Backport Gary's commit adding the IMAGEFORMAT=none to support generating a single rootfs.

debian/changelog

@@ -1,3 +1,11 @@
+livecd-rootfs (2.408.23) UNRELEASED; urgency=medium
+
+  [ Gary Wang ]
+  * Add the IMAGEFORMAT=none to support generating a single rootfs
+    (LP: #1730642)
+
+ -- Łukasz 'sil2100' Zemczak <lukasz.zemczak@ubuntu.com>  Wed, 08 Nov 2017 12:33:37 +0100
+
 livecd-rootfs (2.408.22) xenial; urgency=medium
 
   * Make sure to remove any initramfs that was generated in a minimized

live-build/auto/config

@@ -139,6 +139,9 @@ case $IMAGEFORMAT in
 		PREINSTALLED=true
 		;;
 
+	none)
+		OPTS="${OPTS:+$OPTS }--chroot-filesystem $IMAGEFORMAT"
+		;;
 	*)
 		case $PROJECT in
 			ubuntu-server|ubuntu-touch|ubuntu-touch-custom)
@@ -815,6 +818,9 @@ EOF
 	ubuntu-touch:*|ubuntu-touch-custom:*|ubuntu-core:system-image|ubuntu-desktop-next:system-image|ubuntu-cpc:*)
 		cp -af /usr/share/livecd-rootfs/live-build/${PROJECT}/* \
 			config/
+		if [ "$IMAGEFORMAT" = none ]; then
+			rm -f config/hooks/*.binary*
+		fi
 		;;
 esac