The error message below appears when I attempted to create a disk image of a folder stored on an external disk. The exact same command worked when the folder was moved to an internal drive.
- Pie Lover
Thanks for confirming your experience. As a workaround, try copying the external folder to an internal volume (I used the system volume) and then run the Disk Utility on the copy. The Disk Utility will create a disk image that should be identical to the one created using the utility in Big Sur (or earlier versions of macOS) using the folder on the external volume.
- Pie Lover
Another work-around is to create a stand-alone installer for Big Sur. Boot the Big Sur installer and launch the Disk Utility. This version of this Disk Utility creates the disk image without the need to copy the source files to an internal drive.
- Pie Lover
I don't know the answer to your question but I see the same thing.
Disk Utility on Monterey generates error when creating a disk image
