Syncthing

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Resources

Syncthing is a continuous file synchronization program. It synchronizes files between two or more computers in real time. Syncthing is available on Linux, MacOS, Android, Windows and other operating systems, making it a good choice for cross platform file sharing.

Installation

USE flags

USE flags for net-p2p/syncthing Open Source Continuous File Synchronization

`selinux`	!!internal use only!! Security Enhanced Linux support, this must be set by the selinux profile or breakage will occur
`tools`	Install stdiscosrv, strelaysrv and other tools to /usr/libexec/syncthing/.

Data provided by the Gentoo Package Database · Last update: 2024-04-10 10:36 More information about USE flags

Emerge

root #emerge --ask net-p2p/syncthing

Configuration

To view all available configuration options:

user $man 5 syncthing-config

Files

$HOME/.local/state/syncthing: Configuration files and security certificates, when run as a user service.
/etc/conf.d/syncthing (OpenRC): Config file for /etc/init.d/syncthing
/var/lib/syncthing/.config/syncthing/config.xml (systemd system service): Configuration file location when syncthing is run as a systemd system serivce.

Service

OpenRC

OpenRC can start Syncthing at startup:

root #

rc-update add syncthing default

systemd

Syncthing can be started as a user with systemd:

user $systemctl --user enable syncthing.service

user $systemctl --user start syncthing.service

Firewall

Syncthing requires port 22000 (UDP and TCP) to be open for syncing, and port 21027/UDP to be open for discovery.

Using Ufw, you can allow them like this:

root #ufw allow syncthing

Similarly, using Firewalld you can allow them like this:

root #firewall-cmd --zone=public --add-service=syncthing --permanent

root #firewall-cmd --zone=public --reload

Additionally, if using the web interface from remote machines, the port 8384 needs to be allowed. This service is called syncthing-gui in both Firewalld and UFW, respectively. Keep in mind that this shouldn't be done without TLS and proper authentication; a better approach using SSH tunnels is described below.

Refer to the Syncthing's page on firewalls for further information.

Sandboxing

Since Syncthing can access all files by default, it's a good idea to either run Syncthing in a containerized environment or sandbox it using Firejail or AppArmor.

Usage

Invocation

user $syncthing --help

Usage: syncthing <command>

Flags:
  -h, --help    Show context-sensitive help.

Commands:
  serve
    Run Syncthing

  decrypt <path>
    Decrypt or verify an encrypted folder

  cli
    Command line interface for Syncthing

Run "syncthing <command> --help" for more information on a command.

Running Syncthing as an individual user

Syncthing can be started as a common user:

user $syncthing

It will create the following directories at first use:

${HOME}/.config/syncthing: Configuration files and security certificates.
${HOME}/Sync: The default folder to synchronize.

Syncthing will also fire up a browser page at http://127.0.0.1:8384 for monitoring and configuration.

Running Syncthing as a system server

Upstream mentions the following commands can be used to start syncthing has a system service. Do the following steps when using syncthing in a server to client architecture:

root #systemctl enable syncthing@syncthing.service

This will run the syncthing executable as the syncthing user, which is created when syncthing is installed.

Check the status of the service by issuing:

root #systemctl status syncthing@syncthing.service

Troubleshooting

Changing the user of init service

User and group with which Syncthing creates and modifies the synced files, can be changed by uncommenting the following lines in /etc/conf.d/syncthing:

FILE /etc/conf.d/syncthingChanging the default user of syncthing init service

#SYNCTHING_USER="syncthing"
#SYNCTHING_GROUP="syncthing"

Syncing files with Android

If files are shared with Android, make sure to enable "Ignore Permissions" in the advanced tab. This option disables comparing and syncing file permissions and is useful on systems with nonexistent or custom permissions (e.g. FAT, exFAT, Synology, Android).

Headless syncthing with ssh tunnel

The easiest thing to do is reverse proxy ssh to access the config. It is in the documentation:

user $ssh -L 9090:localhost:8384 <name>@<ip>

Now the page http://localhost:9090 can be opened on the computer and make edits to the browser page.