diff --git a/pack-maker.sh b/pack-maker.sh
index d325dd4..3546cb0 100755
--- a/pack-maker.sh
+++ b/pack-maker.sh
@@ -1,110 +1,206 @@
-#!/bin/bash -e
-# usage:
-#	mixer-pack-maker.sh <to version> <back_count>
-#	mixer-pack-maker.sh 2820 2
-#	mixer-pack-maker.sh 2730 3
+#!/bin/bash
+#
+# Usage:
+#	mixer-pack-maker.sh --to VER [OPTIONS]
+#
+# Create zero packs and/or delta packs for a given swupd build VER.
+#
+# The presence of the --from option enables delta pack creation from the given
+# version. More than one --from option may be specified. If both zero and delta
+# packs should be created at the same time, pass the --zero option in addition
+# to the --from option.
+#
+# To force recreation of all packs (zero and/or delta), use the --force option.
+#
+# Example invocations:
+#
+# 1) Create zero packs for build 7000
+#
+#     mixer-pack-maker.sh --to 7000
+#
+# 2) Create delta packs from build 6000 to 7000, and from 6500 to 7000
+#
+#     mixer-pack-maker.sh --to 7000 --from 6000 --from 6500
+#
+# 3) Create delta packs from build 6900 to 7000, and zero packs for build 7000
+#
+#     mixer-pack-maker.sh --to 7000 --from 6900 --zero
 #
-# For each bundle changed as of the Manifest.MoM at the <to version>,
-# create version-pair packs going back <back_count>
-# versions of that bundle.  For example if bundle "editors" changed in 2650
-# and the script is run as "pack_maker.sh 2650 2", it will find that
-# "editors" last two change points were 2550 and 2260 and thus create a
-# 2550-to-2650 and a 2260-to-2650 version pair pack for the "editors"
-# bundle.
 
-#NOTE: fullfiles must be created before calling this script
-#NOTE: zero packs need similarly created
+FROM_VERS=""
+REPO_DIR=""
+STATE_DIR=/var/lib/update
+TO_VER=""
+FORCE=0
+ZERO_PACKS=0
+PACK_LIST="$(mktemp pack-maker.XXXXXX)"
 
-#NOTE: build numbers are sparse, search back for the next oldest existing build
-#NOTE: in the future isn't simply -10, and when that change happens we must also
-#      consider which version-pair packs are meaningful for intermediate builds
-#      and revert builds.
+usage() {
+	echo -e "Usage: mixer-pack-maker.sh --to VER [OPTIONS]\n"
+	echo -e "\t-h, --help\tDisplay this help output\n"
+	echo -e "\t-f, --from\tCreate delta packs using the given \"from\" version\n"
+	echo -e "\t-R, --repodir\tLocation of swupd-server repo to find swupd_make_pack binary\n"
+	echo -e "\t-S, --statedir\tThe state directory for swupd_make_pack. Defaults to /var/lib/update\n"
+	echo -e "\t-t, --to\tCreate packs for the given version. This option is required.\n"
+	echo -e "\t-x, --force\tRecreate packs if they already exist\n"
+	echo -e "\t-z, --zero-packs\tCreate zero packs. If only --to is specified, this is the default.\n"
+}
 
-export XZ_DEFAULTS="--threads 0"
+error() {
+	echo -e "ERROR: $1\n"
+}
 
-VER=$1
-BACK_COUNT=$2
-UPDATEDIR=$3
-SWUPDREPO=${SWUPDREPO}
+check_mom() {
+	local mom="$1"
+	if [ ! -s "$mom" ]; then
+		error "$mom not found"
+		return 1
+	fi
+	return 0
+}
 
