mic2 0.24.12-1 / usr / share / pyshared / mic / imgcreate / fs.py

#
# fs.py : Filesystem related utilities and classes
#
# Copyright 2007, Red Hat  Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Library General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.


import os
import sys
import errno
import stat
import subprocess
import random
import string
import logging
import time
import fcntl
import struct
import termios

from mic.imgcreate.errors import *
from urlgrabber.grabber import URLGrabber
from urlgrabber.grabber import URLGrabError

def terminal_width(fd=1):
    """ Get the real terminal width """
    try:
        buf = 'abcdefgh'
        buf = fcntl.ioctl(fd, termios.TIOCGWINSZ, buf)
        return struct.unpack('hhhh', buf)[1]
    except: # IOError
        return 80

def truncate_url(url, width):
    if len(url) > width:
        return os.path.basename(url)[0:width]
    return url

class TextProgress(object):
    def start(self, filename, url, *args, **kwargs):
        self.url = url
        self.termwidth = terminal_width()
        sys.stdout.write("Retrieving %s " % truncate_url(self.url, self.termwidth - 17))
        sys.stdout.flush()
        self.indicators = ["-", "\\", "|", "/"]
        self.counter = 0
    def update(self, *args):
        if sys.stdout.isatty():
            sys.stdout.write("\rRetrieving %s %s" % (truncate_url(self.url, self.termwidth - 17), self.indicators[self.counter%4]))
            sys.stdout.flush()
            self.counter += 1
        else:
            pass
    def end(self, *args):
        if sys.stdout.isatty():
            sys.stdout.write("\rRetrieving %s ...OK\n" % (self.url,))
        else:
            sys.stdout.write("...OK\n")
        sys.stdout.flush()

def find_binary_path(binary):
    if os.environ.has_key("PATH"):
        paths = os.environ["PATH"].split(":")
    else:
        paths = []
        if os.environ.has_key("HOME"):
            paths += [os.environ["HOME"] + "/bin"]
        paths += ["/usr/local/sbin", "/usr/local/bin", "/usr/sbin", "/usr/bin", "/sbin", "/bin"]

    for path in paths:
        bin_path = "%s/%s" % (path, binary)
        if os.path.exists(bin_path):
            return bin_path
    raise CreatorError("Command '%s' is not available." % binary)

def makedirs(dirname):
    """A version of os.makedirs() that doesn't throw an
    exception if the leaf directory already exists.
    """
    try:
        os.makedirs(dirname)
    except OSError, (err, msg):
        if err != errno.EEXIST:
            raise

def mksquashfs(in_img, out_img):
    fullpathmksquashfs = find_binary_path("mksquashfs")
    args = [fullpathmksquashfs, in_img, out_img]

    if not sys.stdout.isatty():
        args.append("-no-progress")

    ret = subprocess.call(args, stdout=sys.stdout, stderr=sys.stderr)
    if ret != 0:
        raise SquashfsError("'%s' exited with error (%d)" %
                            (string.join(args, " "), ret))

def resize2fs(fs, size):
    dev_null = os.open("/dev/null", os.O_WRONLY)
    try:
        resize2fs = find_binary_path("resize2fs")
        return subprocess.call([resize2fs, fs, "%sK" % (size / 1024,)],
                               stdout = dev_null, stderr = dev_null)
    finally:
        os.close(dev_null)

def my_fuser(file):
    ret = False
    fuser = find_binary_path("fuser")
    if not os.path.exists(file):
        return ret
    dev_null = os.open("/dev/null", os.O_WRONLY)
    rc = subprocess.call([fuser, "-s", file], stderr=dev_null) 
    if rc == 0:
        fuser_proc = subprocess.Popen([fuser, file], stdout=subprocess.PIPE, stderr=dev_null)
        pids = fuser_proc.communicate()[0].strip().split()
        for pid in pids:
            fd = open("/proc/%s/cmdline" % pid, "r")
            cmdline = fd.read()
            fd.close()
            if cmdline[:-1] == "/bin/bash":
                ret = True
                break
    os.close(dev_null)
    return ret

