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Can't Unmount Volume to Reinstall MacOS

I ran Disk Utility to check my computer before updating to the latest Mac OS System. Macintosh HD Data is corrupted. I restarted in Recovery mode to reinstall Ventura, but was unable to do so because the volume could not be unmounted. I also tried to check the volume an repair the volume in Terminal, but that also failed.

MacBook Pro 13″, macOS 13.6

Posted on Nov 26, 2023 6:38 AM

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5 replies

Nov 28, 2023 11:33 AM in response to Nancy Blazis

Did you try running First Aid while booted into Recovery Mode? If you are using an Intel Mac, then try booting into Internet Recovery Mode using Command + Option + R instead to access the most recent version of macOS installer. Unfortunately some Macs may only boot to the oldest online installer instead regardless of the key used for booting.


Within Disk Utility you can select the volume and click the "Unmount" button. If you are planning to erase the drive anyway, then force unmounting is Ok.


If your Mac still boots normally or into Safe Mode, then I highly recommend creating a bootable macOS USB installer so you may more options available (2018-2020 Intel Macs probably won't work in many cases to boot from USB especially if the internal SSD has been erased). If you have an Apple Silicon Mac, then you can use a firmware "Restore" to push a clean OS onto the internal SSD if you have access to another Mac running macOS 12.4+.


FYI, it really helps to know the exact model Mac so we can narrow down the possible suggestions to just your particular hardware.

Can't Unmount Volume to Reinstall MacOS

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