can be done by slightly modifying the startup scripts included in the package to use an environment variable if available, or a default if it is not provided. It is then very easy to pass an environment variable to the Docker image on startup.