So many of you are wondering how you can mount a DMG (disk image) clone which will allow you to use migration assistant to pull data from it. Here I'll show you the easiest and best way to do this.
Background: As of Mavericks (10.9 and the current OSs) Apple did something stupid, they removed DMG support for migration assistant. Actually they didnt remove support, they changed the way migration assistant logged out of the current user, which in turn unmounted all DMGs. Major bummer for the tech savvy people out there. So then came a way to use the sudo command in the terminal to mount the DMG as the root user, thus keeping it mounted even after the logout. BUT, if you've ever tried to mount a large DMG, the OS will run a checksum (verification) which can take FOREVER (hours even).
open terminal on the mac you want to run migration assistant on
type the following command: sudo hdiutil attach -noverify /Path/To/Image.dmg
** replace the red text with the path of the DMG file you wish to mount. you can simply drag and drop the DMG file in the terminal window and it will auto complete the path.
Why is this awesome? Because the option "-noverify" skips the OS verification and the DMG mounts instantly. You're welcome.