Erasing an M1 Mac system drive from recovery mode

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Level 10

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Erasing an M1 Mac system drive from recovery mode

The internet seems to be undecided about this. Some say it can't be done properly, though Apple support pages says it can.

Support says do this

In Disk Utility, select the volume you want to erase in the sidebar, then click Erase in the toolbar.

I'm in Recovery Disk Utility and see this

I'm guessing I can't erase the root level drive. Do I erase the container, or Macintosh HD volume that contains two other volumes? Do I delete the data and system volumes first?

There seems to be some issue that when the volumes are erased there is no longer a recognized user to run the system installation from recovery, and installation can only be done from a boot installer or from Configurator.

Can anyone who has done this successful offer any guidance.

Thank you very much.

Posted on Aug 11, 2021 4:46 AM

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Answer 1

Loner T

Level 9

59,566 points

Aug 11, 2021 5:13 AM in response to Tom Wolsky

Install a copy of macOS on an external disk first, so you have a boot method available. Once you have a fallback mechanism, click on the AP0512Q media and check available options in Disk Utility. If you see an Erase option, you can use it.

See Use macOS Recovery on a Mac with Apple silicon - Apple Support for reference.

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Answer 2

Tom Wolsky Author

Level 10

152,877 points

Aug 11, 2021 6:42 AM in response to Owl-53

Yes indeed. Though there are issues with that when Recovery refuses to do it because it thinks there is no admin user, even when there is one and even if you set the admin in Recovery.

What’s really unclear when you have an external and internal boot drive, both with Recovery volumes, is which Recovery volume you’re in when you load options. This may be the cause of the problem I mentioned above, the system wants to go into recovery for the assigned startup disk and can’t find it.

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Answer 3

Loner T

Level 9

59,566 points

Aug 11, 2021 8:31 AM in response to Tom Wolsky

Tom Wolsky wrote:

What’s really unclear when you have an external and internal boot drive, both with Recovery volumes, is which Recovery volume you’re in when you load options. This may be the cause of the problem I mentioned above, the system wants to go into recovery for the assigned startup disk and can’t find it.

At least the Intel Macs can boot from either (provided Startup Security allows it) external or internal disks. 😜. On the Intel Boot Manager, when Alt/Option is used, you can see whether it is an external or an internal device for Recovery HD. With APFS, it becomes a bit more complicated.

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Answer 4

Tom Wolsky Author

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152,877 points

Aug 11, 2021 6:11 AM in response to Loner T

Thanks for the suggestion and the link.

That page links to another about erasing from recovery, which is where the line I quoted comes from.

A word of warning to others about external boot drives on M1 machines. If the system assigned boot drive is not available, the system often will not boot. It will not go into recovery options, even after the Load Options appears, but just keeps trying to start and failing. So if you're going to use an external drive as backup make sure it has been set as the system assigned boot volume before you wipe the system drive.

Thanks again Loner T.

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Answer 5

Tom Wolsky Author

Level 10

152,877 points

Aug 11, 2021 8:33 AM in response to Loner T

Yes indeed, the Intel Macs are much simpler and more forgiving. All of this I'm sure is in the interest of security, but if it impinges too much on the user experience, it's probably not a good thing.

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Answer 6

Owl-53

Level 10

106,913 points

Aug 11, 2021 6:34 AM in response to Tom Wolsky

Extra Special Notation regarding the Touch ID equipped Apple Computer. About Startup Security Utility and Must Enable from Recovery Mode the ability to boot from External Drive Before Attempting

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Erasing an M1 Mac system drive from recovery mode

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