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i486dx2-66

macrumors 6502
Original poster
Feb 25, 2013
366
411
Hey folks, I picked up a Late 2015 27" 5K iMac, and seem to be caught in a bind with erasing/reinstalling it.

Machine specs:
* iMac17,1 (Late 2015 iMac 5K)
* Monterey 12.6.2 (installed and working)
* System was in a wiped state when I received it (new user setup, etc)
* 500GB SSD which identifies as "APPLE SSD SM0512G"
* SSD is formatted APFS



As standard for any used machine, I'd like to do my own erase and reinstall for a clean start.


Booting with Command + R, I get the macOS Recovery option.
Select Disk Utility
The Apple support guides say to select the first device in the list "Macintosh HD", click erase, and reformat the drive before reinstalling the OS.

However, my machine has "AppleAPFSMedia" as the first device, which it says is 500.07 GB of "Uninitialized", with "Macintosh HD - Data" ("500.07 GB Logical Volume APFS"), Preboot, Recover, Update, and VM as children of it. My machine also has a top level "APPLE SSD SM0512G Media" listed, "500.28 GB PCI Internal Physical Disk", which is second in the list but at the same level as "AppleAPFSMedia".


The problem is that none of these devices can be reformatted as APFS. Disk Utility in the recovery mode only offers Mac OS Extended (four versions of it), ExFAT, and FAT. 🤨

I tried the internet version of the recovery mode, and after the lengthy load time, it gave the same result - identifying the APFS volume, but not letting me reformat as the same.


To actually erase this machine, do I really have to reformat with a different filesystem, install an old OS (10.12 Sierra is what Recovery offers), update the OS, and convert the drive to APFS to get back to the current state? 🤨 🤨

Thanks in advance
 

Bigwaff

Contributor
Sep 20, 2013
2,231
1,500
Boot into Internet Recovery (Option+Command+R) to install the latest macOS version supported by your hardware. You'll be prompted to enter wireless network info, etc and be patient... internet recovery boot times can be very long as they are dependent on the download speed of your internet connection.

Alternatively you can download a specific version of macOS you want -

and create bootable installer on USB media.
 
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i486dx2-66

macrumors 6502
Original poster
Feb 25, 2013
366
411
Thanks @Bigwaff. Would that bootable installer provide a different Disk Utility version do you know? (one that supports erasing as APFS?)
 

chrfr

macrumors G5
Jul 11, 2009
13,592
7,134
Thanks @Bigwaff. Would that bootable installer provide a different Disk Utility version do you know? (one that supports erasing as APFS?)
You're just having trouble erasing the disk using recovery because the recovery partition is on the disk you're trying to erase. If you start up from internet recovery you'll be able to erase the entire disk without a problem, and without having to bother making a bootable disk.
 
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i486dx2-66

macrumors 6502
Original poster
Feb 25, 2013
366
411
I just tried internet recovery again, and after the lengthy loading process I get the globe with the exclamation point. :(
The text below it reads:
apple.com/support
-5101F
Googling this error seems to be a lot of people throwing darts at what might be wrong... 🤷‍♂️
 

i486dx2-66

macrumors 6502
Original poster
Feb 25, 2013
366
411
I tried one of the "darts", and reset my router and tried again. It took ~24 minutes of the progress bar, counting down as it went, then failed again with the same "-5101F" error...
 

i486dx2-66

macrumors 6502
Original poster
Feb 25, 2013
366
411
Alternatively you can download a specific version of macOS you want -
and create bootable installer on USB media.
Looks like this was the trick! :D

I was able to download the latest Monterey full installer, and upon rebooting from that USB stick, got a different recovery console which had a distinctly different version of Disk Utility. With this, my existing SSD showed up as "Macintosh HD" instead of "APPLE SSD SM0512G Media", and it gave me a good number of APFS-specific options including the erase I was looking for. Now I'm part way through the Monterey reinstall.

Thanks for the link, @Bigwaff, appreciate it! 👍👍
 
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