Per the suggestions, we exclude all binary hooks when IMAGEFORMAT is none.

debian/changelog

@@ -1,3 +1,9 @@
+livecd-rootfs (2.480) UNRELEASED; urgency=medium
+
+  * Add the IMAGEFORMAT=none to support generating a single rootfs.
+
+ -- Gary Wang <gary.wang@canonical.com>  Mon, 06 Nov 2017 20:03:30 +0800
+
 livecd-rootfs (2.479) bionic; urgency=medium
 
   * Purge initramfs-tools from minimized images.

live-build/auto/config

@@ -183,6 +183,9 @@ case $IMAGEFORMAT in
 		exit 0
 		;;
 
+	none)
+		OPTS="${OPTS:+$OPTS }--chroot-filesystem $IMAGEFORMAT"
+		;;
 	*)
 		case $PROJECT in
 			ubuntu-server|ubuntu-touch|ubuntu-touch-custom)
@@ -834,6 +837,9 @@ EOF
 	ubuntu-touch:*|ubuntu-touch-custom:*|ubuntu-core:system-image|ubuntu-desktop-next:system-image|ubuntu-cpc:*|ubuntu-server:live)
 		cp -af /usr/share/livecd-rootfs/live-build/${PROJECT}/* \
 			config/
+		if [ "$IMAGEFORMAT" = none ]; then
+			rm -f config/hooks/*.binary*
+		fi
 		;;
 esac