( directories ; beforefiles) | create_hierarchy
mount_union "" $LOWER_DIR0
-mount -t unionfs -o remount,add=$LOWER_DIR1 none $MOUNTPOINT || exit $?
-mount -t unionfs -o remount,add=:$LOWER_DIR2=ro none $MOUNTPOINT || exit $?
-mount -t unionfs -o remount,del=$LOWER_DIR1,add=$LOWER_DIR3 none $MOUNTPOINT || exit $?
-mount -t unionfs -o remount,mode=$LOWER_DIR0=ro,del=$LOWER_DIR2 none $MOUNTPOINT || exit $?
+mount -t unionfs -o remount,add=$LOWER_DIR1 $MOUNTPOINT $MOUNTPOINT || exit $?
+mount -t unionfs -o remount,add=:$LOWER_DIR2=ro $MOUNTPOINT $MOUNTPOINT || exit $?
+mount -t unionfs -o remount,del=$LOWER_DIR1,add=$LOWER_DIR3 $MOUNTPOINT $MOUNTPOINT || exit $?
+mount -t unionfs -o remount,mode=$LOWER_DIR0=ro,del=$LOWER_DIR2 $MOUNTPOINT $MOUNTPOINT || exit $?
# test if the union contains only f0 and f3
test -f $MOUNTPOINT/f0 || exit $?