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Real-time File Synchronization Across Devices Using Syncthing

Last edited on 2025-10-29 • Tagged under  #syncthing   #lmde   #debian   #linux 

Syncthing is a real-time, continuous file synchronization program. Once installed and configured, it will keep files synced between multiple computers (known as "devices") in real time.

I have the program installed and configured for syncing on:

1. Start Here (Desktop)

Syncthing is under active development and hosts a dedicated [Debian package repository](apt.syncthing.net](https://apt.syncthing.net/) for the latest stable release. Verify the authenticity of Syncthing's packages by adding the release PGP key:

sudo curl -L -o /etc/apt/keyrings/syncthing-archive-keyring.gpg https://syncthing.net/release-key.gpg

2. Apt Sources

The stable channel is updated with stable release builds, usually every first Tuesday of the month.

Add to apt sources:

echo "deb [signed-by=/etc/apt/keyrings/syncthing-archive-keyring.gpg] https://apt.syncthing.net/ syncthing stable" | sudo tee /etc/apt/sources.list.d/syncthing.list

3. Apt Pin

Set a preference for installing Syncthing's own packaged version over the default Debian package by increasing its pin-priority:

printf "Package: *\nPin: origin apt.syncthing.net\nPin-Priority: 990\n" | sudo tee /etc/apt/preferences.d/syncthing.pref

Update and display the new priorities:

$ sudo apt update && apt-cache policy syncthing
syncthing:
  Installed: (none)
  Candidate: 1.30.0
  Version table:
     1.30.0 990
        990 https://apt.syncthing.net syncthing/stable amd64 Packages
     1.29.7 990
        990 https://apt.syncthing.net syncthing/stable amd64 Packages
     1.29.5~ds1-2 500
        500 https://deb.debian.org/debian trixie/main amd64 Packages

4. Install and Autostart

sudo apt install syncthing

Autostart syncthing as a user without requiring root privileges by setting up a systemd user service.

Create a folder to hold user services:

mkdir -p ~/.config/systemd/user

Copy the syncthing.service file into the load path of the user instance:

cp /usr/lib/systemd/user/syncthing.service ~/.config/systemd/user/

Enable and start the service:

systemctl --user enable syncthing.service
systemctl --user start syncthing.service

A default ~/Sync folder for synchronization is automatically created.

Check the status:

systemctl --user status syncthing.service

View the logs for the user service:

journalctl -e --user-unit=syncthing.service

5. Administration

5.1 Localhost

The administration GUI starts automatically and remains available on localhost:8384.

Go to Actions->Settings->GUI and add a username and password to the web interface.

5.2 Remote hosts

By default, we can't connect to the GUI running on a remote computer. Syncthing is only listening for connections from 127.0.0.1.

Allow connections to the GUI from network devices by first logging into the remote host, then editing ~/.local/state/syncthing/config.xml.

Change the line:

<gui enabled="true" tls="false" debugging="false" sendBasicAuthPrompt="false">
 <address>127.0.0.1:8384</address>

to

<gui enabled="true" tls="true" debugging="false" sendBasicAuthPrompt="false">
 <address>0.0.0.0:8384</address>

Restart the service:

systemctl --user restart syncthing.service

Remote host is now accessible at <ip_address>:8384.

Go to Actions->Settings-GUI and add a username and password to the web interface.

6. Add Devices and Folders

See this video tutorial for adding devices and folders for synchronization.

6.1 Syncthing on Android

Install the Syncthing-Fork application on the phone.

Enable syncing between the phone and desktop:

  • On the desktop: Actions->Show ID to display QR code
  • On the phone: Devices, click + to Add Device, click QR icon for Device ID to launch camera app and scan remote device's QR code
  • On the desktop: Click accept to add new device, set config options

Share a folder (example: the phone's camera folder at /storage/emulated/0/DCIM):

  • On the phone: Click on folder, enable file sharing to the remote device
  • On the desktop: Click accept to add new folder, set config options

7. Resources

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