Deploying Syncthing on Synology DSM 7.3: Stable Setup with Container Manager

On Synology DSM 7.3, the recommended way to deploy Syncthing is to run it with Container Manager (Docker). This keeps upgrades, migration, and rebuilds cleaner, while separating Syncthing’s configuration directory from the shared folders you want to sync.

Syncthing needs read and write access to shared folders on the NAS. The most common deployment problem is usually not the image itself, but the runtime user permissions and volume mappings: the container should start with the correct PUID and PGID, and the folder path entered in the web UI must be the path inside the container.

Preparation

First, sign in to Synology over SSH and check the user ID you want Syncthing to run as:

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id your-admin-username

Record the uid and gid from the output. In many setups, uid is around 1026 and gid is 100. These values will be used as PUID and PGID.

Then open File Station, go to the docker shared folder, and create this directory:

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/docker/syncthing

This directory stores Syncthing’s configuration files, database, and runtime state. If you rebuild the container later, the configuration can be preserved as long as this directory remains in place.

Download the Syncthing Image

Open Container Manager, go to “Registry” on the left, and search for:

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syncthing

Select the official image syncthing/syncthing, use the latest tag, and download it. After the download finishes, go to “Image”, select syncthing/syncthing, and click “Run”.

Create the Container

Set the container name to:

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syncthing

It is also recommended to enable automatic restart, so Syncthing starts again automatically after the NAS reboots.

Configure Environment Variables

In the advanced settings, add or modify these environment variables:

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PUID=1026
PGID=100
TZ=Asia/Shanghai

Replace PUID and PGID with the actual values you found earlier using id username. When Syncthing reads and writes shared folders, it will access the Synology file system as this user.

Pin the Ports

For easier access and troubleshooting, manually fix the port mappings:

If the Synology firewall is enabled, allow these ports as well. For LAN-only use, at minimum make sure 8384 is reachable from your computer.

Configure Volume Mappings

Volume mappings fall into two groups: Syncthing’s own configuration directory, and the Synology shared folders you want to sync.

Map the configuration directory like this:

Then add the data directory you want to sync. For example, if you want to sync /volume1/NasData on Synology, map it like this:

This is important: when adding a folder in the Syncthing web UI later, enter the container path, for example:

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/NasData

Do not enter the Synology host path /volume1/NasData. Syncthing runs inside the container and can only see the paths mounted into that container.

If you want to sync multiple shared folders, add more mappings, for example:

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/volume1/Photos  ->  /Photos
/volume1/Backup  ->  /Backup
/volume1/NasData ->  /NasData

Start and Access Syncthing

After confirming the environment variables, ports, and volume mappings, click “Done” to start the container.

Then open this address in your browser:

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http://your-Synology-IP:8384

After entering the Syncthing management UI, the first thing to do is set a username and password for the web interface. The path is:

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Actions -> Settings -> GUI

Do not leave the Syncthing management UI exposed on your LAN for long without a password.

Add a Sync Folder

Click “Add Folder” and enter the container path configured earlier in “Folder Path”, for example:

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/NasData

If the permissions are configured correctly, Syncthing can read and write this shared folder. After that, add a remote device, select the folder to share, and syncing can begin.

Summary

There are three key points when deploying Syncthing on Synology DSM 7.3:

• Run syncthing/syncthing with Container Manager;
• Use the correct PUID and PGID to handle shared-folder permissions;
• Use the container path in the Syncthing web UI, not the Synology host path.

Once these three parts are configured correctly, Syncthing runs reliably on Synology and can be expanded with more sync directories later.