Names are wacky. This is for my personal use, so it's not exactly
config-file-ified. Just edit the scripts. For the record, my setup is:

  * macOS laptop running OpenZFSonOSX that houses a zpool for my home
    directory on a Core Storage encrypted volume.

      hostname: dialga
      pool: zhome
      filesystems: bjc

  * FreeBSD NAS which accepts snapshots from macOS laptop for backup
    purposes, as well as housing long-term archival stuff (music,
    random software, movies, etc.,) on a 5 drive RAIDZ1 setup.

      hostname: ditto
      pool: babar
      filesystems: bjc (unmounted snapshots from zhome)
                   shared (media)
                   various snapshots from when I was moving data
                   around that I haven't needed to delete yet.

  * External USB drive for full backup of RAIDZ1 pool from FreeBSD NAS
    (or, at least as much of the most recent data it can get once it
    fills up).

      hostname: ditto
      pool: backup
      filesystems: all of the above (unmounted snapshots)

Permissions on zhome:
Local+Descendent permissions:
	user bjc compression,create,hold,mount,mountpoint,receive,send,snapshot
Permissions on babar/bjc:
Local+Descendent permissions:
	user bjc compression,create,hold,mount,mountpoint,receive,send,snapshot

It's a good idea to run send-to-babar before running cull-snapshots,
because only the most recent snapshot is kept after a run of
send-backup, so if you accidentally delete that snapshot from the NAS,
you're going to have a bad time. At some point this should migrate to
bookmarks, rather than snapshots, so that's no longer possible, but I
haven't done that yet. I probably will after I screw up following my
own instructions and hate my life for a week.

cull-snapshots tries to be Time Machine like, and keep hourly
snapshots for 24 hours, then daily snapshots for a month, then go
weekly forever. There's no logic for removing old weekly snapshots,
because I've never come close to running out of space, so it can just
be done by hand.

send-backup is used approximately once per week or so, when I plug in
an external USB drive to sync it up with the NAS, in case of
catastrophic NAS failure. Scrubs are run approximately every month on
both the NAS and the USB.

Locations for files:

On Mac:
  * com.kublai.zfs.make-snapshot.plist -> ~/Library/LaunchAgents
  * make-snapshot -> wherever it's referenced by launch agent .plist
  * send-to-babar -> somewhere in $PATH

On NAS:
  * zbackup.pl, zdest.pl, cull-snapshots send-backup -> /usr/local/bin