scripts/mkinstaller/mkinstaller.py - fuchsia - Git at Google

 #!/usr/bin/env python3.8
 # Copyright 2020 The Fuchsia Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.

 from __future__ import print_function

 import argparse
 import functools
 import json
 import logging
 import os
 import platform
 import stat
 import subprocess
 import sys
 import time
 import typing

 from typing import List

 try:
   global CGPT_BIN
   import paths
   CGPT_BIN = os.path.join(paths.PREBUILT_DIR, 'tools/cgpt',
                                 paths.PREBUILT_PLATFORM, 'cgpt')
 except ImportError as e:
   # If we're being run via `fx`, we take paths for cgpt and the Fuchsia images from
   # the `import paths` above. Otherwise, we expect the paths to be provided via
   # command-line arguments. The command-line arguments also override the autodetected
   # paths if they're both present.
   pass

 if sys.hexversion < 0x030700F0:
   logging.critical(
       'This script requires Python >= 3.7 to run (you have %s), please upgrade!'
       % (platform.python_version()))
   sys.exit(1)

 WORKSTATION_INSTALLER_GPT_GUID = '4dce98ce-e77e-45c1-a863-caf92f1330c1'
 ZIRCON_R_GPT_GUID = 'a0e5cf57-2def-46be-a80c-a2067c37cd49'

 def make_unique_name(name, type):
   return f'{name}_{type}'

 class ManifestImage:
   """ Represents an entry in the 'images.json' manifest that will be installed to disk. """
   def __init__(self, name: str, guids: List[str], type: str, dest_name: str = None):
     """
     Args:
       name: 'name' of the partition in the image manifest.
       guids: List of GPT GUIDs that this partition should be written to the disk with.
       type: 'type' of the partition in the image manifest.
     """
     self.name = name
     self.guids = guids
     self.type = type
     if dest_name:
         self.dest_name = dest_name
     else:
         self.dest_name = name

   def unique_name(self):
     return make_unique_name(self.name, self.type)


 # This is the list of Fuchsia build images we write to the final image,
 # and the partition types they will have (passed to cgpt)
 IMAGES = [
     # The recovery image for chromebook-x64.
     ManifestImage('recovery-installer.signed', ['kernel'], 'zbi.signed', 'zircon-r'),

     # The recovery image and a bootloader for x64.
     ManifestImage('recovery-installer', [ZIRCON_R_GPT_GUID], 'zbi', 'zircon-r'),
     ManifestImage('fuchsia.esp', ['efi'], 'blk'),

     # Standard x64 partitions
     # This is the EFI system partition that will be installed to the target.
     ManifestImage('fuchsia.esp', [WORKSTATION_INSTALLER_GPT_GUID], 'blk'),
     ManifestImage('zircon-a', [WORKSTATION_INSTALLER_GPT_GUID], 'zbi'),
     ManifestImage('zircon-r', [WORKSTATION_INSTALLER_GPT_GUID], 'zbi'),

     # ChromeOS partitions
     # The zircon-r.signed partition is used as both zedboot on the installation
     # disk and also the installed zircon-r partition.
     ManifestImage('zircon-r.signed', [WORKSTATION_INSTALLER_GPT_GUID], 'zbi.signed'),
     ManifestImage('zircon-a.signed', [WORKSTATION_INSTALLER_GPT_GUID], 'zbi.signed'),

     # Common partitions - installed everywhere.
     ManifestImage('storage-sparse', [WORKSTATION_INSTALLER_GPT_GUID], 'blk'),
 ]

 def ParseSize(size):
   """Parse a size.

   Args:
     size: '<number><suffix>', where suffix is 'K', 'M', or 'G'.

   Returns:
     A size in bytes equivalent to the human-readable size given.
   Raises:
     A ValueError if <suffix> is unrecognised or <number> is not a base-10
     number.
   """
   units = ['K', 'M', 'G']
   if size.isdigit():
     return int(size)
   else:
     unit = size[-1].upper()
     size_bytes = int(size[:-1]) * 1024

   if unit not in units:
     raise ValueError('unrecognised unit suffix "{}" for size {}'.format(
         unit, size))

   while units.pop(0) != unit:
     size_bytes *= 1024
   return size_bytes


 def PrettySize(size):
   """Returns a size in bytes as a human-readable string."""
   units = 'BKMGT'

   unit = 0
   # By the time we get to 3072, the error caused by
   # shifting units is <2%, so we don't care.
   while size > 3072 and unit < len(units) - 1:
     size /= 1024
     unit += 1

   return '{:1.1f}{}'.format(size, units[unit])


 class Partition:
   """Represents a single partition to be written to the disk.

