blob: e8056a33ac412ef19fd300f8a3520d10b1c76616 [file] [log] [blame]
# Copyright (c) 2012 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 should be relative to your script's location.
. "$(dirname "$0")/"
# Flags.
DEFINE_string image "" \
"The image that needs to be aligned to the latest shipping image."
DEFINE_string src_image "" \
"The image to align against."
# 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.
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 "${src_root_fs_dir}"
add_cleanup_action "sudo umount \"${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 \"${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}"
# 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}"
# Unmount the src and dst root fs so that we can replace the rootfs later.
# 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 "${root_fs_dir}"
add_cleanup_action "sudo umount \"${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
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 "${FLAGS_image}" ]; then
die "--image is required."
if [ ! -f "${FLAGS_image}" ]; then
die "Cannot find the specified image."
if [ -z "${FLAGS_src_image}" ]; then
die "--src_image is required."
if [ ! -f "${FLAGS_src_image}" ]; then
die "Cannot find the specified source 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 src_root_fs_size=$(partsize "${FLAGS_src_image}" 3)
local new_root_fs_size=$(partsize "${FLAGS_image}" 3)
if [ ${src_root_fs_size} -ne ${new_root_fs_size} ]; then
warn "The source rootfs and the new rootfs are not the same size."
exit 0
# Extract the rootfs from the src image and use this as a template
# for the new image.
temp_root_fs=$(mktemp "/tmp/align_rootfs_temp_rootfs.XXXX")
add_cleanup_action "sudo rm -f \"${temp_root_fs}\""
info "Extracting rootfs from src image"
extract_image_partition "${FLAGS_src_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 "${FLAGS_image}"
main "$@"