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Question: How I successfully Made an M1 External Boot Drive.

Several weeks ago I bought a new M1 Mac mini. One of the first things that I needed to do was to set-up a bootable external drive. I thought that this would be straight forward just like on an intel Mac, but it was not.


No matter what I tried to do I always ran into issues/errors, and upon doing a lot of research I quickly learned that I was not alone. Many other people, both here, and on other Apple forums were having the same frustrating  issues trying to make a M1 bootable external drive for their M1 also. 


After thinking about what might be going wrong, I decided today to take a different approach to the issue. Everyone was being told to copy over their data partition, either by using CCC or by using Migration Assistant, and then once that process was completed to go into Recovery and install a fresh new copy of 11.1 to their external drive. This always ended up with the above mentioned issues/errors. 


So today I decided to strip the process down so that I could learn what might be going wrong. My goal was to simply make a bootable drive, with no saved data on it. I simply wanted to externally boot into a fresh copy of 11.1. I figured that if I could get that far, then I could copy all of my old files over later. 


Well guess what? It worked!


Here’s how I did it, but keep in mind that you need to perform every step from your M1. First I formatted my external drive down to the bone. Then you need to log into Recovery by doing the  following;


Make sure that your Mac is turned off. If it is not off then click on the Apple logo (upper left corner or your screen) and choose Shut Down.


Next press the power button on your M1 and keep pressing the power button down until you see a message on your screen saying that it is loading Options. You can now let go of the power button. 


Next, click on Options (far right side) then click on Continue.


If asked, select a user, click on Next, and enter in your Administrator Password. 


You are now successfully logged into the M1’s Recovery mode.



Now choose Reinstall macOS Big Sur as shown above, and follow the prompts after you choose which external drive you want to boot from. It can take up to several hours for Mac Big Sur to install, but once it does it will reboot (several times) and then it will open up your desktop. Enter in your admin password and that’s it, you now have a bootable external M1 drive! 


From there I simply used CCC to copy over my data from my backup hard drive. All that is left is to use Migration Assistant to copy over your user account. That is were I am currently at. It keeps saying that I need to update before Migration Assistant can run, so I’m looking for a way to get around that, or I’ll just wait until 11.2 is released (see screenshot below).



For my external boot drive I am using an Inland Professional NVMe M.2 PCIe SSD, and it is crazy fast. For the SSD Enclosure I am using an Trebleet Thunderbolt 3 enclosure, which comes with a Thunderbolt 3 cable. BTW, I have tried using several top shelf Thunderbolt 3 cables with this same set-up, and they all seem to work great. I will post performance data later, but I already know it is extremely fast and buttery smooth. 


If anyone knows how to get around the Migration Assistant error mentioned above, please post. If you are successful making a M1 boot drive, please also share your success here with everyone. I sincerely hope that this helps others.


Mac mini, macOS 10.13

Posted on Dec 25, 2020 6:08 PM

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Dec 26, 2020 4:02 AM in response to MyApple8MyPC In response to MyApple8MyPC

I have done your process multiple times to the T and when it gets here:


MyApple8MyPC wrote:

...but once it does it will reboot (several times) and then it will open up your desktop. Enter in your admin password and that’s it, you now have a bootable external M1 drive! 


Is where it fails miserably. It starts to reboot then all "shuts down" for about a minute

and then just ends up rebooting to the internal drive.


However, since you finally achieved some success with the TB3 solution,

it could be that all my combinations of interfacing my SATA SSD to

my MBA that I have available will simply not work.


I think I may pick up an NVMe based USB-C drive today and try attempting

that. It's a lower cost alternative to TB3 and I can get my grubby hands on

one with just a 30 minute drive and if it doesn't work, I need a drive for

my 2021 photos anyway.

Dec 26, 2020 4:02 AM

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Dec 26, 2020 4:36 AM in response to woodmeister50 In response to woodmeister50

woodmeister50 wrote:


I have done your process multiple times to the T and when it gets here:

However, since you finally achieved some success with the TB3 solution,
it could be that all my combinations of interfacing my SATA SSD to
my MBA that I have available will simply not work.

