root / image_creator / disk.py @ 8e3065a0
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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 warn, progress, success, output, FatalError |
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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 re |
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import sys |
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import guestfs |
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import time |
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from sendfile import sendfile |
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class DiskError(Exception): |
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pass
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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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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): |
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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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self._cleanup_jobs = []
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self._devices = []
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self.source = source
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def _add_cleanup(self, job, *args): |
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self._cleanup_jobs.append((job, args))
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def _losetup(self, fname): |
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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(losetup, '-d', loop) |
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return loop
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def _dir_to_disk(self): |
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raise NotImplementedError |
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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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while len(self._devices): |
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device = self._devices.pop()
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device.destroy() |
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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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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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success('looks like a directory')
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return self._losetup(self._dir_to_disk()) |
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elif stat.S_ISREG(mode):
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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 ValueError("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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success('looks like a block device')
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# Take a snapshot and return it to the user
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output("Snapshotting media source...", False) |
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size = blockdev('--getsize', sourcedev)
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cowfd, cow = tempfile.mkstemp() |
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os.close(cowfd) |
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self._add_cleanup(os.unlink, cow)
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# Create 1G cow sparse file
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dd('if=/dev/null', 'of=%s' % cow, 'bs=1k', \ |
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'seek=%d' % (1024 * 1024)) |
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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(dmsetup, 'remove', snapshot) |
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# Sometimes dmsetup remove fails with Device or resource busy,
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# although everything is cleaned up and the snapshot is not
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# used by anyone. Add a 2 seconds delay to be on the safe side.
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self._add_cleanup(time.sleep, 2) |
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finally:
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os.unlink(table) |
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success('done')
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return "/dev/mapper/%s" % snapshot |
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def get_device(self, media): |
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"""Returns a newly created DiskDevice instance."""
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new_device = DiskDevice(media) |
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self._devices.append(new_device)
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new_device.enable() |
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return new_device
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def destroy_device(self, device): |
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"""Destroys a DiskDevice instance previously created by
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get_device method.
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"""
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self._devices.remove(device)
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device.destroy() |
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class DiskDevice(object): |
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"""This class represents a block device hosting an Operating System
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as created by the device-mapper.
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"""
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def __init__(self, device, bootable=True): |
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"""Create a new DiskDevice."""
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self.device = device
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self.bootable = bootable
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self.progress_bar = None |
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self.g = guestfs.GuestFS()
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self.g.add_drive_opts(self.device, readonly=0) |
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#self.g.set_trace(1)
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#self.g.set_verbose(1)
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self.guestfs_enabled = False |
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def enable(self): |
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"""Enable a newly created DiskDevice"""
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new_progress = progress("Launching helper VM: ")
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self.progressbar = new_progress()
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self.progressbar.next()
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eh = self.g.set_event_callback(self.progress_callback, |
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guestfs.EVENT_PROGRESS) |
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self.g.launch()
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self.guestfs_enabled = True |
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self.g.delete_event_callback(eh)
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if self.progressbar is not None: |
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self.progressbar.send(100) |
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self.progressbar = None |
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output('Inspecting Operating System...', False) |
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roots = self.g.inspect_os()
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if len(roots) == 0: |
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raise FatalError("No operating system found") |
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if len(roots) > 1: |
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raise FatalError("Multiple operating systems found." |
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"We only support images with one filesystem.")
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self.root = roots[0] |
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self.ostype = self.g.inspect_get_type(self.root) |
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self.distro = self.g.inspect_get_distro(self.root) |
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success('found a %s system' % self.distro) |
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def destroy(self): |
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"""Destroy this DiskDevice instance."""
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if self.guestfs_enabled: |
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self.g.umount_all()
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self.g.sync()
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# Close the guestfs handler if open
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self.g.close()
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def progress_callback(self, ev, eh, buf, array): |
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position = array[2]
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total = array[3]
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self.progressbar.send((position * 100) // total) |
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if position == total:
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self.progressbar = None |
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def mount(self): |
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"""Mount all disk partitions in a correct order."""
