Mac OS X Power Hound, Second Edition

Disk Utility

For Panther, Apple merged the abilities of the old Disk Copy (for making disk images) and the old Disk Utility (for repairing disks) into the all-new, super-convenient Disk Utility. At the same time, however, Apple moved disk image-opening capabilities into the invisible DiskImageMounter program, which launches every time you double-click a disk image in the Finder or download one in Safari.

Still, Disk Utility holds plenty of hidden tricks. You can find the → program in Applications → > Utilities.

UP TO SPEED Disk Images

No, disks aren’t especially concerned with their image. Instead, a disk image is like a digital envelope that can maintain, store, and transfer a bunch of files together, as a unit—or as a single file attached to an email message.

The usual lifecycle of a disk-image file that you download from the Web is illustrated here. First, you download it from a Web site or email message. The result is an icon with a name that usually ends in .img or .dmg (top).

Second, when you double-click this icon, Disk Utility creates an icon that simulates a new disk (middle). Finally, when you double-click this icon, you see exactly what the original creator of the image wanted you to see (bottom). This virtual disk behaves exactly like a CD that you’ve inserted.

When you’re finished working with it, you can “eject” it like a CD. You can also throw away the original .dmg file, ...