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Usually, factory reset instructions say that I should remove a volume or volume group. But to be sure that the installation is really clean, I prefer to use another option:

  1. In Disk Utility select View > Show All Devices
  2. Select APPLE SSD
  3. Click Erase, choosing GUID Partition Map

I know Intel machines allow to boot from either Internet Recovery or USB drive after such an erase. But M1 seems to be more like iPhone, which can end up in a DFU mode and require another computer to "revive" it.

Will M1 Mac boot from an external drive or from the Internet, if I wipe the entire SSD?

I guess, if I'm lucky and successfully install macOS right after the wipe, then everything is fine. So my question is, if I erase everything on SSD and restart the computer, will it be able to boot into recovery by itself or at least into recovery on the external drive?

Boot modes for a Mac with Apple silicon says that there's "Fallback recoveryOS", which relies on "second copy of recoveryOS that is kept for resiliency". Will it also be wiped?

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  • Define 'really clean' on a computer that's less than a year old! There was a danger of rendering the Mac useless by wiping the disk with the first release of Big Sur, but I believe it's been fixed. Still, I see very little point in wiping anything outside of the User Data volume. The System is a read-only, signed volume. That probably goes for the Recovery, too.
    – benwiggy
    Aug 4, 2021 at 12:48
  • @benwiggy just ignore it. By clean I merely mean a state at which I’m guaranteed to restore the Mac (without resorting to revival process), no matter how the data on SSD was screwed.
    – Dmitri Urbanowicz
    Aug 4, 2021 at 12:56

3 Answers 3

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Yes, it’s safe. First, boot into recovery mode using this guide: https://eshop.macsales.com/blog/74502-boot-an-m1-mac-into-recovery-mode/

Then clear the disk using disk utility (under the utilities menu bar item), and finally, click reinstall MacOS Big Sur.

Disk utility in recovery mode doesn’t show the entire disk by default, so make sure to go into the view menu bar option and select show all devices.

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  • Sure. But what if the installation fails? Will I be able to boot from external drive?
    – Dmitri Urbanowicz
    Aug 4, 2021 at 12:39
  • @DmitriUrbanowicz See this article about external booting on M1 Macs. eclecticlight.co/2020/12/22/…
    – benwiggy
    Aug 4, 2021 at 13:07
  • Is it still save if you secureErase with the diskutil command? I have read that secure Erasing will damage the ssd and its only for hdds suitable
    – Lano
    Aug 5, 2021 at 7:56
  • @DarwinOSX secureErase is bad for SSDs because it adds unnecessary write-erase cycles to the SSD. However, a one pass (or minimum by apple: 2 pass) is uncommonly used to make sure that disk recover tools such as Disk Drill cannot recover the data on the ssd. However, 3-part and 7-pass erases aren’t necessary. It shouldn’t do damage to the disk, but it will add excess wear to the ssd.
    – anonymous
    Aug 5, 2021 at 21:41
  • Do you have a definitive reference on what will happen if I just wipe the entire SSD on M1 Mac and then reboot immediately? Will it be capable of booting at least from external drive?
    – Dmitri Urbanowicz
    Aug 6, 2021 at 4:49
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The best information I could find suggests that erasing entire SSD is not safe (or even not allowed by standard tools) unless you have another Mac to perform DFU restore. From https://discussions.apple.com/thread/253777530 :

Erasing the entire internal drive on an Apple silicon Mac won't work, because that never truly happens (unless you perform a DFU restore). This is because the iBoot System Container (Apple_APFS_ISC, disk0s1) is system critical; your Mac literally cannot start up without it. The System Recovery Container (Apple_AFPS_Recovery) is also super important; it contains an additional copy of macOS Recovery in case the regular copy gets damaged (or in your case, outright deleted).

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0

As of Ventura, you can Erase All Content and Settings (e.g. the Data volume) from System Settings, which gives you a 'clean' disk without needing to wipe the whole device.

This is much safer than erasing everything.

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