class BindChrootMount:
    """Represents a bind mount of a directory into a chroot."""
    def __init__(self, src, chroot, dest = None, option = None):
        self.src = src
        self.root = os.path.abspath(os.path.expanduser(chroot))
        self.option = option

        if not dest:
            dest = src
        self.dest = self.root + "/" + dest

        self.mounted = False
        self.mountcmd = find_binary_path("mount")
        self.umountcmd = find_binary_path("umount")

    def ismounted(self):
        ret = False
        dev_null = os.open("/dev/null", os.O_WRONLY)
        catcmd = find_binary_path("cat")
        args = [ catcmd, "/proc/mounts" ]
        proc_mounts = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=dev_null)
        outputs = proc_mounts.communicate()[0].strip().split("\n")
        for line in outputs:
            if line.split()[1] == os.path.abspath(self.dest):
                ret = True
                break
        os.close(dev_null)
        return ret

    def has_chroot_instance(self):
        lock = os.path.join(self.root, ".chroot.lock")
        return my_fuser(lock)

    def mount(self):
        if self.mounted or self.ismounted():
            return

        makedirs(self.dest)
        rc = subprocess.call([self.mountcmd, "--bind", self.src, self.dest])
        if rc != 0:
            raise MountError("Bind-mounting '%s' to '%s' failed" %
                             (self.src, self.dest))
        if self.option:
            rc = subprocess.call([self.mountcmd, "--bind", "-o", "remount,%s" % self.option, self.dest])
            if rc != 0:
                raise MountError("Bind-remounting '%s' failed" % self.dest)
        self.mounted = True

    def unmount(self):
        if self.has_chroot_instance():
            return

        if self.ismounted():
            subprocess.call([self.umountcmd, "-l", self.dest])
        self.mounted = False

class LoopbackMount:
    """LoopbackMount  compatibility layer for old API"""
    def __init__(self, lofile, mountdir, fstype = None):
        self.diskmount = DiskMount(LoopbackDisk(lofile,size = 0),mountdir,fstype,rmmountdir = True)
        self.losetup = False
        self.losetupcmd = find_binary_path("losetup")

    def cleanup(self):
        self.diskmount.cleanup()

    def unmount(self):
        self.diskmount.unmount()

    def lounsetup(self):
        if self.losetup:
            rc = subprocess.call([self.losetupcmd, "-d", self.loopdev])
            self.losetup = False
            self.loopdev = None

    def loopsetup(self):
        if self.losetup:
            return

        losetupProc = subprocess.Popen([self.losetupcmd, "-f"],
                                       stdout=subprocess.PIPE)
        losetupOutput = losetupProc.communicate()[0]

        if losetupProc.returncode:
            raise MountError("Failed to allocate loop device for '%s'" %
                             self.lofile)

        self.loopdev = losetupOutput.split()[0]

        rc = subprocess.call([self.losetupcmd, self.loopdev, self.lofile])
        if rc != 0:
            raise MountError("Failed to allocate loop device for '%s'" %
                             self.lofile)

        self.losetup = True

    def mount(self):
        self.diskmount.mount()

class SparseLoopbackMount(LoopbackMount):
    """SparseLoopbackMount  compatibility layer for old API"""
    def __init__(self, lofile, mountdir, size, fstype = None):
        self.diskmount = DiskMount(SparseLoopbackDisk(lofile,size),mountdir,fstype,rmmountdir = True)

    def expand(self, create = False, size = None):
        self.diskmount.disk.expand(create, size)

    def truncate(self, size = None):
        self.diskmount.disk.truncate(size)

    def create(self):
        self.diskmount.disk.create()

class SparseExtLoopbackMount(SparseLoopbackMount):
    """SparseExtLoopbackMount  compatibility layer for old API"""
    def __init__(self, lofile, mountdir, size, fstype, blocksize, fslabel):
        self.diskmount = ExtDiskMount(SparseLoopbackDisk(lofile,size), mountdir, fstype, blocksize, fslabel, rmmountdir = True)


    def __format_filesystem(self):
        self.diskmount.__format_filesystem()

    def create(self):
        self.diskmount.disk.create()

