Run Migration Assistant from Mac OS Recovery

The loop you're stuck in is incredibly frustrating, but common: Migration Assistant cannot run directly from Recovery because it requires an active, booted OS to function.

To break this loop, you need to completely wipe the drive and install a clean OS first, then restore your data. Here is the short solution:

1. Wipe the Drive Clean

1. Boot into Recovery Mode.

2. Open Disk Utility, click View (top left) > Show All Devices.

3. Select the top-level physical drive (e.g., Apple SSD...), not the sub-volumes.

4. Click Erase.

 Format: ⁠APFS⁠

 Scheme: ⁠GUID Partition Map⁠

5. Confirm. This clears the corrupted OS state that is confusing the Recovery system.

2. Clean OS Install

1. Quit Disk Utility and select Reinstall macOS.

2. Choose your newly erased drive and let the installation complete.

3. Run Migration Assistant

1. When the Mac boots up, you will see the Setup Assistant (the welcome screen).

2. When asked how you want to transfer your information, select From a Time Machine backup.

3. Connect your backup drive and restore your data.

djhalnon wrote:

Thanks for all of this but the drive had been erased long ago and as I said numerous installs of the OS have been made to it.

Not a single one of which appears to have been honored. The computer still hallucinates, falsely telling me there is no OS when I know full well there is one.

What's required to convince the computer there's actually an OS and it can go ahead and do what I want it to do?

P.S. This still keeps coming back to the nature of Time Machine backups. Why did it backup the entire drive (including the OS) if it's not going to restore the OS along with the rest of the data on the drive? Why does it need an OS separately installed, in advance?

Exactly which Mac model and year are you working with here?

Exactly which macOS version are you trying to install on this Mac?

There have been ongoing problems with Sierra and High Sierra in particular.

Since macOS 11 Big Sur, Time Machine no longer backs up the complete OS and therefore a TM backup is not a bootable volume.

Typically, the single most common critical error I see users make when trying to erase a drive is not enabling Disk Utility to View > Show All Devices. If not done, yes, the drive volumes may be selected and erased, but the internal drive device itself cannot be. Apple's guidance is not especially clear on this point.

Use Disk Utility to erase an Intel-based Mac - Apple Support

For further help call 1-800-MY-APPLE or go to support.apple.com