hoakley February 9, 2021 Macs, Technology

How to roll your M1 Mac back to Big Sur 11.1

Quite a few users who updated their M1 Macs to Big Sur 11.2 recently are regretting having done so. Those who rely on SoftRAID to access an external RAID system are among the most obvious, as the current release of SoftRAID is incompatible with 11.2, and lost all access to any disk requiring it. If that happens to contain your backups, then your Mac is in trouble.

But no worries: according to many accounts, all you have to do is to restore your internal disk to 11.1 using a snapshot. The only snag with those accounts is that it doesn’t appear to be true. Neither of my updated M1 Macs has any trace of a snapshot of the 11.1 System volume, now that they’ve been updated to 11.2. So what strategies might be open to you if you need to revert to 11.1?

Revert to a System snapshot of 11.1

According to these instructions given by SoftRAID, you can enter 1 True Recovery (1TR) and revert to a previous Time Machine snapshot of 11.1.

To try this, press and hold the Power button until the display shows Loading Startup Options, then release it. This takes you to the Startup Options screen. Select the Options icon, then click Continue underneath it. In the macOS Recovery window select your user icon and click Next. Enter your password in the dialog, select Restore from Time Machine and click Continue. Click Continue in the next window. Time Machine System Restore will then list Restore Sources. To restore from a previous backup, select your backup disk and click Continue. Then select the backup which you wish to restore. To revert to the previous version of macOS, select the last snapshot containing that version, then click Continue. A dialog should then invite you to install that version of macOS, which you would accept. The snapshot should then be restored, and your Mac will reboot from that version of macOS.

However, at present neither the macOS installer nor Time Machine keeps snapshots of the System volume which you can restore using this method. Instead, when you do try to select a Time Machine backup – assuming that one is accessible – you’re told to install macOS instead, which of course will merely deliver 11.2 again.

Boot from an external disk with 11.1

Although I’m not sure how this might help you revert your internal disk to 11.1, it might at least give you a way of restoring access to whatever broke in the update to 11.2. Unfortunately, as I’ll describe in a separate article, once your Mac has been updated to 11.2, it appears impossible to boot it from an external disk with 11.1 installed, presumably because of firmware incompatibility.

If you do try this, you’re likely to find that your Mac gets stuck in a boot loop because of a kernel panic. This is the result of the booter being unable to find IOAESAccelerator, and can only be resolved by shutting down, disconnecting the external disk, starting up in 1TR, and setting it to start up from the internal boot disk again. Your Mac should restart normally, back into 11.2 again.

Download the 11.1 full installer

When Apple released the update to 11.2, it removed all access to the full installer for 11.1. Unless you have a copy saved on an accessible disk, you will thus be unable to obtain 11.1 to create a bootable installer.

Restore in DFU mode

One sure way to restore your M1 Mac to 11.1 is to wipe it completely and restore the firmware and software for 11.1, in DFU mode. To do this, you require another Mac running at least a late version of Catalina, a USB-C or compatible cable to connect the two Macs back to back, and a copy of Apple Configurator 2 installed on the other Mac. The process may appear daunting at first, but it turns out to be relatively quick and simple, provided that you follow Apple’s instructions carefully.

Before attempting this, it’s worth downloading the 11.1 IPSW file, athough Configurator will do that for you if necessary. Mr Macintosh maintains a list of links to available IPSW files which make that straightforward.

If you’re unable to perform a restore in DFU mode, then the only remaining option is to get an Apple Service Provider to do this for you. Unless you’re in an area in which Apple’s stores remain open, that could be far from convenient.

Should you update an M1 Mac?

Currently, the only reliable way to restore an older version of macOS to an M1 Mac is using DFU mode, which inevitably wipes the entire contents of its internal storage. If you can’t or won’t do that, then you should be extremely cautious before installing any further macOS updates. This applies most importantly to those who rely on kernel or system extensions, which are at greatest risk of being disabled when macOS is updated.

Until Apple provides a more accessible way to restore the previous System volume, anyone who can’t wipe their M1 Mac and restore it in DFU mode would be wisest not to install any further updates to macOS.

15Comments

Add yours

1

EcleX on February 9, 2021 at 9:10 am

Thanks for the useful article.

LikeLiked by 1 person
2

Joey Jay on February 9, 2021 at 4:47 pm

I guess then it’s a good thing that it’s not currently possible to upgrade an external disk install of 11.1 to 11.2 using Software Update!

LikeLiked by 1 person
- 3
  
  hoakley on February 10, 2021 at 12:21 am
  
  Later this morning I look at just that – at 0730 UTC.
  Howard.
  
  LikeLike
4

Ivan Drucker on February 9, 2021 at 6:56 pm

Is it feasible to first copy the internal drive to another disk using the new SMB Target Disk Mode, then do the DFU restore if needed, and (presumably manually) migrate the data back?

LikeLiked by 1 person
- 5
  
  hoakley on February 10, 2021 at 12:25 am
  
  It might be, although it’s generally best to install Big Sur into a container with an existing Data volume, which should then make the Volume Group. But you can’t copy the System volume and its snapshot successfully – you have to install from a full installer to get those to work.
  Howard.
  
