zfs-backup/zfs-backup.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

from __future__ import annotations

import os
from subprocess import Popen, PIPE, check_output
import config
from sys import exit
import re


"""
Erstes Backup muss für alle notwendigen Datasets durchgeführt werden mit
# zfs send -Rv rpool/ROOT@zfs-auto-snap_daily-2018-06-14-1648 | zfs receive -dvF backup1
"""


class Command:
    def __init__(self, command, strict=True):
        process = Popen(command, stdout=PIPE)
        self.stdout, self.stderr = process.communicate()
        self.exit_code = process.wait()
        if strict and self.exit_code != 0:
            raise Exception("Kritisches Kommando fehlgeschlagen. Breche ab.")


def find_backup_pool():
    print("Suche nach externer Festplatte für Backups")
    present_uuids = Command(["ls", "/dev/disk/by-uuid"])
    for key in list(config.backup_pool.keys()):
        uuid = config.backup_pool[key]
        if uuid in present_uuids.stdout.decode():
            print("Gefundene Platte: " + key)
            return key
    else:
        raise IOError("Konnte keine Backup-Platte finden!")


class Dataset:
    def __init__(self, name: str):
        self.name = name

    def __repr__(self):
        return self.name

    @classmethod
    def from_local_pool(cls) -> list[Dataset]:
        datasets_str = (
            Command([config.ZFS, "list", "-H", "-d", "1", "-o", "name", config.local_pool])
                .stdout.strip()
                .decode()
        )
        # we omit the first return value, which is the pool, not the dataset
        datasets_list = datasets_str.split("\n")[1:]
        to_backup = [Dataset(d) for d in datasets_list if d not in config.do_not_backup]
        print("Folgende Datasets und alle darunter befindlichen Kinder werden gesichert:")
        for item in to_backup:
            print("  " + str(item))
        return to_backup


def get_snapshots(pool):
    return (
        Command([config.ZFS, "list", "-r", "-t", "snapshot", "-o", "name", "-H", pool])
        .stdout.strip()
        .decode()
        .split("\n")
    )


def last_snapshot(pool):
    snapshots = get_snapshots(pool)
    # check if the snapshot_tags appear in the snapshot name in order they are provided
    relevant = [
        s for s in snapshots if re.search("@" + ".*".join(config.snapshot_tag), s)
    ]
    # sort chronologically
    relevant.sort()
    # the most recent snapshot is the last one
    try:
        last_entry = relevant[-1]
    # didn't find any snapshots at all
    except IndexError:
        return
    last_snapshot = last_entry.strip().split("@")[-1]
    return last_snapshot


def export_pool(pool):
    container_name = "crypt-" + pool
    print("Exportiere Pool " + pool)
    Command([config.ZPOOL, "export", pool])
    print("Schließe verschlüsselten Container")
    Command([config.CRYPTSETUP, "close", container_name])
    print("Fertig!")
    print("Sie können die externe Festplatte jetzt entfernen.")


def import_pool(pool):
    uuid = config.backup_pool[pool]
    container_name = "crypt-" + pool
    present_mappers = Command(["ls", "/dev/mapper/"]).stdout.decode().strip()
    if container_name in present_mappers:
        msg = (
            "verschlüsselter Container "
            + container_name
            + " scheint bereits in Verwendung zu sein. Breche ab."
        )
        raise Exception(msg)
    print("Öffne verschlüsselten Container\n")
    Command([config.CRYPTSETUP, "open", "/dev/disk/by-uuid/" + uuid, container_name])
    print("")
    print("Importiere Pool " + pool)
    # -N: no mount
    # -d: directory to search the pool in
    Command([config.ZPOOL, "import", "-N", "-d", "/dev/mapper", pool])


def present_locally(snapshot):
    local_snapshots = get_snapshots(config.local_pool)
    for each_snapshot in local_snapshots:
        if snapshot in each_snapshot:
            return True
    else:
        return False


