build_image

#!/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 build a bootable keyfob-based chromeos system image from within
# a chromiumos setup. This assumes that all needed packages have been built into
# the given target's root with binary packages turned on. This script will
# build the Chrome OS image using only pre-built binary packages.

# Load common CrOS utilities.  Inside the chroot this file is installed in
# /usr/lib/crosutils.  Outside the chroot we find it relative to the script's
# location.
find_common_sh() {
  local common_paths=(/usr/lib/crosutils $(dirname "$0"))
  local path

  SCRIPT_ROOT=
  for path in "${common_paths[@]}"; do
    local common="${path}/common.sh"
    if ([ -r "${common}" ] && . "${common}" && [ -d "${SCRIPTS_DIR}" ]); then
      SCRIPT_ROOT=${path}
      break
    fi
  done
}

find_common_sh
. "${SCRIPT_ROOT}/common.sh" || ! echo "Unable to load common.sh" || exit 1

# Load functions and constants for chromeos-install
[ -f /usr/lib/installer/chromeos-common.sh ] && \
  INSTALLER_ROOT=/usr/lib/installer || \
  INSTALLER_ROOT=$(dirname "$(readlink -f "$0")")

. "${INSTALLER_ROOT}/chromeos-common.sh" || \
  die "Unable to load chromeos-common.sh"

locate_gpt

# Script must be run inside the chroot.
restart_in_chroot_if_needed "$@"

get_default_board

# Flags.
DEFINE_string board "${DEFAULT_BOARD}" \
  "The board to build an image for."
DEFINE_string build_root "/build" \
  "The root location for board sysroots."
DEFINE_integer build_attempt 1 \
  "The build attempt for this image build."
DEFINE_string output_root "${DEFAULT_BUILD_ROOT}/images" \
  "Directory in which to place image result directories (named by version)"
DEFINE_boolean eclean ${FLAGS_TRUE} \
  "Perform eclean-<board> -d as part of this script to remove obsolete packages"
DEFINE_boolean replace ${FLAGS_FALSE} \
  "Overwrite existing output, if any."
DEFINE_boolean withdev ${FLAGS_TRUE} \
  "Include useful developer friendly utilities in the image."
DEFINE_boolean installmask ${FLAGS_TRUE} \
  "Use INSTALL_MASK to shrink the resulting image."
DEFINE_integer jobs -1 \
  "How many packages to build in parallel at maximum."
DEFINE_boolean statefuldev ${FLAGS_TRUE} \
  "Install development packages on stateful partition rather than the rootfs"
DEFINE_string to "" \
  "The target image file or device"
DEFINE_boolean factory_install ${FLAGS_FALSE} \
  "Build a smaller image to overlay the factory install shim on; this argument \
is also required in image_to_usb."
DEFINE_integer rootfs_partition_size 1024 \
  "rootfs partition size in MiBs."
DEFINE_integer rootfs_size 850 \
  "rootfs filesystem size in MiBs."
# ceil(0.1 * rootfs_size) is a good minimum.
DEFINE_integer rootfs_hash_pad 8 \
  "MiBs reserved at the end of the rootfs image."
DEFINE_integer statefulfs_size 1024 \
  "stateful filesystem size in MiBs."
DEFINE_boolean preserve ${FLAGS_FALSE} \
  "Attempt to preserve the previous build image if one can be found (unstable, \
kernel/firmware not updated)"
DEFINE_boolean fast ${DEFAULT_FAST} \
  "Call many emerges in parallel"
DEFINE_string boot_args "noinitrd" \
  "Additional boot arguments to pass to the commandline"

DEFINE_string usb_disk /dev/sdb3 \
  "Path syslinux should use to do a usb boot. Default: /dev/sdb3"

# TODO(clchiou): Remove this flag after arm verified boot is stable
DEFINE_boolean crosbug12352_arm_kernel_signing ${FLAGS_TRUE} \
  "Sign kernel partition for ARM images (temporary hack)."

DEFINE_boolean enable_rootfs_verification ${FLAGS_TRUE} \
  "Default all bootloaders to use kernel-based root fs integrity checking."
DEFINE_integer verity_error_behavior 3 \
  "Kernel verified boot error behavior (0: I/O errors, 1: panic, 2: nothing, \
3: cros) Default: 3"
DEFINE_integer verity_max_ios -1 \
  "Number of outstanding I/O operations dm-verity caps at. Default: -1"
DEFINE_string verity_algorithm "sha1" \
  "Cryptographic hash algorithm used for kernel vboot. Default : sha1"

