What area of internal drive to erase before full reinstall

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Level 1

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What area of internal drive to erase before full reinstall

While installing an external drive on my MM M4 today, I followed the online instructions on how to point the startup file to the external drive. However, when I restarted my machine, it “appeared” to boot from the old file. When I boot, I receive a desktop screen and a request to enter my password. When entering my password (I am 100% confident about it), a processing symbol and a password error warning appear for a short time.

I have tried to reload the operating from the restoration button several times, and it appears to process that instruction, but I continue to be locked out. Thus, the thought was to reload an entire OS. I have downloaded the Sequoia OS and want to use it.

But where do I put it? First, I want to erase that portion of my MM M4 internal drive and reload the complete OS.

Would someone point me in the right direction?

Thanks, Bob Bytnar

And, of course, Happy Holidays from the Cayman Islands!

Mac mini (M4)

Posted on Dec 24, 2024 12:40 PM

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Answer 1

Dec 24, 2024 12:53 PM in response to Robbbwpb

If you want to startup from an external drive, you must first ensure that external drive is formatted properly for the Mac. Your Mac mini M4 requires a drive formatted with APFS and with a GUID partition map. You will use Disk Utility to format that drive. Erase and reformat a storage device in Disk Utility on Mac - Apple Support

With that done, you can restart the Mac in recovery mode to install the macOS onto the newly formatted drive. The process will ask you to select the drive that you wish the OS to be installed on. At that point you will select the external drive. If the external is not formatted properly it may not be presented as a selection choice.

Install macOS on an external storage device and use it as a startup disk - Apple Support

Optionally, you may install macOS onto the external drive by downloading macOS from the App Store. The download will deposit an installer app in the Applications folder. You would double-click that to launch and start the install process. With this process you will also be asked which drive you wish to install the OS onto. Select the properly formatted external drive.

How to download and install macOS - Apple Support

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Answer 2

HWTech

Level 9

66,842 points

Dec 24, 2024 12:55 PM in response to Robbbwpb

Here is an Apple article with instructions for reinstalling macOS including a clean install:

How to reinstall macOS - Apple Support

The other option would be to perform a DFU Firmware Restore which resets the security enclave chip, system firmware, internal SSD, and pushes a clean copy of macOS onto the internal SSD. Unfortunately this option requires access to another Mac probably running macOS 15.x Sequoia.

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