Fix encrypted dataset restore and make backup cron setting optional

[rdelcorro]

• As stated in the docs, the cron config should be optional. When not providing a cron config, it was crashing on backup as its dereferenced in the add_job call.

• The tool was correctly using the raw method to upload the send binary but on receive / restore, it was first creating a datastore and then forcing a rewrite with the -F flag. This poses a problem on encrypted datasets as you can't restore with -F. See zfs receive -F cannot be used to destroy an encrypted filesystem openzfs/zfs#6793 for more information. This change removes the -F but also does not create the dataset, which should be fine as receive would do that anyways. Tested on encrypted datasets and now its working

[ddebeau]

Thank you for the contribution!

I added the -F option to fix an issue where the restore would fail if data had been written to the file system since the most recent snapshot. #33

I'll have to look into your issue in more detail. It may be worth adding some tests that replicate #33 and the encrypted restore issue.

[rdelcorro]

I can try to add the test for the encrypted case, but this is basically the workflow:

zfs create -o encryption=on -o keylocation=prompt -o keyformat=passphrase ztest/sourceenc
touch /ztest/sourceenc/file

In the config, set this up:
[ztest/sourceenc]
max_snapshots = 7
max_incremental_backups_per_full = 6
max_backups = 7

zfsup backup
zfsup restore ztest/sourceenc --destination ztest/destenc (this datastore does not exist)

result:

root@rover:/etc/zfs_uploader# zfsup restore ztest/sourceenc --destination ztest/destenc
time=2023-01-18T04:25:48.286 level=INFO file_path=config.cfg msg="Loading configuration file."
time=2023-01-18T04:25:48.772 level=INFO filesystem=ztest/destenc snapshot_name=20230118_042500 s3_key=ztest/sourceenc/20230118_042500.full msg="Restoring snapshot."
Traceback (most recent call last):
  File "/usr/local/sbin/zfsup", line 8, in <module>
    sys.exit(cli())
  File "/etc/zfs_uploader/env/lib/python3.10/site-packages/click/core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
  File "/etc/zfs_uploader/env/lib/python3.10/site-packages/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "/etc/zfs_uploader/env/lib/python3.10/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/etc/zfs_uploader/env/lib/python3.10/site-packages/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/etc/zfs_uploader/env/lib/python3.10/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/etc/zfs_uploader/env/lib/python3.10/site-packages/click/decorators.py", line 26, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/etc/zfs_uploader/env/lib/python3.10/site-packages/zfs_uploader/__main__.py", line 135, in restore
    job.restore(backup_time, destination)
  File "/etc/zfs_uploader/env/lib/python3.10/site-packages/zfs_uploader/job.py", line 265, in restore
    self._restore_snapshot(backup, filesystem)
  File "/etc/zfs_uploader/env/lib/python3.10/site-packages/zfs_uploader/job.py", line 413, in _restore_snapshot
    raise ZFSError(stderr)
zfs_uploader.zfs.ZFSError: cannot receive new filesystem stream: zfs receive -F cannot be used to destroy an encrypted filesystem or overwrite an unencrypted one with an encrypted one

Should we consider adding a boolean flag to the restore operation to pass in the -F like (--force)? Restoring on top of a dataset that has changes would indeed cause data loss

[ddebeau]

@rdelcorro Could you merge in master? The zfs receive -F issues should be resolved now.

[rdelcorro]

@ddebeau code is now merged. Thanks!

[ddebeau]

Just a couple quick fixes and the PR should be ready to merge.

[rdelcorro]

Corrected the comments. Feel free to merge when possible. I do not seem to have the ability to do so. Do you know why tests are failing?

[ddebeau]

I don't think your PR has access to the secrets required to run the tests. I'll run the tests before I make a release. Thank you for your help!

[ddebeau]

@rdelcorro Just made the release:
https://github.com/ddebeau/zfs_uploader/releases/tag/0.8.1

[rdelcorro]

Thanks, I will test it out