# 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

if [ -z "${FLAGS_board}" ] ; then
  error "--board is required."
  exit 1
fi

# Perform an eclean to remove packages which are not installed
if [[ ${FLAGS_eclean} -eq ${FLAGS_TRUE} ]]; then
  eclean-${FLAGS_board} -d packages
fi

check_blacklist() {
  info "Verifying that the base image does not contain a blacklisted package."
  info "Generating list of packages for chromeos-base/chromeos."
  local package_blacklist_file="${SCRIPTS_DIR}/chromeos_blacklist"
  if [ ! -e "${package_blacklist_file}" ]; then
    warn "Missing blacklist file."
    return
  fi
  local blacklisted_packages=$(${SCRIPTS_DIR}/get_package_list \
      --board="${FLAGS_board}" chromeos-base/chromeos \
      | grep -x -f "${package_blacklist_file}")
  if [ -n "${blacklisted_packages}" ]; then
    die "Blacklisted packages found: ${blacklisted_packages}."
  fi
  info "No blacklisted packages found."
}

check_blacklist

# TODO(vlaviano): Validate command line flags. Check for conflicting flags and
# reconcile them if possible. Exit with an error message otherwise.

export INSTALL_MASK=""
if [ ${FLAGS_installmask} -eq ${FLAGS_TRUE} ] ; then
  INSTALL_MASK="${DEFAULT_INSTALL_MASK}"
fi

# Reduce the size of factory install shim.
if [ ${FLAGS_factory_install} -eq ${FLAGS_TRUE} ]; then
  # Disable --withdev flag when --factory_install is set to True. Otherwise, the
  # dev image produced will be based on install shim, rather than a pristine
  # image
  if [ ${FLAGS_withdev} -eq ${FLAGS_TRUE} ]; then
    info "Incompatible flags: --withdev and --factory_install cannot both be \
set to True. Resetting --withdev to False."
    FLAGS_withdev=${FLAGS_FALSE}
  fi

  # TODO: Build a separated ebuild for the install shim to reduce size.
  INSTALL_MASK="${INSTALL_MASK} ${FACTORY_INSTALL_MASK}"

  info "Fixing the rootfs size at 300 MiB for install shim"
  FLAGS_rootfs_size=280
  FLAGS_rootfs_partition_size=300
  info "Fixing the statefulfs size at 140 MiB for install shim"
  FLAGS_statefulfs_size=140
fi

if [ $((FLAGS_rootfs_size + FLAGS_rootfs_hash_pad)) -gt \
     ${FLAGS_rootfs_partition_size} ] ; then
  die "rootfs ($((FLAGS_rootfs_size + FLAGS_rootfs_hash_pad)) MiB) is \
bigger than partition (${FLAGS_rootfs_partition_size} MiB)."
fi

EMERGE_BOARD_CMD="emerge-${FLAGS_board}"
if [ ${FLAGS_fast} -eq ${FLAGS_TRUE} ]; then
  echo "Using alternate emerge"
  EMERGE_CMD="${GCLIENT_ROOT}/chromite/bin/parallel_emerge"
  EMERGE_BOARD_CMD="${EMERGE_CMD} --board=${FLAGS_board}"
fi

OVERLAY_CHROMEOS_DIR="${SRC_ROOT}/third_party/chromiumos-overlay/chromeos/"

# Determine build version.
. "${OVERLAY_CHROMEOS_DIR}/config/chromeos_version.sh"

BOARD="${FLAGS_board}"
BOARD_ROOT="${FLAGS_build_root}/${BOARD}"

# What cross-build are we targeting?
. "${BOARD_ROOT}/etc/make.conf.board_setup"
LIBC_VERSION=${LIBC_VERSION}

# Figure out ARCH from the given toolchain.
# TODO: Move to common.sh as a function after scripts are switched over.
TC_ARCH=$(echo "${CHOST}" | awk -F'-' '{ print $1 }')
case "${TC_ARCH}" in
  arm*)
    ARCH="arm"
    ;;
  *86)
    ARCH="x86"
    ;;
  *x86_64)
    ARCH="amd64"
    ;;
  *)
    error "Unable to determine ARCH from toolchain: ${CHOST}"
    exit 1
esac

# Configure extra USE or packages for this type of build.
EXTRA_PACKAGES=""
if [ ${FLAGS_factory_install} -eq ${FLAGS_TRUE} ] ; then
  # Factory install needs to have the factory installer added.
  EXTRA_PACKAGES="${EXTRA_PACKAGES} chromeos-base/chromeos-factoryinstall"
  # On x86, we boot the factory install shim from an SD card using
  # initramfs for our root.  On ARM, we boot the factory install shim
  # over the network, so we don't require initramfs, but we do require
  # fbconsole to fix a display driver bug.
  if [ "${ARCH}" = "x86" ] ; then
    export USE="${USE} initramfs"
  fi
  # CONFIG_BLK_DEV_RAM is disabled by default.
  # But tftp install needs it to mount rootfs in ram
  if [ "${ARCH}" = "arm" ] ; then
    export USE="${USE} fbconsole blkdevram"
  fi
fi

emerge_to_image() {
  sudo -E ${EMERGE_BOARD_CMD} --root-deps=rdeps --usepkgonly \
    "$@" ${EMERGE_JOBS}
}