   Attributes:
     label: label of the partition on the output image.
     path: path of the file that is going to be written to the partition on
       the host.
     real_size: size of the file on the host, in bytes.
     size: size of the partition, in bytes. This may not match real_size due
       to sector size alignment or EFI partition rules.
     type: type of the partition, passed to `cgpt`.
   """
   FAT32_MIN_SIZE = (63 * 1024 * 1024)

   def __init__(self, path, part_type, label, size: typing.Optional[int] = None):
     self.path = path
     self.type = part_type
     self.label = label

     # Calculate sector-aligned size of this file.
     if path:
       stat_result = os.stat(path)
       if not stat.S_ISREG(stat_result.st_mode):
         raise ValueError('{} is not a regular file.'.format(path))
       rounded_size = stat_result.st_size
       size = stat_result.st_size
     elif size:
       rounded_size = size
     else:
       raise ValueError('Expected a source file or size')
     if rounded_size % Image.SECTOR_SIZE != 0:
       rounded_size += Image.SECTOR_SIZE
       rounded_size -= rounded_size % Image.SECTOR_SIZE
     if self.type == 'efi':
       # Gigaboot won't be able to load zedboot.bin from an EFI partition that's
       # too small, so we ensure the partition is at least big enough for it to
       # work.
       rounded_size = max(Partition.FAT32_MIN_SIZE, rounded_size)
     self.real_size = size
     self.size = rounded_size


 class Image:
   """Represents a single disk image to be written.

     Attributes:
         filename: output filename of the image.
         is_usb: True if writing to a USB, False if creating an image on the
           host.
         file: filehandle to the output image. Held open while we work to prevent
           auto-mounting of USB.
         block_size: number of bytes to write at a time to the disk.
         file_size: total size of the image, in bytes
         partitions: list of |Partition| objects to write to disk.
   """
   SECTOR_SIZE = 512
   GPT_SECTORS = 2048
   CROS_RESERVED_SECTORS = 2048

   def __init__(self, filename, is_usb, block_size):
     self.filename = filename
     self.is_usb = is_usb
     self.file = open(filename, mode='wb')
     self.block_size = block_size

     # Allocate space for the primary and backup GPTs
     self.file_size = 2 * Image.GPT_SECTORS * Image.SECTOR_SIZE
     self.partitions = []

     # Set up the ChromeOS reserved partition.
     reserved_part = Partition(None, 'reserved', 'reserved',
                               self.CROS_RESERVED_SECTORS * self.SECTOR_SIZE)
     self.AddPartition(reserved_part)

   def _Cgpt(self, args):
     args = [CGPT_BIN] + args
     return subprocess.run(args, capture_output=True)

   def _CgptAdd(self, part, offset):
     """Add a partition to the GPT represnted by thsis |Image|.

     Args:
       part: partition to add
       offset: offset to add partition at. Must be a multiple of SECTOR_SIZE.
     Returns:
       True if add succeded, False if it failed.
     """
     if offset % Image.SECTOR_SIZE != 0:
       raise ValueError('Offset must be a multiple of SECTOR_SIZE!')
     if part.size % Image.SECTOR_SIZE != 0:
       raise ValueError('Size must be a multiple of SECTOR_SIZE!')
     size = part.size // Image.SECTOR_SIZE
     offset //= Image.SECTOR_SIZE
     cgpt_args = ['add', '-s', str(size), '-t', part.type, '-b', str(offset),
                  '-l', part.label, self.filename]

     if part.type == 'kernel':
       # Mark CrOS kernel partition as bootable.
       # We assume that the disk will only have 1 kernel partition.
       # -T 1 = Bootloader will try to boot this partition once.
       # -S 0 = This partition has been successfully booted.
       # -P 2 = Partition priority is 2. Partition with the highest priority gets
       # booted.
       cgpt_args += ['-T', '1', '-S', '1', '-P', '2']

     ret = self._Cgpt(cgpt_args)
     if ret.returncode != 0:
       logging.critical('\n'
             '======= CGPT ADD FAILED! =======\n'
             'Maybe your disk is too small?\n')
       logging.error(ret.stdout)
       logging.error(ret.stderr)
       return False
     return True

   def AddPartition(self, partition):
     """Add a partition to the outputted disk image.

