What is a numerical subordinate user ID?

[truh]

And why is it 10000 in the manual? (sudo usermod --add-subuids 10000-75535 USERNAME)

[eriksjolund]

Regarding the number 10000 here

• podman/docs/source/markdown/podman.1.md

  Line 441 in c66d46c

  $ sudo usermod --add-subuids 10000-75535 USERNAME

The chosen number would typically be the lowest unused subuid.
The chosen range must not overlap with any of the existing ranges in /etc/subuid (or any subuid ranges that are configured via /etc/nsswitch.conf)

Fortunately you often don't need to use usermod --add-subuids very often because useradd configures subuids and subgids automatically for a new user. (At least when running fedora).

This document
https://wiki.gentoo.org/wiki/Subuid_subgid
has a short introduction to the topic of subuids and subgids.

[truh]

Thanks the gentoo wiki is a lot more helpful on this matter than the subgid and podman man pages.

So the numbers in the command is and actual range but in the /etc files it's a starting number and an offset? That's not very ergonomic.

Fortunately you often don't need to use usermod --add-subuids very often because useradd configures subuids and subgids automatically for a new user. (At least when running fedora).

Seems like I'm not so fortunate on RHELL8.