Here is an example %pre section:

%pre  
#!/bin/sh  
hds="" 
mymedia=""  
for file in /proc/ide/h* do   
	mymedia=`cat $file/media`   
	if [ $mymedia == "disk" ] ; then       
		hds="$hds `basename $file`"   
	fi 
done  
set $hds 
numhd=`echo $#`  
drive1=`echo $hds | cut -d' ' -f1` 
drive2=`echo $hds | cut -d' ' -f2`  
#Write out partition scheme based on whether there are 1 or 2 hard drives  
if [ $numhd == "2" ] ; then   
	#2 drives   
	echo "#partitioning scheme generated in %pre for 2 drives" > /tmp/part-include   
	echo "clearpart --all" >> /tmp/part-include   
	echo "part /boot --fstype ext3 --size 75 --ondisk hda" >> /tmp/part-include   
	echo "part / --fstype ext3 --size 1 --grow --ondisk hda" >> /tmp/part-include   
	echo "part swap --recommended --ondisk $drive1" >> /tmp/part-include   
	echo "part /home --fstype ext3 --size 1 --grow --ondisk hdb" >> /tmp/part-include 
else   
	#1 drive   
	echo "#partitioning scheme generated in %pre for 1 drive" > /tmp/part-include   
	echo "clearpart --all" >> /tmp/part-include   
	echo "part /boot --fstype ext3 --size 75" >> /tmp/part-includ   
	echo "part swap --recommended" >> /tmp/part-include   
	echo "part / --fstype ext3 --size 2048" >> /tmp/part-include   
	echo "part /home --fstype ext3 --size 2048 --grow" >> /tmp/part-include 
fi

This script determines the number of hard drives in the system and writes a text file with a different partitioning scheme depending on whether it has one or two drives. Instead of having a set of partitioning commands in the kickstart file, include the line:

%include /tmp/part-include	

The partitioning commands selected in the script are used.