Synnefo » snf-image-creator

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from image_creator.util import get_command

from image_creator.util import warn, progress, success, output, FatalError

from image_creator.gpt import GPTPartitionTable

import stat

import os

import tempfile

import uuid

import re

import sys

import guestfs

import time

from sendfile import sendfile

class DiskError(Exception):

    pass

dd = get_command('dd')

dmsetup = get_command('dmsetup')

losetup = get_command('losetup')

blockdev = get_command('blockdev')

class Disk(object):

    """This class represents a hard disk hosting an Operating System

    A Disk instance never alters the source media it is created from.

    Any change is done on a snapshot created by the device-mapper of

    the Linux kernel.

    """

    def __init__(self, source):

        """Create a new Disk instance out of a source media. The source

        media can be an image file, a block device or a directory."""

        self._cleanup_jobs = []

        self._devices = []

        self.source = source

    def _add_cleanup(self, job, *args):

        self._cleanup_jobs.append((job, args))

    def _losetup(self, fname):

        loop = losetup('-f', '--show', fname)

        loop = loop.strip()  # remove the new-line char

        self._add_cleanup(losetup, '-d', loop)

        return loop

    def _dir_to_disk(self):

        raise NotImplementedError

    def cleanup(self):

        """Cleanup internal data. This needs to be called before the

        program ends.

        """

        while len(self._devices):

            device = self._devices.pop()

            device.destroy()

        while len(self._cleanup_jobs):

            job, args = self._cleanup_jobs.pop()

            job(*args)

    def snapshot(self):

        """Creates a snapshot of the original source media of the Disk

        instance.

        """

        output("Examining source media `%s'..." % self.source, False)

        sourcedev = self.source

        mode = os.stat(self.source).st_mode

        if stat.S_ISDIR(mode):

            success('looks like a directory')

            return self._losetup(self._dir_to_disk())

        elif stat.S_ISREG(mode):

            success('looks like an image file')

            sourcedev = self._losetup(self.source)

        elif not stat.S_ISBLK(mode):

            raise ValueError("Invalid media source. Only block devices, "

                            "regular files and directories are supported.")

        else:

            success('looks like a block device')

        # Take a snapshot and return it to the user

        output("Snapshotting media source...", False)

        size = blockdev('--getsize', sourcedev)

        cowfd, cow = tempfile.mkstemp()

        os.close(cowfd)

        self._add_cleanup(os.unlink, cow)

        # Create 1G cow sparse file

        dd('if=/dev/null', 'of=%s' % cow, 'bs=1k', \

                                        'seek=%d' % (1024 * 1024))

        cowdev = self._losetup(cow)

        snapshot = uuid.uuid4().hex

        tablefd, table = tempfile.mkstemp()

        try:

            os.write(tablefd, "0 %d snapshot %s %s n 8" % \

                                        (int(size), sourcedev, cowdev))

            dmsetup('create', snapshot, table)

            self._add_cleanup(dmsetup, 'remove', snapshot)

            # Sometimes dmsetup remove fails with Device or resource busy,

            # although everything is cleaned up and the snapshot is not

            # used by anyone. Add a 2 seconds delay to be on the safe side.

            self._add_cleanup(time.sleep, 2)

        finally:

            os.unlink(table)

        success('done')

        return "/dev/mapper/%s" % snapshot

    def get_device(self, media):

        """Returns a newly created DiskDevice instance."""

        new_device = DiskDevice(media)

        self._devices.append(new_device)

        new_device.enable()

        return new_device

    def destroy_device(self, device):

        """Destroys a DiskDevice instance previously created by

        get_device method.

        """

        self._devices.remove(device)

        device.destroy()

class DiskDevice(object):

    """This class represents a block device hosting an Operating System

    as created by the device-mapper.

    """

    def __init__(self, device, bootable=True):

        """Create a new DiskDevice."""

        self.real_device = device

        self.bootable = bootable

        self.progress_bar = None

        self.guestfs_device = None

        self.size = None

        self.parttype = None

        self.g = guestfs.GuestFS()

        self.g.add_drive_opts(self.real_device, readonly=0)

        #self.g.set_trace(1)

        #self.g.set_verbose(1)

        self.guestfs_enabled = False

    def enable(self):

        """Enable a newly created DiskDevice"""

        self.progressbar = progress("Launching helper VM: ", "percent")

        self.progressbar.max = 100

        self.progressbar.goto(1)

        eh = self.g.set_event_callback(self.progress_callback,

                                                    guestfs.EVENT_PROGRESS)

        self.g.launch()

        self.guestfs_enabled = True

        self.g.delete_event_callback(eh)

        if self.progressbar is not None:

            output("\rLaunching helper VM...\033[K", False)

            success("done")

            self.progressbar = None

        output('Inspecting Operating System...', False)

        roots = self.g.inspect_os()

        if len(roots) == 0:

            raise FatalError("No operating system found")

        if len(roots) > 1:

            raise FatalError("Multiple operating systems found."