     This function does not write any data - call Finalise() to write the
     disk image once all partitions have been added.

     Args:
       partition: partition to add
     """
     self.partitions.append(partition)
     self.file_size += partition.size

   def WritePart(self, part, offset):
     """Writes data to a partition on the output device.

     Args:
       part: partiton to write
       offset: offset in bytes to write to
     """
     if part.path is None:
       return
     self.file.seek(offset, 0)

     written = 0
     logging.info(
         '   Writing image {} to partition {}... '.format(
             part.path.split('/')[-1], part.label)
         )
     with open(part.path, 'rb') as fh:
       start = time.perf_counter()
       for block in iter(functools.partial(fh.read, self.block_size), b''):
         written += len(block)
         self.file.write(block)
       # flush and fsync to get accurate timing results
       self.file.flush()
       os.fsync(self.file.fileno())
       finish = time.perf_counter()
     per_second = written / (finish - start)
     logging.info('     Wrote {} in {:1.2f}s, {}/s'.format(
         PrettySize(written), finish - start, PrettySize(per_second)))

   def Finalise(self):
     """Write all the partitions this image represents to disk/file."""
     if not self.is_usb:
       # first, make sure the file is big enough.
       logging.info('Create image of size={} bytes'.format(self.file_size))
       self.file.truncate(self.file_size)
       self.file.flush()
       os.fsync(self.file.fileno())

     logging.info('Creating new GPT partition table...')
     self._Cgpt(['create', self.filename])
     self._Cgpt(['boot', '-p', self.filename])
     logging.info('Done.')

     logging.info('Creating and writing partitions...')
     current_offset = Image.SECTOR_SIZE * Image.GPT_SECTORS
     for part in self.partitions:
       if not self._CgptAdd(part, current_offset):
         logging.warning('Write failed, aborting.')
         self.file.close()
         return
       self.WritePart(part, current_offset)
       current_offset += part.size
     logging.info('Done.')
     self.file.close()

 def GetPartitions(build_dir, images_file):
   """Get all partitions to be written to the output image.

   The list of partitions is currently determined by the IMAGES dict
   at the top of this file.

   Args:
     build_dir: path to the build directory containing images.
     images_file: path to images.json. If None, will generate from build_dir

   Returns:
     a list of |Partition| objects to be written to the disk.
   """
   images = {}
   if images_file == '':
     images_file = os.path.join(build_dir, 'images.json')
   try:
     with open(images_file) as f:
       images_list = json.load(f)
       for image in images_list:
         images[make_unique_name(image['name'], image['type'])] = image
   except IOError as err:
     logging.critical('Failed to find image manifest. Have you run `fx build`?', exc_info=err)
     return []

   ret = []
   is_bootable = False
   target_images = IMAGES
   for image in target_images:
     if image.unique_name() not in images:
       logging.debug("Skipping image that wasn't built: {}".format(image.unique_name()))
       continue

     for part_type in image.guids:
       full_path = os.path.join(build_dir, images[image.unique_name()]['path'])
       ret.append(Partition(full_path, part_type, image.dest_name))
       # Assume that any non-installer partition is a bootable partition.
       if part_type != WORKSTATION_INSTALLER_GPT_GUID:
         is_bootable = True

   if not is_bootable:
     logging.critical('ERROR: mkinstaller would generate an unbootable image.' +
           'Are you building for a supported platform?')
     return []

   return ret


 def GetUsbDisks():
   """Get a list of all USB disks on the system.

