Monitor a Synology Docker Stack

A Synology NAS ends up running more than it was bought for: a media server, a database, a couple of web applications, a reverse proxy, and a backup script nobody has checked since it was written. Container Manager will show you they exist. It will not tell you when one of them stops working.

Maintenant is a single container that adds the watching part.

Install through Container Manager

In Container Manager, create a Project, choose to paste a docker-compose file, and use:

services:
  maintenant:
    image: ghcr.io/kolapsis/maintenant:latest
    ports:
      - "9080:8080"
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - /proc:/host/proc:ro
      - /volume1/docker/maintenant:/data
    environment:
      MAINTENANT_ADDR: "0.0.0.0:8080"
      MAINTENANT_DB: "/data/maintenant.db"
    restart: unless-stopped

Three DSM-specific adjustments are baked into that file:

• Port 9080 on the host. DSM reserves a long list of ports and 8080 is frequently one of them. Any free high port works; the container still listens on 8080 internally.
• /volume1/docker/maintenant for data. Create the folder first, in the docker shared folder DSM already uses for container data. Adjust the volume number if yours differs.
• Socket access needs privilege. DSM restricts the Docker socket. The mount is read-only — Maintenant observes and never writes — but the container still needs enough privilege to open it, which Container Manager will prompt about.

Reach it at http://your-nas:9080. If you want it available outside the LAN, put it behind DSM’s reverse proxy with authentication, or a VPN. Maintenant ships no login of its own, deliberately.

What it covers on a NAS

• every container Container Manager runs: state, health checks, restart loops, logs;
• HTTP and TCP endpoints, including DSM services and anything else on the network;
• SSL/TLS certificate expiry, auto-detected from those endpoints — DSM’s own certificate renewals included, if you point a check at it;
• backup and cron deadlines, through heartbeat URLs, so a script that silently stopped running raises an alert instead of being discovered during a restore;
• per-container CPU, memory, network and disk metrics;
• image updates, by comparing registry digests against your running tags.

Resource cost

Maintenant is a single Go binary with an embedded frontend and SQLite as its only datastore — no Redis, no Postgres, no message queue. On a NAS whose RAM is mostly spoken for by the file system cache, that matters more than on a server.

Community is free and open source, covers the machine it runs on, and is the right starting point. If the NAS is one of several machines you watch, Personal reaches up to 20 of them for 149 € once, for life.