The ref-* files are used by checkchroot to find unwanted packages in the chroots.

# cp ref-* /usr/local/chroot/

 - stable-old is potato
 - stable is woody
 - different for diff arches
 - you can basically get the list using something like:

 	 grep-available -F priority -e -s package "(required|standard)" $CHROOT/var/lib/dpkg/available| \
	 awk '{print $2}'|sort

 - the only extras should be:
	apt
	build-essential
	fakeroot (some arches only use sudo and change $fakeroot config item)
	ssmtp
	sudo
