Should you ever find yourself in the need to create blank disk images, OS X’s built-in Disk Utility is your friend. A disk image usually has a .dmg extension and appears, looks and behaves like any ordinary file, with one key exception: launching it prompts OS X to mount the volume on the desktop.
These mountable disk images can be useful in a number of situations. For example, you may want to create blank disk images for storage.
Furthermore, disk images can be used as a virtual disk for software distribution, to burn CDs or DVDs and so forth. In this step-by-step tutorial, you’ll learn how to create blank disk images in Disk Utility, at any size, with optional password protection, formatting options and more.