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Docker hosts

Most workloads in this homelab run on Kubernetes. A handful do not — and for those, plain Docker is the right tool. This page collects the ones that exist.

When Docker, when Kubernetes​

Use Docker hostUse Kubernetes
Single-node, single-purpose appliance (Syncthing, Home Assistant on a NAS)Anything multi-replica, multi-node, or with internal dependencies
Local dev / experimentation (k3d)Anything serving real users
Hardware that can't run Kubernetes (NAS app catalog, ARM SBCs)The two real clusters: Talos and K3s

The split is pragmatic — Kubernetes is the default; Docker hosts cover the cases where pulling in a whole cluster is overkill.

Synology DS723+ — Syncthing​

The Synology DS723+ hot-storage NAS runs Docker on its own engine through Synology's built-in Container Manager (the modern replacement for Synology Docker). One container is interesting:

  • Syncthing — runs continuously, replicating selected datasets between the homelab and the NAS. The NAS is the "hot" off-site target; Syncthing is the only continuous mover keeping the remote dataset live.

The Synology node sits on the home management VLAN at 192.168.0.5, and is a member of the home NetBird network — so the homelab clusters can reach Syncthing's REST API without it being publicly exposed.

# Container summary
services:
  syncthing:
    image: lscr.io/linuxserver/syncthing
    network_mode: host
    volumes:
      - /volume1/syncthing/config:/config
      - /volume1/syncthing/data:/data
    restart: unless-stopped

Why Docker and not in-cluster Syncthing? Because the NAS itself is the destination — running the agent on the box that owns the disks avoids a hop and keeps replication working even if the cluster is down.

k3d — local Kubernetes for development​

k3d wraps K3s in a Docker container, giving you a throwaway Kubernetes cluster on a workstation in seconds. Useful for:

  • Validating manifests before pushing to the real cluster.
  • Testing Renovate-bumped charts locally.
  • Reproducing a bug from production with a known image and config.

Quick start:

k3d cluster create \
  --volume /home/johnny/arr:/data \
  -p "30000-30010:30000-30010" \
  arr

The --volume mount and port range are placeholders — swap in whatever the test setup needs. k3d cluster delete arr when you're done.

Ansible-provisioned Docker hosts​

Any Linux host that needs the Docker engine is brought up to spec by the docker-host Ansible role. The role handles:

  • Engine + CLI install
  • Daemon defaults (storage-driver, log rotation)
  • The docker group + non-root membership

That same role is reusable for any future appliance — set the host's group to docker_hosts and apply.

Where to look next​

  • Hot storage (Synology) — physical context for the Syncthing host
  • Ansible — how Docker hosts are configured
  • K3s — when "almost-Kubernetes" is the right choice instead of plain Docker