    def resize(self, size = None):
        return self.diskmount.__resize_filesystem(size)

    def mount(self):
        self.diskmount.mount()

    def __fsck(self):
        self.extdiskmount.__fsck()

    def __get_size_from_filesystem(self):
        return self.diskmount.__get_size_from_filesystem()

    def __resize_to_minimal(self):
        return self.diskmount.__resize_to_minimal()

    def resparse(self, size = None):
        return self.diskmount.resparse(size)

class Disk:
    """Generic base object for a disk

    The 'create' method must make the disk visible as a block device - eg
    by calling losetup. For RawDisk, this is obviously a no-op. The 'cleanup'
    method must undo the 'create' operation.
    """
    def __init__(self, size, device = None):
        self._device = device
        self._size = size

    def create(self):
        pass

    def cleanup(self):
        pass

    def get_device(self):
        return self._device
    def set_device(self, path):
        self._device = path
    device = property(get_device, set_device)

    def get_size(self):
        return self._size
    size = property(get_size)


class RawDisk(Disk):
    """A Disk backed by a block device.
    Note that create() is a no-op.
    """
    def __init__(self, size, device):
        Disk.__init__(self, size, device)

    def fixed(self):
        return True

    def exists(self):
        return True

class LoopbackDisk(Disk):
    """A Disk backed by a file via the loop module."""
    def __init__(self, lofile, size):
        Disk.__init__(self, size)
        self.lofile = lofile
        self.losetupcmd = find_binary_path("losetup")

    def fixed(self):
        return False

    def exists(self):
        return os.path.exists(self.lofile)

    def create(self):
        if self.device is not None:
            return

        losetupProc = subprocess.Popen([self.losetupcmd, "-f"],
                                       stdout=subprocess.PIPE)
        losetupOutput = losetupProc.communicate()[0]

        if losetupProc.returncode:
            raise MountError("Failed to allocate loop device for '%s'" %
                             self.lofile)

        device = losetupOutput.split()[0]

        logging.debug("Losetup add %s mapping to %s"  % (device, self.lofile))
        rc = subprocess.call([self.losetupcmd, device, self.lofile])
        if rc != 0:
            raise MountError("Failed to allocate loop device for '%s'" %
                             self.lofile)
        self.device = device

    def cleanup(self):
        if self.device is None:
            return
        logging.debug("Losetup remove %s" % self.device)
        rc = subprocess.call([self.losetupcmd, "-d", self.device])
        self.device = None



class SparseLoopbackDisk(LoopbackDisk):
    """A Disk backed by a sparse file via the loop module."""
    def __init__(self, lofile, size):
        LoopbackDisk.__init__(self, lofile, size)

    def expand(self, create = False, size = None):
        flags = os.O_WRONLY
        if create:
            flags |= os.O_CREAT
            if not os.path.exists(self.lofile):
                makedirs(os.path.dirname(self.lofile))

        if size is None:
            size = self.size

        logging.debug("Extending sparse file %s to %d" % (self.lofile, size))
        if create:
            fd = os.open(self.lofile, flags, 0644)
        else:
            fd = os.open(self.lofile, flags)

        os.lseek(fd, size, os.SEEK_SET)
        os.write(fd, '\x00')
        os.close(fd)

    def truncate(self, size = None):
        if size is None:
            size = self.size

        logging.debug("Truncating sparse file %s to %d" % (self.lofile, size))
        fd = os.open(self.lofile, os.O_WRONLY)
        os.ftruncate(fd, size)
        os.close(fd)

    def create(self):
        self.expand(create = True)
        LoopbackDisk.create(self)

class Mount:
    """A generic base class to deal with mounting things."""
    def __init__(self, mountdir):
        self.mountdir = mountdir

    def cleanup(self):
        self.unmount()

    def mount(self, options = None):
        pass

    def unmount(self):
        pass

class DiskMount(Mount):
    """A Mount object that handles mounting of a Disk."""
    def __init__(self, disk, mountdir, fstype = None, rmmountdir = True):
        Mount.__init__(self, mountdir)

        self.disk = disk
        self.fstype = fstype
        self.rmmountdir = rmmountdir