   Returns:
     A list where each entry is of the format '/path/to/disk - <disk name>'
   """
   res = subprocess.run(['fx', 'list-usb-disks'], capture_output=True)
   res.check_returncode()

   disks = [d for d in res.stdout.decode('utf-8').split('\n') if d]
   return disks


 def IsUsbDisk(path):
   """Is the given path a USB disk?

   Args:
     path: a path that may represent a USB disk. Does not have to exist.

   Returns:
     True if the path represents a USB disk, False otherwise.
   """
   return path in map(lambda a: a.split()[0], GetUsbDisks())


 def EjectDisk(path):
   """Eject the given USB disk from the system."""
   system = platform.system()
   if system == 'Linux':
     subprocess.run(['eject', path])
   elif system == 'Darwin':
     subprocess.run(['diskutil', 'eject', path])
   logging.info('Ejected USB disk')


 def Main(args):
   path = args.FILE
   if args.create:
     if not args.force and os.path.exists(path):
       logging.critical(
           'File {} already exists, not creating an image. Use --force if you want to proceed.'
           .format(path))
       return 1
   else:
     if not os.path.exists(path):
       logging.critical(
           ('Path {} does not exist, use --create to create a disk image.\n'
            'Detected USB devices:\n'
            '{}').format(path, '\n'.join(GetUsbDisks())))
       return 1
     if not IsUsbDisk(path):
       logging.critical(
           ('Path {} is not a USB device. Use -f to force.\n'
            'Detected USB devices:\n'
            '{}').format(path, '\n'.join(GetUsbDisks())))
       return 1

     if not os.access(path, os.W_OK) and sys.stdin.isatty():
       logging.warning('Changing ownership of {} to {}'.format(path,
                                                     os.environ.get('USER')))
       subprocess.run(
           ['sudo', 'chown', os.environ.get('USER'), path],
           stdin=sys.stdin,
           stdout=sys.stdout,
           stderr=sys.stderr)
     elif not os.access(path, os.W_OK):
       logging.critical('Cannot write to {}. Please check file permissions!'.format(path))
       return 1

   build_dir = args.build_dir
   if build_dir == '':
     build_dir = paths.FUCHSIA_BUILD_DIR
   parts = GetPartitions(build_dir, args.images)
   if not parts:
     return 1

   output = Image(args.FILE, not args.create, ParseSize(args.block_size))
   for p in parts:
     output.AddPartition(p)

   output.Finalise()
   if not args.create:
     EjectDisk(path)
   return 0


 if __name__ == '__main__':
   parser = argparse.ArgumentParser(
       description='Create a Fuchsia installer image.', prog='fx mkinstaller')
   parser.add_argument(
       '-c',
       '--create',
       action='store_true',
       help='Create a disk image instead of writing to an existing disk.')
   parser.add_argument(
       '-f',
       '--force',
       action='store_true',
       help='Force writing to an image that already exists or a disk that might not be a USB.'
   )
   parser.add_argument(
       '-b',
       '--block-size',
       type=str,
       default='2M',
       help='Block size (optionally suffixed by K, M, G) to write. Default is 2M'
   )
   parser.add_argument(
       '-v',
       '--verbose',
       action='store_true',
       help='Be verbose while creating disk images.'
   )
   parser.add_argument(
       '--cgpt-path',
       type=str,
       default='',
       help='Path to cgpt in the Fuchsia tree. The script will try and guess if no path is provided.'
   )
   parser.add_argument(
       '--images',
       type=str,
       default='',
       help='Path to images.json in the Fuchsia tree. Default to build_dir/images.json.'
   )
   parser.add_argument(
       '--build-dir',
       type=str,
       default='',
       help='Path to the Fuchsia build directory. The script will try and guess if no path is provided.'
   )
   parser.add_argument(
       '--new-installer',
       action='store_true',
       help='DEPRECATED. Has no effect.'
   )
   parser.add_argument('FILE', help='Path to USB device or installer image')
   argv = parser.parse_args()
   level = logging.WARNING
   if argv.verbose:
     level = logging.DEBUG
   if argv.cgpt_path:
     CGPT_BIN = argv.cgpt_path
   logging.basicConfig(format='mkinstaller: %(levelname)s: %(message)s', level=level)
   sys.exit(Main(argv))
	#!/usr/bin/env python3.8
	# Copyright 2020 The Fuchsia Authors. All rights reserved.
	# Use of this source code is governed by a BSD-style license that can be
	# found in the LICENSE file.

