Update

Turns out, when you update the SteamOS, it completely over-writes the operating system. All of the setup I had originally written was great, if I never update, which is unacceptable. Not all is lost; the quest simply gets harder. If I can’t rely on system-wide services, then I rely on user services.

The Wrong Way: System-Wide Services

My first attempt was to setup Syncthing as a system-wide service managed by systemd, installed via pacman. There are several problems with this. First, it requires disabling the read-only file-system. Next, pacman is not setup nor reliable, since every SteamOS update will over-write any changes I make to any of the read-only file-system, including the directories that pacman relies on. Related, the update will also erase the Syncthing package. This means I either never update (inadvisable, and unacceptable), or I setup Syncthing not in the read-only file-system.

The Right Way: User Services

systemd allows for non-root-based services, called user services. The Arch Wiki systemd/User article describes this functionality much more than I will. Here are the relevant details:

• User services can be enabled to start when a user logs in
• Service files are stored in the user’s home directory (specifically ~/.config/systemd/user)
• No root privileges are required. No modifying the read-only file-system

Syncthing

Syncthing is incredible. I’ve written about it before, but the setup here is a bit more involved. The Steam Deck runs Arch Linux (and have I told you yet today that I do too?), so the Arch Wiki article on Syncthing gives some good insight. When I initially started this process, I installed the SyncthingGTK application from the Discover Store. This means it is a Flatpak application, and so doesn’t require elevated user privileges. I also tried the Syncthingy application, which explicitly calls out Steam Deck users. However, both require running the Flatpak in the background (like some users do for Discord or Spotify). I don’t like this, it feels off, and thus I sought a different approach.

SSHD: Still Incredibly Useful

I got real tired real quick of using the on-screen keyboard. After complaining, a friend recommended I enable sshd and just remote in to the device. Doing so was a breeze, and I recommend to others who don’t have a physical keyboard they can plug into their device. Drop to desktop mode (hold the power button for a few seconds, and select the option), and start a terminal (default is Konsole). Before remotely accessing the device, or using elevated privileges via sudo, I need to set a password for the default user, deck. In the terminal, type passwd and set it (and then put it in your password vault so you don’t forget. You do have a password vault, right?). Start the service, sudo systemctl start sshd, and optionally enable it to have sshd automatically started on each boot (sudo systemctl enable sshd). Get the device IP with ip addr list, from my desktop run ssh deck@ip-address, type in the password, and now I’m a grade-A Hackermans.

This setting is not reset on SteamOS updates, that I can tell. Once enabled, this will always start at boot, and always be on until explicitly turned off. Be mindful of that if you decide to wander away from your home network; maybe turn it off in public if you don’t need it.

Setup

There are 2 things required: a systemd service file, and the syncthing binary. Syncthing is written in Go, and a compiled binary can be downloaded that has no dependencies or installation requirements. It can be downloaded from the Syncthing Releases page for many platforms and architectures. The Steam Deck is a Linux platform, using the AMD64 architecture (or x86_64), so I grab that one. I’ll note here, since I have SSH access, I do all the editing and downloading on my desktop, and then transfer the files using scp to the Deck. All of these steps can be done on the Deck itself, without SSH access. Once the proper tarball has been downloaded, extract it, and within will be the syncthing binary, ready to rock. I copy/move the binary to ~/.local/bin/syncthing on the Deck. The exact location is less important than ensuring the binary is within my home directory on the Deck.

The systemd serivce file can also be taken from the extracted tarball, but requires modification. In the tarball, it is etc/linux-systemd/user/syncthing.service. Copy this file to ~/.config/systemd/user on the Deck, and edit the “ExecStart” line in the “[Service]” section from

...
[Service]
ExecStart=/usr/bin/syncthing serve --no-browser --no-restart --logflags=0
...

to

...
[Service]
ExecStart=/home/deck/.local/bin/syncthing serve --no-browser --no-restart --logflags=0
...

(or wherever you decided to put the local syncthing binary)

With everything in place, I can now enable and start the Syncthing user service:

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

Since I don’t have a physical keyboard plugged in, I modify my SSH command slightly to forward the Syncthing web-UI from the Deck to my local machine:

ssh -L 31337:deck-ip-goes-here:8384 deck@deck-ip-goes-here

Now, on my local machine I can open one tab to localhost:8384, to show Syncthing on my local machine, and another tab to localhost:31337 to show Syncthing on my Deck. From here, I add my local machine as a device on my Deck, and begin sharing folders.

Closing Thoughts

I’ve been using this setup for about a week now. I’ve synced almost 20GB of files, including configurations and saves for Retroarch. It works after restarts, OS and client upgrades, and waking the device from sleep. It sits quietly in the background, without having to start up applications. The biggest problem is that it doesn’t automatically update to the newest version of Syncthing. It’s also a bit involved to setup. To that end, I’ve written a tool to help with setup: Steam Deck Syncthing Setup. I’m still finishing it up, but I intend to make use of it to keep my version of Syncthing up-to-date. If you use it, let me know!