Migrate time machine backup to new Mac

kabaker wrote:

I used Migration Assistant to set up a new MacBook Pro 14" 2021 from an iMac late 2015 running latest Big Sur. With both machines shut down and powered off, I moved my Time Machine drive to the MB, booted up and in TM Preferences selected the drive for new backups.

When I enter Time Machine, it does not recognize the old backups. It says there are none and wants to start an entirely new set of backups.

I'm thinking of changing the name of the backups folder on the backup drive from

Backups.backupdb/Harvey's iMac

to

Backups.backupdb/Harvey's MacBook Pro

Will that work? If not, is there another way to integrate the old backups into Time Machine?

How to move your content to a new Mac Move your content to a new Mac - Apple Support

If your new Mac inherits your backup history:

You can move the backup history from one Mac to another, but after the new Mac “inherits” the backup history, you can’t use the backup history on the original Mac.

...

If you plan to continue to use your old Mac, click Create New Backup to preserve the backup history and start separate backups for the new Mac.

Above from:

If your new Mac inherits your backup history - Apple Support

The Time Machine drive on that new MBP will require APFS/GUID formatting, and as far as I know, it cannot read the old HFS+ backups.backupd folder on it. My Big Sur and Monterey Time Machine drives that are formatted as APFS now directly write a date/time folder hierarchy for each Time Machine backup. Looks like this:

This is common. To see your old backups once in TM use command-shift-c which will let you go back in your drive user directory

What I have done is to keep my old TM drive and then start a new drive and backup. That way just in case I need some older file I can still get it if required.