This is going to be my next experiment, trying to make a non-TB3 bootable drive.


Should know in a day or two if it's possible.


Are. you doing everything from the M1? Even the formatting needs to be from the M1.

Dec 26, 2020 4:36 AM

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Dec 26, 2020 6:23 AM in response to MyApple8MyPC In response to MyApple8MyPC

I attempted to use my NVME drive in USB-C enclosure with my MBA M1 and I could not compete the process to make the external drive work. I then put the drive in my TB3 enclosure and no issue. I did find something interesting. With the USB-C enclosure I was getting about 900 MB/s read/write from my 2019 iMac connected to TB3 port. The same config on my MBA only shows 600 Mb/s. I wonder why this is? I also formatted my drive using my iMac and not the MBA so not sure if this played any part. Seems like APFS is APFS no matter from where formatted but who knows.

Dec 26, 2020 6:23 AM

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Dec 26, 2020 7:12 AM in response to MyApple8MyPC In response to MyApple8MyPC

MyApple8MyPC wrote:
....

Are. you doing everything from the M1? Even the formatting needs to be from the M1.

I haven't even fired up my iMac since getting my M1 MacBook Air

just before Thanksgiving. So yes, everything has been done on the M1.


Dec 26, 2020 7:12 AM

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Dec 26, 2020 7:15 AM in response to tbirdvet In response to tbirdvet

tbirdvet wrote:

I attempted to use my NVME drive in USB-C enclosure with my MBA M1 and I could not compete the process to make the external drive work. I then put the drive in my TB3 enclosure and no issue.

I am going to also try using a USB-C enclosure. Will post my results here. It doesn't make any sense that USB-C would not be supported, but that's the way it's looking.


I can verify that you'll need to do the entire process of making your external boot drive from your M1.

Dec 26, 2020 7:15 AM

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Dec 26, 2020 7:19 AM in response to woodmeister50 In response to woodmeister50

woodmeister50 wrote:

everything has been done on the M1.

I'll be making a USB-C M1 external drive soon. Once I know more I'll post whether it's possible to use USB-C or not. All of my other attempts failed, but now that I know of a process that has been verified to work (with TB3) I'll see what happens when I use that same process with a USB-C drive.

Dec 26, 2020 7:19 AM

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Dec 26, 2020 9:08 AM in response to MyApple8MyPC In response to MyApple8MyPC

Well, stranger things have happened I guess.


I went down to the nearby Wally World and picked up the $19 Apple

USB-C -> USB-A adapter. Did some drive "juggling" and put the drive

I intended to use for my external boot drive into a StarTech USB 3

portable enclosure (the aluminum one that's around $20-25 on

Amazon). I then plugged in the Apple adapter plug the drive in

and started through "the procedure". Well the install went along

much further than any previous attempt (as indicated by drive activity)

and then seemingly stopped for a very, very long time, however

never went to boot into the internal as before. So at that point I thought

it was another borked attempt. Turn off my M1 MBA, and though well

let's see if it boots anyway in recovery,


Guess what? Selected it to boot and low and behold I was presented

with the welcome screen! Went through all the usual setup steps

and I am currently migrating the Time Machine backup that I

made this morning. I have had similar. occurrences in days past

where it would seem an install or update would stall but upon reboot

things completed.


Whether this can be consistently bootable or not remains to be seen

but this the closest to success that I have had!


So, my combination for success (fingers crossed) was putting the

SanDisk 512 GB SSD into a StarTech enclosure:

https://www.amazon.com/StarTech-com-USB-C-Hard-Drive-Enclosure/dp/B00XLB0EOW/ref=sr_1_6?dchild=1&keywords=startech%2Busb%2Benclosure&qid=1609001246&sr=8-6&th=1

and then use the Apple USB-C -> USB-A adapter.


