MacOS – How to remove ‘untitled’ partition from terminal or disk utility

Never mind - problem solved.

Turns out that the whole drive's partition table cannot be modified if one partition has encryption on, since CoreStorage is on. (The one that I had on was the encrypt feature for Time Machine.)

There is nothing like a real "sparse image partition" on your disk. Or with other words: a sparse image partition is no physical partition on your hard disk.

Disk images are in fact files which contain a file system which can be mounted, unmounted or even increased or decreased in size. Mounted images usually appear in the file system in /Volumes/. Then they are listed in the diskutil list output but as /dev/diskX (disk image).

Since they are virtual disks they can't be deleted with diskutil on a physical disk. Instead use the Finder. If you don't know where the image file resides but the image is mounted just enter hdiutil info. The image path is listed then:

...
image-path      : /Users/me/Pictures/ext.sparseimage

Now you can delete the image in the Finder or in the shell with rm ....

I think under the hood the app Disk Utility doesn't use diskutil but hdiutil to deal with disk image files. Therefore you can create them but you can't delete them.