Symptom
When you attempt to erase a volume, Disk Utility only offers you Mac OS Standard (HFS) and Mac OS Extended (HFS Plus) file formats for certain volumes.
Normally, Disk Utility has four formats available:
- Mac OS Standard (HFS)
- Mac OS Extended (HFS Plus)
- MS-DOS File System
- UNIX File System (UFS)
Disk Utility may offer you all for formats for some volumes, while offering only HFS and HFS Plus for others.
Note: This issue only affects volumes on partitioned disks.
Solution
Start up from the Mac OS X CD-ROM to reformat the targeted volume as desired.
Disk Utility behavior explained
First, remember that a startup volume and a startup device are not the same thing. A "startup device," a hard drive for example, is a physical device that draws electricity from your computer and has moving parts. The startup device contains a disk that may be logically divided ("partitioned") into two or more "volumes" of information. At any given time, only one of these volumes contains the instance of the operating system software from which the computer is started up, thus making it the "startup volume." A volume that is contained on the startup device but that does not contain the active operating system software could be called a "nonstartup volume" on the startup device. A secondary or tertiary hard drive installed in your computer that does not contain the startup volume is a "nonstartup device" for purpose of this discussion.
Neither Disk Utility nor its predecessor Drive Setup will erase the startup volume. Disk Utility has the further restriction of not allowing you to switch a nonstartup volume that is contained on the startup device between Mac OS (HFS and HFS Plus) and UNIX file formats. If your computer has multiple hard drives installed, you should see that Disk Utility will offer all four of its available disk formats for volumes contained on nonstartup devices. This explains the symptom described above.