Updated to High Sierra, all Admin accounts now Standard

Hopefully you'll have resolved it by now but just in case, and for the benefit of anyone else in the same predicament, this is what I did when an install of High Sierra Beta (17A291j) demoted my Admin account to a Standard account, rendering it impossible to install Xcode. Not sure if these steps are what you tried when you mentioned 'resetting' the setup, but at least for me it did allow a new user to be setup.

+ Reboot macOS into Single-User mode by holding down Command-S

+ Remove the file controlling whether the setup process is run by typing: rm /var/db/.AppleSetupDone

+ Reboot by typing: reboot

+ When the setup assistant appears, create a new account called admin (or any name other than the actual account name)

Once this was done I had my previous account (still Standard) and a new admin account. Using System Preferences > Users & Groups I could then elevate the standard account back to admin by ticking 'Allow user to administer this computer'. Alternatively you could leave the account as standard and just use the admin's credentials when prompted for authentication.

I have the same error! My main account is now standard and I don't know what to do. Can't install any program...

...I just spent 3400 USD for a new Macbook Pro and this is absolutely ridiculous.

Guys I have found the solution for the problem!

I am running High Sierra 10.13 on a 2017 touchbar Macbook Pro.

Follow these steps:

Start up the Mac whilst holding down ⌘-S. After a few moments, you'll see the Mac boot to the command line.

Before continuing, the filesystem must be checked and mounted, so files are't immediately accessible to interact with. To do this, enter the two commands that are displayed within the prompt, one at a time.

The following command will check the filesystem to ensure there are no problems. Enter:

/sbin/fsck -fy

The next command will then mount the filesystem for it to be accessible:

/sbin/mount -uw /

With the filesystem mounted and accessible, it's time to remove the file so OS X will re-run Setup Assistant:

rm /var/db/.AppleSetupDone

After that, simply enter reboot and your Mac will restart and boot normally. Only this time, Setup Assistant will launch after you login.

hi i have exact same problem - did you find a solution ?

Note: This solution might be specific to High Sierra

Try this:

Solution 1:

On startup, click on "Other"

Enter username: root and leave the password empty. Press enter. (Try twice)

If you're able to log in (hurray, you're the admin now), then head over to System Preferences>Users & Groups and create a new Admin account.

Now restart and login to the new Admin Account (you may need a new Apple Id). Once you're logged into this new Admin Id, you can again proceed to your System Preferences>Users & Groups. Open the Lock Icon with your new Admin ID/Password. Assign "Allow user to administer this computer" to your original Apple ID. Restart.

Now login with your original Apple Id. (In case you wish to remove the "Other" login option on startup read this: https://support.apple.com/en-in/HT204012

Solution 2:

If you're unable to login at startup using username: root and empty password, then login with your existing account (standard user).

Again, head over to System Preferences>Users & Groups. Click on the Lock Icon. When prompted for username and password, type username: root and leave the password empty. Press enter. This might throw an error, but try again immediately with the same username: root and empty password. This should unlock the Lock Icon. If it does, try Solution 1 next.

P.S. Solution 2 worked for me. No idea how or why. Hope this helps.