FreedomBox/actions/snapshot

#!/usr/bin/python3
#
# This file is part of FreedomBox.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
"""
Configuration helper for filesystem snapshots.
"""

import argparse
import json
import os
import signal
import subprocess

import augeas
import dbus

FSTAB = '/etc/fstab'
AUG_FSTAB = '/files/etc/fstab'
DEFAULT_FILE = '/etc/default/snapper'


def parse_arguments():
    """Return parsed command line arguments as dictionary."""
    parser = argparse.ArgumentParser()
    subparsers = parser.add_subparsers(dest='subcommand', help='Sub command')

    subparser = subparsers.add_parser('setup', help='Configure snapper')
    subparser.add_argument(
        '--old-version', type=int, required=True,
        help='Earlier version of the app that is already setup.')
    subparsers.add_parser('list', help='List snapshots')
    subparsers.add_parser('create', help='Create snapshot')
    subparsers.add_parser('get-config', help='Configurations of snapshot')

    subparser = subparsers.add_parser('delete',
                                      help='Delete a snapshot by number')
    subparser.add_argument('number', help='Number of snapshot to delete')

    subparser = subparsers.add_parser('delete-all',
                                      help='Delete all the snapshots')

    subparser = subparsers.add_parser('set-config',
                                      help='Configure automatic snapshots')
    subparser.add_argument('config')
    subparsers.add_parser('kill-daemon',
                          help='Kill snapperd to reload configuration')

    subparser = subparsers.add_parser('rollback', help='Rollback to snapshot')
    subparser.add_argument('number', help='Number of snapshot to rollback to')

    subparser = subparsers.add_parser('disable-apt-snapshot',
                                      help='enable/disable apt snapshots')
    subparser.add_argument('state')

    subparsers.required = True
    return parser.parse_args()


def subcommand_setup(arguments):
    """Configure snapper."""
    # Check if root config exists.
    command = ['snapper', 'list-configs']
    process = subprocess.run(command, stdout=subprocess.PIPE, check=True)
    output = process.stdout.decode()

    # Create root config if needed.
    if 'root' not in output:
        command = ['snapper', 'create-config', '/']
        subprocess.run(command, check=True)

    _add_fstab_entry('/')
    if arguments.old_version == 0:
        _set_default_config()
    elif arguments.old_version <= 3:
        _migrate_config_from_version_3()
    else:
        pass  # After version 4 and above don't reset configuration


def _migrate_config_from_version_3():
    """Upgrade configuration from version <=3.

    - This configuration was not using ranges for limits which would make free
      space setting unused.
    - Force set yes to cleanups.
    - Reset all number cleanup settings.
    - Make free space setting 30% by default instead of 20%.

    """
    config = _get_config()

    def convert_to_range(key):
        value = config[key]
        value = value if '-' in value else '0-{}'.format(value)
        return '{}={}'.format(key, value)

    command = [
        'snapper',
        'set-config',
        'TIMELINE_CLEANUP=yes',
        'TIMELINE_MIN_AGE=0',
        convert_to_range('TIMELINE_LIMIT_HOURLY'),
        convert_to_range('TIMELINE_LIMIT_DAILY'),
        convert_to_range('TIMELINE_LIMIT_WEEKLY'),
        convert_to_range('TIMELINE_LIMIT_MONTHLY'),
        convert_to_range('TIMELINE_LIMIT_YEARLY'),
        'NUMBER_CLEANUP=yes',
        'NUMBER_MIN_AGE=0',
        'NUMBER_LIMIT=0-100',
        'NUMBER_LIMIT_IMPORTANT=0-20',
        'EMPTY_PRE_POST_MIN_AGE=0',
        'FREE_LIMIT=0.3',
    ]
    subprocess.run(command, check=True)


def _set_default_config():
    command = [
        'snapper',
        'set-config',
        'TIMELINE_CLEANUP=yes',
        'TIMELINE_CREATE=yes',
        'TIMELINE_MIN_AGE=0',
        'TIMELINE_LIMIT_HOURLY=0-10',
        'TIMELINE_LIMIT_DAILY=0-3',
        'TIMELINE_LIMIT_WEEKLY=0-2',
        'TIMELINE_LIMIT_MONTHLY=0-2',
        'TIMELINE_LIMIT_YEARLY=0-0',
        'NUMBER_CLEANUP=yes',
        'NUMBER_MIN_AGE=0',
        'NUMBER_LIMIT=0-100',
        'NUMBER_LIMIT_IMPORTANT=0-20',
        'EMPTY_PRE_POST_MIN_AGE=0',
        'FREE_LIMIT=0.3',
    ]
    subprocess.run(command, check=True)


def _add_fstab_entry(mount_point):
    """Add mountpoint for subvolumes."""
    snapshots_mount_point = os.path.join(mount_point, '.snapshots')

    aug = augeas.Augeas(flags=augeas.Augeas.NO_LOAD +
                        augeas.Augeas.NO_MODL_AUTOLOAD)
    aug.set('/augeas/load/Fstab/lens', 'Fstab.lns')
    aug.set('/augeas/load/Fstab/incl[last() + 1]', FSTAB)
    aug.load()

    spec = None
    for entry in aug.match(AUG_FSTAB + '/*'):
        entry_mount_point = aug.get(entry + '/file')
        if entry_mount_point == snapshots_mount_point:
            return

        if entry_mount_point == mount_point and \
           aug.get(entry + '/vfstype') == 'btrfs':
            spec = aug.get(entry + '/spec')