# Check that the build root is sane.
"${SCRIPTS_DIR}/test_build_root" --root="${BOARD_ROOT}"

# Freshen kernel with correct USE flags. This is a noop if we have
# the right kernel prebuilt. Factory install uses USE="initramfs".
# We don't allow building from source with the image as a target,
# and it's not possible to store prebuilts for the same package
# with different use flags.
sudo -E ${EMERGE_BOARD_CMD} -uDNv -g virtual/kernel

# Use canonical path since some tools (e.g. mount) do not like symlinks.
# Append build attempt to output directory.
IMAGE_SUBDIR="${CHROMEOS_VERSION_STRING}-a${FLAGS_build_attempt}"
OUTPUT_DIR="${FLAGS_output_root}/${FLAGS_board}/${IMAGE_SUBDIR}"

OUTSIDE_OUTPUT_DIR="../build/images/${FLAGS_board}/${IMAGE_SUBDIR}"

# If we are creating a developer image, also create a pristine image with a
# different name.
DEVELOPER_IMAGE_NAME=
PRISTINE_IMAGE_NAME=chromiumos_image.bin
if [ ${FLAGS_withdev} -eq ${FLAGS_TRUE} ]; then
  PRISTINE_IMAGE_NAME=chromiumos_base_image.bin
  DEVELOPER_IMAGE_NAME=chromiumos_image.bin
# Rename pristine image for factory install shim
elif [ ${FLAGS_factory_install} -eq ${FLAGS_TRUE} ]; then
  PRISTINE_IMAGE_NAME=factory_install_shim.bin
fi

PRISTINE_IMG="${OUTPUT_DIR}/${PRISTINE_IMAGE_NAME}"
DEVELOPER_IMG="${OUTPUT_DIR}/${DEVELOPER_IMAGE_NAME}"

ROOT_FS_IMG="${OUTPUT_DIR}/rootfs.image"
ROOT_FS_DIR="${OUTPUT_DIR}/rootfs"
ROOT_FS_HASH="${OUTPUT_DIR}/rootfs.hash"

STATEFUL_FS_IMG="${OUTPUT_DIR}/stateful_partition.image"
STATEFUL_FS_DIR="${OUTPUT_DIR}/stateful_partition"

ESP_FS_IMG=${OUTPUT_DIR}/esp.image
ESP_FS_DIR=${OUTPUT_DIR}/esp

DEVKEYSDIR="/usr/share/vboot/devkeys"

LOOP_DEV=
STATEFUL_LOOP_DEV=
ESP_LOOP_DEV=

# ${DEV_IMAGE_ROOT} specifies the location of where developer packages will
# be installed on the stateful dir.  On a Chromium OS system, this will
# translate to /usr/local.
DEV_IMAGE_ROOT="${STATEFUL_FS_DIR}/dev_image"

if [ ${FLAGS_jobs} -ne -1 ]; then
  EMERGE_JOBS="--jobs=${FLAGS_jobs}"
fi

if [[ ${FLAGS_crosbug12352_arm_kernel_signing} -eq ${FLAGS_TRUE} ]]; then
  crosbug12352_flag="--crosbug12352_arm_kernel_signing"
else
  crosbug12352_flag="--nocrosbug12352_arm_kernel_signing"
fi
if [[ ${FLAGS_enable_rootfs_verification} -eq ${FLAGS_TRUE} ]]; then
  enable_rootfs_verification_flag="--enable_rootfs_verification"
fi

# Hack to fix bug where x86_64 CHOST line gets incorrectly added.
# ToDo(msb): remove this hack.
PACKAGES_FILE="${BOARD_ROOT}/packages/Packages"
sudo sed -e "s/CHOST: x86_64-pc-linux-gnu//" -i "${PACKAGES_FILE}"

# Handle existing directory.
if [[ -e "${OUTPUT_DIR}" ]]; then
  if [[ ${FLAGS_replace} -eq ${FLAGS_TRUE} ]]; then
    sudo rm -rf "${OUTPUT_DIR}"
  else
    echo "Directory ${OUTPUT_DIR} already exists."
    echo "Use --build_attempt option to specify an unused attempt."
    echo "Or use --replace if you want to overwrite this directory."
    exit 1
  fi
fi

