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I acquired a 2009 iMac that had a Windows partition which was apparently erased during formatting to be sold. The computer now tries to boot, via EFI, the missing Windows partition as default. I can invoke Startup Manager and start macOS and have rm'd the Microsoft entries from EFI as a recommended fix but the problem persists.

A recommended fix is to re-install macOS (High Sierra) but the broken default EFI boot seems to hijack Recovery Mode start, i.e. I can't invoke any of the recovery modes using keyboard combos. There is no recovery partition so that one makes sense but can't invoke Internet Recovery either. I've tried a couple of keyboards to try to eliminate hardware as the issue. Prefer not to create via USB unless as last resort.

So, is there another way to invoke recovery sans keyboard combos? Are there other options - erase EFI partition? edit boot64.efi?

agarza
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beachboy
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  • I am now attempting to re-install via the App Store OS Update, so far it seems to to be progressing as needed... – beachboy Jan 18 '23 at 06:46
  • The re-install via App Store download failed with this same error as [link] (https://apple.stackexchange.com/questions/317149/osx-prohibited-symbol-on-boot-high-sierra-update-caused) – beachboy Jan 18 '23 at 07:09
  • The link contains many potential fixes. Which have you tried? Do you have an Apple wired keyboard to test? Some Macs don't respond well to a Win or wireless keyboard at boot. – Tetsujin Jan 18 '23 at 09:58
  • I have tried two different, wired Apple keyboards and no recovery, or safe start combo works. The only combo that works is "Option" for startup Manager. – beachboy Jan 18 '23 at 18:58
  • I am reluctant to delete extension files without a better understanding of implications. Some discussions refer to corrupting the system if critical files are deleted. – beachboy Jan 18 '23 at 19:01
  • I'd just go for a bootable installer on USB in that case, & completely nuke & pave, wipe the entire drive & start over. - the 09 should be able to boot from USB. It certainly can't boot to Internet Recovery, it's too early, & if there's no Recovery partition, then that option is gone. – Tetsujin Jan 18 '23 at 19:03
  • I have come to the same conclusion re: the bootable USB route. I am hoping that I may be able to use a networked HD (WD MyBook) as I don't have a usb stick at this location (w/o purchase at small town prices). – beachboy Jan 19 '23 at 00:30
  • the comment that 09 was too early for internet recovery would certainly explain why I can't get there. It was something I didn't realize before, thanks for that. – beachboy Jan 19 '23 at 00:32
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    After having tried several potential solutions including installing an OS update, the original issue is resolved (i.e. the imac was defaulting to a missing EFI boot) the machine now boots to macOS and I can invoke restore mode as expected. I don't feel this is a proper answer as it doesn't answer the original question and i can't categorically state what resolved the main issue of faulty bootup. I will still, however, attempt to erase and reinstall the entire OS as that is the state I presumed the computer to be in when I got it. – beachboy Jan 19 '23 at 04:44

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