Make image_to_usb.sh warn if given a partition.

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.
@@ skipping 37 matching lines @@
 function do_cleanup {
   sudo losetup -d "$LOOP_DEV"
 }
 
 # Copy MBR and rootfs to output image
 if [ -b "$FLAGS_to" ]
 then
   # Output to a block device (i.e., a real USB key), so need sudo dd
   echo "Copying USB image ${FLAGS_from} to device ${FLAGS_to}..."
 
+  # Warn if it looks like they supplied a partition as the destination.
+  if echo $FLAGS_to | grep -q '[0-9]$'; then
+    drive=$(echo $FLAGS_to | sed -re 's/[0-9]+$//')
+    if [ -b "$drive" ]; then
+      echo
+      echo "NOTE: It looks like you may have supplied a partition as the "
+      echo "destination.  This script needs to write to the drive's device "
+      echo "node instead (i.e. ${drive} rather than ${FLAGS_to})."
+      echo
+    fi
+  fi
+
   # Make sure this is really what the user wants, before nuking the device
   if [ $FLAGS_yes -ne $FLAGS_TRUE ]
   then
     echo "This will erase all data on this device:"
     sudo fdisk -l "$FLAGS_to" | grep Disk | head -1
     read -p "Are you sure (y/N)? " SURE
     SURE="${SURE:0:1}" # Get just the first character
     if [ "$SURE" != "y" ]
     then
       echo "Ok, better safe than sorry."
@@ skipping 64 matching lines @@
   echo "Done.  To copy to USB keyfob, outside the chroot, do something like:"
   echo "   sudo dd if=${FLAGS_to} of=/dev/sdb bs=4M"
   echo "where /dev/sdb is the entire keyfob."
   if [ $INSIDE_CHROOT -eq 1 ]
   then
     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/usb.img)."
   fi
 fi