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Factory reset

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Pieslewis

macrumors newbie
Original poster
Mar 24, 2025
7
0
I have followed several different ways to factory reset my 2015 iMac.
I have already exported all my data to a Mac Mini.
I'm stuck at this position - I have restarted my iMac in the 'Recovery' setting. Navigated to 'Utilities' > Disk utility and the 'Erase' function is greyed out. How do I get past this?
 
What version of macOS installed on iMac? What version of macOS is Recovery?
 
Thank you for responding. The OS is Monterey 12.7.6 and also recovery. I just want to factory reset it so I can sell it.
 
Boot into Recovery. Open Disk Utility. Select menu View > Show All Devices. Select the top most node in device tree for your internal storage. Perform erase and format.
 
I did as you instructed and the top node of the tree is 'Fusion Drive' and Erase is still greyed out!
 
Pieslewis said:
I did as you instructed and the top node of the tree is 'Fusion Drive' and Erase is still greyed out!
Click to expand...
Make sure that you've started from Internet Recovery (command-option-r). If you're using the regular recovery partition you can't erase the disk fully because the recovery partition is on that disk.
 
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When you say 'Recovery partition' is this important to the HD? I only want to erase the data that may still be on the HD so I can sell it as a 'Factory reset'.
 
Pieslewis said:
When you say 'Recovery partition' is this important to the HD? I only want to erase the data that may still be on the HD so I can sell it as a 'Factory reset'.
Click to expand...
When you boot from internet recovery and fully erase the disk and then reinstall macOS, a new recovery partition will be created.
 
This is getting a bit complicated for me. Can you tell me how to factory reset my computer so I can resell it please?
 
Is your Mac logged out of iCloud? That is very important otherwise the new owner might not be able to use it.

I would boot into Internet Recovery with the latest available macOS version for your Mac "Option(alt)-Command-R" and try to format the drive from there instead from the drive itself.

If that is working I would recommend to install macOS again.

When at the end of installation it comes to creating a user account or use an Apple ID to login just shut it off. That's what the new owner has to do. It will start there when turned on again.

That would be like a factory reset with macOS already installed and directly usable for the new owner after he logged in to iCloud or created a local only account first.


Start up your Intel-based Mac in macOS Recovery​

  1. On your Mac, choose Apple menu
    2f77cc85238452e25cb517130188bf99.png
    > Restart.
  2. Immediately press and hold one of the following key combinations until you see the startup screen:
    • Command-R: Start up from the built-in macOS Recovery System. Use this key combination to reinstall the latest macOS that was installed on your system, or to use the other apps in macOS Recovery.
    • Option-Command-R: Start up from macOS Recovery over the internet. Use this key combination to reinstall macOS and upgrade to the latest version of macOS that’s compatible with your Mac.
    • Option-Shift-Command-R: Start up from macOS Recovery over the internet. Use this key combination to reinstall the version of macOS that came with your Mac or the closest version that’s still available.
  3. If you see a lock, enter the password for your Mac.
  4. If you have multiple volumes on your disk, select the volume you want to recover, then click Next.
  5. If requested, choose an administrator account, click Next, enter the password for the account, then click Continue.
    When the Recovery app appears in the menu bar, you can choose any of the available options in the window or the menu bar.

Source: https://support.apple.com/guide/mac...d-mac-mchl338cf9a8/15.0/mac/15.0#mchl69906860
 
Need to see screenshot of Disk Utility with menu View > Show All Devices selected. Without, it is not possible to know whether your Fusion Drive has been split. Process for factory reset your iMac depends on this information.
 
Is this what you want?
 

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Yes. Based on the screenshot, you should be able to follow the instructions here. The top most "Macintosh HD" is the one referred to in the support doc. You will erase and reinstall macOS.

Use Disk Utility to erase an Intel-based Mac - Apple Support

How to erase (format) the built-in startup disk of an Intel-based Mac.
support.apple.com support.apple.com

Now, if you want to securely erase the data, you will need to split the Fusion Drive, erase each component drive using the secure erase option, and then recreate the Fusion Drive... using commands in Terminal. Here's a blog post detailing the process. You need to read very carefully as your drive is formatted APFS and this blog is based on HFS+ formatting.

Secure Erasing a Mac Fusion Drive – Tech Otaku

www.tech-otaku.com www.tech-otaku.com

It's unfortunate your iMac does not support the T2 security chip, otherwise, Monterey supports the "Erase All Content And Settings". This option would have made this process ludicrously easy.
 
Bigwaff said:
Yes. Based on the screenshot, you should be able to follow the instructions here. The top most "Macintosh HD" is the one referred to in the support doc. You will erase and reinstall macOS.

Use Disk Utility to erase an Intel-based Mac - Apple Support

How to erase (format) the built-in startup disk of an Intel-based Mac.
support.apple.com support.apple.com

Now, if you want to securely erase the data, you will need to split the Fusion Drive, erase each component drive using the secure erase option, and then recreate the Fusion Drive... using commands in Terminal. Here's a blog post detailing the process. You need to read very carefully as your drive is formatted APFS and this blog is based on HFS+ formatting.

Secure Erasing a Mac Fusion Drive – Tech Otaku

www.tech-otaku.com www.tech-otaku.com

It's unfortunate your iMac does not support the T2 security chip, otherwise, Monterey supports the "Erase All Content And Settings". This option would have made this process ludicrously easy.
Click to expand...

Okay, it's unencrypted...

What about enabling FileVault before formatting? Wouldn't that be secure enough? It will take a while with that amount of data but would be much easier. I remember it from older Macs even with SSD, when turned on not right at the beginning it always took several hours. Would't most of the drive be overwritten in this case with the encrypted files?
Or did this change with APFS?

But the chance is really very low that someone is looking for old HDDs to get the data, especially if it's empty and has to be recovered.

Maybe @Pieslewis knows the new owner even personally and also what will happen to the Mac, like it just gets used as it is.
 
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