Cannoy reset my MacOS on my 2017 imac that I need to sell

Please help me.

About 6 months ago a good friend sold to me for a good payment my 2021 24" iMac. In so doing, I thought it was wise to sell my 2017 21.5" 4k retina iMac quad core Intel Core i5 which I had bought from new and upgraded it with 32gb ram and 2tb SSD which I had used for years.

I've erased the disks on the macOS disk utilities and first aided them BUT now I cannot set it up for a potential new buyer with MacOS as it keeps indicating an error over and over again. I have tried setting up on disk utility but for some reason I just cannot get it sorted correctly.

Have a look at the pics from disk utility - I can't seem to set up this correctly to prepare for reinstall macOS (sierra).

Also the terminal time is wrong - at the time of pic its indicated 10.56am when its actually 6.56pm?


Your advice will be really helpful - thanks in advance.


Rob Vine








[Edited by Moderator]

iMac (2017 – 2020)

Posted on Aug 21, 2025 11:10 AM

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Question marked as Top-ranking reply

Posted on Aug 22, 2025 7:22 AM

My first guess is you have the "Untitled" volume formatted as APFS which cannot be used by macOS 10.12 Sierra. For macOS 10.12 Sierra the volume needs to be formatted (erased) as GUID partition and MacOS Extended (Journaled). You neglected to show a picture of that very critical item.


I highly recommend you try booting into Internet Recovery Mode using Command + Option + R to attempt to access the macOS 13.x Ventura online installer. Unfortunately some Macs may still only boot to the online installer for the OS which originally shipped with the Mac from the factory. And Apple doesn't maintain the older online installers very well so you are more likely to encounter issues with the reinstall process.

3 replies
Question marked as Top-ranking reply

Aug 22, 2025 7:22 AM in response to rvin28

My first guess is you have the "Untitled" volume formatted as APFS which cannot be used by macOS 10.12 Sierra. For macOS 10.12 Sierra the volume needs to be formatted (erased) as GUID partition and MacOS Extended (Journaled). You neglected to show a picture of that very critical item.


I highly recommend you try booting into Internet Recovery Mode using Command + Option + R to attempt to access the macOS 13.x Ventura online installer. Unfortunately some Macs may still only boot to the online installer for the OS which originally shipped with the Mac from the factory. And Apple doesn't maintain the older online installers very well so you are more likely to encounter issues with the reinstall process.

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Cannoy reset my MacOS on my 2017 imac that I need to sell

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