Restore question with Time Machine

[ced89]

Hi, I have one MacBook Pro 2019 that was initially with Mojave, now with Big Sur.
The current backup with Time Machine is obviously with Big Sur, so, I wonder, when I'll upgrade to Monterey, will I be able to restore back to BigSur??
Or it will be Mojave because the chip inside has the Mojave image?
If this is the case, shall I upgrade to Big Sur and then restore my backup from Time Machine?

Same case, if I upgrade to Monterey and for some reason I need to restore the system.
Suppose that the backup restore fail, shall I restore the laptop to Mojave, upgrade to Big Sur and then to Monterey before to make a Time Machine restore??

 

[Lifeisabeach]

Once you upgrade to Monterey and complete a Time Machine backup, the backup is only valid for Monterey, and specifically for the version it was updated to. I don't know what you mean by "a chip inside [that] has the Mojave image".

If you have to restore your system, and want Monterey, just go straight to Monterey. There's no good reason to install an older version, upgrade to a less older version, then upgrade again to the current. Just go straight to the current. Upgrades usually go smoothly, but not always. There's just no reason to do it that way in this scenario.

 

[toMACsh]

OP, correct me if I'm wrong...
You want to know that in case you decide you don't want Monterey, will your previous Time Machine backup be able to restore your OS to Bug Sur; is that right?

Mac gurus, correct me if I'm wrong...
The answer to the above question is no. My understanding is that Time Machine can be used to restore files, but I don't know what else beyond that, if anything, that it can restore.

 

[ced89]

Once you upgrade to Monterey and complete a Time Machine backup, the backup is only valid for Monterey, and specifically for the version it was updated to. I don't know what you mean by "a chip inside [that] has the Mojave image".

If you have to restore your system, and want Monterey, just go straight to Monterey. There's no good reason to install an older version, upgrade to a less older version, then upgrade again to the current. Just go straight to the current. Upgrades usually go smoothly, but not always. There's just no reason to do it that way in this scenario.

My objective is to prevent a bad surprise, where for example I can't restore. I don't want to plan the restore of BigSur even though there is Monterey in the market, or in my Time Machine backup.
I just need to make sure that if I have a backup of the system with Big Sur, in case the upgrade to Monterey goes wrong, I'd like to restore the situation as before with Time Machine.

You may ask, why would you want to do it? Well, one case is if the upgrade restore process itself goes wrong, and the previous state of the system can be recovered only with Time Machine.

OP, correct me if I'm wrong...
1. You want to know that in case you decide you don't want Monterey, will your previous Time Machine backup be able to restore your OS to Bug Sur; is that right?

2. Mac gurus, correct me if I'm wrong...
The answer to the above question is no. My understanding is that Time Machine can be used to restore files, but I don't know what else beyond that, if anything, that it can restore.

1. Yes and no, you mentioned one interesting case, but I may also need to restore in case things go wrong, as explained above.

2. It definitely restore files, but also system files as far as I know, therefore the OS.
I never tested this, I'll try to test it on my MacOS VM, I think it will restore also the OS but I was in doubt about the image stored on the separate EEPROM or whatever that chip is.
I had a quick look into the file list in Time Machine, there are many system files, as well as system utilities, I think that all these files, despite they are system files, they don't depend from the OS, or at least Apple supports backward compatibility till a certain version, otherwise I can't explain how the restore would be successful.

 

[Rod]

Time Machine does not copy your Operating System, you cannot restore Monterey back to Big Sur using Time Machine. TM is for User Data only.

Retuning to a previous macOS is a complicated and difficult process requiring a complete erase of your internal drive, obtaining the appropriate macOS Instal app, the creation of a bootable installer and the restoration of your personal files from eg. Time machine.

So, always think well before Upgrading your macOS. Read up on other peoples experience and reputable web sites that describe what to expect on Monterey. eg. When to Expect Apple to Release macOS 12.1 With SharePlay and More. macOS 12 Monterey review: Should you download?. macOS Monterey review: A compelling refinement of Big Sur | AppleInsider

As stated by Lifeisabeach, "Once you upgrade to Monterey and complete a Time Machine backup, the backup is only valid for Monterey"

My opinion is that Monterey is really just a refinement of Big Sur and if you are happy with Big Sur you will almost certainly be happy with Monterey.

 

[ced89]

Time Machine does not copy your Operating System, you cannot restore Monterey back to Big Sur using Time Machine. TM is for User Data only.

Retuning to a previous macOS is a complicated and difficult process requiring a complete erase of your internal drive, obtaining the appropriate macOS Instal app, the creation of a bootable installer and the restoration of your personal files from eg. Time machine.

So, always think well before Upgrading your macOS. Read up on other peoples experience and reputable web sites that describe what to expect on Monterey. eg. When to Expect Apple to Release macOS 12.1 With SharePlay and More. macOS 12 Monterey review: Should you download?. macOS Monterey review: A compelling refinement of Big Sur | AppleInsider

As stated by Lifeisabeach, "Once you upgrade to Monterey and complete a Time Machine backup, the backup is only valid for Monterey"

My opinion is that Monterey is really just a refinement of Big Sur and if you are happy with Big Sur you will almost certainly be happy with Monterey.

Thanks, I believe this is what I knew already in terms of data restore.

But there is one critical point, the OS image must be on a separate chip, because I erased the M2 completely and the OS could be re-installed (twice ).
I didn't bother for the boot loader, it was always there.

I didn't play with the UEFI though, not yet at least.

I need to check the rest of the Apple arch to see where it is, but mate, it's there , I didn't download the OS, I don't even think you can do it when you restore.

 

[MacInWin]

But there is one critical point, the OS image must be on a separate chip, because I erased the M2 completely and the OS could be re-installed (twice ).
I didn't bother for the boot loader, it was always there.

I didn't play with the UEFI though, not yet at least.

I need to check the rest of the Apple arch to see where it is, but mate, it's there , I didn't download the OS, I don't even think you can do it when you restore.

Not a separate chip. IN the M1 system there is dedicated storage for what is called Sealed System Volume. In that hidden, encrypted volume that no user can get to is a copy of whatever version of macOS that is on the machine. Let's say you upgrade to Monterey 12.2.1. The software to do the upgrade has the encrypted key to the SSV, so it installs the OS to the SSV, then runs hash calculations on every file, then every folder and finally on the full system. It then compares those values to the ones that Apple knows SHOULD be there, and if they match, the SSV is sealed again. Next, the system makes a snapshot of that verified copy of the OS, and that is the system from which the system is actually booted. Before booting, however, the snapshot is again hashed and checked against the SSV to verify that the snapshot is intact.

So, when you need to "reinstall" the OS, what takes place is the current snapshot is erased, the SSV is accessed to create a new snapshot, it is verified as correct and the system boots from it. But all of this activity takes place INSIDE the M1 system, no external chips.

 

[Rod]

Maybe I’m a bit slow here but how can a 2019 MBP be an M1?

 

[MacInWin]

Maybe I’m a bit slow here but how can a 2019 MBP be an M1?

My bad, I think in another thread he referred to an M1 system and then in this thread talked about the system being "on a separate chip" in Post #6. I put those two together.

But if he is talking about the 2019, there isn't an operating system on any chip in the system, either. On older machines the OS is stored on the internal drive and nowhere else.

 

[Rod]

My thoughts as well, so I'm puzzled by his statement, "But there is one critical point, the OS image must be on a separate chip, because I erased the M2 completely and the OS could be re-installed (twice )".