Mac Mini M4 will not boot from external HD

I may have changed security settings in a previous version several years ago and it may have carried over with migration assistant with each new Mac I have purchased which is many. I cannot really remember. You can boot into recovery and select security from top menu and change if needed.

tbirdvet wrote:

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.

Platform issues aside, this is likely a security thing Apple has in place. Any macOS installation has an "ownership" linked not only to an admin user but also to the machine. This is likely to prevent anyone with a "generic" external boot drive from plugging into any Mac, booting it, and then scraping data from a stolen machine.

tbirdvet wrote:

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.

They are all Silicon these days (I guess) but you may mean Apple or Intel processors.

Ian R. Brown wrote:

When you format the SSD make sure you format the Physical Disk and not a Volume.

I made that mistake a year ago and wondered why it would not boot.

This is a sticking point on the route to cleaning and replacing the file system on a new SSD. The instructions on the Apple help site are not clear about navigating the different things Drive/Volume/Volume Group/Container/Media. Selecting the right name/label for such things is quite important.

https://www.seagate.com/gb/en/support/kb/how-to-format-your-drive-apfs-on-macos-big-sur-and-later/

The legacy bootable feature is part of CCC but not very reliable. So you need to boot into recovery to install the OS on the external. This applies mostly to silicon Macs. With Intels the legacy system usually works.

I have three minis.

a 2018

a m1

a m2

I use samsung t-5 t-7 t-9 and shirt pocket superduper clones.

took me forever but all three work.

i now want a m4 I want to replace the 2018. So I will wait a bit and then get the m4.

looks like it will be a pain to do . ugh

I use my boot drive only to backup files and also to test any new OS before I update my internal. Just a word of caution for anyone wanting to save cost by getting a small internal drive and using a larger external. Apple is starting to make some functions inoperable when using an external drive. Apple Intelligence and Apple Pay will not work. I suspect in the future there will be other functions and perhaps apps that will not work from the external.

tbirdvet wrote:

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.

Thanks for the info. I guess there are these precautions and options to make a bootable external drive on Silicon Macs:

Remove all 3rd party virus apps, "cleaning", "optimizing", "speed-up" and VPN apps that might corrupt the system. Connect the external SSD drive directly to the Silicon Mac. Disconnect any hubs and unneeded external devices that might be incompatible. Erase the external device (not just volumes under it) as APFS, GUID, case insensitive with that Mac's Disk Utility (or use the Disk Utility while in Recovery mode or while booted into USB installer).

#1. Download macOS installer from App Store and use it to install to the external drive.

#2. Boot into Recovery or Internet Recovery and use its installer to install to the external drive (this should bypass any corruption caused by those 3rd party apps). Booting into Recovery is fast but I guess also it must then download the actual installer files from the Internet and that might be slow and unreliable, right?

#3. Download macOS from App Store, prepare a bootable USB macOS installer with the Terminal via Apple's instructions, Option-boot to it, and install to the external drive (this should bypass any corruption caused by those 3rd party apps). The install phase is faster than in #2 because there is no need for further downloads (iCloud stuff can be skipped but I have not tested if can this be done completely off-line).

#4. Use Carbon Copy Cloner's default data-clone or Super Duper to the external disk, and make it bootable by applying a full macOS install with some #1-3 method.

#5. Use Carbon Copy Cloner's "legacy mode" or Super Duper to make a bootable clone to the external disk. Should work on Intel Macs but might not be bootable in Silicon Macs. Might the external drive then be made bootable by applying a full macOS install on top of the old system? Or maybe the "ownership" is then incorrect and the external drive is not bootable anyway?

David & Luis,

I am raising my hand as well. I have an M1 MacMini, and I have spent the last 4 days reading and watching every source possible, to learn how to boot from my external SSD drive. I get the exact same error - " OS needs to be Updated"...This is basically inexcusable from Apple. Why are we all rushing to expand our external bootable storage????

Booting from an external drive( until now) has been beyond-simple....Now they have made it impossible..to make matters worse :>> If they knew that it cannot be done, it would be nice if they let us all know that....

Guys, will a "patch" or update allow us to use an external SSD... or do you think this is a permanent situation for all Silicon CPUs ?

Thank you both very much for your comments above, to inform us on the situation.

Cheers,

Mike

[Edited by Moderator]

mechanic1357 wrote:

"Silicon CPU" ? They're all made of silicon! The options are Intel or Apple sources.

Apple refers to their M-series CPUs as Apple Silicon CPUs.

These are "System on Chip" designs that contain GPU cores, Neural Engine cores, display generators, and other I/O controllers in addition to CPU cores.

The phrase "Apple Silicon" emphasizes that these are Apple designs, and that Apple has the ability to design its own chips.

Coming back to this - I bought a new ssd and enclosure and followed the method of using ccc to clone the drive and installing the os on it, in recovery mode on the new machine. It worked a treat, unfortunately it did mean I had to buy a new ssd and enclosure - but I suppose I have another incase I run into this issue again!

Servant of Cats wrote:

mechanic1357 wrote:

"Silicon CPU" ? They're all made of silicon! The options are Intel or Apple sources.

Apple refers to their M-series CPUs as Apple Silicon CPUs.

These are "System on Chip" designs that contain GPU cores, Neural Engine cores, display generators, and other I/O controllers in addition to CPU cores.

The phrase "Apple Silicon" emphasizes that these are Apple designs, and that Apple has the ability to design its own chips.

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?

Guys.....It does NOT work...Everything installs properly. The drives are all recognized as they should be, but when we actually try to re-boot to an EXTERNAL drive using OSX 15.xxxx and a M1 -M4 CPU it will not boot to that external drive.

I spent way to much time on this, changing cables, changing SSD drives, changing external enclosures............still it does not boot..

Mike S

"Download and reinstall the OS. The original OS on it my have been corrupted. This will often happen when it is downloaded via Wi-Fi. Better to use a wired Ethernet connection."

I tried this and it worked perfectly!