        self.mounted = False
        self.rmdir   = False
        if fstype:
            self.mkfscmd = find_binary_path("mkfs." + self.fstype)
        else:
            self.mkfscmd = None
        self.mountcmd = find_binary_path("mount")
        self.umountcmd = find_binary_path("umount")

    def cleanup(self):
        Mount.cleanup(self)
        self.disk.cleanup()

    def unmount(self):
        if self.mounted:
            logging.debug("Unmounting directory %s" % self.mountdir)
            synccmd = find_binary_path("sync")
            subprocess.call([synccmd]) # sync the data on this mount point
            rc = subprocess.call([self.umountcmd, "-l", self.mountdir])
            if rc == 0:
                self.mounted = False
            else:
                raise MountError("Failed to umount %s" % self.mountdir)
        if self.rmdir and not self.mounted:
            try:
                os.rmdir(self.mountdir)
            except OSError, e:
                pass
            self.rmdir = False


    def __create(self):
        self.disk.create()


    def mount(self, options = None):
        if self.mounted:
            return

        if not os.path.isdir(self.mountdir):
            logging.debug("Creating mount point %s" % self.mountdir)
            os.makedirs(self.mountdir)
            self.rmdir = self.rmmountdir

        self.__create()

        logging.debug("Mounting %s at %s" % (self.disk.device, self.mountdir))
        if options:
            args = [ self.mountcmd, "-o", options, self.disk.device, self.mountdir ]
        else:
            args = [ self.mountcmd, self.disk.device, self.mountdir ]
        if self.fstype:
            args.extend(["-t", self.fstype])

        rc = subprocess.call(args)
        if rc != 0:
            raise MountError("Failed to mount '%s' to '%s' with command '%s'. Retval: %s" %
                             (self.disk.device, self.mountdir, " ".join(args), rc))

        self.mounted = True

class ExtDiskMount(DiskMount):
    """A DiskMount object that is able to format/resize ext[23] filesystems."""
    def __init__(self, disk, mountdir, fstype, blocksize, fslabel, rmmountdir=True, skipformat = False, fsopts = None):
        DiskMount.__init__(self, disk, mountdir, fstype, rmmountdir)
        self.blocksize = blocksize
        self.fslabel = fslabel.replace("/", "")
        self.uuid  = None
        self.skipformat = skipformat
        self.fsopts = fsopts
        self.dumpe2fs = find_binary_path("dumpe2fs")
        self.tune2fs = find_binary_path("tune2fs")

    def __parse_field(self, output, field):
        for line in output.split("\n"):
            if line.startswith(field + ":"):
                return line[len(field) + 1:].strip()

        raise KeyError("Failed to find field '%s' in output" % field)

    def __format_filesystem(self):
        if self.skipformat:
            logging.debug("Skip filesystem format.")
            return
        logging.debug("Formating %s filesystem on %s" % (self.fstype, self.disk.device))
        proc = subprocess.Popen([self.mkfscmd,
                              "-F", "-L", self.fslabel,
                              "-m", "1", "-b", str(self.blocksize),
                              self.disk.device], stdout=subprocess.PIPE,
                              stderr=subprocess.PIPE)
        rc = proc.wait()
        output = proc.communicate()[0].replace('\b', ' ')
        sys.stdout.write(output.decode('UTF-8'))
        #                      str(self.disk.size / self.blocksize)])
        if rc != 0:
            raise MountError("Error creating %s filesystem on disk %s" % (self.fstype,self.disk.device))

        dev_null = os.open("/dev/null", os.O_WRONLY)
        try:
            out = subprocess.Popen([self.dumpe2fs, '-h', self.disk.device],
                                   stdout = subprocess.PIPE,
                                   stderr = dev_null).communicate()[0]
        finally:
            os.close(dev_null)

        self.uuid = self.__parse_field(out, "Filesystem UUID")
        logging.debug("Tuning filesystem on %s" % self.disk.device)
        subprocess.call([self.tune2fs, "-c0", "-i0", "-Odir_index",
                         "-ouser_xattr,acl", self.disk.device],
                         stdout=sys.stdout, stderr=sys.stderr)

