How to boot from an external SSD - USB or Thunderbolt

[pistonpilot]

I have solved the current problem booting external SSD from a Mac Mini M1:

I looked at various threads and followed all suggestions. Nothing worked.

I used the regular USB 3 cable, not the thunderbolt.

Here is the solution: Partition the SSD as exfat. I suppose FAT or NTFS would work as long as you format the drive differently. Telling it to erase the APFS with another APFS including volumes, did nothing. After you format as EXFAT, then you can partition again as APFS.

I installed the external SSD while booted into Big Sur on the internal Mac Mini SSD.

I invoked the Big Sur Installer from my desktop and told it to install on the external SSD.

I can boot from USB 3 and from USB C Thunderbolt.

I am encrypting with Filevault now.

Everything works as it should.

I DID NOT downgrade security.

 

[russell_314]

I have solved the current problem booting external SSD from a Mac Mini M1:

I looked at various threads and followed all suggestions. Nothing worked.

I used the regular USB 3 cable, not the thunderbolt.

Here is the solution: Partition the SSD as exfat. I suppose FAT or NTFS would work as long as you format the drive differently. Telling it to erase the APFS with another APFS including volumes, did nothing. After you format as EXFAT, then you can partition again as APFS.

I installed the external SSD while booted into Big Sur on the internal Mac Mini SSD.

I invoked the Big Sur Installer from my desktop and told it to install on the external SSD.

I can boot from USB 3 and from USB C Thunderbolt.

I am encrypting with Filevault now.

Everything works as it should.

I DID NOT downgrade security.

That's awesome! Can you choose to boot from the internal SSD and go back and forth easily or is it once you set to boot from external it's just left that way? I mean is it easy to switch back and forth? I still have an Intel Mac mini but I'm really thinking about getting an M1 version.

 

[pistonpilot]

I have not tried yet and won't until my iMac i9 come back from repair. I bought the M1 for my son, but also as a spare so I could use it when I have to give up my iMac.

I don't dare try to find out. It works, it reboots, and I'll let you know in two weeks when my iMac returns.

 

[jdb8167]

That's awesome! Can you choose to boot from the internal SSD and go back and forth easily or is it once you set to boot from external it's just left that way? I mean is it easy to switch back and forth? I still have an Intel Mac mini but I'm really thinking about getting an M1 version.

You should be able to use Startup Disk as normal.

 

[pistonpilot]

You should be able to use Startup Disk as normal.

Perhaps, but it took 10 hours to transfer my data from my iMac to the Mini onto the SSD. I'm not repeating that.

 

[jdb8167]

Perhaps, but it took 10 hours to transfer my data from my iMac to the Mini onto the SSD. I'm not repeating that.

Not sure what you mean. Your internal SSD should still be bootable with all your data. You should be able to switch between the internal and external as bootable disks.

 

[pistonpilot]

Since the device or Big Sur is buggy, I am not going to tip the boat. I have a fantastic system to use while they repair my iMac.

 

[jdb8167]

Since the device or Big Sur is buggy, I am not going to tip the boat. I have a fantastic system to use while they repair my iMac.

No doubt that is true. If I can’t switch at will though, having bootable external isn’t very useful.

 

[pistonpilot]

No doubt that is true. If I can’t switch at will though, having bootable external isn’t very useful.

Ok, you find out. I am not going to risk it. In two weeks when my son wants to use his Mac Mini again, I will switch back to the internal, and then switch to the external to know. So, you can wait, or do what I did to find out for yourself.

 

[russell_314]

No doubt that is true. If I can’t switch at will though, having bootable external isn’t very useful.

I'm guessing the point of an external boot drive is the internal one is too small. You could buy an external 1TB TB3 drive pretty cheap. If it's a desktop you're not going to unplug it and plug it back in all the time. If you just use it and leave it the external one would be fine.

 

[pistonpilot]

I'm guessing the point of an external boot drive is the internal one is too small. You could buy an external 1TB TB3 drive pretty cheap. If it's a desktop you're not going to unplug it and plug it back in all the time. If you just use it and leave it the external one would be fine.

You are correct. Had I know when I bought the M1 three weeks ago how much time I would have to waste, I might have opted for a bigger internal drive. I opted to get 16GB instead of a larger SSD.

 

[Mike Boreham]

I have solved the current problem booting external SSD from a Mac Mini M1:

I looked at various threads and followed all suggestions. Nothing worked.

I used the regular USB 3 cable, not the thunderbolt.