# Find previous build, if any...
PREVIOUS_DIR=$($SCRIPTS_DIR/get_latest_image.sh --board="$BOARD")

cleanup_rootfs_loop() {
  sudo umount -d "${ROOT_FS_DIR}"
}

cleanup_stateful_fs_loop() {
  sudo umount "${ROOT_FS_DIR}/usr/local"
  sudo umount "${ROOT_FS_DIR}/var"
  sudo umount -d "${STATEFUL_FS_DIR}"
}

cleanup_esp_loop() {
  sudo umount -d "${ESP_FS_DIR}"
}

cleanup() {
  # Disable die on error.
  set +e

  if [[ -n "${STATEFUL_LOOP_DEV}" ]]; then
    cleanup_stateful_fs_loop
    STATEFUL_LOOP_DEV=
  fi

  if [[ -n "${LOOP_DEV}" ]]; then
    cleanup_rootfs_loop
    LOOP_DEV=
  fi

  if [[ -n "${ESP_LOOP_DEV}" ]]; then
    cleanup_esp_loop
    ESP_LOOP_DEV=
  fi

  # Turn die on error back on.
  set -e
}

delete_prompt() {
  echo "An error occurred in your build so your latest output directory" \
    "is invalid."

  # Only prompt if both stdin and stdout are a tty. If either is not a tty,
  # then the user may not be present, so we shouldn't bother prompting.
  if tty -s && tty -s <&1 && [ "${USER}" != 'chrome-bot' ]; then
    read -p "Would you like to delete the output directory (y/N)? " SURE
    SURE="${SURE:0:1}" # Get just the first character.
  else
    SURE="y"
    echo "Running in non-interactive mode so deleting output directory."
  fi
  if [ "${SURE}" == "y" ] ; then
    sudo rm -rf "${OUTPUT_DIR}"
    echo "Deleted ${OUTPUT_DIR}"
  else
    echo "Not deleting ${OUTPUT_DIR}."
  fi
}

# $1 - Directory where developer rootfs is mounted.
# $2 - Directory where developer stateful_partition is mounted.
# $3 - Directory where the ESP partition is mounted.
mount_gpt_cleanup() {
  local rootfs="${1-$ROOT_FS_DIR}"
  local statefs="${2-$STATEFUL_FS_DIR}"
  local espfs="${3-$ESP_FS_DIR}"
  "${SCRIPTS_DIR}/mount_gpt_image.sh" \
    -u -r "${rootfs}" -s "${statefs}" -e "${espfs}"
  delete_prompt
}

# Takes no arguments and populates the configuration for
# cros_make_image_bootable.
create_boot_desc() {
  cat <<EOF > ${OUTPUT_DIR}/boot.desc
  --arch="${ARCH}"
  --output_dir="${OUTPUT_DIR}"
  --boot_args="${FLAGS_boot_args}"
  --rootfs_size="${FLAGS_rootfs_size}"
  --rootfs_hash_pad="${FLAGS_rootfs_hash_pad}"
  --rootfs_hash="${ROOT_FS_HASH}"
  --rootfs_mountpoint="${ROOT_FS_DIR}"
  --statefulfs_mountpoint="${STATEFUL_FS_DIR}"
  --espfs_mountpoint="${ESP_FS_DIR}"
  --verity_error_behavior="${FLAGS_verity_error_behavior}"
  --verity_max_ios="${FLAGS_verity_max_ios}"
  --verity_algorithm="${FLAGS_verity_algorithm}"
  --keys_dir="${DEVKEYSDIR}"
  --usb_disk="${FLAGS_usb_disk}"
  --nocleanup_dirs
  ${crosbug12352_flag}
  ${enable_rootfs_verification_flag}
EOF
}

# Modifies an existing image to add development packages
update_dev_packages() {
  local image_name=$1

  echo "Adding developer packages to ${image_name}"

  trap "mount_gpt_cleanup" EXIT

  ${SCRIPTS_DIR}/mount_gpt_image.sh --from "${OUTPUT_DIR}" \
    --image "${image_name}" -r "${ROOT_FS_DIR}" \
    -s "${STATEFUL_FS_DIR}" -e "${ESP_FS_DIR}"

  # Determine the root dir for developer packages.
  local root_dev_dir="${ROOT_FS_DIR}"
  [ ${FLAGS_statefuldev} -eq ${FLAGS_TRUE} ] && \
    root_dev_dir="${ROOT_FS_DIR}/usr/local"

  # Install developer packages described in chromeos-dev.
  emerge_to_image --root="${root_dev_dir}" -uDNv chromeos-dev

  if [[ $FLAGS_preserve -eq ${FLAGS_TRUE} ]] ; then
    # Clean out unused packages
    emerge_to_image --root="${ROOT_FS_DIR}" --depclean
  fi

  # Install the bare necessary files so that the "emerge" command works
  if [ ${FLAGS_statefuldev} -eq ${FLAGS_TRUE} ]; then
    sudo cp -a ${root_dev_dir}/share/portage ${ROOT_FS_DIR}/usr/share
    sudo sed -i s,/usr/bin/wget,wget, \
      ${ROOT_FS_DIR}/usr/share/portage/config/make.globals
  fi
  sudo mkdir -p ${ROOT_FS_DIR}/etc/make.profile

