I was seeing this using the docker image below from a terminal. What else would you like for a context?
Currently, I am also building my image using docker-stacks:
commit 6c3390a9292e8475d18026eb60f8d712b5b901db (origin/master, origin/HEAD, psdev-296/fix, master)
Merge: 1e37452 310afbf
Author: Min RK <email@example.com>
Date: Thu Jul 4 15:58:00 2019 +0200
As far as it looking in a configuration file for a new user, that would be nonstandard. At least it is not what “man id” says nor what happens on a vanilla bionic system.
Print user and group information for the specified USER, or
(when USER omitted) for the current user.
Have you run these from your own jupyter container? It would be interesting to see what your results are.