Password no longer works after changing UID

[machelp32]

I used 'sudo dscl . -change /Users/john UniqueID 501 1000' to change my uid (since I wanted to fix file permission issues on a NFS mount). Now my desktop is all messed up, probably because all the setting files became unreadable (good times). I'm already at the point where I just want to setup my broken system from scratch, except when I do System Settings -> General -> Transfer or Reset -> Erase All Content and Settings my password is rejected. Any idea what could get me out of this mess?

 

[machelp32]

Ok long pressing the power button allows me to enter the options menu where my password is accepted.

 

[machelp32]

Not really! Mac OS was downloaded and installed from scratch apparently but no user settings erased, so the problem remains

 

[machelp32]

finally I used disk utility to erase the volume and now it's working again