  # Re-run ldconfig to fix /etc/ldconfig.so.cache.
  sudo /sbin/ldconfig -r "${ROOT_FS_DIR}"

  # Mark the image as a developer image (input to chromeos_startup).
  sudo mkdir -p "${ROOT_FS_DIR}/root"
  sudo touch "${ROOT_FS_DIR}/root/.dev_mode"

  # Additional changes to developer image.

  # Leave core files for developers to inspect.
  sudo touch "${ROOT_FS_DIR}/root/.leave_core"

  # This hack is only needed for devs who have old versions of glibc, which
  # filtered out ldd when cross-compiling.  TODO(davidjames): Remove this hack
  # once everybody has upgraded to a new version of glibc.
  if [[ ! -x "${ROOT_FS_DIR}/usr/bin/ldd" ]]; then
    sudo cp -a "$(which ldd)" "${ROOT_FS_DIR}/usr/bin"
  fi

  # If vim is installed, then a vi symlink would probably help.
  if [[ -x "${ROOT_FS_DIR}/usr/local/bin/vim" ]]; then
    sudo ln -sf vim "${ROOT_FS_DIR}/usr/local/bin/vi"
  fi

  # If pygtk is installed in stateful-dev, then install a path.
  if [[ -d \
      "${ROOT_FS_DIR}/usr/local/lib/python2.6/site-packages/gtk-2.0" ]]; then
    sudo bash -c "\
        echo gtk-2.0 > \
        ${ROOT_FS_DIR}/usr/local/lib/python2.6/site-packages/pygtk.pth"
  fi

  # If python is installed on stateful-dev, fix python symlinks.
  local python_path="/usr/local/bin/python2.6"
  if [ -e "${ROOT_FS_DIR}${python_path}" ]; then
    info "Fixing python symlinks for developer and test images."
    local python_paths="/usr/bin/python /usr/local/bin/python \
        /usr/bin/python2 /usr/local/bin/python2"
    for path in ${python_paths}; do
      sudo rm -f "${ROOT_FS_DIR}${path}"
      sudo ln -s  ${python_path} "${ROOT_FS_DIR}${path}"
    done
  fi

  # Check that the image has been correctly created.  Only do it if not
  # building a factory install shim, as the INSTALL_MASK for it will make
  # test_image fail.
  if [ ${FLAGS_factory_install} -eq ${FLAGS_FALSE} ]; then
    "${SCRIPTS_DIR}/test_image" \
      --root="${ROOT_FS_DIR}" \
      --target="${ARCH}"
  fi
  echo "Developer image built and stored at ${image_name}"

  trap - EXIT
  ${SCRIPTS_DIR}/mount_gpt_image.sh -u -r "${ROOT_FS_DIR}" \
    -s "${STATEFUL_FS_DIR}" -e "${ESP_FS_DIR}"
}

# Update the base package on an existing image.
update_base_packages() {
  local image_name=$1

  echo "Updating base packages on ${image_name}"

  # Create stateful partition of the same size as the rootfs.
  trap "mount_gpt_cleanup" EXIT

  ${SCRIPTS_DIR}/mount_gpt_image.sh --from "${OUTPUT_DIR}" \
    --image "${image_name}" -r "${ROOT_FS_DIR}" \
    -s "${STATEFUL_FS_DIR}" -e "${ESP_FS_DIR}"

  # Emerge updated packages, exactly like when creating base image
  emerge_to_image --root="${ROOT_FS_DIR}" -uDNv chromeos ${EXTRA_PACKAGES}

  # Clean out unused packages
  emerge_to_image --root="${ROOT_FS_DIR}" --depclean

  trap - EXIT
  ${SCRIPTS_DIR}/mount_gpt_image.sh -u -r "${ROOT_FS_DIR}" \
    -s "${STATEFUL_FS_DIR}" -e "${ESP_FS_DIR}"
}

zero_free_space() {
  local fs_mount_point=$1
  info "Zeroing freespace in ${fs_mount_point}"
  # dd is a silly thing and will produce a "No space left on device" message
  # that cannot be turned off and is confusing to unsuspecting victims.
  ( sudo dd if=/dev/zero of="${fs_mount_point}/filler" oflag=sync bs=4096 \
    || true ) 2>&1 |grep -v "No space left on device"
  sudo rm -f "${fs_mount_point}/filler"
  sudo sync
}

create_base_image() {
  local image_name=$1

  trap "cleanup && delete_prompt" EXIT

  # Create and format the root file system.

  # Check for loop device before creating image.
  LOOP_DEV=$(sudo losetup -f)
  if [ -z "${LOOP_DEV}" ] ; then
    echo "No free loop device.  Free up a loop device or reboot.  exiting. "
    exit 1
  fi