    if spec:
        aug.set(AUG_FSTAB + '/01/spec', spec)
        aug.set(AUG_FSTAB + '/01/file', snapshots_mount_point)
        aug.set(AUG_FSTAB + '/01/vfstype', 'btrfs')
        aug.set(AUG_FSTAB + '/01/opt', 'subvol')
        aug.set(AUG_FSTAB + '/01/opt/value', '.snapshots')
        aug.set(AUG_FSTAB + '/01/dump', '0')
        aug.set(AUG_FSTAB + '/01/passno', '1')
        aug.save()


def _get_snapper_list():
    command = ['snapper', 'list']
    process = subprocess.run(command, stdout=subprocess.PIPE, check=True)
    return process.stdout.decode().splitlines()


def subcommand_list(_):
    """List snapshots."""
    lines = _get_snapper_list()
    keys = ('number', 'type', 'pre_number', 'date', 'user', 'cleanup',
            'description')
    snapshots = []
    for line in lines[2:]:
        parts = [part.strip('* ') for part in line.split('|')]
        snapshots.append(dict(zip(keys, parts)))

    default = _get_default_snapshot()
    for snapshot in snapshots:
        snapshot['is_default'] = (snapshot['number'] == default)

    snapshots.reverse()
    print(json.dumps(snapshots))


def _get_default_snapshot():
    """Return the default snapshot by looking at default subvolume."""
    command = ['btrfs', 'subvolume', 'get-default', '/']
    process = subprocess.run(command, stdout=subprocess.PIPE, check=True)
    output = process.stdout.decode()

    output_parts = output.split()
    if len(output_parts) >= 9:
        path = output.split()[8]
        path_parts = path.split('/')
        if len(path_parts) == 3 and path_parts[0] == '.snapshots':
            return path_parts[1]

    return None


def subcommand_disable_apt_snapshot(arguments):
    """Set flag to Enable/Disable apt software snapshots in config files"""
    # Initialize Augeas
    aug = augeas.Augeas(flags=augeas.Augeas.NO_LOAD +
                        augeas.Augeas.NO_MODL_AUTOLOAD)
    aug.set('/augeas/load/Shellvars/lens', 'Shellvars.lns')
    aug.set('/augeas/load/Shellvars/incl[last() + 1]', DEFAULT_FILE)
    aug.load()

    aug.set('/files' + DEFAULT_FILE + '/DISABLE_APT_SNAPSHOT', arguments.state)
    aug.save()


def subcommand_create(_):
    """Create snapshot."""
    command = ['snapper', 'create', '--description', 'manually created']
    subprocess.run(command, check=True)


def subcommand_delete(arguments):
    """Delete a snapshot by number."""
    command = ['snapper', 'delete', arguments.number]
    subprocess.run(command, check=True)


def subcommand_delete_all(_):
    """Delete all the snapshots (except the active one)."""
    lines = _get_snapper_list()
    snapshot_range = [line.split('|')[0].strip() for line in lines[3:]]
    default_snapshot = _get_default_snapshot()
    if snapshot_range:
        if default_snapshot:
            index = snapshot_range.index(default_snapshot)
            range_before = snapshot_range[:index]
            range_after = snapshot_range[index + 1:]
            to_delete = [range_before, range_after]
        else:
            to_delete = [snapshot_range]

        delete_args = filter(None, map(_get_delete_arg, to_delete))
        for arg in delete_args:
            subprocess.run(['snapper', 'delete', arg], check=True)


def _get_delete_arg(range_list):
    """Return 'a-b' when given ['a', ..., 'b']."""
    if not range_list:
        return None
    elif len(range_list) == 1:
        return range_list[0]
    else:
        return range_list[0] + '-' + range_list[-1]


def subcommand_set_config(arguments):
    command = ['snapper', 'set-config'] + arguments.config.split()
    subprocess.run(command, check=True)


def _get_config():
    command = ['snapper', 'get-config']
    process = subprocess.run(command, stdout=subprocess.PIPE, check=True)
    lines = process.stdout.decode().splitlines()
    config = {}
    for line in lines[2:]:
        parts = [part.strip() for part in line.split('|')]
        config[parts[0]] = parts[1]
    return config


def subcommand_get_config(_):
    config = _get_config()
    print(json.dumps(config))


def subcommand_kill_daemon(_):
    """Kill the snapper daemon.

    This is generally not necessary because we do configuration changes via
    snapperd. However, when the configuration is restored from a backup. We
    need to kill the daemon to reload configuration.

    Ideally, we should be able to reload/terminate the service using systemd.

    """
    bus = dbus.SystemBus()

    dbus_object = bus.get_object('org.freedesktop.DBus', '/')
    dbus_interface = dbus.Interface(dbus_object,
                                    dbus_interface='org.freedesktop.DBus')
    try:
        pid = dbus_interface.GetConnectionUnixProcessID('org.opensuse.Snapper')
    except dbus.exceptions.DBusException:
        pass
    else:
        os.kill(pid, signal.SIGTERM)


def subcommand_rollback(arguments):
    """Rollback to snapshot."""
    command = [
        'snapper', 'rollback', '--description', 'created by rollback',
        arguments.number
    ]
    subprocess.run(command, check=True)


def main():
    """Parse arguments and perform all duties."""
    arguments = parse_arguments()

    subcommand = arguments.subcommand.replace('-', '_')
    subcommand_method = globals()['subcommand_' + subcommand]
    subcommand_method(arguments)


if __name__ == '__main__':
    main()