Docker Syncthing

This is a Dockerfile to set up Syncthing.

Mount any desired directories to sync using -v <host_dir>:<host_dir> when running the container. The config/logging directory will live in a data-only volume (/config). We have to either run Syncthing using supervisord to allow Syncthing to restart itself without killing off the container or using an external container manager like systemd to restart the container after Syncthing restarts.

Build

Create config volume and set permissions:

# docker run -v /config --name syncthing_config ubuntu chown -R 22000 /config

Decide which version of the Dockerfile to use: use the default version if you have an external container manager like systemd that will restart the container automatically when Syncthing restarts. Otherwise use the .supervisord version.

Update Syncthing version to latest values in the Dockerfile, update desired <username> in the Dockerfile and supervisord.conf.

NOTE: the userid of the <username> you select will not necessarily match the username on your host if the UID isn't the same. If you need it to match, add the '-uid xxxx' option to the useradd command in the Dockerfile.

If you want to run Syncthing as root, remove the 'user=' line from supervisord.conf and comment out the 'useradd' and the 'USER' line in the Dockerfile.

# docker build -t syncthing .

Run

Systemd service file available. Edit to enable or disable 'host' networking as necessary for local discovery needs.

# docker run -d --net='host' -v /mnt/media:/mnt/media --volumes-from syncthing_config -p 22000:22000 -p 8384:8384 -p 21027:21027/udp --name syncthing_run syncthing

Local Discovery

Local discovery between nodes will not work unless the container is run with 'host' networking instead of the default 'bridge' networking. Enable 'host' networking by adding --net=host to the docker run line.

See here for precautions when running the container with 'host' networking.

If you are running an nginx reverse-proxy inside a container on the same host to redirect traffic to the syncthing GUI (e.g. syncthing.myip.net -> <containerIP:GUIport>), you will not be able to run syncthing in 'host' networking mode and still have it accessible via the reverse proxy. At least not without some more complex configuring!