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

scripts/image_signing/common.sh

Index: scripts/image_signing/common.sh
diff --git a/scripts/image_signing/common.sh b/scripts/image_signing/common.sh
index 5a3e600b316c86c622d418a1364ec0ad07f15386..5465feb81e95629a84ef37ebc17c99c47cd29d96 100755
--- a/scripts/image_signing/common.sh
+++ b/scripts/image_signing/common.sh
@@ -12,6 +12,75 @@ GPT=cgpt
 # The tag when the rootfs is changed.
 TAG_NEEDS_TO_BE_SIGNED="/root/.need_to_be_signed"
 
+# Array of actions that are executed during the clean up process.
+declare -a cleanup_actions
+
+# Adds an action to be executed during the clean up process.
+# Actions are executed in the reverse order of when they were added.
+# ARGS: ACTION
+add_cleanup_action() {
+  cleanup_actions[${#cleanup_actions[*]}]=$1
+}
+
+# Performs the latest clean up action and removes it from the list.
+perform_latest_cleanup_action() {
+  local num_actions=${#cleanup_actions[*]}
+  if [ ${num_actions} -gt 0 ]; then
+    eval "${cleanup_actions[$num_actions-1]}" > /dev/null 2>&1
+    unset cleanup_actions[$num_actions-1]
+  fi
+}
+
+# Performs clean up by executing actions in the cleanup_actions array in
+# reversed order.
+cleanup() {
+  set +e
+
+  while [ ${#cleanup_actions[*]} -gt 0 ]; do
+    perform_latest_cleanup_action
+  done
+
+  set -e
+}
+
+# ANSI color codes used when displaying messages.
+# Taken from src/scripts/common.sh.
+V_RED="\e[31m"
+V_YELLOW="\e[33m"
+V_BOLD_GREEN="\e[1;32m"
+V_BOLD_RED="\e[1;31m"
+V_BOLD_YELLOW="\e[1;33m"
+V_VIDOFF="\e[0m"
+
+# Prints an informational message.
+# Taken from src/scripts/common.sh.
+# Arg: MESSAGE
+info() {
+  echo -e >&2 "${V_BOLD_GREEN}INFO   : $1${V_VIDOFF}"
+}
+
+# Prints a warning message.
+# Taken from src/scripts/common.sh.
+# Arg: MESSAGE
+warn() {
+  echo -e >&2 "${V_BOLD_YELLOW}WARNING: $1${V_VIDOFF}"
+}
+
+# Prints the specified error and exit the script with an error code.
+# Taken from src/scripts/common.sh.
+# Args: MESSAGE
+error() {
+  echo -e >&2   "${V_BOLD_RED}ERROR  : $1${V_VIDOFF}"
+}
+
+# Prints an error message and exit with an error code.
+# Taken from src/scripts/common.sh.
+# Args: MESSAGE
+die() {
+  error "$1"
+  exit 1
+}
+
 # Finds and loads the 'shflags' library, or return as failed.
 load_shflags() {
   # Load shflags
@@ -245,5 +314,7 @@ no_chronos_password() {
   sudo grep -q '^chronos:\*:' "$rootfs/etc/shadow"
 }
 
-trap "cleanup_temps_and_mounts" EXIT
+trap "cleanup" INT TERM EXIT
+
+add_cleanup_action "cleanup_temps_and_mounts"