Am 2017-07-03 16:08, schrieb dev:
> Sounds like a "won't fix", too:
>

>   "So, yeah, I don't think there's anything to fix in systemd here."
>    - Poettering

>
> Not sure what's more troubling here[1]; the lack of concern, the
> digression from POSIX, or the bug/backdoor itself. Maybe all three.
>
> useradd 0day works on Devuan. adduser 0day does not. Which is correct?

According to POSIX:
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_437

the only restriction is, the name should not begin with a hyphen.

Some systems have more restrictions, but that is not a must.
http://www.circlingcycle.com.au/fun-projects/IEEE-Std-1003.1-2001-and-valid-characters-usernames.html

Jochen