root / image_creator / disk.py @ 01a7cff3
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#!/usr/bin/env python
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import losetup |
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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 pbs |
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from pbs import dd |
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class DiskError(Exception): |
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pass
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def find_sbin_command(command, exception): |
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search_paths = ['/usr/local/sbin', '/usr/sbin', '/sbin'] |
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for fullpath in map(lambda x: "%s/%s" % (x, command), search_paths): |
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if os.path.exists(fullpath) and os.access(fullpath, os.X_OK): |
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return pbs.Command(fullpath)
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continue
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raise exception
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try:
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from pbs import dmsetup |
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except pbs.CommandNotFound as e: |
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dmsetup = find_sbin_command('dmsetup', e)
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try:
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from pbs import blockdev |
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except pbs.CommandNotFound as e: |
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blockdev = find_sbin_command('blockdev', e)
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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.find_unused_loop_device() |
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loop.mount(fname) |
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self._add_cleanup(loop.unmount)
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return loop.device
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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 get_device(self): |
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"""Returns a newly created DiskDevice instance.
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This instance is a snapshot of the original source media of
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the Disk instance.
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"""
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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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return self._losetup(self._dir_to_disk()) |
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elif stat.S_ISREG(mode):
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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("Value for self.source is invalid") |
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# Take a snapshot and return it to the user
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size = blockdev('--getsize', sourcedev)
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cowfd, cow = tempfile.mkstemp() |
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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', '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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finally:
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os.unlink(table) |
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new_device = DiskDevice("/dev/mapper/%s" % snapshot)
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self._devices.append(new_device)
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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.g = guestfs.GuestFS()
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self.g.set_trace(1) |
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self.g.add_drive_opts(device, readonly=0) |
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self.g.launch()
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roots = self.g.inspect_os()
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if len(roots) == 0: |
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raise DiskError("No operating system found") |
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if len(roots) > 1: |
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raise DiskError("Multiple operating systems found") |
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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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def destroy(self): |
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"""Destroy this DiskDevice instance."""
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self.g.umount_all()
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self.g.sync()
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# Close the guestfs handler
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self.g.close()
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def mount(self): |
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"""Mount all disk partitions in a correct order."""
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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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print "%s (ignored)" % msg |
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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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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 DiskError("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 DiskError("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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print "Warning: 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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output = self.g.tune2fs_l(part_dev)
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block_size = int(filter(lambda x: x[0] == 'Block size', output)[0][1]) |
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block_cnt = int(filter(lambda x: x[0] == 'Block count', output)[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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return (end + 1) * sector_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'] |
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# vim: set sta sts=4 shiftwidth=4 sw=4 et ai :
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