Docker run not appending arguments to image entrypoint

Solution 1:

It turns out the answer is to use the array form of ENTRYPOINT (and/or CMD) in order for appending from command line to work

with:

ENTRYPOINT ["uwsgi", "--ini", "/home/docker/app/uwsgi_app.ini"]

then:

$ docker run -itP uwsgi_app:0.2 --uid=docker
...
user docker not found.

(okay, an error, but shows the arg was accepted)

This behaviour is actually described in the docs:
https://docs.docker.com/reference/builder/#entrypoint

...I missed that when skim reading them though :)