Add more safeguards to image_to_usb.sh. List USB drives if --to is omitted

src/scripts/image_to_usb.sh

 #!/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 convert the output of build_image.sh to a usb image.
 
 # 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"
 
 # Load functions and constants for chromeos-install
 . "$(dirname "$0")/chromeos-common.sh"
 
 get_default_board
 
 # Flags
 DEFINE_string board "${DEFAULT_BOARD}" "Board for which the image was built"
 DEFINE_string from "" \
   "Directory containing chromiumos_image.bin"
 DEFINE_string to "" "${DEFAULT_TO_HELP}"
 DEFINE_boolean yes ${FLAGS_FALSE} "Answer yes to all prompts" "y"
 DEFINE_boolean force_copy ${FLAGS_FALSE} "Always rebuild test image"
+DEFINE_boolean force_non_usb ${FLAGS_FALSE} \
+  "Write out image even if target (--to) doesn't look like a USB disk"
 DEFINE_boolean factory_install ${FLAGS_FALSE} \
   "Whether to generate a factory install shim."
 DEFINE_boolean factory ${FLAGS_FALSE} \
   "Whether to generate a factory runin image. Implies aututest and test"
 DEFINE_boolean copy_kernel ${FLAGS_FALSE} \
   "Copy the kernel to the fourth partition."
 DEFINE_boolean test_image "${FLAGS_FALSE}" \
   "Copies normal image to chromiumos_test_image.bin, modifies it for test."
 DEFINE_string image_name "chromiumos_image.bin" \
   "Base name of the image" i
@@ skipping 39 matching lines @@
   FLAGS_from="${IMAGES_DIR}/$(ls -t ${IMAGES_DIR} 2>&-| head -1)"
 fi
 
 if [ ! -d "${FLAGS_from}" ] ; then
   echo "Cannot find image directory ${FLAGS_from}"
   exit 1
 fi
 
 if [ -z "${FLAGS_to}" ]; then
   echo "You must specify a file or device to write to using --to."
+  disks=$(list_usb_disks)
+  if [ -n "$disks" ]; then
+    echo "Available USB disks:"
+    for disk in $disks; do
+      echo "  /dev/$disk:"
+      echo "    Manufacturer: $(get_disk_info $disk manufacturer)"
+      echo "         Product: $(get_disk_info $disk product)"
+    done
+  fi
   exit 1
 fi
 
 # Convert args to paths.  Need eval to un-quote the string so that shell
 # chars like ~ are processed; just doing FOO=`readlink -f ${FOO}` won't work.
 FLAGS_from=`eval readlink -f ${FLAGS_from}`
 FLAGS_to=`eval readlink -f ${FLAGS_to}`
 
+# One last check to make sure user is not shooting themselves in the foot
+if [ -b "${FLAGS_to}" ] &&
+  ! list_usb_disks | grep -q '^'${FLAGS_to##*/}'$' &&
+  [ ${FLAGS_force_non_usb} -ne ${FLAGS_TRUE} ]
+then
+  # Safeguard against writing to a real non-USB disk
+  echo "Error: Device ${FLAGS_to} does not appear to be a USB disk!"
+  echo "       To override this safeguard, use the --force_non_usb flag"
+  exit 1
+fi
+
 # Use this image as the source image to copy
 SRC_IMAGE="${FLAGS_from}/${FLAGS_image_name}"
 
 STATEFUL_DIR="${FLAGS_from}/stateful_partition"
 mkdir -p "${STATEFUL_DIR}"
 
 function do_cleanup {
   echo "Cleaning loopback devices: ${STATEFUL_LOOP_DEV}"
   if [ "${STATEFUL_LOOP_DEV}" != "" ]; then
     sudo umount "${STATEFUL_DIR}"
@@ skipping 96 matching lines @@
   echo "   sudo dd if=${FLAGS_to} of=/dev/sdX bs=4M"
   echo "where /dev/sdX is the entire drive."
   if [ ${INSIDE_CHROOT} -eq 1 ]
   then
     example=$(basename "${FLAGS_to}")
     echo "NOTE: Since you are currently inside the chroot, and you'll need to"
     echo "run dd outside the chroot, the path to the USB image will be"
     echo "different (ex: ~/chromeos/trunk/src/build/images/SOME_DIR/$example)."
   fi
 fi