Startup manager corrotto? Mac mini Late 2018

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Accursio2019 Author

Level 1

4 points

Startup manager corrotto? Mac mini Late 2018

Good morning everyone,

I have a rather unusual problem with a Mac mini Late 2018 INTEL.

I bought this Mac used, I received it with SONOMA installed, it starts up regularly and everything seems ok.

I need to downgrade. I boot the Mac from an external disk with Mac OS 10.14.6 and clone the contents on the main hard disk using carbon copy cloner.

From this moment, trying to restart the Mac, the Apple logo appears but immediately afterwards it turns off and restarts cyclically.

It allows me to enter startup manager but if I try to select any disk (external or internal) and press enter it shuts down and restarts again. I have already tried resetting PRAM and SMC but to no avail.

What could have happened?

Posted on Nov 29, 2024 04:59 AM

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Answer 1

Nov 29, 2024 06:41 AM in response to Accursio2019

First make sure you have good backups. It might also be a good idea to make a bootable macOS installer, just in case (either Mojave and/or the latest which that Mac supports which seems to be Sequoia). That way you do not get stranded without a bootable device in case something goes wrong.

Boot to Mojave and use CCC 5 which is compatible with Mojave. Use Mojave Disk Utility to erase the internal device (not just volumes under it) as APFS, GUID, case insensitive and use CCC to clone Mojave to it. Then shutdown, disconnect external drive and try if Option-boot to the cloned internal disk now works. You might use CCC or apply Mojave installer to re-create the Recovery volume to the internal disk to complete the downgrade.

Notice that some libraries like Photos do not work in Mojave if some later macOS version has touched it, and some workarounds must be used to re-gain access to it.

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Answer 2

den.thed

Level 10

88,960 points

Nov 29, 2024 09:30 AM in response to Accursio2019

Cloning software can not and does not guaranty a bootable startup disk.

One option is to Reinstall macOS 10.14 Mojave over the top of the Clone on the internal drive.

Another option is to erase, do a clean Install of macOS 10.14 Mojave, then Migrate from the external Mojave clone.

The why do you want to stay on Mojave question, needs to be asked.

Mojave is no longer supported by updates and most older software can be replaced.

To look for Sonoma and/or Sequoia software replacements, see > https://roaringapps.com/apps

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Answer 3

Accursio2019 Author

Level 1

4 points

Dec 1, 2024 10:16 AM in response to Accursio2019

My post probably wasn't clear enough :-).

The mac mini won't let me boot at all.

I have several bootable disks that work fine on another twin mac mini and on a macbook, but not on this mac mini.

With any startup disk, the white APPLE logo appears and immediately restarts in a cyclical manner.

If I hold down the "option" button it asks me to select recovery from the internet or a startup disk but if I select startup disk>> black screen and reboot.

I tried to start the recovery via the internet by selecting a wifi network. Apparently it seemed to work but it starts downloading the recovery file for about 20 minutes and then restarts, starting again with the selection of the wifi network and repeats the download again (it restarted about 10 times after I gave up).

What do you recommend? can I throw it away?

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