-if [ -z "${BACK_COUNT}" ]; then
-	echo "missing to pack count"
+create_pack() {
+	local from="$1"
+	local to="$2"
+	local bundle="$3"
+
+	if [ -s "$STATE_DIR"/www/${to}/pack-${bundle}-from-${from}.tar ] && [ "$FORCE" -eq 0 ]; then
+		echo "${to}/pack-${bundle}-from-${from}.tar already exists, skipping."
+	else
+		"${REPO_DIR}"swupd_make_pack --statedir "${STATE_DIR}" ${from} ${to} ${bundle}
+	fi
+}
+
+export -f create_pack
+
+create_packs() {
+	# The create_pack function uses these shell variables, so 'parallel'
+	# needs them exported to the environment.
+	export FORCE REPO_DIR STATE_DIR
+	cat "$PACK_LIST" | parallel --colsep '\t' create_pack {1} {2} {3}
+}
+
+get_bundle_version() {
+	local mom="$1"
+	local bundle="$2"
+
+	awk -v B=$bundle '$1 ~ /^M\./ && $4 == B { print $3 }' "$mom"
+}
+
+init_delta_packs() {
+	local from_ver="$1"
+	local from_mom="$STATE_DIR/www/$from_ver/Manifest.MoM"
+	local to_mom="$STATE_DIR/www/$TO_VER/Manifest.MoM"
+
+	check_mom $from_mom || return 1
+	check_mom $to_mom || return 1
+
+	awk '$1 ~ /^M\./ { print $3, $4 }' "$from_mom" | while read FROM BUNDLE; do
+		local TO=$(get_bundle_version "$to_mom" "$BUNDLE")
+
+		# If bundle does not exist in later version, skip
+		[ -z "$TO" ] && continue
+
+		# If versions are equal, skip
+		[ "$FROM" -eq "$TO" ] && continue
+
+		echo -e "${FROM}\t${TO}\t${BUNDLE}" >> "$PACK_LIST"
+	done
+}
+
+init_zero_packs() {
+	local to_mom="$STATE_DIR/www/$TO_VER/Manifest.MoM"
+
+	check_mom $to_mom || return 1
+
+	awk '$1 ~ /^M\./ { print $3, $4 }' "$to_mom" | while read TO BUNDLE; do
+		echo -e "0\t${TO}\t${BUNDLE}" >> "$PACK_LIST"
+	done
+}
+
+deduplicate_pack_list() {
+	sort -u "$PACK_LIST" > "$PACK_LIST".new
+	mv "$PACK_LIST".new "$PACK_LIST"
+}
+
+while [[ $# > 0 ]]; do
+	key="$1"
+	case $key in
+		-f|--from)
+		FROM_VERS="$FROM_VERS $2"
+		shift
+		;;
+		-R|--repodir)
+		REPO_DIR="$2"
+		shift
+		;;
+		-S|--statedir)
+		STATE_DIR="$2"
+		shift
+		;;
+		-t|--to)
+		TO_VER="$2"
+		shift
+		;;
+		-x|--force)
+		FORCE=1
+		;;
+		-z|--zero-packs)
+		ZERO_PACKS=1
+		;;
+		-h|--help)
+		usage
+		exit 0
+		;;
+		*)
+		error "Invalid option"
+		echo ""
+		exit 1
+		;;
+	esac
+	shift
+done
+
+if [ -z "$TO_VER" ]; then
+	error "Missing required --to option"
+	echo ""
+	usage
 	exit 1
 fi
 
-if [ -z "${VER}" ]; then
-	echo "missing to version"
-	exit 1
-fi
-
-if [ -z "${UPDATEDIR}" ]; then
-	echo "Missing STATE_DIR, using /var/lib/update/"
-	UPDATEDIR="/var/lib/update/"
+if [ -z "$FROM_VERS" ]; then
+	ZERO_PACKS=1
 fi
 
 # So we can call swupd_* with a sane path even if it's not / terminated
-if [ ! -z "${SWUPDREPO}" ]; then
-	SWUPDREPO="${SWUPDREPO}/"
+if [ -n "$REPO_DIR" ]; then
+	d=$(dirname $REPO_DIR)
+	b=$(basename $REPO_DIR)
+	REPO_DIR="${d}/${b}/"
 fi
 