    def __resize_filesystem(self, size = None):
        current_size = os.stat(self.disk.lofile)[stat.ST_SIZE]

        if size is None:
            size = self.disk.size

        if size == current_size:
            return

        if size > current_size:
            self.disk.expand(size)

        self.__fsck()

        resize2fs(self.disk.lofile, size)
        return size

    def __create(self):
        resize = False
        if not self.disk.fixed() and self.disk.exists():
            resize = True

        self.disk.create()

        if resize:
            self.__resize_filesystem()
        else:
            self.__format_filesystem()

    def mount(self, options = None):
        self.__create()
        DiskMount.mount(self, options)

    def __fsck(self):
        logging.debug("Checking filesystem %s" % self.disk.lofile)
        subprocess.call(["/sbin/e2fsck", "-f", "-y", self.disk.lofile], stdout=sys.stdout, stderr=sys.stderr)

    def __get_size_from_filesystem(self):
        dev_null = os.open("/dev/null", os.O_WRONLY)
        try:
            out = subprocess.Popen([self.dumpe2fs, '-h', self.disk.lofile],
                                   stdout = subprocess.PIPE,
                                   stderr = dev_null).communicate()[0]
        finally:
            os.close(dev_null)

        return int(self.__parse_field(out, "Block count")) * self.blocksize

    def __resize_to_minimal(self):
        self.__fsck()

        #
        # Use a binary search to find the minimal size
        # we can resize the image to
        #
        bot = 0
        top = self.__get_size_from_filesystem()
        while top != (bot + 1):
            t = bot + ((top - bot) / 2)

            if not resize2fs(self.disk.lofile, t):
                top = t
            else:
                bot = t
        return top

    def resparse(self, size = None):
        self.cleanup()
        minsize = self.__resize_to_minimal()
        self.disk.truncate(minsize)
        self.__resize_filesystem(size)
        return minsize

class VfatDiskMount(DiskMount):
    """A DiskMount object that is able to format vfat/msdos filesystems."""
    def __init__(self, disk, mountdir, fstype, blocksize, fslabel, rmmountdir=True, skipformat = False, fsopts = None):
        DiskMount.__init__(self, disk, mountdir, fstype, rmmountdir)
        self.blocksize = blocksize
        self.fslabel = fslabel.replace("/", "")
        self.uuid = "%08X" % int(time.time())
        self.skipformat = skipformat
        self.fsopts = fsopts
        self.fsckcmd = find_binary_path("fsck." + self.fstype)

    def __format_filesystem(self):
        if self.skipformat:
            logging.debug("Skip filesystem format.")
            return
        logging.debug("Formating %s filesystem on %s" % (self.fstype, self.disk.device))
        blah = [self.mkfscmd, "-n", self.fslabel, "-i", self.uuid, self.disk.device]
        rc = subprocess.call(blah)
        if rc != 0:
            raise MountError("Error creating %s filesystem on disk %s" % (self.fstype,self.disk.device))
        logging.debug("Tuning filesystem on %s" % self.disk.device)

    def __resize_filesystem(self, size = None):
        current_size = os.stat(self.disk.lofile)[stat.ST_SIZE]

        if size is None:
            size = self.disk.size

        if size == current_size:
            return

        if size > current_size:
            self.disk.expand(size)

        self.__fsck()

        #resize2fs(self.disk.lofile, size)
        return size

    def __create(self):
        resize = False
        if not self.disk.fixed() and self.disk.exists():
            resize = True

        self.disk.create()

        if resize:
            self.__resize_filesystem()
        else:
            self.__format_filesystem()

    def mount(self, options = None):
        self.__create()
        DiskMount.mount(self, options)

    def __fsck(self):
        logging.debug("Checking filesystem %s" % self.disk.lofile)
        subprocess.call([self.fsckcmd, "-y", self.disk.lofile])

    def __get_size_from_filesystem(self):
        return self.disk.size

    def __resize_to_minimal(self):
        self.__fsck()