	from __future__ import print_function

	import argparse
	import functools
	import json
	import logging
	import os
	import platform
	import stat
	import subprocess
	import sys
	import time
	import typing

	from typing import List

	try:
	global CGPT_BIN
	import paths
	CGPT_BIN = os.path.join(paths.PREBUILT_DIR, 'tools/cgpt',
	paths.PREBUILT_PLATFORM, 'cgpt')
	except ImportError as e:
	# If we're being run via `fx`, we take paths for cgpt and the Fuchsia images from
	# the `import paths` above. Otherwise, we expect the paths to be provided via
	# command-line arguments. The command-line arguments also override the autodetected
	# paths if they're both present.
	pass

	if sys.hexversion < 0x030700F0:
	logging.critical(
	'This script requires Python >= 3.7 to run (you have %s), please upgrade!'
	% (platform.python_version()))
	sys.exit(1)

	WORKSTATION_INSTALLER_GPT_GUID = '4dce98ce-e77e-45c1-a863-caf92f1330c1'
	ZIRCON_R_GPT_GUID = 'a0e5cf57-2def-46be-a80c-a2067c37cd49'

	def make_unique_name(name, type):
	return f'{name}_{type}'

	class ManifestImage:
	""" Represents an entry in the 'images.json' manifest that will be installed to disk. """
	def __init__(self, name: str, guids: List[str], type: str, dest_name: str = None):
	"""
	Args:
	name: 'name' of the partition in the image manifest.
	guids: List of GPT GUIDs that this partition should be written to the disk with.
	type: 'type' of the partition in the image manifest.
	"""
	self.name = name
	self.guids = guids
	self.type = type
	if dest_name:
	self.dest_name = dest_name
	else:
	self.dest_name = name

	def unique_name(self):
	return make_unique_name(self.name, self.type)


	# This is the list of Fuchsia build images we write to the final image,
	# and the partition types they will have (passed to cgpt)
	IMAGES = [
	# The recovery image for chromebook-x64.
	ManifestImage('recovery-installer.signed', ['kernel'], 'zbi.signed', 'zircon-r'),

	# The recovery image and a bootloader for x64.
	ManifestImage('recovery-installer', [ZIRCON_R_GPT_GUID], 'zbi', 'zircon-r'),
	ManifestImage('fuchsia.esp', ['efi'], 'blk'),

	# Standard x64 partitions
	# This is the EFI system partition that will be installed to the target.
	ManifestImage('fuchsia.esp', [WORKSTATION_INSTALLER_GPT_GUID], 'blk'),
	ManifestImage('zircon-a', [WORKSTATION_INSTALLER_GPT_GUID], 'zbi'),
	ManifestImage('zircon-r', [WORKSTATION_INSTALLER_GPT_GUID], 'zbi'),

	# ChromeOS partitions
	# The zircon-r.signed partition is used as both zedboot on the installation
	# disk and also the installed zircon-r partition.
	ManifestImage('zircon-r.signed', [WORKSTATION_INSTALLER_GPT_GUID], 'zbi.signed'),
	ManifestImage('zircon-a.signed', [WORKSTATION_INSTALLER_GPT_GUID], 'zbi.signed'),

	# Common partitions - installed everywhere.
	ManifestImage('storage-sparse', [WORKSTATION_INSTALLER_GPT_GUID], 'blk'),
	]

	def ParseSize(size):
	"""Parse a size.

	Args:
	size: '<number><suffix>', where suffix is 'K', 'M', or 'G'.

	Returns:
	A size in bytes equivalent to the human-readable size given.
	Raises:
	A ValueError if <suffix> is unrecognised or <number> is not a base-10
	number.
	"""
	units = ['K', 'M', 'G']
	if size.isdigit():
	return int(size)
	else:
	unit = size[-1].upper()
	size_bytes = int(size[:-1]) * 1024

	if unit not in units:
	raise ValueError('unrecognised unit suffix "{}" for size {}'.format(
	unit, size))

	while units.pop(0) != unit:
	size_bytes *= 1024
	return size_bytes


	def PrettySize(size):
	"""Returns a size in bytes as a human-readable string."""
	units = 'BKMGT'

	unit = 0
	# By the time we get to 3072, the error caused by
	# shifting units is <2%, so we don't care.
	while size > 3072 and unit < len(units) - 1:
	size /= 1024
	unit += 1

	return '{:1.1f}{}'.format(size, units[unit])


	class Partition:
	"""Represents a single partition to be written to the disk.

