diff -Nru livecd-rootfs-2.441.5/debian/changelog livecd-rootfs-2.441.6/debian/changelog
--- livecd-rootfs-2.441.5/debian/changelog	2017-09-11 18:59:59.000000000 +0000
+++ livecd-rootfs-2.441.6/debian/changelog	2017-09-13 19:13:10.000000000 +0000
@@ -1,3 +1,19 @@
+livecd-rootfs (2.441.6) zesty; urgency=medium
+
+  [ Robert C Jennings ]
+  * live-build/ubuntu-cpc/functions: Add a function, teardown_mountpoint,
+    to reverse the work done in setup_mountpoint.  Lack of this function
+    has forced users of setup_mountpoint to implement this separately
+    and the implementations have diverged. (LP: #1716992)
+  * live-build/ubuntu-cpc/functions: Remove umount_settle function.
+    The was only used where teardown_mountpoint was lacking.
+
+  [ Steve Langasek ]
+  * Also adjust live-build/ubuntu-server/hooks/032-installer-squashfs.binary
+    to use teardown_mountpoint.
+
+ -- Steve Langasek <steve.langasek@ubuntu.com>  Wed, 13 Sep 2017 12:13:10 -0700
+
 livecd-rootfs (2.441.5) zesty; urgency=medium
 
   [ Colin Watson ]
diff -Nru livecd-rootfs-2.441.5/live-build/functions livecd-rootfs-2.441.6/live-build/functions
--- livecd-rootfs-2.441.5/live-build/functions	2017-09-11 18:54:41.000000000 +0000
+++ livecd-rootfs-2.441.6/live-build/functions	2017-09-13 19:08:47.000000000 +0000
@@ -91,6 +91,19 @@
 
 }
 
+teardown_mountpoint() {
+    # Reverse the operations from setup_mountpoint
+    local mountpoint="$1"
+
+    umount "$mountpoint/tmp"
+    umount "$mountpoint/sys"
+    umount "$mountpoint/proc"
+    umount -R "$mountpoint/dev"
+    udevadm settle
+    sleep 3
+    mv resolv.conf.tmp "$mountpoint/etc/resolv.conf"
+}
+
 mount_partition() {
     partition="$1"
     mountpoint="$2"
@@ -134,16 +147,9 @@
 
 }
 
-umount_settle() {
-    # Unmount device, and let it settle
-    umount $1
-    udevadm settle
-}
-
 umount_partition() {
     local mountpoint=${1}
-    mv resolv.conf.tmp "$mountpoint/etc/resolv.conf"
-    umount -R $mountpoint
+    teardown_mountpoint $mountpoint
     udevadm settle
 
     if [ -n "${rootfs_dev_mapper}" -a -b "${rootfs_dev_mapper}" ]; then
diff -Nru livecd-rootfs-2.441.5/live-build/ubuntu-cpc/hooks/032-root-squashfs.binary livecd-rootfs-2.441.6/live-build/ubuntu-cpc/hooks/032-root-squashfs.binary
--- livecd-rootfs-2.441.5/live-build/ubuntu-cpc/hooks/032-root-squashfs.binary	2017-09-11 18:50:10.000000000 +0000
+++ livecd-rootfs-2.441.6/live-build/ubuntu-cpc/hooks/032-root-squashfs.binary	2017-09-13 19:08:47.000000000 +0000
@@ -36,11 +36,7 @@
 chroot binary/boot/squashfs.dir rm /usr/sbin/grub-probe
 chroot binary/boot/squashfs.dir dpkg-divert --remove --local --rename /usr/sbin/grub-probe
 
-mv resolv.conf.tmp "binary/boot/squashfs.dir/etc/resolv.conf"
-umount "binary/boot/squashfs.dir/proc"
-umount "binary/boot/squashfs.dir/sys"
-umount -R "binary/boot/squashfs.dir/dev"
-umount "binary/boot/squashfs.dir/tmp"
+teardown_mountpoint binary/boot/squashfs.dir
 
 apt-get -qqy install squashfs-tools
 
diff -Nru livecd-rootfs-2.441.5/live-build/ubuntu-server/hooks/032-installer-squashfs.binary livecd-rootfs-2.441.6/live-build/ubuntu-server/hooks/032-installer-squashfs.binary
--- livecd-rootfs-2.441.5/live-build/ubuntu-server/hooks/032-installer-squashfs.binary	2017-09-11 18:50:28.000000000 +0000
+++ livecd-rootfs-2.441.6/live-build/ubuntu-server/hooks/032-installer-squashfs.binary	2017-09-13 19:12:33.000000000 +0000
@@ -28,11 +28,11 @@
 
 mkdir -p "$OVERLAY_ROOT"
 
-setup_mountpoint binary/boot/squashfs.dir
-
 # Create an installer squashfs layer
 mount_overlay "$SQUASH_ROOT/" "$OVERLAY_ROOT/" "$SQUASH_ROOT/"
 
+setup_mountpoint binary/boot/squashfs.dir
+
 # Prepare installer layer.
 
 # Install any requirements for the installer, for things we don't want
@@ -147,17 +147,11 @@
 J4Weia71DnXOnt8cj1VhebVMlyv7B/TGAbGwgprgmQ==
 EOF
 
-mv resolv.conf.tmp "binary/boot/squashfs.dir/etc/resolv.conf"
+teardown_mountpoint "$SQUASH_ROOT"
 
-# Unmount the overlay first, where it is mounted:
+# Then unmount the overlay
 umount "$SQUASH_ROOT"
 
-# Then we can start unmounting the "real" root:
-umount "binary/boot/squashfs.dir/proc"
-umount "binary/boot/squashfs.dir/sys"
-umount -R "binary/boot/squashfs.dir/dev"
-umount "binary/boot/squashfs.dir/tmp"
-
 apt-get -qqy install squashfs-tools
 
 squashfs_f="${PWD}/livecd.${PROJECT}.installer.squashfs"