I added a kick start config file to a Red Hat CD by re-creating the iso (so
the cd is still bootable) like so:

cp ks.cfg /tmp/redhat8
mkisofs -r -j -o red.iso -b images/boot.img /tmp/redhat8
cdrecord -vv dev=0,0,0 red.iso

Note that boot.img is the boot image that boots the CD. When the CD boots
eventually a prompt appears "boot:" and I input

linux ks=cdrom:/ks.cfg

How can I make my own boot.img hence replacing the current, so that I just
boot the CD and my kick start file is read? Without typing the above command,
i.e no "boot:" appears?