-SWUPDWEBDIR="${UPDATEDIR}/www"
+# If delta packs are not being created, this loop does not execute
+for ver in $FROM_VERS; do
+	# The MoMs must exist; else skip this version pair
+	init_delta_packs $ver || continue
+done
 
-MOM=${SWUPDWEBDIR}/${VER}/Manifest.MoM
-if [ ! -e ${MOM} ]; then
-	echo "invalid version (no ${MOM})"
-	exit 1
+if [ "$ZERO_PACKS" -eq 1 ]; then
+	init_zero_packs
 fi
 
-BUNDLE_LIST=$(cat ${MOM} | awk -v V=${VER} '$1 ~ /^M\./ && $3 == V { print $4 }')
+deduplicate_pack_list
 
-# build packs for all bundles changed in $VER
-for BUNDLE in $BUNDLE_LIST; do
-	BUNDLE_VER_LIST=""
-	MANIFEST_VER=$(cat ${SWUPDWEBDIR}/$VER/Manifest.MoM | grep "^previous:" | cut -f 2)
-	BUNDLE_VER=""
-	COUNT=0
-	while [ $COUNT -lt $BACK_COUNT ] && [ $MANIFEST_VER -gt 0 ]; do
-		MOM=${SWUPDWEBDIR}/$MANIFEST_VER/Manifest.MoM
-		if [ -e ${MOM} ]; then
-			BUNDLE_VER=$(cat ${MOM} | grep "	${BUNDLE}$" | cut -f 3)
-			if [ "$BUNDLE_VER" != "" ]; then
-				BUNDLE_VER_LIST="$BUNDLE_VER $BUNDLE_VER_LIST"
-				MANIFEST_VER=$(cat ${SWUPDWEBDIR}/$BUNDLE_VER/Manifest.MoM | grep "^previous:" | cut -f 2)
-				let COUNT=$((COUNT+1))
-			else
-				# back in history to where bundle didn't exist yet
-				MANIFEST_VER=0
-			fi
-		else
-			# seek backwards until a manifest if found
-			MANIFEST_VER=$((MANIFEST_VER-10))
-		fi
-	done
+create_packs
 
-	for v in $BUNDLE_VER_LIST; do
-		if [ -e ${SWUPDWEBDIR}/${VER}/pack-${BUNDLE}-from-$v.tar ]; then
-			echo "${VER}/pack-${BUNDLE}-from-$v.tar already exists, skipping."
-		else
-			${SWUPDREPO}swupd_make_pack --statedir ${UPDATEDIR} $v ${VER} ${BUNDLE} &
-		fi
-	done
-done
+rm "$PACK_LIST"
 
-for job in $(jobs -p)
-do
-	wait ${job}
-	RET=$?
-	if [ "$RET" != "0" ]; then
-		echo "pack creation failure!"
-		exit $RET
-	fi
-done
 
 # NOTE: your devops will want to expose the completed swupd server build to
 # trial usage at some point.  This would be done via code like:
 #
-#	echo ${VER} > ${SWUPDWEBDIR}/../image/LAST_VER
-#	STAGING=$(cat ${SWUPDWEBDIR}/version/formatstaging/latest)
-#	if [ "${STAGING}" -lt "${VER}" ]; then
-#		echo ${VER} > ${SWUPDWEBDIR}/version/formatstaging/latest
+#	echo ${TO_VER} > ${STATE_DIR}/image/LAST_VER
+#	STAGING=$(cat ${STATE_DIR}/www/version/formatstaging/latest)
+#	if [ "${STAGING}" -lt "${TO_VER}" ]; then
+#		echo ${TO_VER} > ${STATE_DIR}/www/version/formatstaging/latest
 #	fi