Does ZFS allow for easy snapshotting like btrfs?

Absolutely

edit a filename while the file is open

Any Linux filesystem will do that

Yes, by staying privately funded and not throwing everything away chasing quarterly profits

Same, I don’t let Docker manage volumes for anything. If I need it to be persistent I bind mount it to a subdirectory of the container itself. It makes backups so much easier as well since you can just stop all containers, backup everything in ~/docker or wherever you put all of your compose files and volumes, and then restart them all.

It also means you can go hog wild with docker system prune -af --volumes and there’s no risk of losing any of your data.

I would separate the media and the Jellyfin image into different pools. Media would be a normal ZFS pool full of media files that gets mounted into any VM that needs it, like Jellyfin, sonarr, radarr, qbittorrent, etc. (preferably read-only mounted in Jellyfin if you’re going to expose Jellyfin to the internet).

As far as networking, from what I could see the only real change casaos was doing was mapping its dashboard to port 80, but not much more. Is there anything more I should be aware in general?

It depends on how you have things set up. If you’re just doing normal docker compose networking with port forwards then there shouldn’t be much to change, but if you’re doing anything more advanced like macvlan then you might have to set up taps on the host to be able to communicate with the container (not sure if CasaOS handles that automatically).

The nice thing about docker is all you need to do is backup your compose file, .env file, and mapped volumes, and you can easily restore on any other system. I don’t know much about CasaOS, but presumably you have the ability to stop your containers and access the filesystem to copy their config and mapped volumes elsewhere? If so this should be pretty easy. You might have some networking stuff to work out, but I suspect the rest should go smoothly and IMO would be a good move.

When self-hosting, the more you know about how things actually work, the easier it is to fix when something is acting up, and the easier it is to make known good backups and restore them.

Would you mind if I added this as a discussion (crediting you and this post!) in the github project?

Yeah that would be fine

Sure, it’s a bit hack-and-slash, but not too bad. Honestly the dockcheck portion is already pretty complete, I’m not sure what all you could add to improve it. The custom plugin I’m using does nothing more than dump the array of container names with available updates to a comma-separated list in a file. In addition to that I also have a wrapper for dockcheck which does two things:

1. dockcheck plugins only run when there’s at least one container with available updates, so the wrapper is used to handle cases when there are no available updates.
2. Some containers aren’t handled by dockcheck because they use their own management system, two examples are bitwarden and mailcow. The wrapper script can be modified as needed to support handling those as well, but that has to be one-off since there’s no general-purpose way to handle checking for updates on containers that insist on doing things in their own custom way.

Basically there are 5 steps to the setup:

1. Enable Prometheus metrics from Docker (this is just needed to get running/stopped counts, if those aren’t needed it can skipped). To do that, add the following to /etc/docker/daemon.json (create it if necessary) and restart Docker:

{
  "metrics-addr": "127.0.0.1:9323"
}

Once running, you should be able to run curl http://localhost:9323/metrics and see a dump of Prometheus metrics

2. Clone dockcheck, and create a custom plugin for it at dockcheck/notify.sh:

send_notification() {
Updates=("$@")
UpdToString=$(printf ", %s" "${Updates[@]}")
UpdToString=${UpdToString:2}

File=updatelist_local.txt

echo -n $UpdToString > $File
}

3. Create a wrapper for dockcheck:

#!/bin/bash

cd $(dirname $0)

./dockcheck/dockcheck.sh -mni

if [[ -f updatelist_local.txt ]]; then
  mv updatelist_local.txt updatelist.txt
else
  echo -n "None" > updatelist.txt
fi

At this point you should be able to run your script, and at the end you’ll have the file “updatelist.txt” which will either contain a comma-separated list of all containers with available updates, or “None” if there are none. Add this script into cron to run on whatever cadence you want, I use 4 hours.

