docs: update SteamCMD server workflow #38
@@ -1,28 +1,73 @@
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# SteamCMD servers
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Use `modules.services.steamcmd` as the low-level runner for one SteamCMD server.
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Create a game module under `configs/nixos/modules/services/games/` for each game.
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This note records the workflow used to add the Valheim server.
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The workflow starts with the lowest useful layer.
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Each later step moves game knowledge into a narrower module.
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The game module owns game-specific defaults and command-line flags.
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The host owns deployment-specific paths, names, secrets, and network placement.
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## Stage 1: Run one server with `steamcmd`
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## Create a game module
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Start by proving the generic SteamCMD runner works on a host.
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Configure `modules.services.steamcmd` directly in the host file.
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1. Create `configs/nixos/modules/services/games/<game>.nix`.
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2. Define options under `modules.services.games.<game>`.
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3. Expose only values the host must choose.
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4. Map those values to `modules.services.steamcmd`.
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5. Set the Steam dedicated-server app ID in the game module.
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6. Set the server executable in the game module.
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7. Generate game-specific arguments in the game module.
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8. Open the game's documented UDP ports in the game module.
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```nix
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modules.services.steamcmd = {
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enable = true;
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steamDir = "/pikachu/data/steamcmd";
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serviceName = "valheim";
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appId = 896660;
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installDir = "/pikachu/data/servers/valheim/main";
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stateDir = "/pikachu/media/games/servers/valheim/main";
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executable = "./valheim_server.x86_64";
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arguments = [
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"-nographics"
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"-batchmode"
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"-name"
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"main"
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"-port"
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"2456"
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"-world"
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"main"
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"-savedir"
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config.modules.services.steamcmd.stateDir
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"-password"
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"foobarbaz"
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"-public"
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"0"
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];
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udpPorts = [
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2456
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2457
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];
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};
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```
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Keep `modules.services.steamcmd` focused on shared SteamCMD behavior.
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Do not put game-specific flags or port rules there.
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This layer owns SteamCMD update behavior and systemd wiring.
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It also owns directory setup for SteamCMD metadata, server files, and state.
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## Configure a host
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Do not pin the game server version in Nix.
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SteamCMD mutates the installed server files.
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During validation, enable the game module directly on a host.
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## Stage 2: Add a game service module
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After direct SteamCMD deployment works, create a game module.
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Use `configs/nixos/modules/services/games/<game>.nix`.
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The game module owns game-specific details:
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- Steam app ID
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- server executable
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- required command-line flags
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- documented UDP ports
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- private or public listing policy
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The host keeps deployment-specific values:
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- host paths
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- server name
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- secret choice
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- guest placement, when a guest exists
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For Valheim, the host config became:
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```nix
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modules.services.games.valheim = {
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@@ -35,37 +80,212 @@ modules.services.games.valheim = {
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};
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```
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Use host paths for direct host deployment.
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Use guest paths after the server moves into a guest.
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The Valheim module translated that into `modules.services.steamcmd`.
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It generated the Valheim argument list and UDP ports.
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## Deploy and test
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## Stage 3: Add UDP ingress
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1. Evaluate the host configuration.
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Valheim uses UDP.
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HTTP virtual hosts do not route Valheim traffic.
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```sh
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nix eval .#nixosConfigurations.<host>.config.system.build.toplevel.drvPath --raw
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```
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Extend `registry.route` with UDP ports:
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2. Deploy the host.
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```nix
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registry.route.pikachu.valheim = {
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domain = "valheim.alexion.dev";
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udp.ports = [
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2456
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2457
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];
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};
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```
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```sh
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deploy-to <host>
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```
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Keep `domain` mandatory.
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Nix does not own public DNS today.
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The route domain still identifies the public route.
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A future LAN DNS module can also consume it.
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3. Check the game service.
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The reverse-proxy module joins `registry.route` with `registry.address`.
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It renders nginx `stream` entries for UDP ports.
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```sh
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sudo systemctl status <game>.service
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sudo journalctl -u <game>.service -n 200 --no-pager
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```
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```nginx
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server {
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listen 2456 udp;
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proxy_pass 10.23.20.197:2456;
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}
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```
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4. Check UDP listeners.
