Disk Utility cannot restore a backup because of "Resource busy"

Number:rdar://19378695 Date Originated:1/5/2015
Status:Open Resolved:
Product:OS X Product Version:10.10.1
Classification:Serious Reproducible:Always
The Disk Utility app cannot restore a valid backup in a disk image because it encounters a "resource busy" error when scanning the image.

Steps to Reproduce:
For this test, you need some media that you can backup, erase and restore. I have used both a 1 TB disk drive and a 1 GB thumb drive.

1. Mount the disk

2. Create a new disk image by selecting the volume on your test drive and clicking "New Image". Set the image format to "read-only" and the encryption to "none".

3. Enter your password so Disk Utility can make changes

4. Verify the disk image was created.

5. Select the test drive and click the "Partition" tab. Select a single partition. Set the format to "Mac OS Extended (Journaled)". Click "Apply" then "Partition" to partition the drive with an empty "Untitled 1" volume.

6. Click on the "Restore" tab

7. Drag the disk image file you created in steps 2-4 into the Source field

8. Drag the "Untitled 1" volume you just created to the Destination field

9. Click "Restore" then "Erase" in the confirmation dialog

10. Enter your password so Disk Utility can make changes

11. Click "Scan Disk Image" when prompted.

Expected Results:
The disk image source would be scanned and the blocks would be copied to the destination.

Actual Results:
You will see a message saying "Unable to scan "Untitled 1." (Resource busy)". You freak the fuck out because YOU CANNOT RESTORE A BACKUP.

10.10.1 (14B25)

Clicking on the "Image..." button causes the same behavior as drag & drop.

The only workaround is to select the disk image in the lefthand sidebar instead of selecting a Source image. After the scan is complete, you have to re-initiate the restore and blocks will start copying.


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