	Attributes:
	label: label of the partition on the output image.
	path: path of the file that is going to be written to the partition on
	the host.
	real_size: size of the file on the host, in bytes.
	size: size of the partition, in bytes. This may not match real_size due
	to sector size alignment or EFI partition rules.
	type: type of the partition, passed to `cgpt`.
	"""
	FAT32_MIN_SIZE = (63 * 1024 * 1024)

	def __init__(self, path, part_type, label, size: typing.Optional[int] = None):
	self.path = path
	self.type = part_type
	self.label = label

	# Calculate sector-aligned size of this file.
	if path:
	stat_result = os.stat(path)
	if not stat.S_ISREG(stat_result.st_mode):
	raise ValueError('{} is not a regular file.'.format(path))
	rounded_size = stat_result.st_size
	size = stat_result.st_size
	elif size:
	rounded_size = size
	else:
	raise ValueError('Expected a source file or size')
	if rounded_size % Image.SECTOR_SIZE != 0:
	rounded_size += Image.SECTOR_SIZE
	rounded_size -= rounded_size % Image.SECTOR_SIZE
	if self.type == 'efi':
	# Gigaboot won't be able to load zedboot.bin from an EFI partition that's
	# too small, so we ensure the partition is at least big enough for it to
	# work.
	rounded_size = max(Partition.FAT32_MIN_SIZE, rounded_size)
	self.real_size = size
	self.size = rounded_size


	class Image:
	"""Represents a single disk image to be written.

	Attributes:
	filename: output filename of the image.
	is_usb: True if writing to a USB, False if creating an image on the
	host.
	file: filehandle to the output image. Held open while we work to prevent
	auto-mounting of USB.
	block_size: number of bytes to write at a time to the disk.
	file_size: total size of the image, in bytes
	partitions: list of \|Partition\| objects to write to disk.
	"""
	SECTOR_SIZE = 512
	GPT_SECTORS = 2048
	CROS_RESERVED_SECTORS = 2048

	def __init__(self, filename, is_usb, block_size):
	self.filename = filename
	self.is_usb = is_usb
	self.file = open(filename, mode='wb')
	self.block_size = block_size

	# Allocate space for the primary and backup GPTs
	self.file_size = 2 * Image.GPT_SECTORS * Image.SECTOR_SIZE
	self.partitions = []

	# Set up the ChromeOS reserved partition.
	reserved_part = Partition(None, 'reserved', 'reserved',
	self.CROS_RESERVED_SECTORS * self.SECTOR_SIZE)
	self.AddPartition(reserved_part)

	def _Cgpt(self, args):
	args = [CGPT_BIN] + args
	return subprocess.run(args, capture_output=True)

	def _CgptAdd(self, part, offset):
	"""Add a partition to the GPT represnted by thsis \|Image\|.

	Args:
	part: partition to add
	offset: offset to add partition at. Must be a multiple of SECTOR_SIZE.
	Returns:
	True if add succeded, False if it failed.
	"""
	if offset % Image.SECTOR_SIZE != 0:
	raise ValueError('Offset must be a multiple of SECTOR_SIZE!')
	if part.size % Image.SECTOR_SIZE != 0:
	raise ValueError('Size must be a multiple of SECTOR_SIZE!')
	size = part.size // Image.SECTOR_SIZE
	offset //= Image.SECTOR_SIZE
	cgpt_args = ['add', '-s', str(size), '-t', part.type, '-b', str(offset),
	'-l', part.label, self.filename]

	if part.type == 'kernel':
	# Mark CrOS kernel partition as bootable.
	# We assume that the disk will only have 1 kernel partition.
	# -T 1 = Bootloader will try to boot this partition once.
	# -S 0 = This partition has been successfully booted.
	# -P 2 = Partition priority is 2. Partition with the highest priority gets
	# booted.
	cgpt_args += ['-T', '1', '-S', '1', '-P', '2']

	ret = self._Cgpt(cgpt_args)
	if ret.returncode != 0:
	logging.critical('\n'
	'======= CGPT ADD FAILED! =======\n'
	'Maybe your disk is too small?\n')
	logging.error(ret.stdout)
	logging.error(ret.stderr)
	return False
	return True

	def AddPartition(self, partition):
	"""Add a partition to the outputted disk image.

