Merge pull request #204 from bjornfor/apcupsd-service

Add apcupsd service

modules/module-list.nix

@@ -117,6 +117,7 @@
   ./services/misc/rogue.nix
   ./services/misc/svnserve.nix
   ./services/misc/synergy.nix
+  ./services/monitoring/apcupsd.nix
   ./services/monitoring/dd-agent.nix
   ./services/monitoring/monit.nix
   ./services/monitoring/nagios/default.nix

modules/services/monitoring/apcupsd.nix

@@ -0,0 +1,83 @@
+{ config, pkgs, ... }:
+
+with pkgs.lib;
+
+let cfg = config.services.apcupsd;
+    configFile = pkgs.writeText "apcupsd.conf" ''
+      ## apcupsd.conf v1.1 ##
+      # apcupsd complains if the first line is not like above.
+      ${cfg.configText}
+    '';
+in
+
+{
+
+  ###### interface
+
+  options = {
+
+    services.apcupsd = {
+
+      enable = mkOption {
+        default = false;
+        type = types.uniq types.bool;
+        description = ''
+          Whether to enable the APC UPS daemon. apcupsd monitors your UPS and
+          permits orderly shutdown of your computer in the event of a power
+          failure. User manual: http://www.apcupsd.com/manual/manual.html.
+          Note that apcupsd runs as root (to allow shutdown of computer).
+          You can check the status of your UPS with the "apcaccess" command.
+        '';
+      };
+
+      configText = mkOption {
+        default = ''
+          UPSTYPE usb
+          NISIP 127.0.0.1
+          BATTERYLEVEL 50
+          MINUTES 5
+        '';
+        type = types.string;
+        description = ''
+          Contents of the runtime configuration file, apcupsd.conf. The default
+          settings makes apcupsd autodetect USB UPSes, limit network access to
+          localhost and shutdown the system when the battery level is below 50
+          percent, or when the UPS has calculated that it has 5 minutes or less
+          of remaining power-on time. See man apcupsd.conf for details.
+        '';
+      };
+
+    };
+
+  };
+
+
+  ###### implementation
+
+  config = mkIf cfg.enable {
+
+    # Give users access to the "apcaccess" tool
+    environment.systemPackages = [ pkgs.apcupsd ];
+
+    # NOTE 1: apcupsd runs as root because it needs permission to run
+    # "shutdown"
+    #
+    # NOTE 2: When apcupsd calls "wall", it prints an error because stdout is
+    # not connected to a tty (it is connected to the journal):
+    #   wall: cannot get tty name: Inappropriate ioctl for device
+    # The message still gets through.
+    #
+    # TODO: apcupsd calls "mail" on powerfail etc. events, how should we
+    # handle that? A configurable mail package or let the event logic be
+    # configured from nix expressions?
+    systemd.services.apcupsd = {
+      description = "UPS daemon";
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = {
+        ExecStart = "${pkgs.apcupsd}/bin/apcupsd -b -f ${configFile} -d1";
+      };
+    };
+
+  };
+
+}