Mapping container volumes on Synology NAS

Portainer is a must-have if you’re running a homelab. Mine is running on Synology NAS. It’s not a normal desktop, so there are a few quirks I need to work around.

One of them is volumes mapping in docker.

If you inspect a docker volume on your local machine, you will see something like

    [
        {
            "CreatedAt": "2022-04-21T21:42:30+02:00",
            "Driver": "local",
            "Labels": null,
            "Mountpoint": "/var/lib/docker/volumes/123/_data",
            "Name": "123",
            "Options": null,
            "Scope": "local"
        }
    ]

As you can see, the mountpoint starts with /var/lib/docker/volumes. Now do the same on your Synology NAS

[
    {
        "CreatedAt": "2022-04-22T22:28:50+02:00",
        "Driver": "local",
        "Labels": null,
        "Mountpoint": "/volume1/@docker/volumes/123/_data",
        "Name": "123",
        "Options": null,
        "Scope": "local"
    }
]

The mountpoint startswith /volume1/@docker/volumes! Not only that, but you need to select the correct volume. I’m running RAID 1 so I have only volume1 at my disposal.

At last, my docker-compose file looks like this

version: "3.8"
services:
  portainer:
    image: portainer/portainer-ce:2.11.1
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - /volume1/@docker/volumes:/var/lib/docker/volumes
      - portainer_data:/data
    env_file:
      - .env
    container_name: portainer
    restart: unless-stopped
    security_opt:
      - no-new-privileges:true

volumes:
  portainer_data:

To recap, the correct volumes mapping on Synology NAS is /volume1/@docker/volumes:/var/lib/docker/volumes. If you wanted to map the entire /var/lib/docker instead, just drop volumes, so /volume1/@docker:/var/lib/docker.