Here is the solution: Partition the SSD as exfat. I suppose FAT or NTFS would work as long as you format the drive differently. Telling it to erase the APFS with another APFS including volumes, did nothing. After you format as EXFAT, then you can partition again as APFS.

I installed the external SSD while booted into Big Sur on the internal Mac Mini SSD.

I invoked the Big Sur Installer from my desktop and told it to install on the external SSD.

I can boot from USB 3 and from USB C Thunderbolt.

I am encrypting with Filevault now.

Everything works as it should.

I DID NOT downgrade security.

I'm glad that you have found a way, but it is certainly not the only way. As reported in other threads I have installed and booted from external USB-C and TB3 drives formatted APFS (not via exFAT). I have also installed directly onto a volume in a shared APFS container on a USB drive. I have found it essential to have the external directly connected to my M1 MBA. I have done my installing from a bootable USB thumbdrive. You are right that reduced security is not required, though many think it is.

There are obviously factors preventing some people being able to do this and I don't think we have a handle on what they are yet.

 

[jdb8167]

Ok, you find out. I am not going to risk it. In two weeks when my son wants to use his Mac Mini again, I will switch back to the internal, and then switch to the external to know. So, you can wait, or do what I did to find out for yourself.

So far I'm still just seeing the same old errors. USB-C to USB 3.0 drive. It gets stuck at about 2-4 minutes left and then tries to reboot and then just gives the same old errors. It is just buggy and sometimes it works but mostly it doesn't. So far I haven't been successful with a USB 3.0 drive.

 

[pistonpilot]

I'm glad that you have found a way, but it is certainly not the only way. As reported in other threads I have installed and booted from external USB-C and TB3 drives formatted APFS (not via exFAT). I have also installed directly onto a volume in a shared APFS container on a USB drive. I have found it essential to have the external directly connected to my M1 MBA. I have done my installing from a bootable USB thumbdrive. You are right that reduced security is not required, though many think it is.

There are obviously factors preventing some people being able to do this and I don't think we have a handle on what they are yet.

You didn't read what I wrote carefully. I formatted it EXFAT so nothing would be left of the APFS from the Intel iMac.

Big Sur will only install to an APFS partition.

 

[Mike Boreham]

You didn't read what I wrote carefully. I formatted it EXFAT so nothing would be left of the APFS from the Intel iMac.

Big Sur will only install to an APFS partition.

Yes I did understand that (why I added the word "via" in my reply. Just saying it wasn't a necessary step in any of my installs. A regular DU erase was sufficient.

 

[pistonpilot]

Bad news. When I woke, the computer did not come out of sleep properly. On reboot, it went into Options automatically. I was never able to boot from the SSD external again. Thanks so much, Apple.

The drive works fine as an attached drive, but I can no longer choose it as a boot disk.

 

[Screensaver]

Bad news. When I woke, the computer did not come out of sleep properly. On reboot, it went into Options automatically. I was never able to boot from the SSD external again. Thanks so much, Apple.

The drive works fine as an attached drive, but I can no longer choose it as a boot disk.

By any chance, has here been another chapter in your saga? I’ve tried three different M1 Mini’s and three different branded SATA 2.5” SSD’s and haven’t had luck. I always get the “SDErrorDomain 104” error.

Were you able to get your external boot working with any more success or trickery?

It’s not too late to get a refund for this Mac due to this issue, you know.

 

[pistonpilot]

By any chance, has here been another chapter in your saga? I’ve tried three different M1 Mini’s and three different branded SATA 2.5” SSD’s and haven’t had luck. I always get the “SDErrorDomain 104” error.

Were you able to get your external boot working with any more success or trickery?

It’s not too late to get a refund for this Mac due to this issue, you know.

It's too late because I purchased it in January. Why isn't it too late?

I bought the Mac Mini for my son and for me to use in an emergency. My iMac went for a repair and it took 2 weeks. I wanted to boot my system from the external drive used on my iMac. I was given bad information from Apple Tier 2 support on more than one occasion that this was possible. My iMac came back from repair so I no longer needed to get that functionality. Apple is disappointing. I have other issues with the M1 and my iMac, and I had to jettison Big Sur which is a BIG SUCK of an OS. I installed it on my external SSD and put Catalina. Screw Apple and Big Sur.

 

[Screensaver]

It's too late because I purchased it in January. Why isn't it too late?

I bought the Mac Mini for my son and for me to use in an emergency. My iMac went for a repair and it took 2 weeks. I wanted to boot my system from the external drive used on my iMac. I was given bad information from Apple Tier 2 support on more than one occasion that this was possible. My iMac came back from repair so I no longer needed to get that functionality. Apple is disappointing. I have other issues with the M1 and my iMac, and I had to jettison Big Sur which is a BIG SUCK of an OS. I installed it on my external SSD and put Catalina. Screw Apple and Big Sur.

