I found the document file for newest version 5.4 at redhat.com
The pre-installation script
section of kickstart cannot manage multiple install trees or source media
. This information must be included for each created ks.cfg file, as the pre-installation script occurs during the second stage of the installation process.
If you configured the network with static IP information, including a nameserver, you can access the network and resolve IP addresses in the %post section. If you configured the network for DHCP, the /etc/resolv.conf file has not been completed when the installation executes the %post section. You can access the network, but you can not resolve IP addresses. Thus, if you are using DHCP, you must specify IP addresses in the %post section.
The post-install script is run in a chroot environment; therefore, performing tasks such as copying scripts or RPMs from the installation media do not work.
and very userful url,tell u about the media cdrom mount point or location during installation:
Anaconda umount's the cdrom that is on /tmp/cdrom
mkdir -p /mnt/source
mount -t iso9660 /tmp/cdrom /mnt/source
make the ks.cfg work in %post --nochroot
: if u want to copy file from media cdrom,you have to choose nochroot environment!!!!
mkdir -p /mnt/cdrom
mount -t iso9660 /tmp/cdrom /mnt/cdrom
#mkdir -p /mnt/sysimage/boot/INSTALL
mkdir -p /mnt/sysimage/soft
cp -a /mnt/cdrom/custom_software/epel-release-5-3.noarch.rpm /mnt/sysimage/soft/epel-release-5-3.noarch.rpm
cp -a /mnt/cdrom/custom_software/nginx-0.8.20.tar.gz /mnt/sysimage/soft/nginx-0.8.20.tar.gz
#--and auto install shell---
tar -zxvf /mnt/sysimage/nginx-0.8.20.tar.gz
rpm --root /mnt/sysimage/ -ivh /mnt/sysimage/soft/epel-release-5-3.noarch.rpm
it works ,,but rpm --root comand got error(only if it has depes other software...),because chroot enviroment...