build_image

#!/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.

# 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 constants.  This should be the first executable line.
# The path to common.sh should be relative to your script's location.
. "$(dirname "$0")/common.sh"

. "$(dirname "$0")/chromeos-common.sh"  # for partoffset
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 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_string arm_extra_bootargs "" \
  "Additional command line options to pass to the ARM kernel."
DEFINE_integer rootfs_partition_size 1024 \
  "rootfs parition size in MBs."
DEFINE_integer rootfs_size 720 \
  "rootfs filesystem size in MBs."
# ceil(0.1 * rootfs_size) is a good minimum.
DEFINE_integer rootfs_hash_pad 8 \
  "MBs reserved at the end of the rootfs image."
DEFINE_integer statefulfs_size 1024 \
  "stateful filesystem size in MBs."
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 ${FLAGS_FALSE} \
  "Call many emerges in parallel (unstable)"

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

DEFINE_boolean enable_rootfs_verification ${FLAGS_FALSE} \
  "Default all bootloaders to use kernel-based root fs integrity checking."
DEFINE_integer verity_error_behavior 2 \
  "Kernel verified boot error behavior (0: I/O errors, 1: reboot, 2: nothing) \
Default: 2"
DEFINE_integer verity_depth 1 \
  "Kernel verified boot hash tree depth. Default: 1"
DEFINE_integer verity_max_ios 1024 \
  "Number of outstanding I/O operations dm-verity caps at. Default: 1024"
DEFINE_string verity_algorithm "sha1" \
  "Cryptographic hash algorithm used for kernel vboot. Default : sha1"

DEFINE_string oem_customization "" \
  "Path to directory containing OEM partner partition contents"

# 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

if [ "$((FLAGS_rootfs_size + FLAGS_rootfs_hash_pad))" -gt \
     "${FLAGS_rootfs_partition_size}" ] ; then
  error "rootfs ($((FLAGS_rootfs_size + FLAGS_rootfs_hash_pad)) MB) is \
bigger than partition (${FLAGS_rootfs_partition_size} MB)."
  exit 1
fi

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

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

# 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
fi

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

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

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"

OEM_FS_IMG="${OUTPUT_DIR}/partner_partition.image"
OEM_FS_DIR="${OUTPUT_DIR}/partner_partition"

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

LOOP_DEV=
STATEFUL_LOOP_DEV=
OEM_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"

# What cross-build are we targeting?
. "${BOARD_ROOT}/etc/make.conf.board_setup"
LIBC_VERSION=${LIBC_VERSION:-"2.10.1-r1"}

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

# Reduce the size of factory install shim.
# TODO: Build a separated ebuild for the factory install shim to reduce size.
if [[ ${FLAGS_factory_install} -eq ${FLAGS_TRUE} ]] ; then
  INSTALL_MASK="${INSTALL_MASK} ${FACTORY_INSTALL_MASK}"
fi

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

# 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"
    ;;
  *)
    error "Unable to determine ARCH from toolchain: ${CHOST}"
    exit 1
esac

# 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_oem_fs_loop() {
  sudo umount -d "${OEM_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 "${OEM_LOOP_DEV}" ]]; then
    cleanup_oem_fs_loop
  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."
  read -p "Would you like to delete the output directory (y/N)? " SURE
  SURE="${SURE:0:1}" # Get just the first character.
  if [ "${SURE}" == "y" ] ; then
    sudo rm -rf "${OUTPUT_DIR}"
    echo "Deleted ${OUTPUT_DIR}"
  else
    echo "Not deleting ${OUTPUT_DIR}. Note dev server updates will not work" \
      "until you successfully build another image or delete this directory"
  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
}

make_image_bootable() {
  local image_name="$1"
  cros_root=/dev/sd%D%P
  if [[ "${ARCH}" = "arm" ]]; then
    # TODO(wad) assumed like in build_gpt for now.
    cros_root=/dev/mmcblk1p3
  fi
  if [[ ${FLAGS_enable_rootfs_verification} -eq ${FLAGS_TRUE} ]]; then
    cros_root=/dev/dm-0
  fi

  # TODO(wad) mount the root fs to LOOP_DEV from the image
  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}"

  # The rootfs should never be mounted rw again after this point without
  # re-calling make_image_bootable.
  sudo mount -o remount,ro "${ROOT_FS_DIR}"
  root_dev=$(mount | grep -- "on ${ROOT_FS_DIR} type" | cut -f1 -d' ' | tail -1)

