User profile for user: simonp_au
simonp_au Author
User level: Level 1
30 points

"This Disk is Locked" Reinstalling macOS

I have a 2017 iMac 27" 5K with a 1TB Fusion Drive.


I have always used an external SSD for the boot drive.


Now I am selling it, I am trying to install macOS on the Fusion Drive.


When I boot into Recovery and try to install macOS I'm asked what drive I want to install macOS on. But the "Mac HD" has the message "The Disk is Locked".


So then I exit out of this and select "Disk Utility", I select "Mac HD" then "Erase" but the only options for format are "APFS" and not "Mac OS Extended".


And if I select "APFS" and try to reformat the drive nothing happens.


I really have no idea what to do at this point.


See images.





iMac 27″ 5K, macOS 11.3

Posted on Aug 27, 2021 7:04 AM

Reply

Similar questions

6 replies
User profile for user: simonp_au
simonp_au Author
User level: Level 1
30 points

Aug 27, 2021 3:46 PM in response to BDAqua

What I did to resolve this:


Booted into macOS using external SSD Drive.


Opened Disk Utility.


Selected (Fusion Drive) Mac HD in the side bar.


Selected "Edit"


Then selected "Delete APFS Volume..."


Then once that was completed I selected "Erase".


Then selected "Mac OS Extended (Journaled)" to reformat the drive.


Then I proceeded to Download the macOS High Sierra Installer.


I then created a macOS High Sierra Bootable Drive on a USB Drive.


Finally I pressed "Option" key at boot and booted up using the installer and proceeded with installation via Recovery.



I followed the instructions found here to created the bootable USB Drive.


https://support.apple.com/en-us/HT201372

Reply

This thread has been closed by the system or the community team. You may vote for any posts you find helpful, or search the Community for additional answers.

"This Disk is Locked" Reinstalling macOS

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.
Learn more Sign up