User ID change in 'Advanced Options' of 'Users & Groups'.

You can try this, but I’m not sure how changing the UID affects being able to alter the old account. It’s usually only the short user name that gets changed, and the account loses admin capability.

I don’t know if you’ll need to change the UID back to 501 and don’t know if the new admin user will get 501 or 503.

Restarting Setup Assistant to create Admi… - Apple Community

MkMalek wrote:

Hi,

I wanted to change my username as my domain id.

I mistakenly changed the User ID from System Preference -> Users & Groups, and entered the "Advanced Options" of the account.

https://discussions.apple.com/content/attachment/dac01cca-863f-49bb-8092-0031aaf6e4261.

Searching on internet, I feel like I mess up big time, as there is no other user and there's no backup.

I'm using Mac Pro (Late 2013), Upgraded to MacOS Monterey.

So what I'm looking is:

Any solution to fix this issue? Steps on how to resolve it.

2. If not, then anyways to retrieve the files? Steps to fresh OS installation.

Thank you

Restore from backup—

Restore your Mac from a backup

Restore your Mac from a backup - Apple Support

This is one of those optional actions that is very risky; I'm not sure you can even recover from it.

But, all is not lost. I assume you have good, recent backups because reinstalling the OS may be your only fix.

If you do that though, do not migrated data back or you just may migrate your current condition. Better to start over and copy data back manually.

I feel others certain will comment; I'm mostly just guessing.

Oops, just saw your "no backups" comment. Once out of this predicament, I suggest you backup up regularly. Certainly before any major or risky evolution.