Level 4

2,149 points

Mac Mini M1 Using External SSD

Hi, I bought the new Mac Mini M1 and would like to use it with a external 1TB SSD. I recently bought a 2018-2019 Mac Mini and was using my external SSD just fine with it, but now with the M1 it is having all kinds of connectivity issues. I thought I would just plug it in the M1 and it would work, since it has the same OS version as the internal SSD, but it wouldn't let me. It said I needed to reinstall 11.01 all over again, so I tried, but it got halfway and then said there was an error and it stopped installing. It then said I had the wrong version of macOS, even though the internal SSD had the same exact version (11.01).

So I formatted my SSD and reinstalled 11.01 onto it. Guess what, yep, you guessed it, it says I can't use it because it needs to be "updated" - even though it is the current version of macOS (11.01).

BTW, I tried the Startup Security Utility as shown here;

https://support.apple.com/en-us/HT208198

but there was no external drive option.

How can I get this M1 to boot into the external SSD?

Posted on Dec 10, 2020 10:41 PM

Top-ranking reply

MarcoT76

Level 1

14 points

Posted on Dec 27, 2020 6:57 PM

Booting on external drive M1 Mac

For background, I’m Coming from 2018 Intel Mac Mini using an external Plugable Thunderbolt 3 NVMe SSD as my boot drive.

I purchased the M1 Mac Mini in the 16gb with 256 SSD thinking I could save the $400 and keep using my external drive. Boy I did not know what apple had in store for me...

After spending hours unsuccessfully trying to use the drive, I turned to this forum for help. Like many I found help and got as far as booting into the drive but unable to clone or backup from time machine to instal all my apps, files, profile, etc. searing other forums, and piecing advice together, I was finally happily running the M1 Mac mini with my external drive as intended.

Her is how I ended up getting it to work:

I Setup new M1 Mac Mini using internal drive. Used migration assistant to clone external intel drive from my 2018 Mac mini to the internal M1 drive. I then booted into M1 internal drive.

Since the M1 Mac can not use a boot drive that was created from an intel Mac, I had to erase the external drive using disc utility and reformatted to APFS and GUID. You have to do this from your M1 Mac. This is a critical step, intel boot drive won’t work on M1 Mac.

Restarted M1 Mac using the new system restore start up options (hold down power button on the Mac mini until options menu loads) from there I had to change security settings to “low security”on the internal M1 drive. (If you don’t do this, migration assistant won’t work) Then instal fresh copy of Big Sur onto external drive using recovery menu within the startup options screen. (You must instal Big Sur from this menu, you can’t instal it through the App Store).

After an hour or so, the M1 Mac booted from the external drive and I was presented with language selection screen. (Be patient, system will restart several times) From there I continued setup and used migration assistance to clone internal M1 drive to the “new” external drive.

Missing any of the steps above will break the chain that allowed this to work.

Good Luck!!

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52 replies

VikingOSX

Level 10

123,218 points

Dec 11, 2020 8:19 AM in response to MyApple8MyPC

Your Intel Mac mini uses the Apple T2 chip and it pees on your drive on the older mini to secure and associate it with that hardware. The M1 mini also has the T2 chip and realizes that the drive belongs to another Mac, and wants you to reinstall the operating system on the drive, so the M1's T2 chip can securely mark it with its own scent.

Hardware security overview.

MyApple8MyPC Author

Level 4

2,149 points

Dec 11, 2020 8:30 AM in response to VikingOSX

VikingOSX wrote:

The M1 mini also has the T2 chip and realizes that the drive belongs to another Mac, and wants you to reinstall the operating system on the drive, so the M1's T2 chip can securely mark it with its own scent.

Hardware security overview.

I thought about that too, which is why I completely reformatted the SSD and then installed a brand new fresh copy of 11.01 on it. The M1 T2 should now see the SSD as a new SSD and show the option for external drives in the Startup Security Utility, but it doesn't.

Dec 12, 2020 4:47 AM in response to MyApple8MyPC

Yep, seeing exactly what you describe.

What may be scarier is if removal of external booting on M1 Macs

is by design and not a bug and the way it will be from now on.

While I have no intension of using an externally bootable drive

on a daily basis, it has always been my Plan A if something went

awry on the main system drive and needed to get back up and running

immediately instead of waiting the 3-4 hours or more for Time Machine

to restore the system.

MyApple8MyPC Author

Level 4

2,149 points

Dec 12, 2020 10:44 AM in response to woodmeister50

woodmeister50 wrote:

What may be scarier is if removal of external booting on M1 Macs

is by design and not a bug and the way it will be from now on.

I don't think that's the case, but if it were, then I know a whole lot of people with M1's that will be returning them and staying away from the new Apple Silicon machines.

Peymon

Level 1

8 points

Dec 13, 2020 8:34 AM in response to woodmeister50

Working just perfectly so far

just for Sh and giggles , I tried installing on

Sandisk 1t SSD and it worked as well with sane procedure as I mentioned

so my thinking is something with Samsung T5

stay Tuned

Peymon

Level 1

8 points

Dec 13, 2020 1:25 PM in response to woodmeister50

Yes I did and perfectly works fine , although speed is not as fast as internal ssd

so I am planning on going to Sandisk extremes pro to speed it up

but , speed list is Negligent , but since I have working after 3 days of calls and working on this

at times it feels like waiting for paint to dry ;)

Dec 14, 2020 5:00 AM in response to MyApple8MyPC

BTW, all this messing around has resulted in a minor issue,

my start up chime is gone. All combinations of checking

and unchecking "Play sound on start up", restarts, shutdown

and restarts, etc. is not bringing it back. I am sure some

buried system preference somewhere got corrupted

or some boot flag is confused.