                            "We only support images with one filesystem.")

        self.root = roots[0]

        self.guestfs_device = self.g.part_to_dev(self.root)

        self.size = self.g.blockdev_getsize64(self.guestfs_device)

        self.parttype = self.g.part_get_parttype(self.guestfs_device)

        self.ostype = self.g.inspect_get_type(self.root)

        self.distro = self.g.inspect_get_distro(self.root)

        success('found a(n) %s system' % self.distro)

    def destroy(self):

        """Destroy this DiskDevice instance."""

        if self.guestfs_enabled:

            self.g.umount_all()

            self.g.sync()

        # Close the guestfs handler if open

        self.g.close()

    def progress_callback(self, ev, eh, buf, array):

        position = array[2]

        total = array[3]

        self.progressbar.goto((position * 100) // total)

    def mount(self):

        """Mount all disk partitions in a correct order."""

        output("Mounting image...", False)

        mps = self.g.inspect_get_mountpoints(self.root)

        # Sort the keys to mount the fs in a correct order.

        # / should be mounted befor /boot, etc

        def compare(a, b):

            if len(a[0]) > len(b[0]):

                return 1

            elif len(a[0]) == len(b[0]):

                return 0

            else:

                return -1

        mps.sort(compare)

        for mp, dev in mps:

            try:

                self.g.mount(dev, mp)

            except RuntimeError as msg:

                warn("%s (ignored)" % msg)

        success("done")

    def umount(self):

        """Umount all mounted filesystems."""

        self.g.umount_all()

    def shrink(self):

        """Shrink the disk.

        This is accomplished by shrinking the last filesystem in the

        disk and then updating the partition table. The new disk size

        (in bytes) is returned.

        ATTENTION: make sure unmount is called before shrink

        """

        output("Shrinking image (this may take a while)...", False)

        if self.parttype not in 'msdos' 'gpt':

            raise FatalError("You have a %s partition table. "

                "Only msdos and gpt partitions are supported" % self.parttype)

        last_partition = self.g.part_list(self.guestfs_device)[-1]

        if last_partition['part_num'] > 4:

            raise FatalError("This disk contains logical partitions. "

                "Only primary partitions are supported.")

        part_dev = "%s%d" % (self.guestfs_device, last_partition['part_num'])

        fs_type = self.g.vfs_type(part_dev)

        if not re.match("ext[234]", fs_type):

            warn("Don't know how to resize %s partitions." % vfs_type)

            return self.size()

        self.g.e2fsck_f(part_dev)

        self.g.resize2fs_M(part_dev)

        out = self.g.tune2fs_l(part_dev)

        block_size = int(

            filter(lambda x: x[0] == 'Block size', out)[0][1])

        block_cnt = int(

            filter(lambda x: x[0] == 'Block count', out)[0][1])

        sector_size = self.g.blockdev_getss(self.guestfs_device)

        start = last_partition['part_start'] / sector_size

        end = start + (block_size * block_cnt) / sector_size - 1

        self.g.part_del(self.guestfs_device, last_partition['part_num'])

        self.g.part_add(self.guestfs_device, 'p', start, end)

        self.size = (end + 1) * sector_size

        success("new image size is %dMB" %

                            ((self.size + 2 ** 20 - 1) // 2 ** 20))

        if self.parttype == 'gpt':

            ptable = GPTPartitionTable(self.real_device)

            self.size = ptable.shrink(self.size)

        return self.size

    def dump(self, outfile):

        """Dumps the content of device into a file.

        This method will only dump the actual payload, found by reading the

        partition table. Empty space in the end of the device will be ignored.

        """

        blocksize = 2 ** 22  # 4MB

        progress_size = (self.size + 2 ** 20 - 1) // 2 ** 20  # in MB

        progressbar = progress("Dumping image file: ", 'mb')

        progressbar.max = progress_size

        with open(self.real_device, 'r') as source:

            with open(outfile, "w") as dest:

                left = self.size

                offset = 0

                progressbar.next()

                while left > 0:

                    length = min(left, blocksize)

                    sent = sendfile(dest.fileno(), source.fileno(), offset,

                                                                        length)

                    offset += sent

                    left -= sent

                    progressbar.goto((self.size - left) // 2 ** 20)

        output("\rDumping image file...\033[K", False)

        success('image file %s was successfully created' % outfile)

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