Create a new file /etc/init.d/umountfs containing the following:
#!/bin/sh
# Begin /etc/init.d/umountfs
source /etc/init.d/functions
echo -n "Deactivating swap..."
/sbin/swapoff -a
evaluate_retval
echo -n "Unmounting file systems..."
/bin/umount -a -r
evaluate_retval
# End /etc/init.d/umountfs