4. The main Python script:

#!/usr/bin/python3

from flask import Flask, jsonify

import os
import time
import requests
import json

app = Flask(__name__)

# Listen addresses for docker metrics
dockerurls = ['http://127.0.0.1:9323/metrics']

# Other dockerstats servers
staturls = []

# File containing list of pending updates
updatefile = '/path/to/updatelist.txt'

@app.route('/metrics', methods=['GET'])
def get_tasks():
  running = 0
  stopped = 0
  updates = ""

  for url in dockerurls:
      response = requests.get(url)

      if (response.status_code == 200):
        for line in response.text.split("\n"):
          if 'engine_daemon_container_states_containers{state="running"}' in line:
            running += int(line.split()[1])
          if 'engine_daemon_container_states_containers{state="paused"}' in line:
            stopped += int(line.split()[1])
          if 'engine_daemon_container_states_containers{state="stopped"}' in line:
            stopped += int(line.split()[1])

  for url in staturls:
      response = requests.get(url)

      if (response.status_code == 200):
        apidata = response.json()
        running += int(apidata['results']['running'])
        stopped += int(apidata['results']['stopped'])
        if (apidata['results']['updates'] != "None"):
          updates += ", " + apidata['results']['updates']

  if (os.path.isfile(updatefile)):
    st = os.stat(updatefile)
    age = (time.time() - st.st_mtime)
    if (age < 86400):
      f = open(updatefile, "r")
      temp = f.readline()
      if (temp != "None"):
        updates += ", " + temp
    else:
      updates += ", Error"
  else:
    updates += ", Error"

  if not updates:
    updates = "None"
  else:
    updates = updates[2:]

  status = {
    'running': running,
    'stopped': stopped,
    'updates': updates
  }
  return jsonify({'results': status})

if __name__ == '__main__':
  app.run(host='0.0.0.0')

The neat thing about this program is it’s nestable, meaning if you run steps 1-4 independently on all of your Docker servers (assuming you have more than one), then you can pick one of the machines to be the “master” and update the “staturls” variable to point to the other ones, allowing it to collect all of the data from other copies of itself into its own output. If the output of this program will only need to be accessed from localhost, you can change the host variable in app.run to 127.0.0.1 to lock it down. Once this is running, you should be able to run curl http://localhost:5000/metrics and see the running and stopped container counts and available updates for the current machine and any other machines you’ve added into “staturls”. You can then turn this program into a service or launch it @reboot in cron or in /etc/rc.local, whatever fits with your management style to start it up on boot. Note that it does verify the age of the updatelist.txt file before using it, if it’s more than a day old it likely means something is wrong with the dockcheck wrapper script or similar, and rather than using the output the REST API will print “Error” to let you know something is wrong.

5. Finally, the Homepage custom API to pull the data into the dashboard:

        widget:
          type: customapi
          url: http://localhost:5000/metrics
          refreshInterval: 2000
          display: list
          mappings:
            - field:
                results: running
              label: Running
              format: number
            - field:
                results: stopped
              label: Stopped
              format: number
            - field:
                results: updates
              label: Updates

Personally, I just have a couple of cheap CyberPower UPSs for my servers. I know I know, but I’m waiting for them to get old and die before I replace them with something better. My modem, router, and primary WiFi AP are on a custom LiFePO4-based UPS that I designed and built, because I felt like it. It’ll keep them running for around 10 hours, long past everything else in the house has shut down.

Anything on a separate disk can be simply remounted after reinstalling the OS. It doesn’t have to be a NAS, DAS, RAID enclosure, or anything else that’s external to the machine unless you want it to be. Actually it looks like that Beelink only supports a single NVMe disk and doesn’t have SATA, so I guess it does have to be external to the machine, but for different reasons than you’re alluding to.

This is a great tool, thanks for the continued support.

Personally, I don’t actually use dockcheck to perform updates, I only use it for its update check functionality, along with a custom plugin which, in cooperation with a python script of mine, serves a REST API that lists all containers on all of my systems with available updates. That then gets pulled into homepage using their custom API function to make something like this: https://imgur.com/a/tAaJ6xf

So at a glance I can see any containers that have updates available, then I can hop into Dockge to actually apply them on my own schedule.