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# Copyright (C) 2011 Canonical
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# This program is free software; you can redistribute it and/or modify it under
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# the terms of the GNU General Public License as published by the Free Software
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# Foundation; version 3.
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# This program is distributed in the hope that it will be useful, but WITHOUT
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# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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# You should have received a copy of the GNU General Public License along with
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# this program; if not, write to the Free Software Foundation, Inc.,
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# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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from __future__ import print_function, unicode_literals
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class AptBtrfsSnapshotError(Exception):
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class AptBtrfsNotSupportedError(AptBtrfsSnapshotError):
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class AptBtrfsRootWithNoatimeError(AptBtrfsSnapshotError):
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class FstabEntry(object):
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""" a single fstab entry line """
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def from_line(cls, line):
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args = line.partition("#")[0].split()
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# use only the first 7 args and ignore anything after them, mount
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# seems to do the same, see bug #873411 comment #7
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return FstabEntry(*args[0:6])
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def __init__(self, fs_spec, mountpoint, fstype, options, dump=0, passno=0):
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self.fs_spec = fs_spec
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self.mountpoint = mountpoint
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self.options = options
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return "<FstabEntry '%s' '%s' '%s' '%s' '%s' '%s'>" % (
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self.fs_spec, self.mountpoint, self.fstype,
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self.options, self.dump, self.passno)
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""" a list of FstabEntry items """
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def __init__(self, fstab="/etc/fstab"):
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super(Fstab, self).__init__()
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with open(fstab) as fstab_file:
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for line in (l.strip() for l in fstab_file):
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if line == "" or line.startswith("#"):
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entry = FstabEntry.from_line(line)
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class LowLevelCommands(object):
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""" lowlevel commands invoked to perform various tasks like
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interact with mount and btrfs tools
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def mount(self, fs_spec, mountpoint):
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ret = subprocess.call(["mount", fs_spec, mountpoint])
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def umount(self, mountpoint):
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ret = subprocess.call(["umount", mountpoint])
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def btrfs_subvolume_snapshot(self, source, dest):
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ret = subprocess.call(["btrfs", "subvolume", "snapshot",
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def btrfs_delete_snapshot(self, snapshot):
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ret = subprocess.call(["btrfs", "subvolume", "delete", snapshot])
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class AptBtrfsSnapshot(object):
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""" the high level object that interacts with the snapshot system """
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SNAP_PREFIX = "@apt-snapshot-"
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# backname when changing
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BACKUP_PREFIX = SNAP_PREFIX+"old-root-"
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def __init__(self, fstab="/etc/fstab"):
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self.fstab = Fstab(fstab)
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self.commands = LowLevelCommands()
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self._btrfs_root_mountpoint = None
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def snapshots_supported(self):
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""" verify that the system supports apt btrfs snapshots
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by checking if the right fs layout is used etc
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# check for the helper binary
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if not os.path.exists("/sbin/btrfs"):
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entry = self._get_supported_btrfs_root_fstab_entry()
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def _get_supported_btrfs_root_fstab_entry(self):
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""" return the supported btrfs root FstabEntry or None """
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for entry in self.fstab:
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if (entry.mountpoint == "/" and
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entry.fstype == "btrfs" and
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"subvol=@" in entry.options):
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def _uuid_for_mountpoint(self, mountpoint, fstab="/etc/fstab"):
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""" return the device or UUID for the given mountpoint """
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for entry in self.fstab:
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if entry.mountpoint == mountpoint:
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def mount_btrfs_root_volume(self):
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uuid = self._uuid_for_mountpoint("/")
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mountpoint = tempfile.mkdtemp(prefix="apt-btrfs-snapshot-mp-")
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if not self.commands.mount(uuid, mountpoint):
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self._btrfs_root_mountpoint = mountpoint
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return self._btrfs_root_mountpoint
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def umount_btrfs_root_volume(self):
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res = self.commands.umount(self._btrfs_root_mountpoint)
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os.rmdir(self._btrfs_root_mountpoint)
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self._btrfs_root_mountpoint = None
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def _get_now_str(self):
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return datetime.datetime.now().replace(microsecond=0).isoformat(str('_'))
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def create_btrfs_root_snapshot(self, additional_prefix=""):
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mp = self.mount_btrfs_root_volume()
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snap_id = self._get_now_str()
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res = self.commands.btrfs_subvolume_snapshot(
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os.path.join(mp, "@"),
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os.path.join(mp, self.SNAP_PREFIX+additional_prefix+snap_id))
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self.umount_btrfs_root_volume()
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def get_btrfs_root_snapshots_list(self, older_than=0):
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""" get the list of available snapshot
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If "older_then" is given (in unixtime format) it will only include
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snapshots that are older then the given date)
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# if older_than is used, ensure that the rootfs does not use
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entry = self._get_supported_btrfs_root_fstab_entry()
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raise AptBtrfsNotSupportedError()
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if "noatime" in entry.options:
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raise AptBtrfsRootWithNoatimeError()
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# if there is no older than, interpret that as "now"
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older_than = time.time()
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mp = self.mount_btrfs_root_volume()
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for e in os.listdir(mp):
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if e.startswith(self.SNAP_PREFIX):
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# fstab is read when it was booted and when a snapshot is
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# created (to check if there is support for btrfs)
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atime = os.path.getatime(os.path.join(mp, e, "etc", "fstab"))
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if atime < older_than:
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self.umount_btrfs_root_volume()
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def print_btrfs_root_snapshots(self):
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print("Available snapshots:")
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print(" \n".join(self.get_btrfs_root_snapshots_list()))
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def _parse_older_than_to_unixtime(self, timefmt):
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if not timefmt.endswith("d"):
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raise Exception("Please specify time in days (e.g. 10d)")
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days = int(timefmt[:-1])
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return now - (days * 24 * 60 * 60)
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def print_btrfs_root_snapshots_older_than(self, timefmt):
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older_than_unixtime = self._parse_older_than_to_unixtime(timefmt)
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print("Available snapshots older than '%s':" % timefmt)
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print(" \n".join(self.get_btrfs_root_snapshots_list(
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older_than=older_than_unixtime)))
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except AptBtrfsRootWithNoatimeError:
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sys.stderr.write("Error: fstab option 'noatime' incompatible with option")
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def clean_btrfs_root_snapshots_older_than(self, timefmt):
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older_than_unixtime = self._parse_older_than_to_unixtime(timefmt)
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for snap in self.get_btrfs_root_snapshots_list(
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older_than=older_than_unixtime):
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res &= self.delete_snapshot(snap)
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except AptBtrfsRootWithNoatimeError:
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sys.stderr.write("Error: fstab option 'noatime' incompatible with option")
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def command_set_default(self, snapshot_name):
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res = self.set_default(snapshot_name)
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print("Please reboot")
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def set_default(self, snapshot_name, backup=True):
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""" set new default """
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mp = self.mount_btrfs_root_volume()
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new_root = os.path.join(mp, snapshot_name)
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default_root = os.path.join(mp, "@")
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backup = os.path.join(mp, self.BACKUP_PREFIX+self._get_now_str())
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os.rename(default_root, backup)
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os.rename(new_root, default_root)
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self.umount_btrfs_root_volume()
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def delete_snapshot(self, snapshot_name):
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mp = self.mount_btrfs_root_volume()
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res = self.commands.btrfs_delete_snapshot(
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os.path.join(mp, snapshot_name))
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self.umount_btrfs_root_volume()
added
removed
DistUpgrade/apt_btrfs_snapshot.py