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

  # Builds the kernel partition image.  The temporary files are kept around
  # so that we can perform a load_kernel_test later on the final image.
  ${SCRIPTS_DIR}/build_kernel_image.sh \
    --arch="${ARCH}" \
    --to="${OUTPUT_DIR}/vmlinuz.image" \
    --hd_vblock="${OUTPUT_DIR}/vmlinuz_hd.vblock" \
    --vmlinuz="${OUTPUT_DIR}/boot/vmlinuz" \
    --working_dir="${OUTPUT_DIR}" \
    --keep_work \
    --rootfs_image=${root_dev} \
    --rootfs_hash=${ROOT_FS_HASH} \
    --verity_hash_alg=${FLAGS_verity_algorithm} \
    --verity_tree_depth=${FLAGS_verity_depth} \
    --verity_max_ios=${FLAGS_verity_max_ios} \
    --verity_error_behavior=${FLAGS_verity_error_behavior} \
    --root=${cros_root} \
    --keys_dir="${DEVKEYSDIR}"

  local rootfs_hash_size=$(stat -c '%s' ${ROOT_FS_HASH})
  info "Appending rootfs.hash (${rootfs_hash_size} bytes) to the root fs"
  if [[ ${rootfs_hash_size} -gt $((FLAGS_rootfs_hash_pad * 1024 * 1024)) ]]
  then
    die "--rootfs_hash_pad reserves less than the needed ${rootfs_hash_size}"
  fi
  # Unfortunately, mount_gpt_image uses mount and not losetup to create the
  # loop devices.  This means that they are not the correct size.  We have to
  # write directly to the image to append the hash tree data.
  local hash_offset="$(partoffset ${OUTPUT_DIR}/${image_name} 3)"
  hash_offset=$((hash_offset + ((1024 * 1024 * ${FLAGS_rootfs_size}) / 512)))
  sudo dd bs=512 \
          seek=${hash_offset} \
          if="${ROOT_FS_HASH}" \
          of="${OUTPUT_DIR}/${image_name}" \
          conv=notrunc
  # We don't need to keep the file around anymore.
  sudo rm "${ROOT_FS_HASH}"

  # Move the verification block needed for the hard disk install to the
  # stateful partition. Mount stateful fs, copy file, and umount fs.
  # In original CL: http://codereview.chromium.org/2868044, this was done in
  # create_base_image(). However, it could break the build if it is a clean
  # build because vmlinuz_hd.vblock hasn't been created by build_kernel_image.sh
  if [[ "${ARCH}" = "x86" ]]; then
    sudo cp "${OUTPUT_DIR}/vmlinuz_hd.vblock" "${STATEFUL_FS_DIR}"
  fi

  # START_KERN_A is set by the first call to install the gpt.
  local koffset="$(partoffset ${OUTPUT_DIR}/${image_name} 2)"
  sudo dd if="${OUTPUT_DIR}/vmlinuz.image" of="${OUTPUT_DIR}/${image_name}" \
    conv=notrunc bs=512 seek=${koffset}

  # Update the bootloaders.  For legacy/efi x86, the EFI system partition
  # will be updated and for arm, the mbr will be updated (for u-boot).
  local kernel_part=
  local bootloader_to=
  local bootloader_to_flags=
  local usb_disk="${FLAGS_usb_disk}"

