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Trying to erase and reinstall system software on an iMac running High Sierra. I’m in recovery mode and it can’t erase the disc. Tells me it can’t unmount the disc. Any idea how to proceed? I’d like to give the machine away.
iMac Line (2012 and Later)
Thanks. I’ve done all that. I’ve done internet reinstalls and pretty much everything else that Apple support could suggest. I was hoping someone might have a workaround when the official versions won’t work. I’d be happy just to make the computer unreadable so I can recycle it.
When in Internet Recovery Mode. Command + Option + r
The Below will Wipe the Entire Drive of ALL DATA and there are no do overs.
1 - It will present options >> Disk Utilities >> View >> View ALL attached Drives.
2 - Choose the Upper Most Drive ( not the volumes indented and list below ).
3 - The drive normally is called Apple Media or Apple SSD - that is the drive to Erase and format as HFD Journaled with the GUID Partition Map.
4 - Once that is done >> backup out of Disk Utilities and choose install macOS.
5 - Follow the prompts and it may automatically reboot several time.
6 - Upon a final reboot - Setup Assist will present with the newer version of macOS.
Sorry - but Fusion Drives are out of my general Knowledge base.
I do know there is another Very Respected Contributor presently on High Sierra and other Forums. Just be patient a while longer and maybe @ BDAqua will pick up this question and walk you thought the Fusion Drive aspect.
Repair a storage device in Disk Utility on Mac
Disk Utility can fix certain disk problems—for example, multiple apps quit unexpectedly, a file is corrupted, an external device doesn’t work properly, or your computer won’t start up. Disk Utility can’t detect or repair all problems that a disk may have.
If you run First Aid on a disk, Disk Utility checks the partition maps on the disk and performs some additional checks, and then checks each volume. If you run First Aid on a volume, Disk Utility verifies all the contents of that volume only.
In the Disk Utility app on your Mac, choose View > Show All Devices.
Note: If you’re checking your startup disk or startup volume, restart your computer in macOS Recovery, select Disk Utility in the macOS Utilities window, then click Continue. If you check your startup volume (Macintosh HD), make sure you also check your data volume (Macintosh HD - Data).
In the sidebar, select a disk or volume, then click the First Aid button .
If Disk Utility tells you the disk is about to fail, back up your data and replace the disk—you can’t repair it. Otherwise, continue to the next step.
Click Run, then click Continue.
If Disk Utility reports that the disk appears to be OK or has been repaired, you’re done. You can click Show Details to see more information about the repairs. Otherwise, you may need to do one of the following.
If Disk Utility reports “overlapped extent allocation” errors, two or more files occupy the same space on your disk, and at least one of them is likely to be corrupted. You need to check each file in the list of affected files. Most of the files in the list have aliases in a DamagedFiles folder at the top level of your disk.
If you can replace a file or re-create it, delete it.
If it contains information you need, open it and examine its data to make sure it hasn’t been corrupted.
If Disk Utility can’t repair your disk, or you receive a report that the First Aid process failed, try to repair the disk or partition again. If that doesn’t work, back up as much of your data as possible, reformat the disk, reinstall macOS, then restore your backed-up data.
If your Mac has a Fusion Drive and you see a flashing question mark or alert, see the troubleshooting section of the Apple Support article About Fusion Drive, a storage option for some Mac computers.
If you continue to have problems with your disk or it can’t be repaired, it may be physically damaged and need to be replaced. For information about servicing your Mac, see Find out how to service or repair your Mac.
In Terminal…
diskutil resetFusion
Many thanks. What I’ve done is restart in internet recovery mode and I was able to delete and reinstall the system. At least that’s working so far. I appreciate your detailed reply.
Thanks. I don’t see that. Under Internal Drives I only have fusion drive, opening out of that is Macintosh Hard Drive. Below is Disk Images and OSX Base System.
Thanks. I’ll also look myself.
TY for jumping in here
Good work! :)
Also, good work :-)
Erase disc to reinstall.