What did not work:

The same SSD, Seagate Thunderbolt "sled", Thunderbolt 2 to Thunderbolt 3

adapter.

The same SSD with a SATA->USB adapter through a USB-C dock.


So, next tests since it "seems" I can get a bootable drive with a TM

migration (will test a couple times to make sure of that), I will attempt

a CCC data clone and see if that messes things. If it does, I may try

the CCC method.


Dec 26, 2020 9:08 AM

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Dec 26, 2020 9:39 AM in response to woodmeister50 In response to woodmeister50

woodmeister50 wrote:

Guess what? Selected it to boot and low and behold I was presented
with the welcome screen!

LOL... yep, when I first saw the welcome screen I couldn't believe it!


Glad it worked out for you :)


BTW, CCC did not mess things up for me when I used it.

Dec 26, 2020 9:39 AM

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Dec 26, 2020 10:07 AM in response to MyApple8MyPC In response to MyApple8MyPC

I did a clone as well with seemingly no ill effects.


Although, I think when I did the Time Machine migration,

it messed up my Apple Pay as I think it created a new

user on the MBA. I am going to update the clone and reboot

to it. Never had Apple Pay on the Mac before so this could

be an issue, though minor since I can just do what I have

done for years with credit cards on the Mac, enter the data.


I got the idea for the Apple USB-C adapter from a post elsewhere

and the person also stated in that post for some reason, only the

Apple adapter worked and generic ones didn't, at least for him.

Dec 26, 2020 10:07 AM

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Dec 26, 2020 11:13 AM in response to woodmeister50 In response to woodmeister50

Some how Keychain or some such mechanism is seeing

the cloned external data and user account as a different user on

my MBA vs. my internal account and as such removes the cards

in Wallet/Apple Pay from use on the MBA. I guess it makes sense

as a security measure.


No biggie as I can count the number of times I have used

Apple Pay on one finger.

Dec 26, 2020 11:13 AM

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Dec 26, 2020 4:23 PM in response to woodmeister50 In response to woodmeister50

woodmeister50 wrote:

I got the idea for the Apple USB-C adapter from a post elsewhere
and the person also stated in that post for some reason, only the
Apple adapter worked and generic ones didn't, at least for him.

This adapter?


https://www.apple.com/shop/product/MJ1M2AM/A/usb-c-to-usb-adapter

Dec 26, 2020 4:23 PM

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Dec 27, 2020 3:54 AM in response to MyApple8MyPC In response to MyApple8MyPC

MyApple8MyPC wrote:


woodmeister50 wrote:

I got the idea for the Apple USB-C adapter from a post elsewhere
and the person also stated in that post for some reason, only the
Apple adapter worked and generic ones didn't, at least for him.
This adapter?

https://www.apple.com/shop/product/MJ1M2AM/A/usb-c-to-usb-adapter

Yes, that is the one I used. The person in the post that gave me

the idea also mentioned that a couple of the "generic" USB-C -> USB-A

adapters they tried did not work.


So, after weeks of frustration, my solution to the external

boot problem cost me $20, a SandDisk Ultra 3D 512 GB

SATA drive I was using as a clone for my iMac, and a

StarTech USB 3 enclosure that I was using for the SSD for

Time Machine (put the TM drive on a SATA->USB3 adapter

which works just fine).


FWIW, while not being the ultimate on speed, I have found

using the SanDisk Ultra 3D series work quite well as boot

drives on all my Macs. I have also been using them as redundant

pairs on my home server as I slowly move away from HDDs.

Dec 27, 2020 3:54 AM

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Dec 27, 2020 8:13 AM in response to woodmeister50 In response to woodmeister50

woodmeister50 wrote:
and a StarTech USB 3 enclosure

Woodmeister50 do you have an exact model number for this enclosure? Making a list of verified products that work (and don't work) for this M1 boot drive. Thanks.

Dec 27, 2020 8:13 AM

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Question: How I successfully Made an M1 External Boot Drive.