refactor(nixos): simplify SteamCMD server options

configs/nixos/hosts/pikachu/default.nix

@@ -68,33 +68,28 @@
 
   modules.services.steamcmd = {
     enable = true;
-    dataDir = "/pikachu/data/steamcmd";
+    steamDir = "/pikachu/data/steamcmd";
     serviceName = "valheim";
     appId = 896660;
+    runtimeAppId = 892970;
     installDir = "/pikachu/data/servers/valheim/main";
-    workingDirectory = "/pikachu/data/servers/valheim/main";
-    group = "storage";
-    dataDirs = [ "/pikachu/media/games/servers/valheim/main" ];
-    packages = [ pkgs.steam-run ];
-    environment = {
-      SteamAppId = "892970";
-      SERVER_PASSWORD = "foobarbaz";
-    };
-    command = [
-      "${pkgs.bash}/bin/bash"
-      "-c"
-      ''
-        export LD_LIBRARY_PATH="$PWD/linux64:$LD_LIBRARY_PATH"
-        exec steam-run ./valheim_server.x86_64 \
-          -nographics \
-          -batchmode \
-          -name main \
-          -port 2456 \
-          -world main \
-          -savedir /pikachu/media/games/servers/valheim/main \
-          -password "$SERVER_PASSWORD" \
-          -public 0
-      ''
+    stateDir = "/pikachu/media/games/servers/valheim/main";
+    executable = "./valheim_server.x86_64";
+    arguments = [
+      "-nographics"
+      "-batchmode"
+      "-name"
+      "main"
+      "-port"
+      "2456"
+      "-world"
+      "main"
+      "-savedir"
+      "/pikachu/media/games/servers/valheim/main"
+      "-password"
+      "foobarbaz"
+      "-public"
+      "0"
     ];
     udpPorts = [
       2456

configs/nixos/modules/services/steamcmd.nix

@@ -7,6 +7,9 @@
 let
   cfg = config.modules.services.steamcmd;
 
+  runtimeAppId = if cfg.runtimeAppId == null then cfg.appId else cfg.runtimeAppId;
+  libraryPath = lib.concatStringsSep ":" cfg.libraryDirs;
+
   prepareScript = pkgs.writeShellScript "steamcmd-${cfg.serviceName}-prepare" ''
     set -eu
 
@@ -14,20 +17,15 @@ let
       -o ${lib.escapeShellArg cfg.user} \
       -g ${lib.escapeShellArg cfg.group} \
       -m 0770 \
-      ${lib.escapeShellArg cfg.dataDir}
-
-    ${pkgs.coreutils}/bin/install -d \
-      -o ${lib.escapeShellArg cfg.user} \
-      -g ${lib.escapeShellArg cfg.group} \
-      -m 0770 \
+      ${lib.escapeShellArg cfg.steamDir} \
       ${lib.escapeShellArg cfg.installDir} \
-      ${lib.escapeShellArgs cfg.dataDirs}
+      ${lib.escapeShellArg cfg.stateDir}
   '';
 
   updateScript = pkgs.writeShellScript "steamcmd-${cfg.serviceName}-update" ''
     set -eu
 
-    export HOME=${lib.escapeShellArg cfg.dataDir}
+    export HOME=${lib.escapeShellArg cfg.steamDir}
     exec ${lib.getExe cfg.package} \
       +force_install_dir ${lib.escapeShellArg cfg.installDir} \
       +login anonymous \
@@ -38,8 +36,10 @@ let
   startScript = pkgs.writeShellScript "steamcmd-${cfg.serviceName}-start" ''
     set -eu
 
-    cd ${lib.escapeShellArg cfg.workingDirectory}
-    exec ${lib.escapeShellArgs cfg.command}
+    cd ${lib.escapeShellArg cfg.installDir}
+    export SteamAppId=${lib.escapeShellArg (toString runtimeAppId)}
+    ${lib.optionalString (cfg.libraryDirs != [ ]) ''export LD_LIBRARY_PATH=${lib.escapeShellArg libraryPath}:''${LD_LIBRARY_PATH-}''}
+    exec ${lib.getExe pkgs.steam-run} ${lib.escapeShellArg cfg.executable} ${lib.escapeShellArgs cfg.arguments}
   '';
 
   restartCommand =
@@ -69,11 +69,11 @@ in
 
     group = lib.mkOption {
       type = lib.types.str;
-      default = "steamcmd";
+      default = "storage";
       description = "Group account that owns writable server files.";
     };
 
-    dataDir = lib.mkOption {
+    steamDir = lib.mkOption {
       type = lib.types.str;
       default = "/data/steamcmd";
       description = "Directory where SteamCMD stores metadata and cache files.";
@@ -82,37 +82,48 @@ in
     appId = lib.mkOption {
       type = lib.types.ints.positive;
       example = 896660;
-      description = "Steam app ID for the dedicated server.";
+      description = "Steam app ID for the dedicated server package.";
+    };
+
+    runtimeAppId = lib.mkOption {
+      type = lib.types.nullOr lib.types.ints.positive;
+      default = null;
+      example = 892970;
+      description = "Steam app ID exposed to the running server through SteamAppId. Defaults to appId.";
     };
 
     installDir = lib.mkOption {
       type = lib.types.str;
       example = "/data/servers/valheim/main";
-      description = "Directory where SteamCMD installs the server files.";
+      description = "Directory where SteamCMD installs the server files and where the game service starts.";
     };
 
