diff --git a/build_library/base_image_util.sh b/build_library/base_image_util.sh
index d06610a306..00c659ede1 100755
--- a/build_library/base_image_util.sh
+++ b/build_library/base_image_util.sh
@@ -227,12 +227,6 @@ create_base_image() {
   # cros_make_image_bootable.
   create_boot_desc "${image_type}"
 
-  # Write out the GPT creation script.
-  # This MUST be done before writing bootloader templates else we'll break
-  # the hash on the root FS.
-  write_partition_script "${image_type}" \
-    "${root_fs_dir}/${PARTITION_SCRIPT_PATH}"
-
   # Populates the root filesystem with legacy bootloader templates
   # appropriate for the platform.  The autoupdater and installer will
   # use those templates to update the legacy boot partition (12/ESP)
diff --git a/build_library/cgpt.py b/build_library/cgpt.py
index 7bf4d52e65..2176cf258e 100755
--- a/build_library/cgpt.py
+++ b/build_library/cgpt.py
@@ -3,10 +3,10 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import copy
 import json
 import os
 import re
+import subprocess
 import sys
 import uuid
 from optparse import OptionParser
@@ -206,61 +206,72 @@ def GetPartitionTableFromConfig(options, layout_filename, image_type):
 
   return partitions
 
-def GetScriptShell():
-  """Loads and returns the skeleton script for our output script.
 
-  Returns:
-    A string containg the skeleton script
-  """
-
-  script_shell_path = os.path.join(os.path.dirname(__file__), 'cgpt_shell.sh')
-  with open(script_shell_path, 'r') as f:
-    script_shell = ''.join(f.readlines())
-
-  # Before we return, insert the path to this tool so somebody reading the
-  # script later can tell where it was generated.
-  script_shell = script_shell.replace('@SCRIPT_GENERATOR@', script_shell_path)
-
-  return script_shell
-
-
-def WriteLayoutFunction(options, sfile, func_name, image_type, config):
-  """Writes a shell script function to write out a given partition table.
+def WritePartitionTable(options, image_type, layout_filename, disk_filename):
+  """Writes the given partition table to a disk image or device.
 
   Args:
     options: Flags passed to the script
-    sfile: File handle we're writing to
-    func_name: Function name to write out for specified layout
     image_type: Type of image eg base/test/dev/factory_install
-    config: Partition configuration file object
+    layout_filename: Path to partition configuration file
+    disk_filename: Path to disk image or device file
   """
 
+  def Cgpt(*args):
+    subprocess.check_call(['cgpt'] + [str(a) for a in args])
+
+  config = LoadPartitionConfig(layout_filename)
   partitions = GetPartitionTable(options, config, image_type)
   disk_block_count = START_SECTOR * config['metadata']['block_size']
 
   for partition in partitions:
     disk_block_count += partition['blocks']
 
-  sfile.write('%s() {\ncreate_image $1 %d %s\n' % (
-      func_name, disk_block_count,
-      config['metadata']['block_size']))
-
-  sfile.write('CURR=%d\n' % START_SECTOR)
-  sfile.write('$GPT create $1\n')
+  sector = START_SECTOR
+  Cgpt('create', '-c', '-s', disk_block_count, disk_filename)
 
   for partition in partitions:
     if partition['type'] != 'blank':
-      sfile.write('$GPT add -i %d -b $CURR -s %s -t %s -l %s -u %s $1 && ' % (
-          partition['num'], str(partition['blocks']), partition['type'],
-          partition['label'], partition['uuid']))
+      Cgpt('add', '-i', partition['num'],
+                  '-b', sector,
+                  '-s', partition['blocks'],
+                  '-t', partition['type'],
+                  '-l', partition['label'],
+                  '-u', partition['uuid'],
+                  disk_filename)
+
+    sector += partition['blocks']
+
+  Cgpt('show', disk_filename)
+
+
+def WriteMbrBoot(options, image_type, layout_filename,
+                 disk_filename, mbr_filename):
+  """Writes the protective MBR with the given boot code.
+
+  The EFI System Partition will be marked as the 'boot' partition.
+
+  Args:
+    options: Flags passed to the script
+    image_type: Type of image eg base/test/dev/factory_install
+    layout_filename: Path to partition configuration file
+    disk_filename: Path to disk image or device file
+    mbr_filename: Path to boot code, usually gptmbr.bin from syslinux.
+  """
+
+  config = LoadPartitionConfig(layout_filename)
+  partitions = GetPartitionTable(options, config, image_type)
+
+  esp_number = None
+  for partition in partitions:
     if partition['type'] == 'efi':
-      sfile.write('$GPT boot -p -b $2 -i %d $1\n' % partition['num'])
+      esp_number = partition['num']
+      break
+  if esp_number is None:
+    raise InvalidLayout('Table does not include an EFI partition.')
 