  # Create root file system disk image.
  ROOT_SIZE_BYTES=$((1024 * 1024 * ${FLAGS_rootfs_size}))

  # Pad out for the hash tree.
  ROOT_HASH_PAD=$((FLAGS_rootfs_hash_pad * 1024 * 1024))
  info "Padding the rootfs image by ${ROOT_HASH_PAD} bytes for hash data"

  dd if=/dev/zero of="${ROOT_FS_IMG}" bs=1 count=1 \
     seek=$((ROOT_SIZE_BYTES + ROOT_HASH_PAD - 1))
  sudo losetup "${LOOP_DEV}" "${ROOT_FS_IMG}"
  # Specify a block size and block count to avoid using the hash pad.
  sudo mkfs.ext2 -b 4096 "${LOOP_DEV}" "$((ROOT_SIZE_BYTES / 4096))"

  # Tune and mount rootfs.
  DISK_LABEL="C-ROOT"
  # Disable checking and minimize metadata differences across builds
  # and wasted reserved space.
  sudo tune2fs -L "${DISK_LABEL}" \
               -U clear \
               -T 20091119110000 \
               -c 0 \
               -i 0 \
               -m 0 \
               -r 0 \
               -e remount-ro \
                "${LOOP_DEV}"
  # TODO(wad) call tune2fs prior to finalization to set the mount count to 0.
  sudo mount -t ext2 "${LOOP_DEV}" "${ROOT_FS_DIR}"

  # Create stateful partition of the same size as the rootfs.
  STATEFUL_LOOP_DEV=$(sudo losetup -f)
  if [ -z "${STATEFUL_LOOP_DEV}" ] ; then
    echo "No free loop device.  Free up a loop device or reboot.  exiting. "
    exit 1
  fi
  STATEFUL_SIZE_BYTES=$((1024 * 1024 * ${FLAGS_statefulfs_size}))
  dd if=/dev/zero of="${STATEFUL_FS_IMG}" bs=1 count=1 \
      seek=$((STATEFUL_SIZE_BYTES - 1))

  # Tune and mount the stateful partition.
  UUID=$(uuidgen)
  DISK_LABEL="C-STATE"
  sudo losetup "${STATEFUL_LOOP_DEV}" "${STATEFUL_FS_IMG}"
  sudo mkfs.ext3 "${STATEFUL_LOOP_DEV}"
  sudo tune2fs -L "${DISK_LABEL}" -U "${UUID}" -c 0 -i 0 "${STATEFUL_LOOP_DEV}"
  sudo mount -t ext3 "${STATEFUL_LOOP_DEV}" "${STATEFUL_FS_DIR}"

  # -- Install packages into the root file system --

  # We need to install libc manually from the cross toolchain.
  # TODO: Improve this? We only want libc and not the whole toolchain.
  # TODO(raymes): Remove this check after some time which ensures
  # backward compatibility with the crossdev location change.
  PKGDIR="/var/lib/portage/pkgs"
  LIBC_TAR="glibc-${LIBC_VERSION}.tbz2"
  NEW_LIBC_PATH="${PKGDIR}/cross-${CHOST}/${LIBC_TAR}"
  OLD_LIBC_PATH="${PKGDIR}/cross/${CHOST}/cross-${CHOST}/${LIBC_TAR}"
  if [ -e "${NEW_LIBC_PATH}" ] ; then
    LIBC_PATH="${NEW_LIBC_PATH}"
  else
    LIBC_PATH="${OLD_LIBC_PATH}"
  fi

  sudo tar jxvpf "${LIBC_PATH}" -C "${ROOT_FS_DIR}" --strip-components=3 \
    --exclude=usr/include --exclude=sys-include --exclude=*.a --exclude=*.o

  # We need to install libstdc++ manually from the cross toolchain.
  # TODO: Figure out a better way of doing this?
  sudo cp -a "${BOARD_ROOT}"/lib/libgcc_s.so* "${ROOT_FS_DIR}/lib"
  sudo cp -a "${BOARD_ROOT}"/usr/lib/libstdc++.so* "${ROOT_FS_DIR}/usr/lib"

  # Prepare stateful partition with some pre-created directories.
  sudo mkdir -p "${DEV_IMAGE_ROOT}"
  sudo mkdir -p "${STATEFUL_FS_DIR}/var"

  # Create symlinks so that /usr/local/usr based directories are symlinked to
  # /usr/local/ directories e.g. /usr/local/usr/bin -> /usr/local/bin, etc.
  setup_symlinks_on_root "${DEV_IMAGE_ROOT}" "${STATEFUL_FS_DIR}/var" \
    "${STATEFUL_FS_DIR}"

