The file OSInstall.mpkg is the key to Leopard installs from a disk image. There is no need either to use the DVD again, or to reboot, to install Leopard to a different volume. After installing any Mac OS once from DVD, I always use Disk Utility to save the installer DVD as a disk image. Any further installs are from copies of that disk image; I put the original DVD away never to touch it again. I keep many external bootable drives, so the fire never goes out, so to speak.

On OS X install disks, it has always been the case (and remains the case with Leopard) that the top-level Install Mac OS X icon wants to reboot, but buried in the disk is a file named OSInstall.mpkg that can install OS X to a different volume without rebooting.

Reports that that is no longer possible with Leopard are in error. What has changed is that the folder structure is now hidden to the Finder. The …

Original post by Erica Sadun