uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

nixos/modules/services/monitoring/telegraf.nix

@@ -0,0 +1,90 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.telegraf;
+
+  settingsFormat = pkgs.formats.toml {};
+  configFile = settingsFormat.generate "config.toml" cfg.extraConfig;
+in {
+  ###### interface
+  options = {
+    services.telegraf = {
+      enable = mkEnableOption "telegraf server";
+
+      package = mkOption {
+        default = pkgs.telegraf;
+        defaultText = literalExpression "pkgs.telegraf";
+        description = "Which telegraf derivation to use";
+        type = types.package;
+      };
+
+      environmentFiles = mkOption {
+        type = types.listOf types.path;
+        default = [];
+        example = [ "/run/keys/telegraf.env" ];
+        description = ''
+          File to load as environment file. Environment variables from this file
+          will be interpolated into the config file using envsubst with this
+          syntax: <literal>$ENVIRONMENT</literal> or <literal>''${VARIABLE}</literal>.
+          This is useful to avoid putting secrets into the nix store.
+        '';
+      };
+
+      extraConfig = mkOption {
+        default = {};
+        description = "Extra configuration options for telegraf";
+        type = settingsFormat.type;
+        example = {
+          outputs.influxdb = {
+            urls = ["http://localhost:8086"];
+            database = "telegraf";
+          };
+          inputs.statsd = {
+            service_address = ":8125";
+            delete_timings = true;
+          };
+        };
+      };
+    };
+  };
+
+
+  ###### implementation
+  config = mkIf config.services.telegraf.enable {
+    systemd.services.telegraf = let
+      finalConfigFile = if config.services.telegraf.environmentFiles == []
+                        then configFile
+                        else "/var/run/telegraf/config.toml";
+    in {
+      description = "Telegraf Agent";
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network-online.target" ];
+      serviceConfig = {
+        EnvironmentFile = config.services.telegraf.environmentFiles;
+        ExecStartPre = lib.optional (config.services.telegraf.environmentFiles != [])
+          (pkgs.writeShellScript "pre-start" ''
+            umask 077
+            ${pkgs.envsubst}/bin/envsubst -i "${configFile}" > /var/run/telegraf/config.toml
+          '');
+        ExecStart="${cfg.package}/bin/telegraf -config ${finalConfigFile}";
+        ExecReload="${pkgs.coreutils}/bin/kill -HUP $MAINPID";
+        RuntimeDirectory = "telegraf";
+        User = "telegraf";
+        Group = "telegraf";
+        Restart = "on-failure";
+        # for ping probes
+        AmbientCapabilities = [ "CAP_NET_RAW" ];
+      };
+    };
+
+    users.users.telegraf = {
+      uid = config.ids.uids.telegraf;
+      group = "telegraf";
+      description = "telegraf daemon user";
+    };
+
+    users.groups.telegraf = {};
+  };
+}