A Nix flake for the Valheim dedicated server, providing both an overlay and a NixOS module.
(Your NixOS system configuration must already be a flake.)
Add this flake as an input, and add the NixOS module. Your config should look something like this.
{
inputs = {
nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.05";
valheim-server.url = "github:aidalgol/valheim-server-flake";
};
outputs = {
self,
nixpkgs,
valheim-server,
}: let
system = "x86_64-linux";
pkgs = import nixpkgs {inherit system;};
in {
nixosConfigurations.my-server= nixpkgs.lib.nixosSystem {
inherit system;
modules = [
./configuration.nix
valheim-server.nixosModules.default
];
};
};
}Then in your configuration.nix,
{
config,
pkgs,
...
}: {
# ...
nixpkgs.config.allowUnfreePredicate = pkg:
builtins.elem (lib.getName pkg) [
"valheim-server"
"steamworks-sdk-redist"
];
# ...
services.valheim = {
enable = true;
serverName = "Some cozy server";
worldName = "Midgard";
openFirewall = true;
password = "sekkritpasswd";
# If you want to use BepInEx mods.
bepinexMods = [
# This does NOT fetch mod dependencies. You need to add those manually,
# if there are any (besides BepInEx).
(pkgs.fetchValheimThunderstoreMod {
owner = "Somebody";
name = "SomeMod";
version = "x.y.z";
hash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
})
# ...
];
bepinexConfigs = [
./some_mod.cfg
# ...
];
};
# ...
}valheim-server uses steam-fetcher which in turn uses DepotDownloader to fetch Steam packages from the Steam Depot. DepotDownloader may produce different results between different versions of DepotDownloader for the exact same depot. If you get an error about a hash mismatch on and have set nixpkgs.follows for this flake input, try removing that. The overlays explicitly use the nixpkgs from this flake input for steam-fetcher to avoid this problem.
Because BepInEx (the mod framework used by just about every Valheim mod) must both be installed in-tree with Valheim, and to be able to write to various files in the directory tree, we cannot run the modded Valheim server from the Nix store. To work around this without completely giving up on immutability, we copy the files out of the Nix store to a directory under /var/lib/valheim and run from there, but wipe and rebuild this directory on each launch.