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have an imac that's been dead since an update tried to reformat the internal hybrid/fusion hdd to APFS.
the mac can only boot into single user mode. recovery hangs, safe mode hangs, boot disks hang.
ive done verbose mode and tried searching the internet using the logs, no luck there.
i formatted the internal drive, both the ssd and the hdd. tried booting the installer media and it still hangs. i've tried booting installer thumb drives for macOS Sierra pre APFS, High Sierra, Mojave randomly, all hang.
What is the mac even comparing to or looking up or looking for when i am just trying to install clean on a newly formatted drive? Obviously this works with Windows and Linux but MacOS is just outsmarting me

Late 2012 - BTO/CTO - iMac13,2 - A1419 - 2546

Example boot output from booting internet recovery:

...
iMac.local com.apple.xpc.launchd[1] (com.apple.bsd/dirhelper.580) <Warning>: Endpoint has been activated through legacy launch(3) APIs. Please switch to XPC or bootstrap_check_in(): com.apple.bsd.dirhelper
iMac.local com.apple.xpc.launchd[1] (org.ntp.sntp.205) <Warning>: Service exited with abnormal code:1

hanging...

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  • If USB installers are causing the iMac to hang, you probably have a hardware issue. What iMac model and year is it?
    – Allan
    Mar 30, 2023 at 1:36
  • just added specs. no hardware was changed, but maybe something died
    – austin
    Mar 30, 2023 at 1:37
  • Try hooting Internet recovery. Opt-Cmd-R. Post the results with an edit. Is this a 21º or 27”?
    – Allan
    Mar 30, 2023 at 1:38
  • 27 serial
    – austin
    Mar 30, 2023 at 1:38
  • 1
    You might have a GPU problem. Recovery doesn’t use the disk - totally loaded in RAM. If it’s failing here, you have a hardware issue. Two more things to try: remove all RAM modules but one and try booting. Keep swapping modules until it works. Boot holding the ºDº key for Diagnostics.
    – Allan
    Mar 30, 2023 at 3:56

1 Answer 1

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The hang may be due to a failed disk that has errors when reading / writing. Especially, considering the age of the iMac. Pretty remarkable that the HDD lasted this long.

If either disk fails in the Fusion pair you will lose all your data. You'll need to boot macOS installer via a USB flash drive. Then examine the SSD & HDD, if they are still considered a Fusion pair you need to split them and run Disk Utility on both devices. Look at the S.M.A.R.T status. If you do find a failed disk then you'll need to replace it.

It is very difficult and risky to take an iMac apart. Even for professionals. You'll need some special tools to break the seal on the glass screen cover and remove it without damaging it. Then you can take the screen out and get to the HDD / SSD. Replace with a larger SSD that is compatible with an iMac. Then you need to replace the seal with a new one and re-assemble. Make sure you source a quality seal, there's some terrible knock-off's out there and you don't want the screen and glass popping out spontaneously.

Rather than perform major surgery on an iMac most people will source a Thunderbolt external SSD drive and boot from a flash drive to install macOS to the external disk. Then you hold Option when booting and you can boot from the external drive. Should be rather fast too. Might even be faster than the disks it came with.

The latest macOS you can run on this 2012 iMac is macOS 10.15.7 Catalina. You can download the installer here on another Mac and build a bootable USB flash drive.

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  • "Might even be faster than the disks it came with." very likely, those Fusion drive iMacs are dog-slow.
    – Tetsujin
    Mar 30, 2023 at 9:26
  • I didn't get good new tape and when I put the screen back on, it fell off eventually and cracked
    – austin
    Jun 4, 2023 at 20:59
  • ++ for thunderbolt external SSD option. with the broken screen, I might also be using a thunderbolt external monitor lol. time for a new machine
    – austin
    Jun 4, 2023 at 21:00

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