I'm in High Sierra (10.13.6) and recently I renamed my account in Users & Group. Now I lost access to my administrator (so I can't install apps or change settings in System Preferences).
I already tried to solve my problem by following I don't have administrator account on my mac but I can't make it past the
rm /var/db/.AppleSetupDone
command, or maybe I'm doing something wrong there?
However, here's the single-user mode screenshot:
rm /var/db/.AppleSetupDone