Restore backup to computer running previous OS?

TidBITS Talk
1

I have a MacBook Pro 16-inch, 2019 running Sonoma 14.5 and make daily backups to alternating external SSDs using SuperDuper. (I also use Time Machine with a dedicated drive.)

If for any reason that computer becomes unusable, would I run into difficulties using Migration Assistant to restore the backup data to a MacBook Pro 15-inch, 2017 that is maxed out at Ventura 13.6.7?

In particular, how would Mail.app and email messages stored in On My Mac be affected?

Thank you,

David

2

If your scenario is based on Macs and drives you currently own, why not do a dry run before a disaster strikes? Then you’ll know for sure what you need to do going forward (keeping in mind, of course, that the 2017 machine should be started up at least once a month to ensure it remains operational).

3

I’m pretty sure Migration Assistant will not permit a down level migration.

And in particular, even if it did, Mail would be a problem. Each time you upgrade macOS to a new major version, it converts the Mail database in ~/Library/Mail. This conversion can’t be reversed.

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4

Thanks, Michael – I thought that was probably the case.

5

I ran into this issue myself a couple years ago. I had just purchased a new Mac and planned on migrating from my “old” Mac. Only problem was, I had just before the new unit arrived, updated the “old” Mac’s macOS such that the macOS the new Mac came with was actually just slightly older and MA promptly refused to migrate. I had to first set up a vanilla admin account on the new Mac so I could update its macOS and only then was I able to migrate from the previous Mac to the new Mac (direct or via TM didn’t make a difference). MA was rather strict about this — this was only a ..x update difference, not a different macOS generation.

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6

This has happened to me several times. The OS image on a shipped computer was probably created before it was packaged, and if you’re lucky, represents the current OS version at that time. It may, of course, be even an older version. If you keep your own computer up to date, it’s almost certain that the ‘new’ computer will be back-leveled.

As a consequence, my usual procedure when migrating to a new computer is to first initialize and bypass all personalization. Then pretend it’s a computer I’m getting rid of and ask that all data and settings be erased. Now I can run an normal initialization and migration.

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7

Just so I understand, why couldn’t the OS be updated with the account that came with the new Mac?

8

Agreed. This has been exactly my go-to approach ever since.

9

A factory Mac does not come with a user account. You set up either vanilla or migrate. I wanted to do the latter, but since MA doesn’t allow for that if the source has a newer macOS than the target, I had to resort to on the new Mac setting up a vanilla account first (without any migration) just to install the macOS updates that would get it on par with the intended source. Once that’s in place, MA will happily play along and set up a brand new account migrated from the previous Mac.

10

I haven’t set up a new computer recently but as I recall, if you decide to initialize the new computer without migrating any data–usually people do this to quickly confirm the hardware and software are functional–you have to be sure to erase and restore the machine to its factory-fresh state before running Migration Assistant. Otherwise, if you launch Migration Assistant from the Finder as an already-set up user, there can be very disruptive OS-user conflicts (if I remember correctly, macOS makes the user setting up a computer User 501 and Migration Assistant launched from the Finder will assign a different User number to the migrated data).

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11

Thanks for straightening me out on this. Even though I have done many new setups, somehow I had this basic concept mixed up in my mind.

12

Interesting. When I get new MBPs, I do a clean state, get all updates, don’t log into iCloud, etc. to test them out. Once they work, then I migrate from another older MBP. However, I only migrate other user (standard level) accounts and not the same one (admin level) I used. I don’t even migrate the old apps. Just accounts.

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