Chosen Solution

Hi All, I bought a second hand imac a week ago. It’s an old 2011 imac, with High Sierra installed. I tried to change the username of the user (which was “azerty”…) using the user and profile tools, but when I restarted the mac as requested, I noticed that :

  1. the username wasn’t changed. 2) it’s not admin user anymore ! It seems to be a know high sierra bug… So I now have a mac with no admin account… I can’t install software nor create folder/ copy/paste file in the backup disk…. I saw that there is some workaround using Single user mode, but now comes the tricky part… I then realized that the mac is EFI locked. I contacted the seller, he said he got it couple of years ago from nearby company when they closed business. What can I do, is there any way I can get an admin account back on this computer? can you help me ? Thanks a lot Flamand

I solved the problem… The guy I bought it from had the EFI password but said it never worked… I found out yesterday that the EFI password must be input as if the keyboard is QWERTY… which is not the case of mine… when you type as if the keyboard is QWERTY… it works… I then went to recovery mode, deleted the .AppleSetupDone and it now all work great !

Sounds like you have a system which has remote administration management installed which can be a bear to clean out. Try restarting your system , format and re-install the OS via internet recovery Reference: How to reinstall macOS