How I fixed it: Sunshine issues on NixOS

Background

I’ve got a couple of computers in the home. One machine in particular is a semi-powerful gaming machine. The weird thing about this machine is that it’s stowed away in a storage room, not a very suitable place to sit and actually use it.

To be honest, I’m not really much of a gamer, and so I mostly use its capabilities for work and other heavier tasks. But it’s always nice to be able to use graphical applications in a performant way. And I do in fact use it for running Zwift with my virtual trainer.

Before switching to Hyprland running on Wayland I used various SPICE and RDP setups that worked well enough running on an X server. However, with my limited patience I didn’t manage to find any suitable solutions working well on Wayland. And when I found people mentioning solutions Sunshine with Moonlight always seemed to be high up on the list of options.

I managed to get Sunshine running on NixOS with minimal effort due to the Sunshine NixOS module. Then on both my NixOS laptop and other Windows desktop computer I’ve installed Moonlight.

The issue

However, after upgrading to NixOS 25.11 I noticed that Moonlight no longer managed to capture input (there were several other issues, but more on that later).

Inspecting the sunshine.service logs I noticed the following warnings:

Warning: Unable to create virtual mouse: Permission denied
Warning: Unable to create virtual keyboard: Permission denied

With a smoking gun I managed to google my way to realize that Sunshine uses udev to emulate HID¹ devices for input capture through the /dev/uinput device.

An sure enough, when I checked the permissions on /dev/uinput I saw that it was only read-writable by root:

❯ ls -l /dev/uinput
crw------- 1 root root 10, 223 Dec 11 22:36 /dev/uinput

Although it might seem tempting to lean up and just chmod 666 /dev/uinput, you don’t want to give everyone access to /dev/uinput, as that would be a security risk. But Sunshine needs access to it, and the NixOS module spins up Sunshine instances through a systemd user service running as your unprivileged user.

Not sure what has changed to cause this to break now, I don’t know. But there must be a simple way to work around it, right?

The fix

As covered on the Sunshine troubleshooting page users need to be a member of the input group when running Sunshine unprivileged. However, this doesn’t really help if /dev/uinput is only read-writable by root.

Luckily NixOS makes it easy to add custom udev rules through it’s configuration system. Adding the following udev rule to my NixOS configuration:

services.udev.extraRules = ''
  KERNEL=="uinput", MODE="0660", GROUP="input", SYMLINK+="uinput"
'';

This creates /dev/uinput with the right permissions.

❯ ls -l /dev/uinput
crw-rw---- 1 root input 10, 223 Dec 11 22:36 /dev/uinput

Then I had to add myself to the input group:

users.users.myme.extraGroups = [ "input" ];

And with that, Moonlight is able to pass captured input to Sunshine and I’m able to control my stowed away gaming machine once again.

Footnotes