Harden build_image to not lose loopback devices.

src/scripts/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.
@@ skipping 97 matching lines @@
     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
 
 # Create the output directory.
 mkdir -p "$OUTPUT_DIR"
 
 cleanup_rootfs_loop() {
-  sudo umount "$LOOP_DEV"
-  sleep 1  # in case $LOOP_DEV is in use.
-  sudo losetup -d "$LOOP_DEV"
+  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 "${STATEFUL_DIR}"
-  sleep 1  # follows from cleanup_root_fs_loop.
-  sudo losetup -d "$STATEFUL_LOOP_DEV"
+  sudo umount -d "${STATEFUL_DIR}"
 }
 
 cleanup_esp_loop() {
-  sudo umount "$ESP_DIR"
-  sleep 1
-  sudo losetup -d "$ESP_LOOP_DEV"
+  sudo umount -d "$ESP_DIR"
 }
 
 cleanup() {
   # Disable die on error.
   set +e
 
   if [[ -n "$STATEFUL_LOOP_DEV" ]]; then
     cleanup_stateful_fs_loop
   fi
 
   if [[ -n "$LOOP_DEV" ]]; then
     cleanup_rootfs_loop
   fi
 
   if [[ -n "$ESP_LOOP_DEV" ]]; then
     cleanup_esp_loop
   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
+}
+
 # ${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=
 
 # Sets up symlinks for the stateful partition based on the root specified by
 # ${1} and var directory specified by ${2}.
 setup_symlinks_on_root() {
   echo "Setting up symlinks on the stateful partition rooted at ${1} with"\
     "var directory located at ${2}"
@@ skipping 13 matching lines @@
   if [ -h "${DEV_IMAGE_ROOT}/var" ] ; then
     sudo unlink "${DEV_IMAGE_ROOT}/var"
   elif [ -e "${DEV_IMAGE_ROOT}/var" ] ; then
     echo "*** ERROR: ${DEV_IMAGE_ROOT}/var should be a symlink if it exists"
     return 1
   fi
 
   sudo ln -s "${2}" "${DEV_IMAGE_ROOT}/var"
 }
 
-trap cleanup EXIT
+trap "cleanup && delete_prompt" EXIT
 
 mkdir -p "$ROOT_FS_DIR"
 
 # 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
@@ skipping 220 matching lines @@
   --target="$ARCH"
 
 # 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"
 
 # Cleanup loop devices.
 cleanup
 
+trap delete_prompt EXIT
+
 # Create the GPT-formatted image
 ${SCRIPTS_DIR}/build_gpt.sh \
    --arch=${ARCH} --board=${FLAGS_board} "${OUTPUT_DIR}" "${OUTPUT_IMG}"
 
 # Clean up temporary files.
 rm -f "${ROOT_FS_IMG}" "${STATEFUL_IMG}" "${OUTPUT_DIR}/vmlinuz.image" \
   "${ESP_IMG}"
 rmdir "${ROOT_FS_DIR}" "${STATEFUL_DIR}" "${ESP_DIR}"
 
 OUTSIDE_OUTPUT_DIR="../build/images/${FLAGS_board}/${IMAGE_SUBDIR}"
 echo "Done.  Image created in ${OUTPUT_DIR}"
 echo "To copy to USB keyfob, OUTSIDE the chroot, do something like:"
 echo "  ./image_to_usb.sh --from=${OUTSIDE_OUTPUT_DIR} --to=/dev/sdX"
 echo "To convert to VMWare image, OUTSIDE the chroot, do something like:"
 echo "  ./image_to_vmware.sh --from=${OUTSIDE_OUTPUT_DIR}"
 echo "from the scripts directory where you entered the chroot."
 
 trap - EXIT