  # Perform binding rather than symlinking because directories must exist
  # on rootfs so that we can bind at run-time since rootfs is read-only.
  echo "Binding directories from stateful partition onto the rootfs"
  sudo mkdir -p "${ROOT_FS_DIR}/usr/local"
  sudo mount --bind "${DEV_IMAGE_ROOT}" "${ROOT_FS_DIR}/usr/local"
  sudo mkdir -p "${ROOT_FS_DIR}/var"
  sudo mount --bind "${STATEFUL_FS_DIR}/var" "${ROOT_FS_DIR}/var"
  sudo mkdir -p "${ROOT_FS_DIR}/dev"

  # We "emerge --root=${ROOT_FS_DIR} --root-deps=rdeps --usepkgonly" all of the
  # runtime packages for chrome os. This builds up a chrome os image from
  # binary packages with runtime dependencies only.  We use INSTALL_MASK to
  # trim the image size as much as possible.
  emerge_to_image --root="${ROOT_FS_DIR}" chromeos ${EXTRA_PACKAGES}

  # Set /etc/lsb-release on the image.
  "${OVERLAY_CHROMEOS_DIR}/scripts/cros_set_lsb_release" \
    --root="${ROOT_FS_DIR}" \
    --board="${BOARD}"

  # Populates the root filesystem with legacy bootloader templates
  # appropriate for the platform.  The autoupdater and installer will
  # use those templates to update the legacy boot partition (12/ESP)
  # on update.
  # (This script does not populate vmlinuz.A and .B needed by syslinux.)
  enable_rootfs_verification=
  if [[ ${FLAGS_enable_rootfs_verification} -eq ${FLAGS_TRUE} ]]; then
    enable_rootfs_verification="--enable_rootfs_verification"
  fi

  ${SCRIPTS_DIR}/create_legacy_bootloader_templates.sh \
    --arch=${ARCH} \
    --to="${ROOT_FS_DIR}"/boot \
    --boot_args="${FLAGS_boot_args}" \
    --install \
    ${enable_rootfs_verification}

  # Don't test the factory install shim
  if [ ${FLAGS_factory_install} -eq ${FLAGS_FALSE} ]; then
    # Check that the image has been correctly created.
    "${SCRIPTS_DIR}/test_image" \
      --root="${ROOT_FS_DIR}" \
      --target="${ARCH}"
  fi

  # Clean up symlinks so they work on a running target rooted at "/".
  # Here development packages are rooted at /usr/local.  However, do not
  # create /usr/local or /var on host (already exist on target).
  setup_symlinks_on_root "/usr/local" "/var" "${STATEFUL_FS_DIR}"

  # cros_make_image_bootable will clobber vmlinuz.image for x86.
  # Until then, just copy the kernel to vmlinuz.image. It is
  # expected in build_gpt.sh.
  cp "${ROOT_FS_DIR}/boot/vmlinuz" "${OUTPUT_DIR}/vmlinuz.image"

  # Create an empty esp image to be updated in by update_bootloaders.sh.
  ${SCRIPTS_DIR}/create_esp.sh --to="${ESP_FS_IMG}"

  # Zero rootfs free space to make it more compressible so auto-update
  # payloads become smaller
  zero_free_space "${ROOT_FS_DIR}"

  cleanup

  trap delete_prompt EXIT

  # Create the GPT-formatted image.
  ${SCRIPTS_DIR}/build_gpt.sh \
    --arch=${ARCH} \
    --board=${FLAGS_board} \
    --rootfs_partition_size=${FLAGS_rootfs_partition_size} \
    "${OUTPUT_DIR}" \
    "${OUTPUT_DIR}/${image_name}"

  # Pre-set "sucessful" bit in gpt, so we will never mark-for-death
  # a partition on an SDCard/USB stick.
  ${GPT} add -i 2 -S 1 "${OUTPUT_DIR}/${image_name}"

  trap - EXIT
}

generate_au_zip () {
  local lgenerateauzip="${SCRIPTS_DIR}/generate_au_zip.py"
  local largs="-o ${OUTPUT_DIR}"
  test ! -d "${OUTPUT_DIR}" && mkdir -p "${OUTPUT_DIR}"
  info "Running ${lgenerateauzip} ${largs} for generating AU updater zip file"
  $lgenerateauzip $largs
}

# Create the output directory.
mkdir -p "${OUTPUT_DIR}"
mkdir -p "${ROOT_FS_DIR}"
mkdir -p "${STATEFUL_FS_DIR}"
mkdir -p "${ESP_FS_DIR}"