  if [[ "${ARCH}" = "x86" ]]; then
    # x86 should update the esp in place in the image.
    bootloader_to="${OUTPUT_DIR}/${image_name}"
    local esp_offset="$(partoffset ${OUTPUT_DIR}/${image_name} 12)"
    esp_offset=$((esp_offset * 512))  # sectors to bytes
    local esp_size="$(partsize ${OUTPUT_DIR}/${image_name} 12)"
    esp_size=$((esp_size * 512))  # sectors to bytes
    bootloader_to_flags="--to_offset=${esp_offset} --to_size=${esp_size}"
    # Use the kernel partition to acquire configuration flags.
    kernel_part="--kernel_partition='${OUTPUT_DIR}/vmlinuz.image'"
    # Install syslinux on the EFI System Partition.
    kernel_part="${kernel_part} --install_syslinux"
  elif [[ "${ARCH}" = "arm" ]]; then
    # TODO(wad) mmcblk1p3 is hardcoded for arm for now!
    usb_disk="/dev/mmcblk1p3"
    # ARM doesn't support using the kernel image for kernel cmdline flags yet.
    kernel_part="--kernel_cmdline=\"${FLAGS_arm_extra_bootargs}\" "
    # TODO(wad) Integrate dmtable extraction into the arm build
    # E.g.  $(cat ${OUTPUT_DIR}/boot.config | tr -s '\n' ' ')"
    local kpart_offset="--kernel_partition_offset=${koffset}"
    local kpart_size="--kernel_partition_sectors="
    kpart_size="${kpart_size}$(partsize ${OUTPUT_DIR}/${image_name} 2)"
    kernel_part="${kernel_part} ${kpart_size} ${kpart_offset}"
    info "Using addition bootloader arguments: ${kernel_part}"
    bootloader_to="${OUTPUT_DIR}/arm.mbr"
  fi

  # Update partition 12 / legacy bootloaders and arm.
  ${SCRIPTS_DIR}/update_bootloaders.sh \
    --arch=${ARCH} \
    --to="${bootloader_to}" \
    --from="${OUTPUT_DIR}"/boot \
    --vmlinuz="${OUTPUT_DIR}"/boot/vmlinuz \
    --usb_disk="${usb_disk}" \
    ${bootloader_to_flags} \
    $kernel_part

  if [[ "${ARCH}" == "arm" ]]; then
    sudo dd bs=1 conv=notrunc  if="${bootloader_to}" \
      of="${OUTPUT_DIR}/${image_name}"
    sudo rm "${bootloader_to}"
  fi

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

# 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.
  sudo INSTALL_MASK="${INSTALL_MASK}" ${EMERGE_BOARD_CMD} \
      --root="${root_dev_dir}" --root-deps=rdeps \
      --usepkg -uDNv chromeos-dev ${EMERGE_JOBS}

  if [[ $FLAGS_preserve -eq ${FLAGS_TRUE} ]] ; then
    # Clean out unused packages
    sudo INSTALL_MASK="${INSTALL_MASK}" ${EMERGE_BOARD_CMD} \
      --root="${ROOT_FS_DIR}" --root-deps=rdeps \
      --usepkg --depclean ${EMERGE_JOBS}
  fi

  # 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.

  # The ldd tool is a useful shell script but lives in glibc; just copy it.
  sudo cp -a "$(which ldd)" "${root_dev_dir}/usr/bin"

  # 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

  # Check that the image has been correctly created.  Only do it if not
  # building a factory install image, 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
  sudo INSTALL_MASK="${INSTALL_MASK}" ${EMERGE_BOARD_CMD} \
    --root="${ROOT_FS_DIR}" --root-deps=rdeps \
    --usepkg -uDNv chromeos ${EMERGE_JOBS}

  # Clean out unused packages
  sudo INSTALL_MASK="${INSTALL_MASK}" ${EMERGE_BOARD_CMD} \
    --root="${ROOT_FS_DIR}" --root-deps=rdeps \
    --usepkg --depclean ${EMERGE_JOBS}

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

create_base_image() {
  local image_name=$1

  trap "cleanup && delete_prompt" EXIT

  UUID=$(uuidgen)

  # 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 to fit on a 1GB memory stick.
  # 1 GB in hard-drive-manufacturer-speak is 10^9, not 2^30.  950MB < 10^9 bytes.
  if [[ ${FLAGS_factory_install} -eq ${FLAGS_TRUE} ]] ; then
    ROOT_SIZE_BYTES=$((1024 * 1024 * 300))
  else
    ROOT_SIZE_BYTES=$((1024 * 1024 * ${FLAGS_rootfs_size}))
  fi

  # 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.ext3 -b 4096 "${LOOP_DEV}" "$((ROOT_SIZE_BYTES / 4096))"

  # Tune and mount rootfs.
  # TODO(wad) rename the disk label to match the GPT since we
  #           can't change it later.
  DISK_LABEL="C-KEYFOB"
  sudo tune2fs -L "${DISK_LABEL}" -U "${UUID}" -c 0 -i 0 "${LOOP_DEV}"
  sudo mount "${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 "${STATEFUL_LOOP_DEV}"
  sudo mount "${STATEFUL_LOOP_DEV}" "${STATEFUL_FS_DIR}"

