Use dd instead of deleting partitions

tools/pi_sd_prep.sh

@@ -7,6 +7,7 @@ trap cleanup INT
 function cleanup() {
   rm -f /tmp/noobs.zip
   umount -f /tmp/sdcard.$$ >/dev/null 2>&1
+  rmdir /tmp/sdcard.$$
   echo "Aborted."
   exit 1
 }
@@ -41,11 +42,12 @@ fi
 echo "...done"
 
 echo "Preparing partition table on $DEV:"
-echo -e "d\n1\nd\n2\nd\n3\nd\n4\nd\n5\nd\n6\nn\np\n1\n\n\nt\nb\na\n1\nw\nq\n" | fdisk $DEV >/dev/null
+dd if=/dev/zero of=/dev/sdb bs=512 count=10 >/dev/null 2>&1
+echo -e "n\np\n1\n\n\nt\nb\na\n1\nw\nq\n" | fdisk $DEV >/dev/null
 echo "...done"
 
 echo "Formatting partition on $DEV:"
-mkfs.vfat ${DEV}1
+mkfs.vfat -F 16 -n "NOOBS" ${DEV}1
 echo "...done"
 
 echo "Mounting partition on $DEV:"