-    # Increment the CURR counter ready for the next partition.
-    sfile.write('CURR=$(( $CURR + %s ))\n' % partition['blocks'])
-
-  sfile.write('$GPT show $1\n')
-  sfile.write('}\n')
+  subprocess.check_call(['cgpt', 'boot', '-p', '-b', mbr_filename,
+      '-i', str(partition['num']), disk_filename])
 
 
 def GetPartitionByNumber(partitions, num):
@@ -299,26 +310,6 @@ def GetPartitionByLabel(partitions, label):
   raise PartitionNotFound('Partition not found')
 
 
-def WritePartitionScript(options, image_type, layout_filename, sfilename):
-  """Writes a shell script with functions for the base and requested layouts.
-
-  Args:
-    options: Flags passed to the script
-    image_type: Type of image eg base/test/dev/factory_install
-    layout_filename: Path to partition configuration file
-    sfilename: Filename to write the finished script to
-  """
-
-  config = LoadPartitionConfig(layout_filename)
-
-  with open(sfilename, 'w') as f:
-    script_shell = GetScriptShell()
-    f.write(script_shell)
-
-    WriteLayoutFunction(options, f, 'write_base_table', 'base', config)
-    WriteLayoutFunction(options, f, 'write_partition_table', image_type, config)
-
-
 def GetBlockSize(options, layout_filename):
   """Returns the partition table block size.
 
@@ -498,9 +489,14 @@ def DoParseOnly(options, image_type, layout_filename):
 
 def main(argv):
   action_map = {
-    'write': {
-      'usage': ['<image_type>', '<partition_config_file>', '<script_file>'],
-      'func': WritePartitionScript,
+    'write_gpt': {
+      'usage': ['<image_type>', '<partition_config_file>', '<disk_image>'],
+      'func': WritePartitionTable,
+    },
+    'write_mbr': {
+      'usage': ['<image_type>', '<partition_config_file>', '<disk_image>',
+                '<mbr_boot_code>'],
+      'func': WriteMbrBoot,
     },
     'readblocksize': {
       'usage': ['<partition_config_file>'],
diff --git a/build_library/cgpt_shell.sh b/build_library/cgpt_shell.sh
deleted file mode 100644
index dedd0542aa..0000000000
--- a/build_library/cgpt_shell.sh
+++ /dev/null
@@ -1,38 +0,0 @@
-#!/bin/sh
-# Copyright (c) 2012 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.
-
-# This script is automatically generated by @SCRIPT_GENERATOR@
-# Do not edit!
-
-if ! type numsectors >/dev/null 2>&1; then
-  if [ -f "/usr/sbin/chromeos-common.sh" ]; then
-    . "/usr/sbin/chromeos-common.sh"
-  else
-    echo "Can't load chromeos-common.sh, dying!" 1>&2
-    exit 1
-  fi
-fi
-locate_gpt
-
-# Usage: create_image <device> <min_disk_size> <block_size>
-# If <device> is a block device, wipes out the GPT
-# If it's not, it creates a new file of the requested size
-create_image() {
-  local dev=$1
-  local min_disk_size=$2
-  local block_size=$3
-  if [ -b "${dev}" ]; then
-    # Zap any old partitions (otherwise gpt complains).
-    dd if=/dev/zero of="${dev}" conv=notrunc bs=512 count=32
-    dd if=/dev/zero of="${dev}" conv=notrunc bs=512 \
-      seek=$((${min_disk_size} - 1 - 33)) count=33
-  else
-    if [ ! -e "${dev}" ]; then
-      dd if=/dev/zero of="${dev}" bs=${block_size} count=1 \
-        seek=$((${min_disk_size} - 1))
-    fi
-  fi
-}
-
diff --git a/build_library/disk_layout_util.sh b/build_library/disk_layout_util.sh
index 1808603e82..0cb9888eeb 100644
--- a/build_library/disk_layout_util.sh
+++ b/build_library/disk_layout_util.sh
@@ -3,7 +3,6 @@
 # found in the LICENSE file.
 
