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122 lines
4.1 KiB
Python
Executable file
122 lines
4.1 KiB
Python
Executable file
#!/usr/bin/python
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# -*- coding: utf-8 -*-
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"""
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==============================================
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mksparse.py - sparse file / disk image creator
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==============================================
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Usage: mksparse.py <imagefile.img> <size>[k|m|g|t]
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This will create <imagefile.img> with size <size>. If the suffix is
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not given then the size is in bytes, 'k' stands for kilobytes (1024),
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'm' for megabytes and 'g' for gigabyes and 't' for terabytes.
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K/M/G/T are not implemented, one can type some 000-s easy enough.
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Simple python script that creates sparse files on unix / Win2k NTFS5.
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This script opens a file for writing, seeks at the desired position
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(or file size) and truncates the file there. Can be handy while
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playing with KVM / qemu / bochs / loopback images.
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Tested on linux-2.6+ only.
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NB: Check fallocate from util-linux, may work even better for you.
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Author: Doncho N. Gunchev <gunchev at gmail dot com>
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Based on Brad Watson's work mkimage.py from
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http://lists.gnu.org/archive/html/qemu-devel/2004-07/msg00733.html
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http://qemu.dad-answers.com/download/qemu/utilities/QEMU-HD-Create/
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"""
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import os.path
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import re
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import sys
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__version__ = "0.3"
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__author__ = "Doncho Gunchev <gunchev@gmail.com>, Brad Watson"
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__depends__ = ['Python-3']
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# __copyright__ = 'Ask Brad Watson, I want nothing.'
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class MkSparseError(Exception):
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"""MkSpace errors"""
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def mk_sparse(file_name: str, file_size: int):
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"""Create a sparse file by truncating it at given position"""
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try:
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sparse_file = open(file_name, 'wb+')
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except EnvironmentError as exc:
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raise MkSparseError("Error: Can't create file {file_name!r}:\n\t{exc}")
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try:
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# Note that I don't want (you too) to write() anything in the file
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# because this will consume at least one sector/block.
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sparse_file.truncate(int(file_size))
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except EnvironmentError as exc:
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try:
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os.unlink(file_name) # clean the mess...
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except EnvironmentError:
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pass
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try: # could close in finally, but would lose the option to report close error properly.
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sparse_file.close()
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except EnvironmentError:
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pass
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raise MkSparseError("Error: Can't truncate {file_name!r}:\n\t{exc}")
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try:
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sparse_file.close()
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except EnvironmentError as exc:
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raise MkSparseError(f"Error: Can't close {file_name!r}:\n\t{exc}")
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def parse_file_size(file_size: str) -> int:
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"""file size validation and parsing"""
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xlt: dict[str, int] = dict(k=2 ** 10, m=2 ** 20, g=2 ** 30, t=2 ** 40, p=2 ** 50, e=2 ** 60, z=2 ** 70, y=2 ** 80)
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try:
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size_str, dim = re.match('^(\\d+)([' + ''.join(xlt.keys()) + '])?$', file_size).groups()
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except AttributeError: # if it did not match we get None, which has no .groups...
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raise ValueError('Bad image size given: {!r}'.format(file_size))
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size: int = int(size_str) # can not raise...
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if dim is None:
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return size
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return size * xlt[dim]
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def main():
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"""The main function for a command line execution"""
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my_name = os.path.basename(sys.argv[0])
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if len(sys.argv) != 3:
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# .pyo (docstrings stripped) workaround, no idea if needed any more or at all ;-) just having fun obv.
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print((__doc__ and __doc__ or ("Usage: " + my_name + " <image-name> <size>[kmgt]")), file=sys.stderr)
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print("Version:", __version__, file=sys.stderr)
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sys.exit(1)
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# 'Process' command line parameters
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file_name: str = sys.argv[1]
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file_size: str = sys.argv[2]
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def err_exit(reason: str, code: int):
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"""Print error (exception) and exit with error code"""
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print(f'{my_name}: {reason}', file=sys.stderr)
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sys.exit(code)
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# Check if the file exists, -f (force) would be a good parameter to add
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if os.path.exists(file_name):
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err_exit(f'Error: file/directory {file_name!r} already exists!', 17)
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try:
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mk_sparse(file_name, parse_file_size(file_size))
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except MkSparseError as exc:
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err_exit(str(exc), 1)
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except (ValueError, KeyError) as exc:
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err_exit(str(exc), 64) # EX_USAGE
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if __name__ == "__main__":
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main()
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