	This function does not write any data - call Finalise() to write the
	disk image once all partitions have been added.

	Args:
	partition: partition to add
	"""
	self.partitions.append(partition)
	self.file_size += partition.size

	def WritePart(self, part, offset):
	"""Writes data to a partition on the output device.

	Args:
	part: partiton to write
	offset: offset in bytes to write to
	"""
	if part.path is None:
	return
	self.file.seek(offset, 0)

	written = 0
	logging.info(
	' Writing image {} to partition {}... '.format(
	part.path.split('/')[-1], part.label)
	)
	with open(part.path, 'rb') as fh:
	start = time.perf_counter()
	for block in iter(functools.partial(fh.read, self.block_size), b''):
	written += len(block)
	self.file.write(block)
	# flush and fsync to get accurate timing results
	self.file.flush()
	os.fsync(self.file.fileno())
	finish = time.perf_counter()
	per_second = written / (finish - start)
	logging.info(' Wrote {} in {:1.2f}s, {}/s'.format(
	PrettySize(written), finish - start, PrettySize(per_second)))

	def Finalise(self):
	"""Write all the partitions this image represents to disk/file."""
	if not self.is_usb:
	# first, make sure the file is big enough.
	logging.info('Create image of size={} bytes'.format(self.file_size))
	self.file.truncate(self.file_size)
	self.file.flush()
	os.fsync(self.file.fileno())

	logging.info('Creating new GPT partition table...')
	self._Cgpt(['create', self.filename])
	self._Cgpt(['boot', '-p', self.filename])
	logging.info('Done.')

	logging.info('Creating and writing partitions...')
	current_offset = Image.SECTOR_SIZE * Image.GPT_SECTORS
	for part in self.partitions:
	if not self._CgptAdd(part, current_offset):
	logging.warning('Write failed, aborting.')
	self.file.close()
	return
	self.WritePart(part, current_offset)
	current_offset += part.size
	logging.info('Done.')
	self.file.close()

	def GetPartitions(build_dir, images_file):
	"""Get all partitions to be written to the output image.

	The list of partitions is currently determined by the IMAGES dict
	at the top of this file.

	Args:
	build_dir: path to the build directory containing images.
	images_file: path to images.json. If None, will generate from build_dir

	Returns:
	a list of \|Partition\| objects to be written to the disk.
	"""
	images = {}
	if images_file == '':
	images_file = os.path.join(build_dir, 'images.json')
	try:
	with open(images_file) as f:
	images_list = json.load(f)
	for image in images_list:
	images[make_unique_name(image['name'], image['type'])] = image
	except IOError as err:
	logging.critical('Failed to find image manifest. Have you run `fx build`?', exc_info=err)
	return []

	ret = []
	is_bootable = False
	target_images = IMAGES
	for image in target_images:
	if image.unique_name() not in images:
	logging.debug("Skipping image that wasn't built: {}".format(image.unique_name()))
	continue

	for part_type in image.guids:
	full_path = os.path.join(build_dir, images[image.unique_name()]['path'])
	ret.append(Partition(full_path, part_type, image.dest_name))
	# Assume that any non-installer partition is a bootable partition.
	if part_type != WORKSTATION_INSTALLER_GPT_GUID:
	is_bootable = True

	if not is_bootable:
	logging.critical('ERROR: mkinstaller would generate an unbootable image.' +
	'Are you building for a supported platform?')
	return []

	return ret


	def GetUsbDisks():
	"""Get a list of all USB disks on the system.

