Re: Seeking the correct term of art for the (unique) role that is usually called "postgres"—and the mental model that underlies it all

[*] I see that, in my Ubuntu installation, critical programs like "postgres" itself, "initdb", "pg_ctl", "pg_dump" and so on are owned by "root".

The fact that the "bootstrap superuser" term of art denotes a matching pair of two principals (an O/S user and a within-cluster role)

means that some sentences will require extra verbiage to identify which half of the pair the sentence treats. I'm open to suggestions. But I'll start with these these I'm corrected: the "bootstrap (regular) OS-user" and the "bootstrap within cluster superuser role". Sadly, the fact that "super" is baked into the term of art makes it difficult to name the O/S half of the phenomenon.

I can now characterize what I'd observed more clearly, thus: only a bootstrap super user (as defined above) can start a session without mentioning the name of the database to which to connect and the name of the within-cluster role to connect as—and without supplying a password. And it can do this only from as O/S session where the effective O/S user is the bootstrap superuser.