Transfer Disk mode on an A2 chip model

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Level 1

9 points

Transfer Disk mode on an A2 chip model

Background: The internal SSD on my 2018 Mini has some corrupt APFS structures and fails to boot. Disk Utility in Recovery Mode is incompetent to repair them. It also fails to clone ("restore") the internal to an external drive so I can re-virginize the internal and do File Migration later. (Yes, I have no backups, because TM has been failing to run for me for months despite heroic measures, perhaps because of these very same corrupt structures.)

So my next step is to run Transfer Disk Mode from a separate computer and use something like Carbon Copy Cloner to copy the drive to an external to have someplace to recover my files from.

Ah, but the Mini has an A2 chip—so when I try to mount it as an external drive in Transfer Disk Mode, it demands I enter a password... then doesn't allow me to put my cursor into the password field! (How wude!)

I'm thinking, perhaps there is some unit-wide password (like the old firmware password) that I should have set up (there's no reason a login password should work here, as you can have multiple user accounts on the Mini), but I can't find any such thing documented anywhere. Plus, there's the question of, is it something I can set up from Recovery Mode, as I can't get into any other mode on this Mini.

Can somebody tell me how to satisfy this "wonderful" Apple security that works perfectly to protect my sacred files from myself?

Mac mini 2018 or later

Posted on Oct 3, 2020 11:42 AM

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Answer 1

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macswe Author

Level 1

9 points

Oct 3, 2020 12:50 PM in response to hcsitas

Not everybody lives near a Genius Bar. My closest is two hours one-way. Also closed. Which is why I run an independent Apple repair shop for the community here.

Discovered that the trick is that the live computer moderating the transfer also has to have an A2 chip. When an A2 machine tries mounting the TDM device, it offers a list of user IDs on the device and asks for a corresponding password. When an older machine tries, no user ID field appears and the password field cannot be entered. So an A2 device can only be TDMed to another A2 device. Thank you, Apple, for complicating everything.

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Answer 2

macswe Author

Level 1

9 points

Oct 3, 2020 12:12 PM in response to macswe

Addendum: I thought after reading this thread that perhaps the old firmware password was the thing I needed, but quickly discovered that setting the firmware password, even at the lowest possible levels of "protection" settings, disabled booting into Transfer Disk Mode completely (it just boot looped until I went back to Recovery Mode).

Still hoping for an answer here.

I should add just for the record, that I don't run FileVault. It's the A2 chip and the A2 chip alone that is blocking me here.

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Answer 3

pyrodice

Level 1

4 points

Oct 3, 2020 2:43 PM in response to hcsitas

The good news was I figured it would just need the chip and the rest of the hardware was variable, so I lent my 2019 16” MBP to the operation, and set a new account up to provide sort of a “base of operations” that met the encryption standards required. Looks like it’s on its way! TDM to the rescue.

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