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Can't boot from External SSD - Mac Mini M2

Skeptical.me

Skeptical.me

macrumors 6502a
Original poster
Jun 10, 2017
649
632
Australia
I have a brand new 2023 Mac Mini M2 8GB 256GB. I am attempting to use an external SSD (NVMe in an enclosure) as the main drive.

I reformatted the external SSD to AFPS GUID and named it Ext Macintosh HD. I then downloaded the latest Sonoma today from the Mac App Store. I installed Sonoma to the external drive successfully, the Mac Mini then rebooted and it booted back up into the internal drive. I tried setting the Startup Disk to the External SSD in System Settings and then attempted to reboot and I received this message:

An error occurred while setting “Ext Macintosh HD” as the startup disk: The operation couldn’t be completed. (SDErrorDomain error 108.)

I have attempted this a few times with the same result each time.

Does anyone have any experience with this?

I read that the booting into recovery (holding down the power on button on the back of the Mac Mini) and then allowing the Mac to boot from an external drive is possible but I followed the instructions from a website and there was no setting that allowed that, just a reduction in security settings.
 
Apple silicon Macs require a LocalPolicy with an Owner. If that isn’t configured correctly, they will be unable to boot from that external disk. That’s likely the problem. Follow these detailed instructions to properly the bootable drive. Sonoma hasn’t changed from Ventura in this regard.

eclecticlight.co

Make a Ventura bootable external disk for an Apple silicon Mac

Described and illustrated, with key points on cables, and setting up ownership and accounts. And what does happen when the external boot disk is missing?
eclecticlight.co eclecticlight.co
 
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chabig said:
Apple silicon Macs require a LocalPolicy with an Owner. If that isn’t configured correctly, they will be unable to boot from that external disk. That’s likely the problem. Follow these detailed instructions to properly the bootable drive. Sonoma hasn’t changed from Ventura in this regard.

eclecticlight.co

Make a Ventura bootable external disk for an Apple silicon Mac

Described and illustrated, with key points on cables, and setting up ownership and accounts. And what does happen when the external boot disk is missing?
eclecticlight.co eclecticlight.co
Click to expand...
Thanks for the reply.

I solved the issue by using a new NVMe enclosure, the last one must have been incompatible or faulty. The new one enabled me to install macOS Sonoma and I'm using it as my primary drive right now.
 
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I had a similar issue and was able to solve it by replugging the cable from USB-C port to USB-A until installation was done and it booted from external. Then I replugged the cable back to USB-C and it worked fine afterwards. But each time I needed to update macOS I had to repeat the procedure.
 
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I've used SuperDuper to clone a MacBook Pro 14" internal to an external nvme SSD.
Worked fine with Monterey.

For Sonoma, I tried it again, and ran into a glitch. But a reboot seemed to fix that.
Seems to be working ok now.

If you can't create the bootable clone with CCC (which I also use), try SuperDuper instead.
It's provided free to users to do "a full clone" (you pay to enable incremental updates).
It's also very easy to use -- much moreso now than is CCC, which has grown more complex through the years.
 
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Similar situation, trying to verify booting from a SuperDuper clone on an Acasis NVMe enclosure via TB4. No matter if I select the SSD via the boot picker or selecting it as "Startup Disk" fails with the same message "The version of macOS on selected disk needs to be reinstalled". I have done this with earlier versions of Macos on intel. Not sure if it is Ventura or the M2 mini? Commentary, I am really disappointed with Ventura for a number of reason. Was planning to down grade to Monterey only to find out it is not supported. Now stuck with this POS.
 
Last edited:
Re dono's reply 6 above:
"The version of macOS on selected disk needs to be reinstalled"

I suggest you try this:
a. connect the backup that won't boot
b. boot the Mini to recovery
c. initiate a "re-install" of the OS, BUT...
d. "aim" the re-installation at the external backup (NOT at the internal drive)
Give this a try.

More:
" Was planning to down grade to Monterey only to find out it is not supported"

I think you can "get back" to Monterey by doing this:
a. creating a bootable USB flashdrive of the Monterey installer
b. booting from the flashdrive
c. COMPLETELY ERASING the internal drive (go to the "view" menu in disk utility and choose "show all devices" to see it)
d. installing a fresh copy of Monterey, AND THEN...
e. re-installing your data (use migration assistant).

TO CREATE THE FLASHDRIVE...
I believe you need a 32gb USB3 flashdrive
AND
I also suggest you download the new utility named "Mist" to download and create the bootable flashdrive (very nifty):
github.com

Release 0.9.1 · ninxsoft/Mist

Fixed insecure HTTP URLs for certain Firmware files Thanks F1248! Fixed a bug where downloads were not being cancelled when the Escape key was being pressed Thanks F1248! Rolled back the Bootable D...
github.com github.com
(I recommend that you download the ".dmg" file)

Good luck.
 
