Syncthing: A Minimal Self-Hosted Cloud Storage Solution

An Overview of Syncthing

If you've been looking around the self-hosted cloud storage space for a while, you've undoubtedly run into someone suggesting Syncthing as an option. However, it is an unusual alternative for those users out there who are used to having a centralized cloud server that serves as the "controller" of the data and interacts with clients on devices to fetch files.

This post is a walkthrough of the Syncthing software, how I set up my personal storage, and some pros and cons of using the software.

Installing Syncthing

To install Syncthing, visit the Downloads page or install via your device's package manager.

Server & Desktop

You can install Syncthing on servers and desktops via the Downloads page linked above or via the command-line.

For Debian-based distros:

sudo apt install syncthing

For Fedora-based distros:

sudo dnf install syncthing

Mobile

Syncthing for Android is available on F-Droid and Google Play. Syncthing does not have an official iOS client, but there is a third-party client called Möbius Sync.

How Does Syncthing Work?

To start, I wanted to include the main marketing blurb from their website:

Syncthing is a continuous file synchronization program. It synchronizes files between two or more computers in real time, safely protected from prying eyes. Your data is your data alone, and you deserve to choose where it is stored, whether it is shared with some third party, and how it's transmitted over the internet.

Let's break this apart and add in some other details to help explain what exactly Syncthing does in order to sync files between devices.

Local Syncthing Server(s)

Syncthing syncs files between multiple devices by creating a local server on each device. These local servers handle a few different things, such as watching files and directories for changes, hosting an administrative GUI website, and authenticating with connected devices.

You can also start, stop, and restart the Syncthing server via the command-line or web dashboard. If you're running Syncthing on a device with systemd, you can use the following commands:

sudo systemctl start syncthing@username.service
sudo systemctl restart syncthing@username.service
sudo systemctl stop syncthing@username.service

Syncthing Dashboard

This biggest part of Syncthing is the admin GUI website that runs on each device (note that mobile devices will use the Syncthing app rather than the web GUI). The admin GUI is available through the web browser on the local device that is running Syncthing - simply go to http://localhost:8384 or http://127.0.0.1:8384. This web page is the place where you will change settings, add/modify synced files, and add/modify connected devices.

Here's an example web GUI dashboard:

Remote Devices

A cloud storage solution wouldn't be very useful if you aren't able to share data among various devices. Syncthing does this by sharing Device IDs to connect servers, and then by manually sharing Folders with devices that have been connected.

For instance, if you have a laptop running Syncthing and then install the Syncthing mobile app on a phone, you could scan the laptop's QR code for Device ID and then accept the authentication on the laptop's dashboard. Next, you can use either device to select a folder for sharing and dictating which device should send, receive, or both.

When you connect devices, you can set one device as an "Introducer," which can add devices from the introducer to the device list, for mutually shared folders. You can also configure Auto Accept, compression, rate limits, and more settings per device.

My Personal Cloud Storage Set-up

Personally, I use a model similar to a traditional cloud storage service. I have a "centralized" server running 24/7 that acts as an Introducer for my Syncthing network. I think of this as my main storage and all other devices as tertiary client devices. I will likely add additional servers as backups as time goes on so that I don't have to rely on my laptop or phone as the only backups.

Currently, I have one desktop and one mobile device connected to the network, both running intermittently as they are not powered-on 24/7.

The initial set-up of the software was easy enough, but data transfer rates were incredibly slow for me due to the Wi-Fi. Instead, I plugged my laptop into the ethernet network that my server is on and manually copied my folders over to the server with scp. Once complete, Syncthing validated that all files were there and not missing, and it did not need to transfer any data through the WAN.

As slow as the transfer was going, this probably saved me a few days of waiting for my ~100GB sync.

Pros & Cons

I've put together a short list of pros and cons for Syncthing. I thought about my experiences with Nextcloud, WebDAV, proprietary services (Google Drive, iCloud, etc.), and privacy-focused cloud solutions (pCloud, Tresorit, etc.).

Pros:

• I've faced no data loss at all through my two-month trial run.
• No third-parties store your data on their servers.
• You have full control over your data and can take your data and leave at any time.
• It's possible to encrypt client-side easily with software like Cryptomator.
• No proprietary clients or mounted volumes, just plain files and folders.

Cons:

• The learning curve is steeper than traditional cloud services and is focused on a technical audience.
• If a device needs to modify files in a Folder, the devices will need to sync ALL files from the folder, which may be large. To avoid size restraints, split large folders into smaller folders for syncing.
• Syncing can be slow due to the clients/servers initially connecting or re-connecting after sleeping.
• Multiple personal devices are required and require the user to own or rent them as no third-party servers are involved in the storage of data.

Overall, I've had a great experience with Syncthing so far. I've had no data loss, syncing has been quick and easy when changes are made to files, device connections are reliable, and I love the freedom of controlling the clients and servers as I choose.

Not to mention that I appreciate that I - or someone else - could pull the Syncthing source code and continue development/support if the Syncthing Foundation decides to stop developing the software or sells the business.