I am now attempting the same as 4) with 10.15 Catalina instead, which is suggested when booting the iMac via the online recovery console (CMD-OPT-R) anyway. So I opened the iMac and replaced the internal hard drive with a brand new one.
It took 3.5 hours and it worked.Ĥa) I understand that APFS is only available since High Sierra and not Mountain Lion so installing Mountain Lion as per described in 4) is useless even tough it worked, because obviously, the HDD wasn’t mountable using 10.8.
In Disk Utility, I GUID partitioned an external 500GB USB HDD and formatted it as HFS+ then proceeded to install Mac OS X Mountain Lion (10.8) which is what the factory reset console suggests and what my friend says the iMac came with in 2012. I forced a power down on this one as it was not seemingly working at all.Ĥ) Holding down SHIFT-CMD-OPT-R on power up to go to the online factory reset console, this works, it connects to the WiFi and boots into the recovery console successfully. It does not list or show anything happening in that window and there is no cancel or close button either. However, from the Terminal > “diskutil list” command, I can see two partitions inside disk0, but nothing happens when I mount or force mount any of them: disk0s1 (150MB EFI) and disk0s2 (1000GB APFS)ģb) In Disk Utility, I tried to use the First Aid functionality on disk0 (not the actual partitions since Disk Utility does not show them, but rather the root disk element itself) and it’s been sitting there in a popup window displaying “Running First Aid…” without any sort of progress for an hour now. Also, that HDD (disk0) information is very minimal like the drive was inaccessible or something. Here are all the things I’ve tried so far:ġ) Holding down SHIFT on power up to go to safe mode, results in black progress bar followed by prohibited sign.Ģ) Holding down CMD-R on power up to go to the recovery console, results in black progress bar followed by prohibited sign.ģ) Holding down CMD-OPT-R on power up to go to the online recovery console, this works, it connects to the WiFi and boots into the recovery console successfully.ģa) From that online console, I can go to Disk Utility and I see the internal 1TB HDD, but I cannot mount it as it does nothing when selecting the MOUNT item.
My friend’s 2012 iMac attempted to self update over night and it resulted in the prohibited sign on a gray screen this morning and so, the iMac does not boot anymore!