Syncthing on Ubuntu

Last month, after looking at BitTorrent Sync and realizing it was encrypted and private, but not open source, I went digging for an alternative. I found the perfect project, for me: Syncthing. The project is still relatively young and while it has proven to be perfectly functional, it did not come with batteries included – an installer package. It does come with init scripts for some environments, but not for Ubuntu – at least until Ubuntu transitions to systemd. So, without further ado, here’s what I did to install Syncthing as daemon (service) under Ubuntu.

There’s nothing out of the ordinary about installing Syncthing as a service. Above are the details I chose for how I’d install the service. There are two points are worth noting. First, after the initial install the service’s configuration is editable through the web-gui; the XML config will be in /opt/syncthing/etc. Second, sync-able repositories do not have to live in the installation directory. Installing is mostly about creating the extra fluff needed to have init start the binary.

A reminder - this is aimed at an Ubuntu system. Specifically, 14.10 (Utopic) was used, although earlier versions should work too. When Ubuntu transitions to systemd as an init system, the included Upstart script will not be applicable. (Current rumor is that the transition will be in the next release – caveat emptor)

1. Create User and Group for the Daemon

## add home dir first so adduser does not populate it with skel files.
> sudo mkdir /opt/syncthing
> sudo mkdir /opt/syncthing/etc
> sudo adduser --system --group --home /opt/syncthing synct
> sudo chown -R synct.synct /opt/syncthing

The synct group provides the opportunity to add authorized users to make ‘syncable’ folders with the synct group. Those users can manage their folder(s) with out the need for sudo/root privilege.

2. Install the Syncthing Binary

Fetch the binary from the Syncthing GitHub Project. The releases URL is: https://github.com/syncthing/syncthing/releases. Download the tarball appropriate for your architecture. (The example uses amd64, and version 0.10.18)

> cd /tmp
> tar -xvf /path-to/syncthing-linux-amd64-v0.10.18.tar.gz
> sudo mkdir /opt/syncthing/bin
> sudo cp syncthing-linux-amd64-v0.10.18/syncthing /opt/syncthing/bin

The only file needed from the release tarball is the executable itself. The executable is tar’ed with execute permission, but it never hurts to verify its executable.

4. Install an Upstart “Script”

Install the following Upstart configuration file in /etc/init/syncthing.conf

description  "syncthing daemon"
author       "Eric Gustafson <egustafson in launchpad>"

start on (local-filesystems and net-device-up IFACE!=lo)
stop on runlevel [!2345]

setuid synct
setgid synct

env HOME=/opt/syncthing

exec /opt/syncthing/bin/syncthing -home /opt/syncthing/etc

A couple of notes on the conf file:

1. Setting the $HOME env lets syncthing know where to create the default, Sync folder on initial start-up. I had problems before I added this stanza.

2. Using the -home /opt/syncthing/etc flag instructs syncthing to place all configuration files directly into the etc directory. If this flag is missing it will place the configuration in a hidden directory under $HOME.

It would be nice to get a list of supported environment variables and command line switches, but the docs are not there yet. Conversely, I could “read the source luke”, so I should stop whining and go contribute ;)

5. Start and Verify the Service

If the stars are aligned, then the service will start:

> sudo service syncthing start
> sudo tail -f /var/log/upstart/syncthing.log

At this point the service is (hopefully) up. There is a small problem, however: the configuration created on first-run restricts the web-gui to loopback only (127.0.0.1). This is fine if the machine is your desktop, but can be a snag if its remote. The config file can be edited by hand to change this.

In preparation for changing the listening address for the web-gui:

> sudo service syncthing stop

6. Modify the Configuration to expose the Web GUI

Edit the config file: /opt/syncthing/etc/config.xml

## syncthing changes the permissions on etc, sudo is required
> sudo emacs /opt/syncthing/etc/config.xml

The following line should be changed as depicted. The important aspect is to change the 127.0.0.1 to the wildcard address, 0.0.0.0. [The port could be changed too, if need be.]

<gui enabled="true" tls="false">
    <address>0.0.0.0:8080</address>
    ...
</gui>

Now restart the service

> sudo service syncthing start

and point a web browser at port 8080 of the host.

7. (Optional) Firewall Port Redirect

At this point you have a perfectly good, working Syncthing – congratulations.

However, if your host is behind a firewall it may not be reachable for sync-ing. The first point: if you have a consumer firewall that supports UPnP then Syncthing is likely visible as it supports, and enables by default, UPnP. If you don’t have UPnP enabled on your firewall or the Syncthing instance is not visible then following the “Firewalls and Port Forwards” instructions on the wiki will help you resolve the issue.

In short: plumb TCP port 22000 through from your firewall to the server. Port 22000 is the default port for the Block Exchange Protocol (BEP)[¹], and the only port necessary for a remote agent to connect with your server.

That’s it, you’re done. Happy syncing.