Update auto expanding script

It now attempts to use raspi-config and falls back on the (updated) hard coded procedure. This should
help prevent some incompatibility issues.

pishrink.sh

@@ -60,17 +60,69 @@ if [ "$should_skip_autoexpand" = false ]; then
   mountdir=`mktemp -d`
   mount $loopback $mountdir
 
-  if [ `md5sum $mountdir/etc/rc.local | cut -d ' ' -f 1` != "a27a4d8192ea6ba713d2ddd15a55b1df" ]; then
+  if [ `md5sum $mountdir/etc/rc.local | cut -d ' ' -f 1` != "0542054e9ff2d2e0507ea1ffe7d4fc87" ]; then
     echo Creating new /etc/rc.local
     mv $mountdir/etc/rc.local $mountdir/etc/rc.local.bak
-    ###Do not touch the following 6 lines including EOF###
+    #####Do not touch the following lines#####
-cat <<\EOF > $mountdir/etc/rc.local
+cat <<\EOF1 > $mountdir/etc/rc.local
 #!/bin/bash
-/usr/bin/raspi-config --expand-rootfs
+do_expand_rootfs() {
-rm -f /etc/rc.local; cp -f /etc/rc.local.bak /etc/rc.local; reboot
+  ROOT_PART=$(mount | sed -n 's|^/dev/\(.*\) on / .*|\1|p')
-exit 0
+
+  PART_NUM=${ROOT_PART#mmcblk0p}
+  if [ "$PART_NUM" = "$ROOT_PART" ]; then
+    echo "$ROOT_PART is not an SD card. Don't know how to expand"
+    return 0
+  fi
+
+  # Get the starting offset of the root partition
+  PART_START=$(parted /dev/mmcblk0 -ms unit s p | grep "^${PART_NUM}" | cut -f 2 -d: | sed 's/[^0-9]//g')
+  [ "$PART_START" ] || return 1
+  # Return value will likely be error for fdisk as it fails to reload the
+  # partition table because the root fs is mounted
+  fdisk /dev/mmcblk0 <<EOF
+p
+d
+$PART_NUM
+n
+p
+$PART_NUM
+$PART_START
+
+p
+w
 EOF
-    ###End no touch zone###
+
+cat <<EOF > /etc/rc.local &&
+#!/bin/sh
+echo "Expanding /dev/$ROOT_PART"
+resize2fs /dev/$ROOT_PART
+rm -f /etc/rc.local; cp -f /etc/rc.local.bak /etc/rc.local; /etc/rc.local
+
+EOF
+reboot
+exit
+}
+raspi_config_expand() {
+/usr/bin/env raspi-config --expand-rootfs
+if [[ $? != 0 ]]; then
+  return -1
+else
+  rm -f /etc/rc.local; cp -f /etc/rc.local.bak /etc/rc.local; /etc/rc.local
+  reboot
+  exit
+fi
+}
+raspi_config_expand
+echo "WARNING: Using backup expand..."
+sleep 5
+do_expand_rootfs
+echo "ERROR: Expanding failed..."
+sleep 5
+rm -f /etc/rc.local; cp -f /etc/rc.local.bak /etc/rc.local; /etc/rc.local
+exit 0
+EOF1
+    #####End no touch zone#####
     chmod +x $mountdir/etc/rc.local
   fi
   umount $mountdir