        #
        # Use a binary search to find the minimal size
        # we can resize the image to
        #
        bot = 0
        top = self.__get_size_from_filesystem()
        return top

    def resparse(self, size = None):
        self.cleanup()
        minsize = self.__resize_to_minimal()
        self.disk.truncate(minsize)
        self.__resize_filesystem(size)
        return minsize

class BtrfsDiskMount(DiskMount):
    """A DiskMount object that is able to format/resize btrfs filesystems."""
    def __init__(self, disk, mountdir, fstype, blocksize, fslabel, rmmountdir=True, skipformat = False, fsopts = None):
        self.__check_btrfs()
        DiskMount.__init__(self, disk, mountdir, fstype, rmmountdir)
        self.blocksize = blocksize
        self.fslabel = fslabel.replace("/", "")
        self.uuid  = None
        self.skipformat = skipformat
        self.fsopts = fsopts
        self.blkidcmd = find_binary_path("blkid")
        self.btrfsckcmd = find_binary_path("btrfsck")

    def __check_btrfs(self):
        found = False
        """ Need to load btrfs module to mount it """
        load_module("btrfs")
        for line in open("/proc/filesystems").xreadlines():
            if line.find("btrfs") > -1:
                found = True
                break
        if not found:
            raise MountError("Your system can't mount btrfs filesystem, please make sure your kernel has btrfs support and the module btrfs.ko has been loaded.")

    def __parse_field(self, output, field):
        for line in output.split(" "):
            if line.startswith(field + "="):
                return line[len(field) + 1:].strip().replace("\"", "")

        raise KeyError("Failed to find field '%s' in output" % field)

    def __format_filesystem(self):
        if self.skipformat:
            logging.debug("Skip filesystem format.")
            return
        logging.debug("Formating %s filesystem on %s" % (self.fstype, self.disk.device))
        rc = subprocess.call([self.mkfscmd, "-L", self.fslabel, self.disk.device])
        if rc != 0:
            raise MountError("Error creating %s filesystem on disk %s" % (self.fstype,self.disk.device))

        dev_null = os.open("/dev/null", os.O_WRONLY)
        try:
            out = subprocess.Popen([self.blkidcmd, self.disk.device],
                                   stdout = subprocess.PIPE,
                                   stderr = dev_null).communicate()[0]
        finally:
            os.close(dev_null)

        self.uuid = self.__parse_field(out, "UUID")

    def __resize_filesystem(self, size = None):
        current_size = os.stat(self.disk.lofile)[stat.ST_SIZE]

        if size is None:
            size = self.disk.size

        if size == current_size:
            return

        if size > current_size:
            self.disk.expand(size)

        self.__fsck()
        return size

    def __create(self):
        resize = False
        if not self.disk.fixed() and self.disk.exists():
            resize = True

        self.disk.create()

        if resize:
            self.__resize_filesystem()
        else:
            self.__format_filesystem()

    def mount(self, options = None):
        self.__create()
        DiskMount.mount(self, options)

    def __fsck(self):
        logging.debug("Checking filesystem %s" % self.disk.lofile)
        subprocess.call([self.btrfsckcmd, self.disk.lofile])

    def __get_size_from_filesystem(self):
        return self.disk.size

    def __resize_to_minimal(self):
        self.__fsck()

        return self.__get_size_from_filesystem()

    def resparse(self, size = None):
        self.cleanup()
        minsize = self.__resize_to_minimal()
        self.disk.truncate(minsize)
        self.__resize_filesystem(size)
        return minsize

class DeviceMapperSnapshot(object):
    def __init__(self, imgloop, cowloop):
        self.imgloop = imgloop
        self.cowloop = cowloop

        self.__created = False
        self.__name = None
        self.dmsetupcmd = find_binary_path("dmsetup")

