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I recently used Disk Utility (on macOS 14.0) to create a new blank image, unmounted the image, deleted the .dmg associated with that image, and now can't figure out how to get my allocated storage back. The steps I followed are:

  1. I opened Disk Utility.
  2. I used File > New Image > Blank Image to create a new blank image. I set the size to 10 GB and encryption to 256-bit AES encryption.
  3. I realised that I had forgotten my password, so right-clicked the volume in the sidebar of Disk Utility and clicked Unmount.
  4. I then deleted the .dmg file that Disk Utility had created for my volume and emptied my bin.

After I had done these two things, I realised that Disk Utility was still allocating 10 GB to something (I assume the image I created). I'm not sure what I did wrong or how I can fix it. Strange Disk Image File (.dmg) problem - deleted files in xyz.dmg do not relinquish file space indicates that emptying the bin should have worked, but it does not appear to have.

How can I get my 10 GB back?

3 Answers 3

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A Monterey virtual machine was used to provide the images shown in this answer. Below I followed the steps given in the question. These are show in italics.

  1. I opened Disk Utility.

    The image below shows 165.17 GB in free space.

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  2. I used File > New Image > Blank Image to create a new blank image. I set the size to 10 GB and encryption to 256-bit AES encryption.

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    The image below shows 155.15 GB in free space.

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  3. I realised that I had forgotten my password, so right-clicked the volume in the sidebar of Disk Utility and clicked Unmount.

    The image below shows the volume is unmounted.

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  4. I then deleted the .dmg file that Disk Utility had created for my volume and emptied my bin.

    The image below shows the free space is 155.14 GB. So the 10 GB has not yet been freed.

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Solution: Eject the volume. The result is shown below, where the free space is now 165.14 GB.

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Comment: Restarting would also work, as suggested by Marc Wilson in his answer.

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It's not lost.

Either reboot, or wait for the OS to reclaim it.

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The Disk Image doesn't take space in any specific way that a regular large file wouldn't also take space.

If the space is unavailable, then it means it either is still in your Trash, or possible a disk Snapshot still contains the Disk Image.

If you've checked your trash, then you can use Disk Utility to inspect the snapshots of your disk and see if there's one taken since you created the Disk Image.

In Disk Utility, select your Data volume and use View > Show APFS Snapshots to view the snapshots. If there are snapshots on the list, inspect them to see what they contain. You can safely delete snapshots from this list.

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