Reduce the size of the stateful update by only copying dirs and some clean up.

stateful_update

 #!/bin/sh
 
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This scripts performs update of stateful partition directories useful for
 # dev_mode.
 
 . /usr/lib/shflags
@@ skipping 10 matching lines @@
 # Die on error.
 set -e
 
 remove_quotes() {
   echo "$1" | sed -e "s/^'//; s/'$//"
 }
 
 update_dev_image () {
   LSB_RELEASE="/etc/lsb-release"
   STATEFUL_DIR="/mnt/stateful_partition"
-  STATEFUL_IMAGE="$STATEFUL_DIR/stateful.image"
-  STATEFUL_MOUNT_POINT="/tmp/s"
+  WORK_DIR="${STATEFUL_DIR}/stateful_update"
 
   if [ -n "${FLAGS_ARGV}" ]; then
     BASE_UPDATE_URL=$(remove_quotes "${FLAGS_ARGV}")
   else
-    if [ -f "$STATEFUL_DIR$LSB_RELEASE" ]; then
-      DEVSERVER_URL=$(grep CHROMEOS_DEVSERVER $STATEFUL_DIR$LSB_RELEASE | \
+    if [ -f "${STATEFUL_DIR}${LSB_RELEASE}" ]; then
+      DEVSERVER_URL=$(grep CHROMEOS_DEVSERVER ${STATEFUL_DIR}${LSB_RELEASE} | \
                     cut -f 2 -d '=')
     fi
-    if [ -z "$DEVSERVER_URL" ]; then
-      DEVSERVER_URL=$(grep CHROMEOS_DEVSERVER $LSB_RELEASE | cut -f 2 -d '=')
+    if [ -z "${DEVSERVER_URL}" ]; then
+      DEVSERVER_URL=$(grep CHROMEOS_DEVSERVER ${LSB_RELEASE} | cut -f 2 -d '=')
     fi
     # Sanity check.
-    if [ -z "$DEVSERVER_URL" ]; then
+    if [ -z "${DEVSERVER_URL}" ]; then
       echo >&2 "No CHROMEOS_DEVSERVER URL found in lsb-release file"
       exit 1
     fi
     # Devserver URL should never contain "/update"
-    DEVSERVER_URL=$(echo $DEVSERVER_URL | sed -e 's#/update##')
-    BASE_UPDATE_URL="$DEVSERVER_URL/static"
+    DEVSERVER_URL=$(echo ${DEVSERVER_URL} | sed -e 's#/update##')
+    BASE_UPDATE_URL="${DEVSERVER_URL}/static"
   fi
 
-  STATEFUL_UPDATE_URL="$BASE_UPDATE_URL/stateful.image.gz"
+  STATEFUL_UPDATE_URL="${BASE_UPDATE_URL}/stateful.tgz"
 
   # Prepare directories for update.
-  rm -rf "$STATEFUL_DIR/var_new" "$STATEFUL_DIR/dev_image_new"
+  rm -rf "${WORK_DIR}"
+  mkdir "${WORK_DIR}"
 
-  # Prepare and mount new stateful partition.
-  rm -rf "$STATEFUL_MOUNT_POINT"
-  mkdir -p "$STATEFUL_MOUNT_POINT"
-
-  echo "Download stateful partition image from $STATEFUL_UPDATE_URL"
+  echo "Download stateful image from ${STATEFUL_UPDATE_URL}"
   # Unzip mount and copy the relevant directories.
   # Get the update.
-  eval "wget -qS -T 300 -O - \"$STATEFUL_UPDATE_URL\"" | \
-      gzip -d > $STATEFUL_IMAGE
+  eval "wget -qS -T 300 -O - \"${STATEFUL_UPDATE_URL}\"" | \
+      tar -C ${WORK_DIR} -xz
   echo >&2 "Successfully downloaded update"
-  trap "rm -f \"$STATEFUL_IMAGE\"" EXIT
-  mount -n -o loop "$STATEFUL_IMAGE" "$STATEFUL_MOUNT_POINT"
-  if [ -d "$STATEFUL_MOUNT_POINT/var" ] && \
-      [ -d "$STATEFUL_MOUNT_POINT/dev_image" ] ; then
-    echo >&2 "Copying new /var from stateful update"
-    cp -rf "$STATEFUL_MOUNT_POINT/var" "$STATEFUL_DIR/var_new"
-    echo >&2 "Copying new /usr/local from stateful update"
-    cp -rf "$STATEFUL_MOUNT_POINT/dev_image" "$STATEFUL_DIR/dev_image_new"
+
+  if [ -d "${WORK_DIR}/var" ] && [ -d "${WORK_DIR}/dev_image" ] ; then
     echo >&2 "Notifying startup that an update is available"
-    touch "$STATEFUL_DIR/.update_available"
+    touch "${STATEFUL_DIR}/.update_available"
   else
     echo >&2 "No update available"
   fi
-
-  umount -n -d "$STATEFUL_MOUNT_POINT"
-
-  rm -f "$STATEFUL_IMAGE"
-
-  trap - EXIT
 }
 
 update_old_state () {
-  echo >&2 "Not updating state except for dev_image."
+  echo >&2 "Performing standard stateful update."
 }
 
 update_clean_state () {
   echo >&2 "Restoring state to factory_install with dev_image."
   echo "fast test" > "/mnt/stateful_partition/factory_install_reset"
 }
 
 main () {
   update_dev_image
   if [ "${FLAGS_stateful_change}" = "${OLD_STATE}" ]; then
     update_old_state
   elif [ "${FLAGS_stateful_change}" = "${CLEAN_STATE}" ]; then
     update_clean_state
   else
     echo >&2 "Invalid state given to stateful update.  Aborting..."
     exit 1
   fi
 }
 
 main $@