 CGPT_PY="${BUILD_LIBRARY_DIR}/cgpt.py"
-PARTITION_SCRIPT_PATH="usr/sbin/write_gpt.sh"
 
 cgpt_py() {
   if [[ -n "${FLAGS_adjust_part-}" ]]; then
@@ -20,7 +19,6 @@ cgpt_py() {
 
 get_disk_layout_path() {
   DISK_LAYOUT_PATH="${BUILD_LIBRARY_DIR}/legacy_disk_layout.json"
-  local partition_script_path=$(tempfile)
   for overlay in $(cros_list_overlays --board "$BOARD"); do
     local disk_layout="${overlay}/scripts/disk_layout.json"
     if [[ -e ${disk_layout} ]]; then
@@ -29,23 +27,9 @@ get_disk_layout_path() {
   done
 }
 
-write_partition_script() {
+write_partition_table() {
   local image_type=$1
-  local partition_script_path=$2
-  get_disk_layout_path
-
-  local temp_script_file=$(mktemp)
-
-  sudo mkdir -p "$(dirname "${partition_script_path}")"
-
-  cgpt_py write "${image_type}" "${DISK_LAYOUT_PATH}" \
-          "${temp_script_file}"
-  sudo mv "${temp_script_file}" "${partition_script_path}"
-}
-
-run_partition_script() {
-  local outdev=$1
-  local root_fs_img=$2
+  local outdev=$2
 
   local pmbr_img
   case ${ARCH} in
@@ -61,13 +45,10 @@ run_partition_script() {
     ;;
   esac
 
-  if is_mounted "${root_fs_dir}"; then
-    safe_umount "${root_fs_dir}"
-  fi
-  sudo mount -o loop "${root_fs_img}" "${root_fs_dir}"
-  . "${root_fs_dir}/${PARTITION_SCRIPT_PATH}"
-  write_partition_table "${outdev}" "${pmbr_img}"
-  safe_umount "${root_fs_dir}"
+  get_disk_layout_path
+  cgpt_py write_gpt "${image_type}" "${DISK_LAYOUT_PATH}" "${outdev}"
+  cgpt_py write_mbr \
+      "${image_type}" "${DISK_LAYOUT_PATH}" "${outdev}" "${pmbr_img}"
 }
 
 get_fs_block_size() {
@@ -204,7 +185,7 @@ build_gpt() {
   local oem_img="$5"
 
   get_disk_layout_type
-  run_partition_script "${outdev}" "${rootfs_img}"
+  write_partition_table "${DISK_LAYOUT_TYPE}" "${outdev}"
 
   local sudo=
   if [ ! -w "$outdev" ] ; then
diff --git a/build_library/vm_image_util.sh b/build_library/vm_image_util.sh
index f39a6d38d3..b034ae4a37 100644
--- a/build_library/vm_image_util.sh
+++ b/build_library/vm_image_util.sh
@@ -180,14 +180,8 @@ unpack_source_disk() {
         cp --sparse=always "${alternate_state_image}" "${TEMP_STATE}"
     fi
 
-    TEMP_PMBR="${VM_TMP_DIR}"/pmbr
-    dd if="${VM_SRC_IMG}" of="${TEMP_PMBR}" bs=512 count=1
-
     info "Initializing new partition table..."
-    TEMP_PARTITION_SCRIPT="${VM_TMP_DIR}/partition_script.sh"
-    write_partition_script "${disk_layout}" "${TEMP_PARTITION_SCRIPT}"
-    . "${TEMP_PARTITION_SCRIPT}"
-    write_partition_table "${VM_TMP_IMG}" "${TEMP_PMBR}"
+    write_partition_table "${disk_layout}" "${VM_TMP_IMG}"
 }
 
 resize_state_partition() {
diff --git a/image_to_vm.sh b/image_to_vm.sh
index 3957b626ff..2664257083 100755
--- a/image_to_vm.sh
+++ b/image_to_vm.sh
@@ -68,7 +68,9 @@ if [ -z "${FLAGS_board}" ] ; then
   die_notrace "--board is required."
 fi
 
-BOARD="$FLAGS_board"
+# Loaded after flags are parsed because board_options depends on --board
+. "${BUILD_LIBRARY_DIR}/board_options.sh" || exit 1
+
 
 IMAGES_DIR="${DEFAULT_BUILD_ROOT}/images/${FLAGS_board}"
 # Default to the most recent image