iMac 2015 crash after security update(?)

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iMac 2015 crash after security update(?)

Facts: there is a "security update" to the OS, released April 7 2023. It is for Ventura, which is not supported on this very old hardware. This iMac had Catalina installed (latest supported). I have not manually updated this OS for the security update. It's not compatible.

Symptom: this morning (4/10/23) the Mac displays the "Prohibition" icon that indicates it now has an OS that is incompatible with the hardware.

Suspicion: I suspect I had "do security updates" on automatic. The good folk at apple missed the hardware limitation of the machine, installed OS 13 with the security update, and now I'm dead.

Attempted recovery:

Boot into recovery mode (CMD-R), reinstall Catalina. Done.

Reboot machine, it hangs shortly after startup.

I can no longer get into recovery mode. (CMD-R no longer works)

I have OS SIerra on an external USB drive, the iMac does not see that drive during the boot process (option key)

So at this point the iMac is a doorstop. Suggestions?

I have a modern laptop (here I am :))

iMac 27″, macOS 10.15

Posted on Apr 10, 2023 9:09 AM

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Answer 1

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HWTech

Community+ 2026

Level 9

75,042 points

Apr 11, 2023 9:45 AM in response to Jim Trudeau

My guess is the iMac has a failing hard drive. You can try running the Apple Diagnostics to see if any hardware issues are detected. Unfortunately the diagnostics don't detect most drive failures.

Try a PRAM Reset (hold for several chimes if possible) and try booting your external drive again and Internet Recovery Mode (Command + Option + R) or (Command + Option + Shift + R).

If these are not working, then I would try creating & booting a Knoppix Linux USB stick which will confirm if the hardware is Ok and it has a utility able to check the health of the drives.

Make sure to use a wired USB keyboard to access the special startup key modes.

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Answer 2

Jim Trudeau Author

Level 1

4 points

Apr 18, 2023 7:25 PM in response to Jim Trudeau

I hope closing this... I believe the hard drive is failing. Good info on "file system only." That's useful, didn't know that. I have been able to boot the iMac, but all operations that involve disk access are ridiculously slow.

The good news is, I didn't need access to the iMac to recover my files. I mounted the TimeMachine backup (call this A) to the MacMini, along with the new external hard drive (call this B) intended for media storage. Manually moving from A to B was effective and successful. I had to do this manually because I went from a 3 TB drive on the iMac to an ~256 GB drive on the mini.

Nonetheless, all files restored, the iMac is (however crippled) actually booting. Next up, I'll wipe the drive (if I can) and recycle the beast. :)

It supported and ran MacOS Catalina. My attempt to build a bootable USB failed, but I didn't need it in the end. Note that the App Store wouldn't let me download the Catalina installer since it is not supported by any Mac I currently have (except for the iMac, which is so badly cripped I can do squat). :) Side effect of the nanny-state. "We can't let you have that, it doesn't work on your machine." Which makes sense, but... my use case isn't that odd.

In any event, all's well that ends well.

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Answer 3

Jim Trudeau Author

Level 1

4 points

Apr 14, 2023 6:27 PM in response to HWTech

Appreciate the insight, still wrestling. :) Not beat yet. Key input (so to speak) is a wired keyboard. A very useful visit to the local Apple store, tech was able to get into recovery mode, ran disk first aid, indeed a drive failure, and fixed (perhaps) but it still won't boot, and even with wired keyboard cannot get into recovery mode. I can get into target disk mode, and into "pick your boot drive" mode.

Use Thunderbolt 2 cable, and a TB2>TB3 adapter to plug into the new Mini.

boot iMac into target disk mode. Appears on the Mini. Drag files to new external drive. The data transfer would take 24-28 DAYS for 2 TB. (dog slow data transfer over Thunderbolt2 from iMac. No idea why)
Data migration assistant, same setup. Same dog slow. AND... there is no way to redirect the migration to an external drive. The data does not fit on the Mini's hard drive. IMHO this is a design flaw in the migration assistant, it REQUIRES that the new Mac have a drive as big if not bigger than the old.
Data migration assistant to restore from TimeMachine backup Fails, same reason, data doesn't fit on the Mini

NEXT UP: boot into "pick your boot drive" mode. Put in a USB with Catalina. Except I can't download Catalina from the App Store because it's incompatible with my current hardware. But I'm going to pursue that. If I can boot, I can get at the files in an efficient manner.