        """Load dm_snapshot if it isn't loaded"""
        load_module("dm_snapshot")

    def get_path(self):
        if self.__name is None:
            return None
        return os.path.join("/dev/mapper", self.__name)
    path = property(get_path)

    def create(self):
        if self.__created:
            return

        self.imgloop.create()
        self.cowloop.create()

        self.__name = "imgcreate-%d-%d" % (os.getpid(),
                                           random.randint(0, 2**16))

        size = os.stat(self.imgloop.lofile)[stat.ST_SIZE]

        table = "0 %d snapshot %s %s p 8" % (size / 512,
                                             self.imgloop.device,
                                             self.cowloop.device)

        args = [self.dmsetupcmd, "create", self.__name, "--table", table]
        if subprocess.call(args) != 0:
            self.cowloop.cleanup()
            self.imgloop.cleanup()
            raise SnapshotError("Could not create snapshot device using: " +
                                string.join(args, " "))

        self.__created = True

    def remove(self, ignore_errors = False):
        if not self.__created:
            return
        
        time.sleep(2)
        rc = subprocess.call([self.dmsetupcmd, "remove", self.__name])
        if not ignore_errors and rc != 0:
            raise SnapshotError("Could not remove snapshot device")

        self.__name = None
        self.__created = False

        self.cowloop.cleanup()
        self.imgloop.cleanup()

    def get_cow_used(self):
        if not self.__created:
            return 0

        dev_null = os.open("/dev/null", os.O_WRONLY)
        try:
            out = subprocess.Popen([self.dmsetupcmd, "status", self.__name],
                                   stdout = subprocess.PIPE,
                                   stderr = dev_null).communicate()[0]
        finally:
            os.close(dev_null)

        #
        # dmsetup status on a snapshot returns e.g.
        #   "0 8388608 snapshot 416/1048576"
        # or, more generally:
        #   "A B snapshot C/D"
        # where C is the number of 512 byte sectors in use
        #
        try:
            return int((out.split()[3]).split('/')[0]) * 512
        except ValueError:
            raise SnapshotError("Failed to parse dmsetup status: " + out)

def create_image_minimizer(path, image, minimal_size):
    """
    Builds a copy-on-write image which can be used to
    create a device-mapper snapshot of an image where
    the image's filesystem is as small as possible

    The steps taken are:
      1) Create a sparse COW
      2) Loopback mount the image and the COW
      3) Create a device-mapper snapshot of the image
         using the COW
      4) Resize the filesystem to the minimal size
      5) Determine the amount of space used in the COW
      6) Restroy the device-mapper snapshot
      7) Truncate the COW, removing unused space
      8) Create a squashfs of the COW
    """
    imgloop = LoopbackDisk(image, None) # Passing bogus size - doesn't matter

    cowloop = SparseLoopbackDisk(os.path.join(os.path.dirname(path), "osmin"),
                                 64L * 1024L * 1024L)

    snapshot = DeviceMapperSnapshot(imgloop, cowloop)

    try:
        snapshot.create()

        resize2fs(snapshot.path, minimal_size)

        cow_used = snapshot.get_cow_used()
    finally:
        snapshot.remove(ignore_errors = (not sys.exc_info()[0] is None))

    cowloop.truncate(cow_used)

    mksquashfs(cowloop.lofile, path)

    os.unlink(cowloop.lofile)

def load_module(module):
    found = False
    for line in open('/proc/modules').xreadlines():
        if line.startswith("%s " % module):
            found = True
            break
    if not found:
        print "Loading %s..." % module
        dev_null = os.open("/dev/null", os.O_WRONLY)
        modprobecmd = find_binary_path("modprobe")
        modprobe = subprocess.Popen([modprobecmd, module],
                     stdout=dev_null, stderr=dev_null)
        os.waitpid(modprobe.pid, 0)
        os.close(dev_null)

def myurlgrab(url, filename, proxies):
    g = URLGrabber()
    if url.startswith("file:///"):
        file = url.replace("file://", "")
        if not os.path.exists(file):
            raise CreatorError("URLGrabber error: can't find file %s" % file)
        copycmd = find_binary_path("cp")
        subprocess.call([copycmd, "-f", file, filename])
    else:
        try:
            filename = g.urlgrab(url = url, filename = filename,
                ssl_verify_host = False, ssl_verify_peer = False,
                proxies = proxies, http_headers = (('Pragma', 'no-cache'),), progress_obj = TextProgress())
        except URLGrabError, e:
            raise CreatorError("URLGrabber error: %s: %s" % (e, url))
        except:
            raise CreatorError("URLGrabber error: %s" % url)
    return filename