  LikeLike
6

NinjaTurtle45 on February 9, 2021 at 10:45 pm

Is it possible to clone the system volume group (System + Data) using asr before the upgrade, then revert back if needed?

Example command: sudo asr restore –source /System/Volumes/Data –target /Volumes/yourExternalDrive –toSnapshot snapshotUUIDhere

The snapshot UUID could be obtained by this command: diskutil apfs listSnapshots /

LikeLiked by 1 person
- 7
  
  hoakley on February 10, 2021 at 12:27 am
  
  Not as far as I know: the System volume and its snapshot still can’t be cloned, as far as I’m aware, not on M1 models.
  Howard.
  
  LikeLike
8

Sab Gigo on February 13, 2021 at 1:55 am

This may not be directly related to the topic of rolling back from 11.2 to 11.1, however, I wanted to share my experience of rolling back from 11.3 beta on my external USB SSD to 11.2 shipping release. I had always assumed that it was necessary to erase the volume containing the beta release, then restore the last shipping release that you saved from a backup, such as Time Machine. Instead of that process, I shutdown my external drive running 11.3 beta on my M1 Mac mini. Then I restarted from a 11.2 USB Bootable Installer. After inputting the account names and passwords, I arrived at the Install Big Sur dialog box and selected the external drive containing 11.3 beta. After entering my administrator password, the install proceeded without an issue. When the M1 Mac mini rebooted from the external drive, it was now running the 11.2 shipping release of Big Sur, with all other user data apparently intact. This was a pleasant surprise, and in fact, surprisingly easy to return from beta to previous shipping version. This might not be a new behavior, but it seemed to me like erasing the entire system drive was required previously. Possible, I have confused what I did with the need to erase a volume when rolling back to a previous version of macOS, say returning from Big Sur to Catalina. Even so, it was very easy to roll back from the beta version.
Sab

LikeLiked by 1 person
- 9
  
  hoakley on February 13, 2021 at 1:15 pm
  
  Thank you.
  I presume that, as you had the beta installed on an external disk, you haven’t rolled back the firmware update which probably came with it? AFAIK, the only way to do that is in DFU mode with a full IPSW restore. Although that’s actually quicker than what you went through, for many users it’s simply not possible.
  One further question: now your external disk is running 11.2, have you updated it to 11.2.1 yet?
  Howard.
  
  LikeLiked by 1 person
  - 10
    
    Sab Gigo on February 13, 2021 at 5:27 pm
    
    I can confirm that the M1 firmware has remained the same – when booting to 1TR, the macOS reinstaller is labeled “Reinstall macOS Big Sur Beta”. I believe in one of your other helpful articles, you refer to the fact that presumably, firmware upgrades are backward compatible with older macOS versions, since M1 Recovery executes on the M1 from its internal storage, and not from a recovery partition on an external drive. If DFU mode is used to restore the M1 firmware to an earlier version, I would think that a reinstall of macOS would also be necessary, and likely would be mandatory. I seem to recall seeing dialogs that state that a particular version of macOS is not supported, or some such verbiage. As for my external disk, the USB installer that I created was the latest version downloadable, which seems to be 11.2 – even the App Store Big Sur page does not show a version newer than 11.2, so it seems that the 11.2.1 update was only incremental. I didn’t get the chance to update, as I immediately reinstalled the 11.3 beta all over again. It is interesting that Apple seems to treat betas the same as shipping updates when it comes to updating firmware, at least for the M1 Macs. Backward compatibility would be a must to maintain the ability to boot older OS versions.
    Thank you for providing the most extensive collection of M1 documentation available.
    
    LikeLiked by 1 person
    - 11
      
      hoakley on February 13, 2021 at 10:23 pm
      
      Thank you.
      Although firmware might aim to remain backward compatible with earlier system software, that doesn’t appear to be the case with 10.1 and 10.2, and is less likely to work with M1 models because of their relative immaturity.
      DFU restore installs everything afresh – the whole firmware, and a fresh copy of macOS. It wipes the internal SSD completely, and when started up afterwards, the Mac behaves like a completely new computer.
      Howard.
      
      LikeLike
- 12
  
  Joey Jay on March 7, 2021 at 4:16 pm
  
  I rolled back from 11.3 Beta 3 to 11.2 on the internal M1 Mac Mini drive only to discover apps like Music would no longer work because they were a “newer version” than the OS was looking for.
  
  LikeLiked by 1 person
  - 13
    
    hoakley on March 7, 2021 at 6:36 pm
    
    I’m sorry to hear that. You may need a restore in DFU mode, perhaps – one of the penalties of running betas.
    Howard.
    
    LikeLike
14

Sab Gigo on February 14, 2021 at 3:31 am

Thanks for that information – I forgot that DFU mode fully wipes the internal drive. I’m not sure that using DFU mode would have any effect on an external drive, which is what I was trying to roll back.

LikeLiked by 1 person
- 15
  
  hoakley on February 14, 2021 at 12:43 pm
  
  Thank you.
  Yes, DFU mode restore doesn’t change anything on an external disk. But it does revert any firmware update, which for some may be an important part of reverting from a beta-release.
  Howard.
  
  LikeLike

·Comments are closed.

Share this:

Related