Cannot migrate from time machine - asks for password to non-existant user (System Administrator)

Gregster wrote:

In the end - I went back to the people who sold it to me. They suggested a password which luckily worked. The alternative would have been a full return to factory settings. Infuriating in the case where you buy second-hand or even just forget the password.

This is important information to have in the first post.

People should always perform a clean install of the OS by first erasing the drive followed by reinstalling the OS. You never know what nasty surprises the previous owner may have left behind, or whether macOS may have been damaged or improperly configured over the years. It is so much easier to perform a clean install before a person starts using a pre-owned computer.

Also, here is an Apple article on what the previous owner should have done prior to selling or giving away a Mac:

What to do before you sell, give away, or trade in your Mac - Apple Support

Even if the previous owner performed a clean install of the OS, I personally would perform the clean install myself just to be 100% certain. Plus performing the clean install yourself may even reveal a problem with the computer which may otherwise not be noticed until it is too late to return it for a refund.

Also, make sure to always have frequent and regular backups of the computer and all external media (including the cloud) which contains important & unique data.

Had the EXACT same issue…

went mad trying to disable the “system administrator” user, but it’s a new security feature I’m told, built into the Big Sur OS..

I’ve tried every which way to avoid going down the clone drive option and then doing an update to the relevant OS on top, but in the end had to do exactly this.

used carbon copy cloner on the free trial, and everything seems fine now. So irritating though, and seemingly no real reason why…

all I can think is that it’s an issue with my new NVME drive and slightly older Mac (5,1) and big sur.

Had done updates before and transfer to countless machines wirh differing OS/hardware and all’s been fine. Maybe we’re just both very unlucky!

if anyone’s got a fix or can enlighten please do!

Thanks for the lengthy reply, sadly I observed the clean install method from the start of the project, and it was at the migration assistant stage where I ran into trouble on the freshly created system drive. So strange!

m