syncthing/README-Docker.md

Docker Container for Syncthing

Use the Dockerfile in this repo, or pull the syncthing/syncthing image from Docker Hub.

Use the /var/syncthing volume to have the synchronized files available on the host. You can add more folders and map them as you prefer.

Note that Syncthing runs as UID 1000 and GID 1000 by default. These may be altered with the PUID and PGID environment variables. In addition the name of the Syncthing instance can be optionally defined by using --hostname=syncthing parameter.

To grant Syncthing additional capabilities without running as root, use the PCAP environment variable with the same syntax as that for setcap(8). For example, PCAP=cap_chown,cap_fowner+ep.

To set a different umask value, use the UMASK environment variable. For example UMASK=002.

Example Usage

Docker cli

$ docker pull syncthing/syncthing
$ docker run --network=host  -e STGUIADDRESS= \
    -v /wherever/st-sync:/var/syncthing \
    syncthing/syncthing:latest

Docker compose

---
version: "3"
services:
  syncthing:
    image: syncthing/syncthing
    container_name: syncthing
    hostname: my-syncthing
    environment:
      - PUID=1000
      - PGID=1000
      - STGUIADDRESS=
    volumes:
      - /wherever/st-sync:/var/syncthing
    network_mode: host
    restart: unless-stopped
    healthcheck:
      test: curl -fkLsS -m 2 127.0.0.1:8384/rest/noauth/health | grep -o --color=never OK || exit 1
      interval: 1m
      timeout: 10s
      retries: 3

Discovery

Please note that Docker's default network mode prevents local IP addresses from being discovered, as Syncthing can only see the internal IP address of the container on the 172.17.0.0/16 subnet. This would likely break the ability for nodes to establish LAN connections properly, resulting in poor transfer rates unless local device addresses are configured manually.

It is therefore strongly recommended to stick to the host network mode, as shown above.

Be aware that syncthing alone is now in control of what interfaces and ports it listens on. You can edit the syncthing configuration to change the defaults if there are conflicts.

GUI Security

By default Syncthing inside the Docker image listens on 0.0.0.0:8384. This allows GUI connections when running without host network mode. The example above unsets the STGUIADDRESS environment variable to have Syncthing fall back to listening on what has been configured in the configuration file or the GUI settings dialog. By default this is the localhost IP address 127.0.0.1. If you configure your GUI to be externally reachable, make sure you set up authentication and enable TLS.