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User profile for user: guinevere_
guinevere_ Author
User level: Level 1
10 points

"This disk is locked"

Hi!


Disclaimer: please excuse my poor english.


So I tried to downgrade my Mac from Catalina to Mojave. I create a USB bootable installer that is formatted to Mac OS Extended (Journaled) and it automatically named as "Install mac OS Mojave" and eject it.


When I restarted my Mac to MacOS Utilities, I went to disk utility to delete "Macintosh HD & Data" at the same time, and tried to reinstall MacOS & it shows "Mac OS Catalina" so I didn't went through it. Instead, I went to disk utility to restore new disk "Macintosh" from my USB bootable installer which has MacOS Mojave installer, when it successfully restored. I quit disk utility, and went to startup disk to restart my "Macinstosh". When my Mac successfully restart, it shows in MacOS Utilities "Install MacOS (Mojave)" clicked it but when I need to choose a disk, it says my disk is lock. And when I try to erase my internal disk again (Macintosh) it says there's an error. Even when I run first aid and unmount the disk, nothings changed.


Is there anything I can do? I'm open for any suggestions.

MacBook Air 13", macOS 10.15

Posted on Feb 27, 2020 7:18 AM

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User profile for user: Kappy
Kappy
User level: Level 10
361,765 points

Posted on Feb 27, 2020 12:19 PM

You can try the following:


Internet/Network Recovery of El Capitan or Later on a Clean Disk


     If possible back up your files before proceeding.


  1. Restart the computer. Immediately, at or before the chime, hold down the (Command-Option-Shift-R) keys until a globe appears.
  2. The Utility Menu will appear in from 5-20 minutes. Be patient.
  3. Select Disk Utility and click on the Continue button.
  4. When Disk Utility loads select the target drive (out-dented (topmost) entry w/type and size) from the side list.
  5. Click on the Erase button in Disk Utility's toolbar. A panel will drop down.
  6. Set the partition scheme to GUID.
  7. Set the Format type to APFS (SSDs, only if installing Mojave or Catalina ) or Mac OS Extended, (Journaled.)
  8. Click on the Apply button, then click on the Done button when it activates.
  9. Quit Disk Utility and return to the Utility Menu.
  10. Select Install OS X and click on the Continue button.


This should install the original version of macOS that came installed from the factory. However, the above procedure will only be available for 2011 or later MBAs. You did not indicate which MBA model you have. To find the complete model information select About This Mac from the Apple menu.

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User profile for user: Kappy
Kappy
User level: Level 10
361,765 points

Feb 27, 2020 12:19 PM in response to guinevere_

You can try the following:


Internet/Network Recovery of El Capitan or Later on a Clean Disk


     If possible back up your files before proceeding.


  1. Restart the computer. Immediately, at or before the chime, hold down the (Command-Option-Shift-R) keys until a globe appears.
  2. The Utility Menu will appear in from 5-20 minutes. Be patient.
  3. Select Disk Utility and click on the Continue button.
  4. When Disk Utility loads select the target drive (out-dented (topmost) entry w/type and size) from the side list.
  5. Click on the Erase button in Disk Utility's toolbar. A panel will drop down.
  6. Set the partition scheme to GUID.
  7. Set the Format type to APFS (SSDs, only if installing Mojave or Catalina ) or Mac OS Extended, (Journaled.)
  8. Click on the Apply button, then click on the Done button when it activates.
  9. Quit Disk Utility and return to the Utility Menu.
  10. Select Install OS X and click on the Continue button.


This should install the original version of macOS that came installed from the factory. However, the above procedure will only be available for 2011 or later MBAs. You did not indicate which MBA model you have. To find the complete model information select About This Mac from the Apple menu.

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"This disk is locked"

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