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Answer 4

Apr 14, 2023 9:37 PM in response to Jim Trudeau

Disk Utility First Aid only checks & repairs the file system which has nothing to do with the health of the hard drive, although the hard drive may report a failing condition to macOS/Disk Utility if the failure is severe enough (very seldom happens in my own personal experience).

Did Apple run any service diagnostics on the iMac?

If Apple ran the service diagnostics and they did not show any hard drive failures, then I can provide instructions for creating & using a Linux boot disk to check the health of the hard drive. Let me know if you are interested as it will likely confirm a drive failure. From everything you have described, I am fairly confident the hard drive is failing. Unfortunately Apple does not train their techs to use other methods for checking the health of a drive other than the extremely basic MRI diagnostic which will miss many types of drive failures.

As for TM and Migration/Setup Assistant, I only have a couple of experiences with the latter and no experience with TM. As long as the amount of data is less than the amount of free space on the Mac, then it should transfer, but keep in mind a single macOS user account may contain a lot of data within the hidden Library folder beyond the data you keep in your Desktop, Documents, Downloads, Music, Photos, and Videos folders. It may be possible to launch the TM app on the Mac and navigate to the items you want transferred which will at least give you the data.

Another option would be to install macOS onto an external USB drive on your Mini, then boot from the external drive & migrate/restore the data which may allow you easier access to manually transfer data files to the internal SSD.

If your iMac is a MId-2015 model, then it can run macOS 11.x Big Sur while a Late-2015 model can run macOS 12.x Monterey. Not sure what OS shipped with your newer Mini, but if the Mini shipped with one of those versions of macOS, then you should be able to create that USB installer.

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Answer 5

Apr 18, 2023 7:55 PM in response to Jim Trudeau

Yes, Apple is a bit odd in how inconvenient & difficult they make certain things like creating a bootable macOS USB installer which is just one example. You can provide Apple with product feedback here:

Product Feedback - Apple

FYI, here is an Apple article on things to do when getting rid of an old Mac such as disassociating your AppleID & accounts from the Mac. However, Apple assumes you can actually still access the system, and that the Mac is only using an SSD, or that Filevault is enabled if using a hard drive (this is never mentioned in the article). However, I doubt you can erase the drive using macOS or a macOS installer due to the errors of the failing hard drive.

What to do before you sell, give away, or trade in your Mac - Apple Support

It is hard to say whether you will be able to securely erase the failing hard drive in that iMac using any method. Your best option would be to try using ShredOS which is a bootable USB stick made to write zeroes to a drive to securely erase it by overwriting the existing data. I've never personally used ShredOS, but I think that will be your best option as it is a Linux based option which will have a better chance of booting the system if the internal drive is producing errors. It uses a very old style graphical interface which will seem very odd to you unless you worked with Linux or the very first versions of Windows back in the early 90's (pre-dates Windows 95 and Windows 3.1).

The easiest way of creating a bootable ShredOS USB stick is by using the downloaded ShredOS .img file as a source for Etcher (Mac/Windows/Linux). After creating a bootable ShredOS USB stick, Option-Boot the iMac and select the orange icon most likely labeled "EFI". You will want to use the 64 bit version of ShredOS for USB Flash Drives (aka USB sticks). Just make sure to disconnect all other external devices so you don't accidentally select the wrong drive or device. Make sure to read the documentation on the ShredOS GitHub page since they do mention various details and things you may encounter.

I'm glad you were able to get everything figured out with your new Mac and accessing your TM data. Good work!

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iMac 2015 crash after security update(?)

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