If you already have a Linux installation (MkLinux or Powermac/Linux),
you will already have root and swap partitions and possibly a usr
partition.  If not, you will need to make enough free space (300 - 400
MB) in the partition map of the disk you wish to use for Linux.  This
can be your system's internal hard disk or an external SCSI disk.
Note that `free space' doesn't mean available space in your MacOS
partition as reported by the Finder, it means space that is not
assigned to any partition of the disk.
 
Usually all the disk space on a disk is assigned to MacOS partitions,
so freeing up enough space for Linux will require editing the
partition table with a partitioning tool such as the Apple HD/SC
application, the FWB toolkit, or the Silverlining tools under MacOS.
Alternatively, the Red Hat installer gives you an opportunity to edit
the partition table with the linux `pdisk' utility - the only catch is
that pdisk doesn't initialize MacOS HFS partitions, so it is best to
create new MacOS partitions using a MacOS tool.
 
If it is necessary to shrink a MacOS partition, the safe way to do it
is to back up everything in the partition (at least everything that
you don't want to lose), then delete the partition, create a new
smaller partition, and copy everything back on to it.  If the
partition is your MacOS system volume, you will have to boot from some
other device such as CD-ROM in order to do this.  (You would then be
able to restore your system files by reinstalling the system from
CD-ROM.)
 
I have heard that it is possible to shrink a MacOS partition by a
procedure which involves compacting the partition with a defragmenter
(such as the Norton utilities), and then changing the size of the
partition.  I have not tried this, and I don't know enough to say
whether it should actually work or not, or whether there would be
inconsistencies remaining in the filesystem which should then be fixed
with a tool such as Disk First Aid or the Norton utilities.
 
You will need to create a root partition of at least 50MB.  If your
root partition is less than about 250MB or so, you will need to create
a separate usr partition of at least 200MB (assuming you want to
install X; it's possible to install a minimal system in less than
100MB).  You should also have a swap partition of between (say) 30 and
120MB.  All of these partitions can be created once the Red Hat
installer is running.
 
- Chris Jacobson (fear@athenet.net) -
Using Norton Utilities 3.5' Speed Disk, you have the options of
method of optimization, including "Repartitioning".  Use this option,
then use FWB Hard Disk Toolkit 2.0.5 or newer to resize your partition.
This does NOT affect your block size (i.e, minimum file size).  No
problems resulted, but your mileage may vary.  All standard disclaimers
and the GNU GPL apply where applicable.  :-)