btrfs-autosnapshot

btrfs-autosnapshot

#!/usr/bin/python3

import os
import datetime
import subprocess
import logging
import tempfile
import contextlib
from pathlib import Path

DEV = '/dev/mapper/ssd'
SYSROOT = Path('root')
SNAPSHOT_ROOT = Path('snapshots')
CLONE_NEWNS = 0x20000

logger = logging.getLogger(__name__)

def run_cmd(cmd):
  logger.debug('running cmd: %r', cmd)
  if cmd[0] == 'btrfs':
    subprocess.check_call(cmd, stdout=subprocess.DEVNULL)
  else:
    subprocess.check_call(cmd)

def may_snapshot(path, name, path_name):
  path = path.lstrip('/')
  dst = SNAPSHOT_ROOT / path_name / name

  if not dst.is_dir():
    dir = SNAPSHOT_ROOT / path_name
    if not dir.exists():
      dir.mkdir()

    src = SYSROOT / path
    cmd = ['btrfs', 'subvolume', 'snapshot', '-r',
           src, dst]
    run_cmd(cmd)

def cleanup(path, path_name, nkeep, suffix):
  snapshots = [x for x in (SNAPSHOT_ROOT / path_name).iterdir()
              if x.name.endswith(suffix)]
  snapshots.sort()
  logger.info('known snapshots for path %r (%r): %r',
              path, path_name, [str(x) for x in snapshots])

  locks = set()
  lockfile = os.path.join(SNAPSHOT_ROOT, 'snapshot.lock')
  try:
    with open(lockfile) as f:
      for l in f:
        name, path, snap = l.split()
        if path == path_name:
          locks.add(snap)
  except FileNotFoundError:
    pass

  to_remove = snapshots[:-nkeep]
  for path in to_remove:
    if path.name in locks:
      continue
    cmd = ['btrfs', 'subvolume', 'delete', path]
    run_cmd(cmd)

@contextlib.contextmanager
def setup():
  if hasattr(os, 'unshare'):
    os.unshare(os.CLONE_NEWNS)
  else:
    import ctypes
    libc = ctypes.CDLL('libc.so.6', use_errno=True)
    ret = libc.unshare(CLONE_NEWNS)
    if ret != 0:
      errno = ctypes.get_errno()
      raise OSError(errno, 'unshare failed')

  cmd = ['mount', '--make-rprivate', '/']
  run_cmd(cmd)

  cwd = os.getcwd()
  tmpdir = tempfile.mkdtemp(prefix='btrfs-snapshot-')

  cmd = ['mount', '-o', 'compress=zstd,subvol=/',
         DEV, tmpdir]
  run_cmd(cmd)

  os.chdir(tmpdir)
  yield

  os.chdir(cwd)
  cmd = ['umount', tmpdir]
  run_cmd(cmd)
  os.rmdir(tmpdir)

def main():
  import argparse
  parser = argparse.ArgumentParser(
    description = 'automatically keep snapshots for btrfs',
  )
  parser.add_argument('-n', '--nkeep', type=int,
                      help='keep n snapshots')
  parser.add_argument('-f', '--format', default='%Y-%m-%d-%H',
                      help='datetime format for snapshot names')
  parser.add_argument('filesystem', nargs='+',
                      help='filesystems to do snapshots')
  args = parser.parse_args()

  suffix = '-auto'
  dt = datetime.datetime.now()
  name = '{dt}{suffix}'.format(
    dt = dt.strftime(args.format), suffix = suffix)

  with setup():
    for path in sorted(args.filesystem):
      path_name = path.strip('/').replace('-', '--').replace('/', '-')

      if not path_name:
        path_name = '-'
      may_snapshot(path, name, path_name)

      if args.nkeep:
        cleanup(path, path_name, args.nkeep, suffix)

if __name__ == '__main__':
  import sys
  sys.path.append('/home/lilydjwg/scripts/python/pylib')
  from nicelogger import enable_pretty_logging
  enable_pretty_logging('DEBUG')
  # enable_pretty_logging('INFO')

  main()

yield
这样玩，学习了