emby service: new service

nixos/modules/misc/ids.nix

···
       caddy = 239;
       taskd = 240;
       factorio = 241;
+      emby = 242;
 
       # When adding a uid, make sure it doesn't match an existing gid. And don't use uids above 399!
 
···
       caddy = 239;
       taskd = 240;
       factorio = 241;
+      emby = 242;
 
       # When adding a gid, make sure it doesn't match an existing
       # uid. Users and groups with the same name should have equal

nixos/modules/module-list.nix

···
   ./services/misc/dictd.nix
   ./services/misc/disnix.nix
   ./services/misc/docker-registry.nix
+  ./services/misc/emby.nix
   ./services/misc/etcd.nix
   ./services/misc/felix.nix
   ./services/misc/folding-at-home.nix

nixos/modules/services/misc/emby.nix

···
+{ config, pkgs, lib, mono, ... }:
+
+with lib;
+
+let
+  cfg = config.services.emby;
+  emby = pkgs.emby;
+in
+{
+  options = {
+    services.emby = {
+      enable = mkEnableOption "Emby Media Server";
+
+      user = mkOption {
+        type = types.str;
+        default = "emby";
+        description = "User account under which Emby runs.";
+      };
+
+      group = mkOption {
+        type = types.str;
+        default = "emby";
+        description = "Group under which emby runs.";
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    systemd.services.emby = {
+      description = "Emby Media Server";
+      after = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+      preStart = ''
+        test -d /var/lib/emby/ProgramData-Server || {
+          echo "Creating initial Emby data directory in /var/lib/emby/ProgramData-Server"
+          mkdir -p /var/lib/emby/ProgramData-Server
+          chown -R ${cfg.user}:${cfg.group} /var/lib/emby/ProgramData-Server
+          }
+      '';
+
+      serviceConfig = {
+        Type = "simple";
+        User = cfg.user;
+        Group = cfg.group;
+        PermissionsStartOnly = "true";
+        ExecStart = "${pkgs.mono}/bin/mono ${pkgs.emby}/bin/MediaBrowser.Server.Mono.exe";
+        Restart = "on-failure";
+      };
+    };
+
+    users.extraUsers = mkIf (cfg.user == "emby") {
+      emby = {
+        group = cfg.group;
+        uid = config.ids.uids.emby;
+      };
+    };
+
+    users.extraGroups = mkIf (cfg.group == "emby") {
+      emby = {
+        gid = config.ids.gids.emby;
+      };
+    };
+  };
+}