This section applies to people that are using Macintosh formatted disks. The disk druid method of hard disk partitioning can not currently partition a Macintosh disk. The installer will warn you of this, and force you to use fdisk or pdisk. Fdisk is used edit PC style partitions. It is covered in the Official Red Hat Linux Installation Guide. Pdisk is used to edit Apple disk partitions. Both fdisk and pdisk are similar in the fact they are command line based. If you are not comfortable using pdisk we suggest that you use a commercial Apple partitioning program, such as SilverLining, FWB Toolkit, and Apple's DriveSetup.
The following information is based on ftp://ftp.mklinux.apple.com/pub/wip/pdisk/latest/pdisk.html which is the pdisk documentation.