Why did Big Sur erase my disk?

[mauricev]

I upgraded an external APFS boot volume from Mojave to Big Sur. There were two accounts and a lot of apps. On the first boot, they were all gone and replaced as if I had told the computer to pre-erase the volume, but of course, I did no such thing. Is it supposed to happen this way? What could have happened to cause this?

 

[The Man]

I upgraded an external APFS boot volume from Mojave to Big Sur. There were two accounts and a lot of apps. On the first boot, they were all gone and replaced as if I had told the computer to pre-erase the volume, but of course, I did no such thing. Is it supposed to happen this way? What could have happened to cause this?

If everything is gone, then it has erased prior to install. But sometimes old accounts are for whatever reason archived in Users folder. Be sure to look in there. If all apps are gone, however, then it is likely everything was erased prior to installation. Maybe there was a prompt that you accidentally said yes to?

 

[mauricev]

Nope, the OS install did this on its own with no prompt to me. I knew something was wrong the instant it wanted me to create an account.