root / image_creator / disk.py @ e9a2d318
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# Copyright 2012 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or
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# without modification, are permitted provided that the following
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# conditions are met:
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#
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# 1. Redistributions of source code must retain the above
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# copyright notice, this list of conditions and the following
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# disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following
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# disclaimer in the documentation and/or other materials
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# provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and
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# documentation are those of the authors and should not be
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# interpreted as representing official policies, either expressed
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# or implied, of GRNET S.A.
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from image_creator.util import get_command |
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from image_creator.util import try_fail_repeat |
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from image_creator.util import free_space |
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from image_creator.util import FatalError |
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from image_creator.bundle_volume import BundleVolume |
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from image_creator.image import Image |
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import stat |
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import os |
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import tempfile |
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import uuid |
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import shutil |
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dd = get_command('dd')
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dmsetup = get_command('dmsetup')
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losetup = get_command('losetup')
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blockdev = get_command('blockdev')
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TMP_CANDIDATES = ['/var/tmp', os.path.expanduser('~'), '/mnt'] |
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class Disk(object): |
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"""This class represents a hard disk hosting an Operating System
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A Disk instance never alters the source media it is created from.
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Any change is done on a snapshot created by the device-mapper of
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the Linux kernel.
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"""
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def __init__(self, source, output, tmp=None): |
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"""Create a new Disk instance out of a source media. The source
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media can be an image file, a block device or a directory.
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"""
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self._cleanup_jobs = []
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self._images = []
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self.source = source
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self.out = output
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self.meta = {}
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self.tmp = tempfile.mkdtemp(prefix='.snf_image_creator.', |
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dir=self._get_tmp_dir(tmp))
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self._add_cleanup(shutil.rmtree, self.tmp) |
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def _get_tmp_dir(self, default=None): |
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"""Check tmp directory candidates and return the one with the most
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available space.
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"""
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if default is not None: |
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return default
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space = map(free_space, TMP_CANDIDATES)
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max_idx = 0
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max_val = space[0]
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for i, val in zip(range(len(space)), space): |
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if val > max_val:
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max_val = val |
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max_idx = i |
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# Return the candidate path with more available space
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return TMP_CANDIDATES[max_idx]
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def _add_cleanup(self, job, *args): |
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"""Add a new job in the cleanup list"""
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self._cleanup_jobs.append((job, args))
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def _losetup(self, fname): |
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"""Setup a loop device and add it to the cleanup list. The loop device
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will be detached when cleanup is called.
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"""
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loop = losetup('-f', '--show', fname) |
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loop = loop.strip() # remove the new-line char
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self._add_cleanup(try_fail_repeat, losetup, '-d', loop) |
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return loop
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def _dir_to_disk(self): |
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"""Create a disk out of a directory"""
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if self.source == '/': |
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bundle = BundleVolume(self.out, self.meta) |
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image = '%s/%s.diskdump' % (self.tmp, uuid.uuid4().hex) |
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def check_unlink(path): |
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if os.path.exists(path):
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os.unlink(path) |
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self._add_cleanup(check_unlink, image)
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bundle.create_image(image) |
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return self._losetup(image) |
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raise FatalError("Using a directory as media source is supported") |
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def cleanup(self): |
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"""Cleanup internal data. This needs to be called before the
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program ends.
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"""
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try:
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while len(self._images): |
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image = self._images.pop()
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image.destroy() |
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finally:
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# Make sure those are executed even if one of the device.destroy
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# methods throws exeptions.
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while len(self._cleanup_jobs): |
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job, args = self._cleanup_jobs.pop()
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job(*args) |
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def snapshot(self): |
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"""Creates a snapshot of the original source media of the Disk
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instance.
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"""
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self.out.output("Examining source media `%s' ..." % self.source, False) |
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sourcedev = self.source
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mode = os.stat(self.source).st_mode
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if stat.S_ISDIR(mode):
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self.out.success('looks like a directory') |
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return self._dir_to_disk() |
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elif stat.S_ISREG(mode):
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self.out.success('looks like an image file') |
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sourcedev = self._losetup(self.source) |
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elif not stat.S_ISBLK(mode): |
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raise FatalError("Invalid media source. Only block devices, " |
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"regular files and directories are supported.")
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else:
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self.out.success('looks like a block device') |
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# Take a snapshot and return it to the user
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self.out.output("Snapshotting media source...", False) |
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size = blockdev('--getsz', sourcedev)
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cowfd, cow = tempfile.mkstemp(dir=self.tmp)
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os.close(cowfd) |
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self._add_cleanup(os.unlink, cow)
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# Create cow sparse file
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dd('if=/dev/null', 'of=%s' % cow, 'bs=512', 'seek=%d' % int(size)) |
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cowdev = self._losetup(cow)
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snapshot = uuid.uuid4().hex |
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tablefd, table = tempfile.mkstemp() |
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try:
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os.write(tablefd, "0 %d snapshot %s %s n 8" %
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(int(size), sourcedev, cowdev))
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dmsetup('create', snapshot, table)
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self._add_cleanup(try_fail_repeat, dmsetup, 'remove', snapshot) |
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finally:
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os.unlink(table) |
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self.out.success('done') |
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return "/dev/mapper/%s" % snapshot |
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def get_image(self, media): |
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"""Returns a newly created ImageCreator instance."""
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image = Image(media, self.out)
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self._images.append(image)
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image.enable() |
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return image
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def destroy_image(self, image): |
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"""Destroys an ImageCreator instance previously created by
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get_image_creator method.
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"""
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self._images.remove(image)
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image.destroy() |
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# vim: set sta sts=4 shiftwidth=4 sw=4 et ai :
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