At the moment no big deal, just annoying me that it doesn't

work.

Dec 14, 2020 9:12 AM in response to MyApple8MyPC

I may have made some progress. I went back into recovery and this time it accepted my password. Previously at this step it rejected it. Once it accepted the password it installed 11.01 (even though it was already installed on the drive). Once 11.01 was installed it booted into the screen shown below, and under the icon it just said “Other...”. Then when you click on it a password field opens. The problem is that no matter what name/ password combination I use it rejects it.

Dec 14, 2020 9:30 AM in response to MyMac8MyPC

That's further than I have been able to get. Today I decided to just

download the installer from the MacApp Store and tried installing

that way. The install went well and then it did the usual reboot.

I could see the light flashing on the external drive like it was

starting to load, then a very long pause, then the boot proceeded,

only to be booting from the internal drive.

The last three variations I tried to get the external to boot were all

the same. Seems like the external wants to boot, but something borks in

the process, the MBA gives up and boots to the internal.

I would buy another SSD drive but hesitate if it will only end the same way.

In another thread, someone did some tests and seems that NVMe based

external SSDs may work, but again, not all. That seems to be the case

with some of the USB-C drives being used. The underlying tech is NVMe.

MyApple8MyPC Author

Level 4

2,149 points

Dec 24, 2020 6:12 AM in response to MyApple8MyPC

UPDATE: Got the new NVMe M.2 hard drive and enclosure. Installed everything on it. Using Thunderbolt 3 to connect.

It still does not boot correctly.

Same issue as before, where it does not assign an admin account, so you can't login.

It's looking like Apple is going to be getting this Mac mini back soon.

Dec 25, 2020 4:05 AM in response to MyApple8MyPC

Based on your recent experience using a drive enclosure and drive

that worked on one system but the same set up on your system

didn't work, makes me wonder if we both don't have an obscure file

somewhere that is borked, some obscure combination of settings

somewhere, or some single line in a preference somewhere that is

the cause of the issue.

I bring this up since it seems the issue is some sort of "validity"

check or authorization issue that in my opinion would not be

a hardware issue but some corrupted software process. As

'spaghettified" as things are becoming, it probably would

not take more than a single line in a pref file somewhere

to gum things up.

MyApple8MyPC Author

Level 4

2,149 points

Dec 25, 2020 7:32 AM in response to woodmeister50

woodmeister50 wrote:

Based on your recent experience using a drive enclosure and drive

that worked on one system but the same set up on your system

didn't work, makes me wonder if we both don't have an obscure file

somewhere that is borked, some obscure combination of settings

somewhere, or some single line in a preference somewhere that is

the cause of the issue.

I was thinking along the same lines . I'm wondering if instead of porting over my backup files from my external drive, to instead use my internal "Macintosh HD" files. If it works then I can always add the other files from my backup drive later. It's worth a shot so I will try it later today.

MyApple8MyPC Author

Level 4

2,149 points

Dec 25, 2020 11:12 AM in response to MyApple8MyPC

OK I can't believe I'm saying this but... I just booted into my M1 from my external drive!

In-fact I'm posting this after logging into the external hard drive right now.

Side note: having said that I don't know (just yet) if this is repeatable. Meaning, others have booted externally too but then the next day they weren't able to boot back in from the external, so I haven't gotten that far yet. I'm just sitting here stunned that I even got this far...

I'm going to do more testing, and will report back in a few hours.

tbirdvet

Level 6

17,072 points

Dec 25, 2020 11:55 AM in response to MyApple8MyPC

I just realized you have a mIni and I have a MBA so there may be some operating differences even though both are M1 design. I just tested my external drive once again and no issues booting from it. My issue was not that I could not boot repeatable but just making the boot drive in the first place.

Dec 26, 2020 3:41 AM in response to tbirdvet

tbirdvet wrote:

I just realized you have a mIni and I have a MBA so there may be some operating differences even though both are M1 design. I just tested my external drive once again and no issues booting from it. My issue was not that I could not boot repeatable but just making the boot drive in the first place.

That is the issue I am having with my M1 MBA. I just can't

install an OS on an external drive and boot it by any means

of installation methods or how my drive is interfaced, at least

with the tools I currently have and the SSD I have.

The install just seems to not complete some step that adds

the necessary "stuff" to verify the drive or apparently add

the administrator. Which seems more like a software issue

than a drive issue, but then these days who knows.

I am going to pick up and give a Sandisk NVMe based drive

USB-C drive a shot today sometime. It is much less costly

than a TB3 solution and if it doesn't work, it will serve as

my photo library storage for 2021 (which I have been

looking to pick up anyway). If I bought a TB3 drive and it

didn't work, it would be way to costly for that purpose and

could only be directly connected to the MBA instead of

just sitting on my USB3 hub.

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Mac Mini M1 Using External SSD