diff --git a/findunusedbd.sh b/findunusedbd.sh
index 99eef3f..bca3941 100755
--- a/findunusedbd.sh
+++ b/findunusedbd.sh
@@ -3,93 +3,59 @@
 #
 #    sbuild --chroot-setup-commands='/home/prebuildcmd.sh chroot-setup' --pre-realbuild-commands='/home/prebuildcmd.sh pre-realbuild' --post-realbuild-commands='/home/prebuildcmd.sh post-realbuild'
 
-if [ "$#" -eq 0 ]; then
-	rm -rf /home/myfifo /home/myfifo2 /tmp/pkglists
-	# fifo to receive data
-	mkfifo /home/myfifo
-	# fifo to acknowledge reception
-	mkfifo /home/myfifo2
-	# make sure the sbuild user can write to the fifos
-	chmod a+w /home/myfifo
-	chmod a+w /home/myfifo2
-	mkdir -p /tmp/pkglists
-	# strip the architecture qualifier
-	cat /home/myfifo | sort > initialselection.list
-	echo > /home/myfifo2
-	cat /home/myfifo | sort > fullselection.list
-	echo > /home/myfifo2
-	# get all packages that were installed on top of the base packages
-	comm -13 initialselection.list fullselection.list > bdselection.list
-	while true; do
-		pkgnamever=`cat /home/myfifo`
-		echo > /home/myfifo2
-		# end loop when packagename is empty
-		[ -z "$pkgnamever" ] && break
-		# check if the package was installed as its build dependencies
-		if grep --line-regexp $pkgnamever bdselection.list; then
-			cat /home/myfifo | sort > "/tmp/pkglists/$pkgnamever"
-		else
-			cat /home/myfifo > /dev/null
-		fi
-		echo > /home/myfifo2
-	done
-	cat /home/myfifo | sed 's/, \+/\n/'g \
-		| sed 's/\([a-zA-Z0-9][a-zA-Z0-9+.-]*\).*/\1/' \
-		> /tmp/sbuild-dummy-depends
-	echo > /home/myfifo2
-	SCHROOT_SESSION_ID=`cat /home/myfifo`;
-	echo > /home/myfifo2
-
+if [ "$#" -eq 1 ]; then
+	tmpdir="$1"
+	# once something is written to the fifo, it indicates that fatrace should start
+	SCHROOT_SESSION_ID=`cat "${tmpdir}/myfifo"`;
+	# change to the schroot mount
+	cd /var/lib/schroot/mount/$SCHROOT_SESSION_ID
 	# start fatrace in the mounted directory
-	(
-		cd /var/lib/schroot/mount/$SCHROOT_SESSION_ID;
-		fatrace --current-mount > /home/fatrace.log &
-		FATRACE_PID=$!;
-		cat /home/myfifo > /dev/null;
-		echo > /home/myfifo2
-		kill $FATRACE_PID;
-	)
-
+	fatrace --current-mount > "${tmpdir}/fatrace.log" &
+	FATRACE_PID=$!
+	# give fatrace some time to set up (value is arbitrary)
+	sleep 5
+	# signal that fatrace was started
+	echo > "${tmpdir}/myfifo"
+	# wait for build to finish
+	cat "${tmpdir}/myfifo" > /dev/null
+	kill $FATRACE_PID
 	# clean up the fatrace log to only include unique paths
-	sed 's/\/var\/lib\/schroot\/mount\/[^\/]\+//' /home/fatrace.log \
+	sed 's/\/var\/lib\/schroot\/mount\/[^\/]\+//' "${tmpdir}/fatrace.log" \
 		| awk '{ print $3; }' \
 		| grep -v ^/build \
 		| sort \
 		| uniq \
-		> accessed.log
+		> "${tmpdir}/accessed.log"
 	# now get all packages in /tmp/pkglists that have files that never appear in the collected trace
 	while read namever; do
 		name=`echo $namever | cut -d '=' -f 1 | cut -d ':' -f 1`
 		# FIXME: the following cannot handle dependencies on virtual packages
-		if [ -z "`comm -12 accessed.log /tmp/pkglists/$namever`" ] \
-			&& grep --line-regexp "$name" /tmp/sbuild-dummy-depends > /dev/null; then
+		if [ -z `comm -12 "${tmpdir}/accessed.log" "${tmpdir}/$namever"` ] \
+			&& grep --line-regexp "$name" "${tmpdir}/sbuild-dummy-depends" > /dev/null; then
 			echo $namever
 		fi
-	done > unneededdepends.list < bdselection.list
-else
+	done > "${tmpdir}/unneededdepends.list" < "${tmpdir}/bdselection.list"
+elif [ "$#" -eq 2 ]; then
 	case "$1" in
 		chroot-setup)
-			env
-			dpkg --list | awk '$1 == "ii" { print $2"="$3 }' > /home/myfifo
-			cat /home/myfifo2 > /dev/null
+			tmpdir="$2"
+			dpkg --list | awk '$1 == "ii" { print $2"="$3 }' | sort > "${tmpdir}/initialselection.list"
 			;;
 		pre-realbuild)
+			tmpdir="$2"
 			# get the current selection so that the parent script can find the additional packages that were installed
-			dpkg --list | awk '$1 == "ii" { print $2"="$3 }' > /home/myfifo
-			cat /home/myfifo2 > /dev/null
+			dpkg --list | awk '$1 == "ii" { print $2"="$3 }' | sort > "${tmpdir}/fullselection.list"
+			# get all packages that were installed on top of the base packages
+			comm -13 "${tmpdir}/initialselection.list" "${tmpdir}/fullselection.list" > "${tmpdir}/bdselection.list"
 			# output the files belonging to all packages
 			dpkg --list | awk '$1 == "ii" { print $2, $3 }' | while read namever; do
 				set -- $namever
 				name=$1
 				ver=$2
-				echo "${name}=${ver}" > /home/myfifo
-				cat /home/myfifo2 > /dev/null
-				dpkg -L $name > /home/myfifo
-				cat /home/myfifo2 > /dev/null
+				if grep --line-regexp $pkgnamever "${tmpdir}/bdselection.list"; then
+					dpkg -L $name > "${tmpdir}/${name}=${ver}"
+				fi
 			done
-			# output an empty line to indicate the end
-			echo > /home/myfifo
-			cat /home/myfifo2 > /dev/null
 			# output the dependencies of the sbuild dummy package
 			dpkg --get-selections | awk '{ print $1; }' \
 				| grep sbuild-build-depends \
@@ -97,15 +63,18 @@ else
 				| grep -v sbuild-build-depends-essential-dummy \
 				| grep -v sbuild-build-depends-lintian-dummy \
 				| xargs -I {} dpkg-query --showformat='${Depends}\n' --show {} \
-				> /home/myfifo
-			cat /home/myfifo2 > /dev/null
+				| sed 's/, \+/\n/'g \
+				| sed 's/\([a-zA-Z0-9][a-zA-Z0-9+.-]*\).*/\1/' \
+				> "${tmpdir}/sbuild-dummy-depends"
 			# output the schroot id to start tracing
-			echo $SCHROOT_SESSION_ID > /home/myfifo
-			cat /home/myfifo2 > /dev/null
+			echo $SCHROOT_SESSION_ID > "${tmpdir}/myfifo"
+			# wait for fatrace to be forked
+			cat "${tmpdir}/myfifo" > /dev/null
 			;;
 		post-realbuild)
-			echo "done" > /home/myfifo
-			cat /home/myfifo2 > /dev/null
+			tmpdir="$2"
+			# signal that the build is done
+			echo > "${tmpdir}/myfifo"
 			;;
 		equivs)
 			namever="$2"
@@ -130,4 +99,10 @@ else
 			echo "invalid argument: $1" >&2
 			;;
 	esac
+else
+	echo "usage: " >&2
+	echo "   $0 tmpdir"
+	echo "   $0 [chroot-setup|pre-realbuild|post-realbuild] tmpdir"
+	echo "   $0 equivs pkgname"
+	exit 1
 fi
diff --git a/run.sh b/run.sh
index f81e74a..49e8120 100755
--- a/run.sh
+++ b/run.sh
@@ -5,26 +5,31 @@ if [ $# -eq 0 ]; then
 	exit 1
 fi
 