I purchased mine in January as well, and recently was offered an exchange for a new one, which isn’t any better for me, and so I will return it too. All because Apple wouldn’t level with me and told me that I must have had a defective unit. I guess Apple would rather me keep buying M1 Macs and returning them because they encouraged me to by multiples just to make sure I could find one that would boot from an external SSD successfully. Well, no surprise—none did and now I have a handful of M1 Mini’s to return. I hope Apple gets the message that they can’t release half-cocked products and then blow smoke at their loyal customers.

Anyway, call Apple and ask to speak with technical support. Have them try and help you to boot from an external drive. When that gets you nowhere, ask to speak with a supervisor. Let them know that you can’t use his computer without booting externally and how you’ve gotten the runaround for three months. Tell them that you need a Genius Bar meeting scheduled and that if they cannot get this functionality to work, then they either need to repair what’s wrong, or you need to arrange to have your unit replaced. This functionality not working should be covered by your year of included Apple care. If the Apple Store has your same unit in store, insist that you open it up right in front of them and make sure external
Booting works. If not, you have the right to demand your money back. I wish I avoided all this mess, but I was outside of the 14 day window before I attempted an external boot. Anyway, don’t give up. We can’t let Apple get away with this bait and switch. Let me know how it goes or if I can help.

 

[pistonpilot]

I purchased mine in January as well, and recently was offered an exchange for a new one, which isn’t any better for me, and so I will return it too. All because Apple wouldn’t level with me and told me that I must have had a defective unit. I guess Apple would rather me keep buying M1 Macs and returning them because they encouraged me to by multiples just to make sure I could find one that would boot from an external SSD successfully. Well, no surprise—none did and now I have a handful of M1 Mini’s to return. I hope Apple gets the message that they can’t release half-cocked products and then blow smoke at their loyal customers.

Anyway, call Apple and ask to speak with technical support. Have them try and help you to boot from an external drive. When that gets you nowhere, ask to speak with a supervisor. Let them know that you can’t use his computer without booting externally and how you’ve gotten the runaround for three months. Tell them that you need a Genius Bar meeting scheduled and that if they cannot get this functionality to work, then they either need to repair what’s wrong, or you need to arrange to have your unit replaced. This functionality not working should be covered by your year of included Apple care. If the Apple Store has your same unit in store, insist that you open it up right in front of them and make sure external
Booting works. If not, you have the right to demand your money back. I wish I avoided all this mess, but I was outside of the 14 day window before I attempted an external boot. Anyway, don’t give up. We can’t let Apple get away with this bait and switch. Let me know how it goes or if I can help.

I know the head of customer relations in the USA. I live in Asia. Yes, it's possible but is it practical?

 

[Mike Boreham]

By any chance, has here been another chapter in your saga? I’ve tried three different M1 Mini’s and three different branded SATA 2.5” SSD’s and haven’t had luck. I always get the “SDErrorDomain 104” error.

As you no doubt know from the forum, external booting is working well for some and not for others. Experience seems very varied, and the factors hard to pin down.

However you are the only one I have seen report the “SDErrorDomain 104” error. This is no help to you I know, but if you have tried three different M1 Minis, something other than faulty macs is causing the problem.

 

[satcomer]

If you were a Mac user that followed the release of the new Mac OS Apple locked that down that NOW a Mac user must boot into recovery (forgo doing the Install) mode launch from menu items Security Manager and allow that to happen the old way!

 

[Mike Boreham]

If you were a Mac user that followed the release of the new Mac OS Apple locked that down that NOW a Mac user must boot into recovery (forgo doing the Install) mode launch from menu items Security Manager and allow that to happen the old way!

Not quite sure what this is saying, but you mentioned Security Manager. In case this is referring to the Startup Security Utility, it is not necessary to have reduced security to boot an external on Silicon Macs, unlike T2 equipped Intel Macs where it is.

 

[satcomer]

Not quite sure what this is saying, but you mentioned Security Manager. In case this is referring to the Startup Security Utility, it is not necessary to have reduced security to boot an external on Silicon Macs, unlike T2 equipped Intel Macs where it is.

Excuse Me but this video shows me you still can do it:

 

[Mike Boreham]

Excuse Me but this video shows me you still can do it:

He's wrong. I have installed on external drives without using Reduced Security. I am not the only one. Try it for yourself.