Preserves file system metadata between new build and latest shipping image.

scripts/image_signing/align_rootfs.sh

+#!/bin/bash
+
+# Copyright (c) 2011 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.
+
+# Script to preserve the on-disk file layout of the specified image and
+# the latest shipping image.  This is accomplished by copying the new rootfs
+# over a template rootfs (aka the latest shipping image) to preserve as much
+# of the metadata from the shipping rootfs as possible. This will ensure
+# minimal disk shuffling when applying the auto-update.
+#
+# Note: This script does not recompute the rootfs hash.
+
+# Load common library.  This should be the first executable line.
+# The path to common.sh should be relative to your script's location.
+. "$(dirname "$0")/common.sh"
+
+load_shflags
+
+# Flags.
+DEFINE_string app_id "{87efface-864d-49a5-9bb3-4b050a7c227a}" \
+  "App ID to use when pinging the Omaha server for the latest version."
+DEFINE_string channel "dev-channel" \
+  "Release channel of the build."
+DEFINE_string hardware_id "IEC MARIO PONY 6101" \
+  "The Hardware ID of the latest shipping image to use as a template."
+DEFINE_string image "" \
+  "The image that needs to be aligned to the latest shipping image."
+
+IMAGE_SEARCH_STRING=
+RELEASE_URL=
+RELEASE_ALT_URL=
+
+# Sets up environment variables specific to the board.
+initialize() {
+  if [ "${FLAGS_hardware_id}" = "IEC MARIO PONY 6101" ]; then
+    IMAGE_SEARCH_STRING="*SSD_MP_SIGNED.bin"
+    RELEASE_URL="http://chromeos-images/chromeos-official/${FLAGS_channel}/x86-mario"
+    RELEASE_ALT_URL="${RELEASE_URL}-rc"
+  else
+    die "Hardware ID \"${FLAGS_hardware_id}\" not supported"
+  fi
+}
+
+# Gets the latest shipping version for the specified Hardware ID by pinging
+# the Omaha server.  The latest shipping version is printed to stdout.
+# The caller must use process substition when invoking this function so we
+# use a simple trap for clean up instead of calling add_cleanup_action.
+get_latest_shipping_version() {
+  info "Pinging Omaha for the latest shipping version."
+  local auserver_url="https://tools.google.com/service/update2"
+  local au_request_file=$(mktemp "/tmp/align_rootfs_au_request.XXXX")
+  trap "sudo rm -f \"${au_request_file}\"" INT TERM EXIT

[petkov, 2011/01/05 00:08:50]

no need for sudo?

(this trap seems evil...)

[thieule, 2011/01/05 00:11:44]

Done.

[gauravsh, 2011/01/05 00:15:41]

Wait, won't this ending up clobbering the previous trap you set up for
performing cleanup?

