add -f option to force a client update

src/platform/memento_softwareupdate/memento_updater.sh

 #!/bin/bash
 
 # Copyright (c) 2009 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 is the autoupdater for Memento. When called it consults Omaha to see
 # if there's an update available. If so, it downloads it to the other
 # partition on the Memento USB stick, then alters the MBR and partitions
 # as needed so the next reboot will boot into the newly installed partition.
@@ skipping 40 matching lines @@
   true
 else
   log "Failed to acquire lockfile: $PID_FILE." 
   log "Held by $(cat $PID_FILE)"
   exit 1
 fi
 # remove lockfile when we exit
 trap 'rm -f "$PID_FILE"; log Memento AutoUpdate terminating; exit $?' \
     INT TERM EXIT
 
+if [ x$1 = "x-f" ]; then
+  log "Forced update requested"
+  ForceUpdate="yes"
+  shift
+fi
+
 log Memento AutoUpdate starting
 
 # Get local version
 APP_VERSION=$(grep ^CHROMEOS_RELEASE_VERSION \
               /mnt/stateful_partition/etc/lsb-release | \
               cut -d = -f 2-)
 if [ "x" = "x$APP_VERSION" ]
 then
   # look in the main file
   APP_VERSION=$(grep ^CHROMEOS_RELEASE_VERSION \
                 /etc/lsb-release | cut -d = -f 2-)
 fi
 
 # See if we're forcing an update from a specific URL
 if [ "x" = "x$1" ]
 then
   # abort if autoupdates have been disabled, but only when an update image
   # isn't forced
   UPDATES_DISABLED_FILE="/var/local/disable_software_update"
   if [ -f "$UPDATES_DISABLED_FILE" ]
   then
     log Updates disabled. Aborting.
     exit 0
   fi
 
   # check w/ omaha to see if there's an update
-  OMAHA_CHECK_OUTPUT=$(`dirname "$0"`/ping_omaha.sh $APP_VERSION)
+  if [ "$ForceUpdate" = "yes" ]; then
+    OMAHA_CHECK_OUTPUT=$(`dirname "$0"`/ping_omaha.sh "ForcedUpdate")
+  else
+    OMAHA_CHECK_OUTPUT=$(`dirname "$0"`/ping_omaha.sh $APP_VERSION)
+  fi
   IMG_URL=$(echo "$OMAHA_CHECK_OUTPUT" | grep '^URL=' | cut -d = -f 2-)
   CHECKSUM=$(echo "$OMAHA_CHECK_OUTPUT" | grep '^HASH=' | cut -d = -f 2-)
 else
   log User forced an update from: "$1" checksum: "$2"
   IMG_URL="$1"
   CHECKSUM="$2"
 fi
 
 if [[ -z "$IMG_URL" || -z "$CHECKSUM" ]]
 then
@@ skipping 119 matching lines @@
 NEW_VERSION=$(grep ^GOOGLE_RELEASE "$MOUNTPOINT"/etc/lsb-release | \
               cut -d = -f 2-)
 if [ "x$NEW_VERSION" = "x" ]
 then
   log "Can't find new version number. aborting update"
   umount "$MOUNTPOINT"
   rmdir "$MOUNTPOINT"
   exit 1
 else
   # See if it's newer than us
-  if version_number_greater_than "$APP_VERSION" "$NEW_VERSION"
+  if [ "$ForceUpdate" != "yes" ] &&
+    version_number_greater_than "$APP_VERSION" "$NEW_VERSION"
   then
     log "Can't upgrade to older version: " "$NEW_VERSION"
     umount "$MOUNTPOINT"
     rmdir "$MOUNTPOINT"
     exit 1
   fi
 fi
 
 "$MOUNTPOINT"/postinst "$INSTALL_DEV" 2>&1 | cat >> "$MEMENTO_AU_LOG"; \
   [ "${PIPESTATUS[*]}" = "0 0" ]
@@ skipping 34 matching lines @@
                           -e "s/\(${LOCAL_DEV//\//\\/} .*\), bootable/\1/" \
   > "$LAYOUT_FILE"
 sfdisk --force $ROOT_DEV < "$LAYOUT_FILE" 2>&1 | cat >> "$MEMENTO_AU_LOG"
 abort_update_if_cmd_failed
 
 # mark update as complete so we don't try to update again
 touch "$UPDATED_COMPLETED_FILE"
 
 # tell user to reboot
 log Autoupdate applied. You should now reboot