# Preserve old images by copying them forward for --preserve.
if [[ $FLAGS_preserve -eq ${FLAGS_TRUE} ]] ; then
  if [[ -f ${PREVIOUS_DIR}/${PRISTINE_IMAGE_NAME} ]] ; then
    # Copy forward pristine image, and associated files
    cp ${PREVIOUS_DIR}/*.sh ${PREVIOUS_DIR}/config.txt ${OUTPUT_DIR}
    cp ${PREVIOUS_DIR}/${PRISTINE_IMAGE_NAME} ${OUTPUT_DIR}

    # Copy forward the developer image, if we already copied forward the base.
    if [[ ${FLAGS_withdev} -eq ${FLAGS_TRUE} ]] && \
       [[ -f ${PREVIOUS_DIR}/${DEVELOPER_IMAGE_NAME} ]] ; then
      cp ${PREVIOUS_DIR}/${DEVELOPER_IMAGE_NAME} ${OUTPUT_DIR}
    fi
  fi
fi

# Create the boot.desc file which stores the build-time configuration
# information needed for making the image bootable after creation with
# cros_make_image_bootable.
create_boot_desc

if [[ -f ${PRISTINE_IMG} ]] ; then
  update_base_packages ${PRISTINE_IMAGE_NAME}
else
  create_base_image ${PRISTINE_IMAGE_NAME}
fi

USE_DEV_KEYS=
if [ ${FLAGS_factory_install} -eq ${FLAGS_TRUE} ]; then
  USE_DEV_KEYS="--use_dev_keys"
fi

# Place flags before positional args
${SCRIPTS_DIR}/bin/cros_make_image_bootable "${OUTPUT_DIR}" \
                                            "${PRISTINE_IMAGE_NAME}" \
                                            ${USE_DEV_KEYS} \
                                            ${crosbug12352_flag}

# FIXME Test x86 image, and test arm image if enabled;
# should unconditionally test an image after crosbug12352 is fixed
if [[ "${ARCH}" = "x86" ]] ||
   [[ "${ARCH}" = "arm" &&
      ${FLAGS_crosbug12352_arm_kernel_signing} -eq ${FLAGS_TRUE} ]]; then
  BOOT_FLAG=
  if [ ${FLAGS_factory_install} -eq ${FLAGS_TRUE} ]; then
    BOOT_FLAG="-b 1"  # BOOT_FLAG_DEVELOPER value defined in load_kernel_fw.h
    info "--factory_install set, pass BOOT_FLAG_DEVELOPER flag to \
load_kernel_test"
  fi

  # Verify the final image.
  load_kernel_test "${OUTPUT_DIR}/${PRISTINE_IMAGE_NAME}" \
    "${DEVKEYSDIR}/recovery_key.vbpubk" ${BOOT_FLAG}
fi

# Create a developer image based on the chromium os base image.
if [ ${FLAGS_withdev} -eq ${FLAGS_TRUE} ] ; then
  if [[ ! -f ${DEVELOPER_IMG} ]] ; then
    echo "Creating developer image from base image ${PRISTINE_IMAGE_NAME}"
    cp ${PRISTINE_IMG} ${DEVELOPER_IMG}
  fi

  update_dev_packages ${DEVELOPER_IMAGE_NAME}
  ${SCRIPTS_DIR}/bin/cros_make_image_bootable "${OUTPUT_DIR}" \
                                              "${DEVELOPER_IMAGE_NAME}" \
                                              ${crosbug12352_flag}
fi

# Clean up temporary files.
rm -f "${ROOT_FS_IMG}" "${STATEFUL_FS_IMG}" "${OUTPUT_DIR}/vmlinuz.image" \
  "${ESP_FS_IMG}" "${OUTPUT_DIR}/vmlinuz_hd.vblock"
rmdir "${ROOT_FS_DIR}" "${STATEFUL_FS_DIR}" "${ESP_FS_DIR}"

# Generating AU generator zip file to run outside chroot
generate_au_zip || echo "Failed generating AU zip file - ignoring Error..."
# Create a 'latest' link
rm -f ${FLAGS_output_root}/${FLAGS_board}/latest
ln -s $(basename ${OUTPUT_DIR}) ${FLAGS_output_root}/${FLAGS_board}/latest

echo "Done.  Image created in ${OUTPUT_DIR}"
echo "Chromium OS image created as ${PRISTINE_IMAGE_NAME}"
if [ ${FLAGS_withdev} -eq ${FLAGS_TRUE} ]; then
  echo "Developer image created as ${DEVELOPER_IMAGE_NAME}"
fi

print_time_elapsed

echo "To copy to USB keyfob, do something like:"
echo "  ./image_to_usb.sh --from=${OUTSIDE_OUTPUT_DIR} --to=/dev/sdX"
echo "To convert to VMWare image, INSIDE the chroot, do something like:"
echo "  ./image_to_vm.sh --from=${OUTSIDE_OUTPUT_DIR} --board=${BOARD}"
echo "from the scripts directory where you entered the chroot."