  # Create OEM partner partition.
  OEM_LOOP_DEV=$(sudo losetup -f)
  if [ -z "${OEM_LOOP_DEV}" ] ; then
    echo "No free loop device.  Free up a loop device or reboot.  exiting. "
    exit 1
  fi
  OEM_SIZE_BYTES=$((1024 * 1024 * 16))
  dd if=/dev/zero of="${OEM_FS_IMG}" bs=1 count=1 seek=$((OEM_SIZE_BYTES - 1))

  # Tune and mount OEM partner partition.
  UUID=$(uuidgen)
  DISK_LABEL="C-OEM"
  sudo losetup "${OEM_LOOP_DEV}" "${OEM_FS_IMG}"
  sudo mkfs.ext3 "${OEM_LOOP_DEV}"
  sudo tune2fs -L "${DISK_LABEL}" -U "${UUID}" -c 0 -i 0 "${OEM_LOOP_DEV}"
  sudo mount "${OEM_LOOP_DEV}" "${OEM_FS_DIR}"

  # Populate OEM partner partition.
  if [ ! -z "${FLAGS_oem_customization}" ]; then
    if [ ! -d ${FLAGS_oem_customization} ]; then
      echo "Specified OEM content directory does not exist.  exiting."
      exit 1
    fi
    for ITEM in `ls -A ${FLAGS_oem_customization}`
      do sudo cp -a "${FLAGS_oem_customization}/$ITEM" "${OEM_FS_DIR}"
    done
    sudo find "${OEM_FS_DIR}" -type d -exec chmod 755 "{}" \;
    sudo find "${OEM_FS_DIR}" -type f -exec chmod 644 "{}" \;
    sudo chown -R root:root "${OEM_FS_DIR}"
  else
    echo "Empty OEM partition: OEM customizations will not be applied."
  fi

  # -- 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.
  PKGDIR="/var/lib/portage/pkgs/cross/"
  sudo tar jxvpf \
    "${PKGDIR}/${CHOST}/cross-${CHOST}"/glibc-${LIBC_VERSION}.tbz2 \
    -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=${ROOT_FS_DIR} --root-deps=rdeps --usepkg" all of the
  # runtime packages for chrome os. This builds up a chrome os image from
  # binary packages with runtime dependencies only.  We use INSTALL_MASK to
  # trim the image size as much as possible.
  sudo INSTALL_MASK="${INSTALL_MASK}" ${EMERGE_BOARD_CMD} \
    --root="${ROOT_FS_DIR}" --root-deps=rdeps \
    --usepkg chromeos ${EMERGE_JOBS}

  # Perform any customizations on the root file system that are needed.
  "${SCRIPTS_DIR}/customize_rootfs" \
    --root="${ROOT_FS_DIR}" \
    --target="${ARCH}" \
    --board="${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 \
    --install \
    ${enable_rootfs_verification}

  # Create a working copy so we don't need the rootfs mounted
  sudo mkdir -p "${OUTPUT_DIR}"/boot
  # This will include any built files dropped in /boot as well.
  # Like the current vmlinuz.
  sudo cp -r "${ROOT_FS_DIR}"/boot/. "${OUTPUT_DIR}"/boot/
  sudo chmod -R a+r "${OUTPUT_DIR}"/boot/

  # 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}"

  # 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 and needed by ARM until it supports the
  # full, signed kernel partition format.
  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}"

  cleanup

  trap delete_prompt EXIT

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

  trap - EXIT
}

# Create the output directory.
mkdir -p "${OUTPUT_DIR}"
mkdir -p "${ROOT_FS_DIR}"
mkdir -p "${STATEFUL_FS_DIR}"
mkdir -p "${OEM_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}
    cp -r ${PREVIOUS_DIR}/boot ${OUTPUT_DIR}/boot

    # 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

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

# FIXME: only signing things for x86 right now.
if [[ "${ARCH}" = "x86" ]]; then
  # Verify the final image.
  load_kernel_test "${OUTPUT_DIR}/${PRISTINE_IMAGE_NAME}" \
    "${DEVKEYSDIR}/recovery_key.vbpubk"
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}
  make_image_bootable ${DEVELOPER_IMAGE_NAME}
fi

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

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, OUTSIDE the chroot, 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}"
echo "from the scripts directory where you entered the chroot."