Mac Mini M4 will not boot from external HD

I have exactly the same problem, got my M4 the day of the release to swap a M1 Mac mini which I have booting from this external drive, when I started the M4 and connect the external WD NVME on a TB Acacis case I get an "SDErrorDomain error 104". Escalate to a senior engineer on Sunday from apple and they haven't get back to me. Getting frustrated because Apple shouldn't block this kind of practice to force people to purchase their savage and expensive storage ! If I don't resolve this in the next days I'll return the machine.

I have an external boot drive for my new Mini M4. I use a WD NVME in a TB enclosure. I use carbon Copy Cloner(CCC) to clone the data, then I booted into recovery and installed 15.1 on the external and it works fine. I did not use the CCC legacy bootable tool as that does not work most of the time with Silicon Macs.

All I can say is that I have a one year old USB 3.0 SSD (Sonoma) and a three week old Thunderbolt NVMe (Sequoia 15.1.1) which my M2 mini can boot from so there doesn't appear to be anything wrong with the M-series architecture.

I haven't tried the M4 but many others on YouTube etc. have and they all appear to work so there must be something different about your setup or modus operandi.

Are you sure you are formatting the Physical Disk and not a Volume? Very often by default, Disk Utility is set to View/Show Only Volumes which you must not use for formatting.

You must select "Show All Devices" which will display Physical Disks which can be corroborated as shown by the arrow.

I had the same issue. With the new Mac you need to make a new bootable drive. The previous bootable drive will not work. The Platform is not compatible. I redid my bootable drive using the new M4 Mac and works fine. That being said I did use my previous external clone drive to migrate to my new Mac M4 and had no issues. It just could not be used as a boot drive until I redid it using the new Mac M4.

Yes it does work.

I have installed Sequoia 15.1.1 on an external SSD and even an external Fusion Drive.

When installing the OS directly to a freshly formatted drive ( I tend to use

sudo diskutil partitionDisk drive(xx) 1 gpt jhfs+ DriveName 100%

rather than Disk Utility), it works perfectly.

Carbon Copy Cloner nearly works when using Legacy Copy. You still have to install the OS afterward, but that doesn't take too long.

im In this same exact situation.. all the videos I’ve watched just show people using new drives / ones they’ve erased. I have so many important programs on my external which i need.. hoping something comes up on resolving it

for what's it's worth.

I purchased a Mac mini M4 base model when it launched. Yesterday I took an external USB C-SSD That I had purchased from CostCo years ago (I connected it to the front USB 3.? connectors as I knew it was USB 3 or slower)

I launched the recovery and formatted the external SSD using Disk Utility from the recovery tools. I loaded the latest MacOS from the recovery to the external drive.

I restarted the recovery and booted into the external drive. The only thing I lost running the external drive was Apple Intelligence will do operate on a external drive (I have no idea why??)

To change boot drives I use the boot drive selector from the System settings...

I got same issue with my m2 Mac mini bootable external drive. I used to use external macOS 15.1.1 on my m2 Mac mini. When I upgraded to m4 pro Mac mini. I couldn’t boot my from my old drive. At last I have to transfer it to my internal SSD on the m4 pro Mac mini. Based on the reports that m4 macs cannot virtualize macOS version earlier than 13.4. I guess the macOS 15 on M1-3 and M4 chips are not exactly the same one.

mechanic1357 wrote:

Yes we all know Apple designed these CPU chips, hard to avoid the fuss around the launch of the latest M series

in the press a few months ago. The point I made was that the phrase 'Silicon CPU' was a bit redundant and possibly jarred with people bought up at the time when Apple used Intel processors in earlier Macs and when the help pages offered options based on the CPU source (checks - they still do). Maybe people thought there were Germanium or Gallium Arsenide chips in the pipeline? Maybe Apple licensed Nvidia or AMD to produce such processors?

Or maybe it's just a name and you're overthinking it?

This is the same enclosure and drive I have, how did you make it work? Can you please help me !

Those all in one docks have never been a reliable system for a bootable external drive.

You really need to use a standalone external USB4 or Thunderbolt enclosure for a bootable SSD and even then you need to make sure you have the right combination of enclosure and SSD, not just for boot ability but even just to work fast and reliable. Many combinations simply don't work on a Mac (or a PC for that matter).

david3_1415 wrote:

Bootable SSD will boot with iMac and Macbook running 15.1.

Are those machines Intel-based or Apple-Silicon-based?

I would not be too surprised to find that any particular installation of macOS works only with one processor type. Sequoia runs both on Apple Silicon Macs and on some Intel Macs, but that would not necessarily mean that you could take a Sequoia startup drive from an Intel Mac, and boot from it on an Apple Silicon Mac, or vice versa.