"I thought Monterey did not support the M2 pro mini?"

Oops, I missed that. (I miss too much in old age)
You're correct!
 
dono42 said:
Similar situation, trying to verify booting from a SuperDuper clone on an Acasis NVMe enclosure via TB4. No matter if I select the SSD via the boot picker or selecting it as "Startup Disk" fails with the same message "The version of macOS on selected disk needs to be reinstalled". I have done this with earlier versions of Macos on intel. Not sure if it is Ventura or the M2 mini? Commentary, I am really disappointed with Ventura for a number of reason. Was planning to down grade to Monterey only to find out it is not supported. Now stuck with this POS.
Click to expand...
Response from Dave at Shirt Pocket

Sometimes the OS requires you to reinstall even though it's been successfully replicated. Why - alas, since Apple requires that we use their tool to copy the OS, the "problem" is theirs, and they're not explaining...
--
Dave Nanian
Shirt Pocket
 
I’m curious on if you could let me know how well this setup is working for you. I’m at the point where I need a full TB dedicated to my Photo Library; I ran dual drives in the past on my 2014 and it was a pain in the rear, so I’d like to do a 2 TB external drive and just pick up a cheap 256 Gig Mini.
 
What happens to performance if you're booting from an external SSD? Doesn't this set aside the advantages of Unified Memory? The external SSD can't be included in Unified Memory.
 
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"What happens to performance if you're booting from an external SSD? Doesn't this set aside the advantages of Unified Memory? The external SSD can't be included in Unified Memory."

The external drive can't match the speed of the internal drive.

There once was a time (back when Apple put platter-based HDD's and fusion drives into Macs) when booting from an external SSD made sense. I still recommend doing so for folks with older iMacs, etc.

But with new Macs -- not any more.
The SSDs that Apple now uses beat just about any external storage, by leaps and bounds.

I also recommend that buyers of Macs now eschew the "stock" SSD configuration (such as 512gb on an m2pro Mini), and buy "one size up". Do that, and you get EVEN FASTER speeds.

That's because (due to internal SSD chip designs), the "base model" SSD will generally run at .5x (one-half) the speed of the "next size up" (in the case of an m2pro Mini, this would be a 1tb SSD).

Pay the extra $200 for the SSD upgrade, and get 2x the speed.
 
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Fishrrman said:
"What happens to performance if you're booting from an external SSD? Doesn't this set aside the advantages of Unified Memory? The external SSD can't be included in Unified Memory."

The external drive can't match the speed of the internal drive.

There once was a time (back when Apple put platter-based HDD's and fusion drives into Macs) when booting from an external SSD made sense. I still recommend doing so for folks with older iMacs, etc.

But with new Macs -- not any more.
The SSDs that Apple now uses beat just about any external storage, by leaps and bounds.

I also recommend that buyers of Macs now eschew the "stock" SSD configuration (such as 512gb on an m2pro Mini), and buy "one size up". Do that, and you get EVEN FASTER speeds.

That's because (due to internal SSD chip designs), the "base model" SSD will generally run at .5x (one-half) the speed of the "next size up" (in the case of an m2pro Mini, this would be a 1tb SSD).

Pay the extra $200 for the SSD upgrade, and get 2x the speed.
Click to expand...
Yeah, I'm having dramas with this setup ... boot problems, and Bluetooth problems for some reason
 
colinsky said:
Doesn't this set aside the advantages of Unified Memory?
Click to expand...
The Unified Memory has nothing to do with an SSD. The Unified Memory is the RAM.

If you get a Thunderbolt enclosure for the external SSD stick, and buy a fast SSD from whomever (e.g. Samsung), I bet you'll not be disappointed with the boot time.

Online tests of people who compare external to internal boot times on these M series Macs show differences of a few seconds.
 
I am trying this with a external Samsung T7 but cant get it to work, get the same error as you guys.

Maybe I need to buy that enclosure also... this really sucks.
 
FOUND A SOLUTION:


I found a solution. M2 MacBook Air 2022. I tried to install different version but never was able to boot. SDErrorDomain error 108.)
Now Running Ventura from External SSD with USB writing this :)

The problem was that I was using the DFU USB-C port to install, which even apple officially says shall not be used to install MacOS. So using a non DFU port, made it worked.

Also I used a thunderbolt cable instead of a usb cable, but I am certain this wasn't the main issue.
I hope this helps other as I was spending days to figure this out, thats why I created an account to post this here so someone else may be spared that waste life time ;)

Sometimes its seem to be worth while checking out official guides....
https://support.apple.com/en-us/111336
 
swealpha said:
I am trying this with a external Samsung T7 but cant get it to work, get the same error as you guys.

Maybe I need to buy that enclosure also... this really sucks.
Click to expand...
Hi do you have Apple Silicon? Make Sure not to use the DFU port, or it will give you this error
 
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