-echo > buildsuccess.list
-for dsc in $1; do
-	echo $dsc
-	/home/findunusedbd.sh &
-	sbuild --no-arch-all \
-		--chroot-setup-commands='/home/findunusedbd.sh chroot-setup' \
-		--pre-realbuild-commands='/home/findunusedbd.sh pre-realbuild' \
-		--post-realbuild-commands='/home/findunusedbd.sh post-realbuild' \
+build () {
+	dsc="$1"
+	archall="$2"
+	tmpdir=`mktemp -d --tmpdir=/home`
+	mkfifo "${tmpdir}/myfifo"
+	chmod a+w "${tmpdir}/myfifo"
+	/home/findunusedbd.sh "$tmpdir" &
+	sbuild --$archall \
+		--chroot-setup-commands="/home/findunusedbd.sh $tmpdir chroot-setup" \
+		--pre-realbuild-commands="/home/findunusedbd.sh $tmpdir pre-realbuild" \
+		--post-realbuild-commands="/home/findunusedbd.sh $tmpdir post-realbuild" \
 		"$dsc"
 	ret=$?
 	rm -f *.deb *.udeb *.changes
 	if [ $ret -eq 0 ] && [ -s unneededdepends.list ]; then
-		mv unneededdepends.list `basename $dsc .dsc`.unusedbd
-		echo $dsc >> buildsuccess.list
+		mv "${tmpdir}/unneededdepends.list" `basename $dsc .dsc`.${archall}.unusedbd
+		echo $dsc >> buildsuccess.${archall}.list
 	fi
-done
+	rm -rf "$tmpdir"
+}
 
-while read dscname; do
-	echo $dscname
-	unusedbdname=`basename $dscname .dsc`.unusedbd
+check () {
+	dscname="$1"
+	archall="$2"
+	unusedbdname=`basename $dscname .dsc`.${archall}.unusedbd
 	while read bd; do
 		# now run sbuild with "findunusedbd.sh equivs" creating a fake equivs package
 		sbuild --no-arch-all \
@@ -35,4 +40,17 @@ while read dscname; do
 		fi
 		rm -f *.deb *.udeb *.changes
 	done < $unusedbdname
-done < buildsuccess.list
+}
+
+for a in "arch-all" "no-arch-all"; do
+	echo > buildsuccess.${a}.list
+	for dsc in $@; do
+		echo $dsc
+		build "$dsc" "$a"
+	done
+
+	while read dscname; do
+		echo $dscname
+		check $dscname "$a"
+	done < buildsuccess.${a}.list
+done