Disk Utility Erase process failed: couldn't unmount disk, in use by process

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Disk Utility Erase process failed: couldn't unmount disk, in use by process

Help. I am trying to erase my iMac (21.5-inch, late 2021, running OS Catalina) before I give it away or sell it, following the Apple instructions here: Use Disk Utility to erase an Intel-based Mac - Apple Support

I've encountered this problem and I can't figure out what to do next. I'll appreciate any suggestions. I'm not super tech savvy, so please keep it simple. Thank you.

iMac 21.5″, macOS 10.15

Posted on Dec 27, 2024 12:42 PM

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Answer 1

Dec 27, 2024 12:56 PM in response to mcstace

Hello!

I have two troubleshooting steps for you to try. For the first one, could you fully shut down your computer and try rebooting into recovery mode (Command R). After that, retry the same steps. If that does not work or it looks different please send another picture.

Thanks!

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Answer 2

mcstace Author

Level 1

12 points

Dec 27, 2024 1:03 PM in response to ChromiumOverload

Thanks for your help: I tried to erase again and it worked this time . . . so the problem solved itself. I appreciate your support.

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Answer 3

Dec 27, 2024 1:04 PM in response to mcstace

Of course! Glad it worked out.

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Disk Utility Erase process failed: couldn't unmount disk, in use by process

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