-    workingDirectory = lib.mkOption {
+    stateDir = lib.mkOption {
       type = lib.types.str;
-      default = cfg.installDir;
-      defaultText = lib.literalExpression "config.modules.services.steamcmd.installDir";
-      example = "/data/servers/valheim/main";
-      description = "Directory where the game service starts.";
+      example = "/data/state/valheim/main";
+      description = "Writable directory for durable game server state.";
     };
 
-    command = lib.mkOption {
+    executable = lib.mkOption {
+      type = lib.types.str;
+      example = "./valheim_server.x86_64";
+      description = "Server executable, relative to installDir or absolute.";
+    };
+
+    arguments = lib.mkOption {
       type = lib.types.listOf lib.types.str;
+      default = [ ];
       example = [
-        "/data/servers/valheim/main/valheim_server.x86_64"
         "-name"
         "main"
       ];
-      description = "Command that starts the game server.";
+      description = "Arguments passed to the server executable.";
     };
 
-    environment = lib.mkOption {
-      type = lib.types.attrsOf lib.types.str;
-      default = { };
-      description = "Environment variables for the game service.";
+    libraryDirs = lib.mkOption {
+      type = lib.types.listOf lib.types.str;
+      default = [ "linux64" ];
+      description = "Library directories added to LD_LIBRARY_PATH before starting the server.";
     };
 
     environmentFiles = lib.mkOption {
@@ -121,13 +132,6 @@ in
       description = "Environment files loaded by the game service.";
     };
 
-    dataDirs = lib.mkOption {
-      type = lib.types.listOf lib.types.str;
-      default = [ ];
-      example = [ "/media/games/servers/valheim/main" ];
-      description = "Additional writable directories created before the game service starts.";
-    };
-
     updateOnStart = lib.mkOption {
       type = lib.types.bool;
       default = true;
@@ -140,12 +144,6 @@ in
       description = "Passes validate to SteamCMD app_update.";
     };
 
-    packages = lib.mkOption {
-      type = lib.types.listOf lib.types.package;
-      default = [ ];
-      description = "Packages added to the game service path.";
-    };
-
     tcpPorts = lib.mkOption {
       type = lib.types.listOf lib.types.port;
       default = [ ];
@@ -198,16 +196,17 @@ in
         isSystemUser = true;
         uid = config.registry."stable-uid".${config.networking.hostName}.steamcmd;
         group = cfg.group;
-        home = cfg.dataDir;
+        home = cfg.steamDir;
       };
 
       systemd.tmpfiles.rules = [
-        "d ${cfg.dataDir} 0770 ${cfg.user} ${cfg.group} - -"
-        "z ${cfg.dataDir} 0770 ${cfg.user} ${cfg.group} - -"
+        "d ${cfg.steamDir} 0770 ${cfg.user} ${cfg.group} - -"
+        "z ${cfg.steamDir} 0770 ${cfg.user} ${cfg.group} - -"
         "d ${cfg.installDir} 0770 ${cfg.user} ${cfg.group} - -"
         "z ${cfg.installDir} 0770 ${cfg.user} ${cfg.group} - -"
-      ] ++ map (dataDir: "d ${dataDir} 0770 ${cfg.user} ${cfg.group} - -") cfg.dataDirs
-        ++ map (dataDir: "z ${dataDir} 0770 ${cfg.user} ${cfg.group} - -") cfg.dataDirs;
+        "d ${cfg.stateDir} 0770 ${cfg.user} ${cfg.group} - -"
+        "z ${cfg.stateDir} 0770 ${cfg.user} ${cfg.group} - -"
+      ];
 
       systemd.services = {
         "steamcmd-${cfg.serviceName}-update" = {
@@ -218,7 +217,7 @@ in
             Type = "oneshot";
             User = cfg.user;
             Group = cfg.group;
-            WorkingDirectory = "-${cfg.dataDir}";
+            WorkingDirectory = "-${cfg.steamDir}";
             ExecStartPre = "+${prepareScript}";
             ExecStart = updateScript;
           };
@@ -232,13 +231,12 @@ in
           ];
           wants = [ "network-online.target" ];
           wantedBy = [ "multi-user.target" ];
-          path = cfg.packages;
-          environment = cfg.environment;
+          path = [ pkgs.steam-run ];
           serviceConfig = {
             Type = "simple";
             User = cfg.user;
             Group = cfg.group;
-            WorkingDirectory = "-${cfg.workingDirectory}";
+            WorkingDirectory = "-${cfg.installDir}";
             EnvironmentFile = cfg.environmentFiles;
             ExecStartPre = [
               "+${prepareScript}"