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Trying to erase HD on my old iMac.

Opened Disk Utility to erase HD but Erase button is greyed out. Hovering mouse over button brings message "This operation cannot be performed because you cannot unmount the volume you are booted from." What to do now?

iMac 21.5", macOS 10.13

Posted on Jun 30, 2019 3:50 PM

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Question marked as Top-ranking reply

Posted on Jul 3, 2019 10:30 PM

Hi, judyfromelgin,


When I had to do an erase and reinstall on my ‘11 26” iMac for the Apple GiveBack program, “powered by phobio”, they sent me these instructions on what to do (see attached). Besides erasing all of my data off of it, it had to be operational so they could immediately sign-in, upon arrival. Only, the instructions didn’t work for me, either.


It took awhile over the phone with Apple Support (https://support.apple.com/en-us/HT201232), who then had to transfer me on to a super tech guy, who was, finally, able to resolve my problem. Never quite understood what the difficulty was, unless it was that I’d had the 2T hard drive, while the ‘system’ — and reimbursement was only set up for a 1T size.


I was glad I’d called, as I never, ever would have figured it out for myself. And I learned calling Apple Support was the right thing to do. They were happy to help.


Hopeful this is helpful!

Linda

12 replies
Question marked as Top-ranking reply

Jul 3, 2019 10:30 PM in response to judyfromelgin

Hi, judyfromelgin,


When I had to do an erase and reinstall on my ‘11 26” iMac for the Apple GiveBack program, “powered by phobio”, they sent me these instructions on what to do (see attached). Besides erasing all of my data off of it, it had to be operational so they could immediately sign-in, upon arrival. Only, the instructions didn’t work for me, either.


It took awhile over the phone with Apple Support (https://support.apple.com/en-us/HT201232), who then had to transfer me on to a super tech guy, who was, finally, able to resolve my problem. Never quite understood what the difficulty was, unless it was that I’d had the 2T hard drive, while the ‘system’ — and reimbursement was only set up for a 1T size.


I was glad I’d called, as I never, ever would have figured it out for myself. And I learned calling Apple Support was the right thing to do. They were happy to help.


Hopeful this is helpful!

Linda

Jul 3, 2019 6:15 PM in response to babowa

It's a mid-2011 21.5" model that has been updated to High Sierra over the years. I'm the keeper of everything but no install disks included in packing box. It was a good 'puter for my means but became very slow despite Disk Utility First Aid. Bought 27" Mac a couple wks ago and thought I'd give the old Mac to my sister. Erased HD (thank you for your guidance above) but cannot get the iOS reinstalled. After 25 mins of downloading, I get message -- "Could not create a reboot volume for APFS install." About the only thing I'm sure of is that there is nothing left on the HD to be concerned about because I've erased it many times over the course of the past two nights. Guess Apple's third party recycler is my best bet at this point in time.



Jul 3, 2019 6:35 PM in response to judyfromelgin

So you erased the drive in recovery?


If that is the case, boot back into recovery, go to Disk Utility and reformat the drive to Mac OS Extended (Journaled) - you need to get rid of the new APFS file system format. Once it is back to that, you should be able to reinstall an OS while still in recovery (when the formatting is done, just choose reinstall OS). That may not be the newest one, which is fine. let your sister update AFTER she sets it up with her own Apple ID.

Jul 3, 2019 8:39 PM in response to babowa

Believe it or not, I've unpacked the Mac and willing to try the above. Booted back into recovery. When I go to Disk Utility, I presume I'm supposed to go to Erase (again!) and format to Mac OS Extended (Journaled). Unfortunately, my only choices are APFS, APFS (Encrypted), APFS (Case-sensitive) and APFS (Case-sensitive, Encrypted). Perhaps I'm looking at the wrong button?


Jul 4, 2019 8:45 AM in response to judyfromelgin

You are welcome! That is what we get the big bucks for, LOL.


Hopefully, you turned it off at the setup screen? It's best to let her set it up with her own Apple ID, etc. In case you didn't, you can do this dance again by booting into recovery, erase, and reinstall. When the download is finished, turn it off. It should then boot up at that same screen.


And the app store will let you know which OS you can update to. If you were at High Sierra, she should be able to get back to that.

Trying to erase HD on my old iMac.

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