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output("Mounting image...", False) |
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mps = self.g.inspect_get_mountpoints(self.root) |
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# Sort the keys to mount the fs in a correct order.
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# / should be mounted befor /boot, etc
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def compare(a, b): |
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if len(a[0]) > len(b[0]): |
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return 1 |
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elif len(a[0]) == len(b[0]): |
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return 0 |
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else:
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return -1 |
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mps.sort(compare) |
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for mp, dev in mps: |
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try:
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self.g.mount(dev, mp)
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except RuntimeError as msg: |
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warn("%s (ignored)" % msg)
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success("done")
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def umount(self): |
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"""Umount all mounted filesystems."""
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self.g.umount_all()
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def shrink(self): |
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"""Shrink the disk.
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This is accomplished by shrinking the last filesystem in the
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disk and then updating the partition table. The new disk size
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(in bytes) is returned.
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"""
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output("Shrinking image (this may take a while)...", False) |
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dev = self.g.part_to_dev(self.root) |
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parttype = self.g.part_get_parttype(dev)
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if parttype != 'msdos': |
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raise FatalError("You have a %s partition table. " |
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"Only msdos partitions are supported" % parttype)
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last_partition = self.g.part_list(dev)[-1] |
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if last_partition['part_num'] > 4: |
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raise FatalError("This disk contains logical partitions. " |
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"Only primary partitions are supported.")
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part_dev = "%s%d" % (dev, last_partition['part_num']) |
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fs_type = self.g.vfs_type(part_dev)
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if not re.match("ext[234]", fs_type): |
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warn("Don't know how to resize %s partitions." % vfs_type)
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return
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self.g.e2fsck_f(part_dev)
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self.g.resize2fs_M(part_dev)
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out = self.g.tune2fs_l(part_dev)
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block_size = int(
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filter(lambda x: x[0] == 'Block size', out)[0][1]) |
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block_cnt = int(
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filter(lambda x: x[0] == 'Block count', out)[0][1]) |
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sector_size = self.g.blockdev_getss(dev)
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start = last_partition['part_start'] / sector_size
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end = start + (block_size * block_cnt) / sector_size - 1
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self.g.part_del(dev, last_partition['part_num']) |
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self.g.part_add(dev, 'p', start, end) |
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new_size = (end + 1) * sector_size
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success("new image size is %dMB" %
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((new_size + 2 ** 20 - 1) // 2 ** 20)) |
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return new_size
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def size(self): |
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"""Returns the "payload" size of the device.
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The size returned by this method is the size of the space occupied by
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the partitions (including the space before the first partition).
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"""
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dev = self.g.part_to_dev(self.root) |
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last = self.g.part_list(dev)[-1] |
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return last['part_end'] + 1 |
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def dump(self, outfile): |
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"""Dumps the content of device into a file.
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This method will only dump the actual payload, found by reading the
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partition table. Empty space in the end of the device will be ignored.
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"""
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blocksize = 2 ** 22 # 4MB |
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size = self.size()
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progress_size = (size + 2 ** 20 - 1) // 2 ** 20 # in MB |
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new_progress = progress("Dumping image file: ")
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progressbar = new_progress(progress_size) |
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source = open(self.device, "r") |
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try:
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dest = open(outfile, "w") |
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try:
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left = size |
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offset = 0
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progressbar.next() |
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while left > 0: |
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length = min(left, blocksize)
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sent = sendfile(dest.fileno(), source.fileno(), offset, |
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length) |
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offset += sent |
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left -= sent |
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for i in range((length + 2 ** 20 - 1) // 2 ** 20): |
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progressbar.next() |
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finally:
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dest.close() |
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finally:
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source.close() |
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success('Image file %s was successfully created' % outfile)
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# vim: set sta sts=4 shiftwidth=4 sw=4 et ai :
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