+  cat > "${au_request_file}" << EOF
+<?xml version="1.0" encoding="UTF-8"?>
+<o:gupdate xmlns:o="http://www.google.com/update2/request"
+   version="ChromeOSUpdateEngine-0.1.0.0"
+   updaterversion="ChromeOSUpdateEngine-0.1.0.0" protocol="2.0" ismachine="1">
+    <o:os version="Indy" platform="Chrome OS" sp="ForcedUpdate_i686"></o:os>
+    <o:app appid="${FLAGS_app_id}"
+       version="0.0.0.0" lang="en-US" track="${FLAGS_channel}"
+       hardware_class="${FLAGS_hardware_id}" delta_okay="true">
+        <o:updatecheck></o:updatecheck>
+    </o:app>
+</o:gupdate>
+EOF
+
+  wget -q --header="Content-Type: text/xml" \
+    --post-file="${au_request_file}" -O - ${auserver_url} |
+    sed 's/.*\(ChromeOSVersion="\)\([0-9\.]*\)"\(.*\)/\2/'
+}
+
+# Downloads the image from the specified |URL| using ${IMAGE_SEARCH_STRING} as
+# a wildcard match and write the image to |OUTPUT_FILE|.
+# Args: URL OUTPUT_FILE
+download_image() {
+  # Since we don't know the exact name, we'll just download recursively based
+  # on a wildcard. Then we'll rename that download file to the desired output
+  # file. It's important that the IMAGE_SEARCH_STRING matches only one file.
+  local url=$1
+  local output_file=$2
+  local retcode=0
+
+  local download_dir=$(mktemp -d "/tmp/align_rootfs_download_dir.XXXX")
+  add_cleanup_action "sudo rm -rf \"${download_dir}\""
+
+  wget -A "${IMAGE_SEARCH_STRING}" --progress=bar -r -l1 -nd \
+    -P "${download_dir}" ${url} || retcode=$?
+  if [ ${retcode} -eq 0 ]; then
+    mv -f "${download_dir}"/* "${output_file}"
+  else
+    return ${retcode}
+  fi
+}
+
+# Retrieves the latest shipping image and saves it to |IMAGE|.
+# Args: VERSION IMAGE
+get_shipping_image() {
+  # The image may reside in one of two URLs. We don't know exactly which one
+  # so we'll have to try both.
+  local version=$1
+  local image=$2
+  local url="${RELEASE_URL}/${version}"
+  download_image "${url}" "${image}" || retcode=$?
+  if [ ${retcode} -gt 0 ]; then
+    url="${RELEASE_ALT_URL}/${version}"
+    download_image "${url}" "${image}"
+  fi
+}
+
+# Copies the rootfs from |SRC_IMAGE| to the |DST_ROOT_FS| and preserves as
+# much of the file system metadata in |DST_ROOT_FS| as possible.
+# Args: SRC_IMAGE DST_ROOT_FS
+copy_root_fs() {
+  local src_image=$1
+  local dst_root_fs=$2
+
+  # Mount the src and dst rootfs.
+  local src_root_fs_dir=$(mktemp -d "/tmp/align_root_fs_src_mount_dir.XXXX")
+  add_cleanup_action "sudo rm -rf \"${src_root_fs_dir}\""
+  mount_image_partition_ro "${src_image}" 3 "${src_root_fs_dir}"
+  add_cleanup_action "sudo umount -d \"${src_root_fs_dir}\""
+
+  local dst_root_fs_dir=$(mktemp -d "/tmp/align_root_fs_dst_mount_dir.XXXX")
+  add_cleanup_action "sudo rm -rf \"${dst_root_fs_dir}\""
+  sudo mount -o loop "${dst_root_fs}" "${dst_root_fs_dir}" -o loop
+  add_cleanup_action "sudo umount -d \"${dst_root_fs_dir}\""
+
+  # Temporarily make immutable files on the dst rootfs mutable.
+  # We'll need to track these files in ${immutable_files} so we can make them
+  # mutable again.
+  local immutable_files=()
+  sudo find "${dst_root_fs_dir}" -xdev -type f |
+    while read -r file; do
+      immutable=$(sudo lsattr "${file}" | cut -d' ' -f1 | grep -q i ; echo $?)
+      if [ $immutable -eq 0 ]; then
+        immutable_files=("${immutable_files[@]}" "${file}")
+        sudo chattr -i "${file}"
+      fi
+    done
+
+  # Copy files from the src rootfs over top of dst rootfs.
+  # Use the --inplace flag to preserve as much of the file system metadata
+  # as possible.
+  sudo rsync -v -a -H -A -x --force --inplace --numeric-ids --delete \
+      "${src_root_fs_dir}"/ "${dst_root_fs_dir}"
+
+  # Make immutable files immutable again.
+  for file in ${immutable_files[*]} ; do
+    sudo chattr +i "${file}"
+  done
+
+  # Unmount the src and dst root fs so that we can replace the rootfs later.
+  perform_latest_cleanup_action
+  perform_latest_cleanup_action
+  perform_latest_cleanup_action
+  perform_latest_cleanup_action
+}
+
+# Zeroes the rootfs free space in the specified image.
+# Args: IMAGE
+zero_root_fs_free_space() {
+  local image=$1
+  local root_fs_dir=$(mktemp -d "/tmp/align_rootfs_zero_free_space_dir.XXXX")
+  add_cleanup_action "sudo rm -rf \"${root_fs_dir}\""
+  mount_image_partition "${image}" 3 "${root_fs_dir}"
+  add_cleanup_action "sudo umount -d \"${root_fs_dir}\""
+
+  info "Zeroing free space in rootfs"
+  sudo dd if=/dev/zero of="${root_fs_dir}/filler" oflag=sync bs=4096 || true
+  sudo rm -f "${root_fs_dir}/filler"
+  sudo sync
+
+  perform_latest_cleanup_action
+  perform_latest_cleanup_action
+}
+
+main() {
+  # Parse command line.
+  FLAGS "$@" || exit 1
+  eval set -- "${FLAGS_ARGV}"
+
+  # Only now can we die on error.  shflags functions leak non-zero error codes,
+  # so will die prematurely if 'set -e' is specified before now.
+  set -e
+
+  # Make sure we have the required parameters.
+  if [ -z "${FLAGS_image}" ];  then
+    die "--image is required."
+  fi
+
+  if [ ! -f "${FLAGS_image}" ]; then
+    die "Cannot find the specified image."
+  fi
+
+  # Initialize some variables specific to the board.
+  initialize
+
+  # Download the latest shipping image.
+  local latest_shipping_version=$(get_latest_shipping_version)
+  local latest_shipping_image=$(mktemp "/tmp/align_rootfs_shipping_image.XXXX")
+  add_cleanup_action "sudo rm -f \"${latest_shipping_image}\""
+  info "Downloading image (${latest_shipping_version})"
+  get_shipping_image "${latest_shipping_version}" "${latest_shipping_image}"
+
+  # Make sure the two rootfs are the same size.
+  # If they are not, then there is nothing for us to do.
+  # Note: Exit with a zero code so we do not break the build workflow.
+  local shipping_root_fs_size=$(partsize "${latest_shipping_image}" 3)
+  local new_root_fs_size=$(partsize "${FLAGS_image}" 3)
+  if [ ${shipping_root_fs_size} -ne ${new_root_fs_size} ]; then
+    warn "The latest shipping rootfs and the new rootfs are not the same size."
+    exit 0
+  fi
+
+  # Extract the rootfs from the shipping image and use this as a template
+  # for the new image.
+  temp_root_fs=$(mktemp "/tmp/align_rootfs_temp_rootfs.XXXX")
+  add_cleanup_action "sudo rm -f \"${temp_root_fs}\""
+  info "Extracting rootfs from shipping image"
+  extract_image_partition "${latest_shipping_image}" 3 "${temp_root_fs}"
+  enable_rw_mount "${temp_root_fs}"
+
+  # Perform actual copy of the two root file systems.
+  info "Copying rootfs"
+  copy_root_fs "${FLAGS_image}" "${temp_root_fs}"
+
+  # Replace the rootfs in the new image with the aligned version.
+  info "Replacing rootfs"
+  replace_image_partition "${FLAGS_image}" 3 "${temp_root_fs}"
+
+  # Zero rootfs free space.
+  zero_root_fs_free_space "${FLAGS_image}"
+}
+
+main "$@"