man useradd:
Usernames must start with a lower case letter or an underscore, followed by lower case letters, digits, underscores, or dashes. They can end with a dollar sign. In regular expression terms: [a\-z_][a\-z0\-9_\-]*[$]?
Takze ano, ked si niekto opatchuje shadow-utils, tak musi opatchovat vsetko, co ma rovnaku semantiku. V tomto pripade je maslo na hlave Redhatu, ze zmenili nieco iba na jednom mieste a nie na druhom. Preto si to aj opravili.
Pre tych, co stale maju problem s chapanim citaneho textu: nie, to nie je obhajoba 0day a davanie roota pouzivatelovi.
A pozeram, ze stale nemas ani najmensi zaujem pochopit, co systemd vlastne robi, tak si pekne hejtuj dalej a tschus.