def do_backup(dataset, last_local_snapshot, last_remote_snapshot, backup_pool):
    print("Sichere Dataset " + dataset)
    # print(dataset, last_local_snapshot, backup_pool, last_remote_snapshot)
    # return
    if not snapshot_present_in_dataset(dataset, last_remote_snapshot, backup_pool):
        print("  Dieses Dataset wurde nicht zur Sicherung eingerichtet.")
        print("  Verwende ein Kommando in der Art")
        print(
            "  # zfs send -Rv rpool/[DATASET]@zfs-auto-snap_daily-yyyy-mm-dd-hhmm | zfs receive -dvF backupN"
        )
        return
    if last_local_snapshot == last_remote_snapshot:
        print(
            "  Letzter lokaler Snapshot ist identisch mit letzten entferntem Snapshot"
        )
        print("  Führe kein Backup für dieses Dataset durch")
        return
    send = Popen(
        [
            config.ZFS,
            "send",
            "-R",
            "-I",
            last_remote_snapshot,
            dataset + "@" + last_local_snapshot,
        ],
        stdout=PIPE,
    )
    # -d  Discard the first element of the sent snapshot's file system name
    # -F  Force a rollback of the file system to the most recent snapshot before performing the receive operation.
    # -u  File system that is associated with the received stream is not mounted.
    check_output([config.ZFS, "receive", "-d", "-F", "-u", backup_pool], stdin=send.stdout)
    exit_code = send.wait()
    if exit_code != 0:
        raise Exception("Kritisches Kommando fehlgeschlagen. Breche ab.")


def snapshot_present_in_dataset(dataset, last_snapshot, pool):
    snapshots = get_snapshots(pool)
    # get just the dataset name without the pool
    actual_dataset = dataset.split("/")[-1]
    for snapshot in snapshots:
        if (actual_dataset + "@" + last_snapshot) in snapshot:
            return True
    else:
        return False


def clean_old_snapshots(dataset, pool):
    snapshots = get_snapshots(pool)  # full name like 'pool/dataset@snapshot'
    # get just the dataset name without the pool
    actual_dataset = dataset.split("/")[-1]
    # print('actual_dataset', actual_dataset)
    for interval in config.keep.keys():
        # print('interval', interval)
        # e.g. 'data@zfs-auto-snap_daily', 'ubuntu@zfs-auto-snap_hourly', ...
        pattern = actual_dataset + "@" + config.snapshot_tag[0] + ".*" + interval
        snapshots_in_interval = []
        for snapshot in snapshots:
            result = re.search(pattern, snapshot)
            if result is not None:
                snapshots_in_interval.append(snapshot)
        snapshots_in_interval.sort()
        for i in range(len(snapshots_in_interval) - config.keep[interval]):
            to_delete = snapshots_in_interval[i]
            print("  Lösche veralteten Snapshot {}".format(to_delete))
            zfs_destroy(to_delete, recursive=True)


def zfs_destroy(full_name, recursive=False):
    if config.local_pool in full_name:
        msg = "Wollte in falschem Pool löschen! Dies sollte niemals passieren! Abbruch!"
        raise Exception(msg)
    else:
        cmdline = [config.ZFS, "destroy"]
        if recursive:
            cmdline.append("-r")
        cmdline.append(full_name)
        Command(cmdline)


def main():
    verify_running_as_root()
    datasets = Dataset.from_local_pool()
    backup_pool = find_backup_pool()
    import_pool(backup_pool)
    try:
        send_datasets_to_backup_pool(backup_pool, datasets)
    finally:
        export_pool(backup_pool)


def send_datasets_to_backup_pool(backup_pool, datasets):
    last_local_snapshot = last_snapshot(config.local_pool)
    if not last_local_snapshot:
        print("Es scheint keine Snapshots im Speicherpool zu geben")
        print("Breche ab.")
        export_pool(backup_pool)
        exit()
    last_remote_snapshot = last_snapshot(backup_pool)
    if not last_remote_snapshot:
        print("Es scheint keine Snapshots auf der Backup-Festplatte zu geben")
        print("Breche ab.")
        export_pool(backup_pool)
        exit()
    if not present_locally(last_remote_snapshot):
        print(
            """
Kann keine inkrementelle Sicherung durchführen, da es im Backup und auf dem Server
keinen gemeinsamen Snapshot gibt. Vermutlich wurde diese externe Festplatte vor
zu langer Zeit das letzte mal als Backup verwendet"""
        )
        return
    for dataset in datasets:
        do_backup(dataset, last_local_snapshot, last_remote_snapshot, backup_pool)
        clean_old_snapshots(dataset, backup_pool)


def verify_running_as_root():
    if os.getuid() > 0:
        print("Muss als root ausgeführt werden.")
        exit(1)


if __name__ == "__main__":
    main()