	Returns:
	A list where each entry is of the format '/path/to/disk - <disk name>'
	"""
	res = subprocess.run(['fx', 'list-usb-disks'], capture_output=True)
	res.check_returncode()

	disks = [d for d in res.stdout.decode('utf-8').split('\n') if d]
	return disks


	def IsUsbDisk(path):
	"""Is the given path a USB disk?

	Args:
	path: a path that may represent a USB disk. Does not have to exist.

	Returns:
	True if the path represents a USB disk, False otherwise.
	"""
	return path in map(lambda a: a.split()[0], GetUsbDisks())


	def EjectDisk(path):
	"""Eject the given USB disk from the system."""
	system = platform.system()
	if system == 'Linux':
	subprocess.run(['eject', path])
	elif system == 'Darwin':
	subprocess.run(['diskutil', 'eject', path])
	logging.info('Ejected USB disk')


	def Main(args):
	path = args.FILE
	if args.create:
	if not args.force and os.path.exists(path):
	logging.critical(
	'File {} already exists, not creating an image. Use --force if you want to proceed.'
	.format(path))
	return 1
	else:
	if not os.path.exists(path):
	logging.critical(
	('Path {} does not exist, use --create to create a disk image.\n'
	'Detected USB devices:\n'
	'{}').format(path, '\n'.join(GetUsbDisks())))
	return 1
	if not IsUsbDisk(path):
	logging.critical(
	('Path {} is not a USB device. Use -f to force.\n'
	'Detected USB devices:\n'
	'{}').format(path, '\n'.join(GetUsbDisks())))
	return 1

	if not os.access(path, os.W_OK) and sys.stdin.isatty():
	logging.warning('Changing ownership of {} to {}'.format(path,
	os.environ.get('USER')))
	subprocess.run(
	['sudo', 'chown', os.environ.get('USER'), path],
	stdin=sys.stdin,
	stdout=sys.stdout,
	stderr=sys.stderr)
	elif not os.access(path, os.W_OK):
	logging.critical('Cannot write to {}. Please check file permissions!'.format(path))
	return 1

	build_dir = args.build_dir
	if build_dir == '':
	build_dir = paths.FUCHSIA_BUILD_DIR
	parts = GetPartitions(build_dir, args.images)
	if not parts:
	return 1

	output = Image(args.FILE, not args.create, ParseSize(args.block_size))
	for p in parts:
	output.AddPartition(p)

	output.Finalise()
	if not args.create:
	EjectDisk(path)
	return 0


	if __name__ == '__main__':
	parser = argparse.ArgumentParser(
	description='Create a Fuchsia installer image.', prog='fx mkinstaller')
	parser.add_argument(
	'-c',
	'--create',
	action='store_true',
	help='Create a disk image instead of writing to an existing disk.')
	parser.add_argument(
	'-f',
	'--force',
	action='store_true',
	help='Force writing to an image that already exists or a disk that might not be a USB.'
	)
	parser.add_argument(
	'-b',
	'--block-size',
	type=str,
	default='2M',
	help='Block size (optionally suffixed by K, M, G) to write. Default is 2M'
	)
	parser.add_argument(
	'-v',
	'--verbose',
	action='store_true',
	help='Be verbose while creating disk images.'
	)
	parser.add_argument(
	'--cgpt-path',
	type=str,
	default='',
	help='Path to cgpt in the Fuchsia tree. The script will try and guess if no path is provided.'
	)
	parser.add_argument(
	'--images',
	type=str,
	default='',
	help='Path to images.json in the Fuchsia tree. Default to build_dir/images.json.'
	)
	parser.add_argument(
	'--build-dir',
	type=str,
	default='',
	help='Path to the Fuchsia build directory. The script will try and guess if no path is provided.'
	)
	parser.add_argument(
	'--new-installer',
	action='store_true',
	help='DEPRECATED. Has no effect.'
	)
	parser.add_argument('FILE', help='Path to USB device or installer image')
	argv = parser.parse_args()
	level = logging.WARNING
	if argv.verbose:
	level = logging.DEBUG
	if argv.cgpt_path:
	CGPT_BIN = argv.cgpt_path
	logging.basicConfig(format='mkinstaller: %(levelname)s: %(message)s', level=level)
	sys.exit(Main(argv))