persistence

How do I add an overlay fs to my iso image??
the kdelive config isoclient has

IMAGE='/dev/loop7;openSUSE-13.1-livecd-kde.x86_64;2.8.0'
UNIONFS_CONFIG='/dev/ram1,/dev/loop7,overlay'

while my suse build’s config isoclient has

IMAGE='/dev/ram1;dale14846s_openSUSE_13.1_KDE_4_desktop.x86_64;0.0.7'
UNIONFS_CONFIG='/dev/ram1,/dev/loop7,clicfs'

I think I need to change clicfs to overlay, but how