diff --git a/README b/README
index f3aa9f2..dd9dea0 100644
--- a/README
+++ b/README
@@ -27,6 +27,10 @@ of Qubes-specific rpms to install you want to use (e.g. qubes-gui-vm, etc).
 
 # ./qubeize_image <img> <template-name>
 
+3a) You should remove yum cached files, and override unused block with
+zeroes, via
+# ./cleanup_image qubeized_images/name-root.img
+
 4) Make sure the symlinks in vm_kernels_XXX/ point to correct kernel and initramfs
 files you want to use for the template:
 
diff --git a/cleanup_image b/cleanup_image
new file mode 100755
index 0000000..ec17beb
--- /dev/null
+++ b/cleanup_image
@@ -0,0 +1,26 @@
+#!/bin/sh
+
+IMG=$1
+
+if ! [ $# -eq 1 ]; then
+	echo "usage $0 <img_file_name>"
+	exit 1
+fi
+
+
+if ! [ -f $IMG ]; then
+	echo $IMG does not exist 
+	exit 1
+fi	
+ls -als $IMG
+mount -o loop,offset=$((63*512)) $IMG mnt || exit 1
+INSTALLDIR=`pwd`/mnt/
+yum clean packages --installroot=$INSTALLDIR 
+dd if=/dev/zero of=mnt/fillme bs=1M
+sync
+rm mnt/fillme
+umount mnt
+cp --sparse=always $IMG $IMG.new
+mv  $IMG.new $IMG
+ls -als $IMG
+