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Configure public DNS outside Nix:
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```sh
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sudo ss -lunp | grep -E '<port>|<port-plus-one>|<game>'
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```
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```text
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valheim.alexion.dev -> public IP
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```
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5. Connect from the game client.
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Configure LAN DNS outside Nix:
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The Valheim server is ready after the log contains `Game server connected`.
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It can spend time generating a new world before it accepts connections.
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```text
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valheim.alexion.dev -> reverse-proxy guest IP
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```
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Configure router forwarding outside Nix:
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```text
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2456/udp -> reverse-proxy guest:2456
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2457/udp -> reverse-proxy guest:2457
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```
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## Stage 4: Move the server into a guest
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After the host-level game module works, add a guest module.
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Use `configs/nixos/guests/<game>.nix`.
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The guest module wraps `modules.services.games.<game>`.
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It also maps host paths into guest paths.
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For Valheim, the host config became:
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```nix
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guests.valheim = {
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enable = true;
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vlan = 20;
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address = "10.23.20.197";
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steamPath = "/pikachu/data/steamcmd";
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installPath = "/pikachu/data/servers/valheim/main";
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statePath = "/pikachu/media/games/servers/valheim/main";
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serverName = "main";
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reverseProxy = {
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enable = true;
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route = {
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domain = "valheim.alexion.dev";
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udp.ports = [
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config.guests.valheim.port
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(config.guests.valheim.port + 1)
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];
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};
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};
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};
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```
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The generic guest machinery publishes registry entries.
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```nix
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guests.valheim.address = "10.23.20.197";
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```
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becomes:
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```nix
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registry.address.pikachu.valheim = "10.23.20.197";
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```
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The guest route becomes:
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```nix
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registry.route.pikachu.valheim = config.guests.valheim.reverseProxy.route;
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```
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## Secrets
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Use SOPS for the game server password.
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Use one shared secret for game servers:
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```yaml
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services:
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game-servers:
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password: <password>
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```
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The Valheim guest defaults to:
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```nix
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passwordSecret = "services/game-servers/password";
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```
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The host decrypts the secret.
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The guest module bind-mounts the decrypted file into the guest.
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The Valheim module reads the password file at runtime.
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Edit shared secrets with the host key:
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```sh
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cd configs/nixos
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sops-host secrets/shared.yaml
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```
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## Validation
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Evaluate the host:
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```sh
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nix eval .#nixosConfigurations.pikachu.config.system.build.toplevel.drvPath --raw
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```
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Deploy the host:
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```sh
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deploy-to pikachu
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```
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Check the host secret:
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```sh
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sudo test -s /run/secrets/services/game-servers/password && echo secret-ok
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```
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Check the Valheim guest:
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```sh
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sudo systemctl status container@valheim.service --no-pager
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```
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Check the guest secret:
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```sh
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sudo nixos-container run valheim -- test -s /run/secrets/services/game-servers/password
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```
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Check the Valheim service:
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```sh
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sudo nixos-container run valheim -- systemctl status valheim.service --no-pager
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sudo nixos-container run valheim -- journalctl -u valheim.service -n 200 --no-pager
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```
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Wait for these log lines:
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```text
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Game server connected
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Opened Steam server
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```
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Check Valheim UDP listeners:
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```sh
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sudo nixos-container run valheim -- ss -lunp | grep -E '2456|2457|valheim'
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```
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Check reverse-proxy UDP listeners:
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```sh
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sudo nixos-container run reverse-proxy -- ss -lunp | grep -E '2456|2457|nginx'
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```
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Test the client through LAN DNS or public DNS:
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```text
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valheim.alexion.dev:2456
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```
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Test direct guest connectivity when ingress fails:
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```text
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10.23.20.197:2456
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```
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## Operational notes
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A first Valheim start can spend time generating a world.
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The service accepts connections after `Opened Steam server` appears.
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SteamCMD can leave old ownership on migrated server files.
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The SteamCMD module uses recursive tmpfiles repair for its managed directories.
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Reference in New Issue
Block a user