fstrim: Add service

nixos/modules/module-list.nix

@@ -283,6 +283,7 @@
   ./services/misc/etcd.nix
   ./services/misc/felix.nix
   ./services/misc/folding-at-home.nix
+  ./services/misc/fstrim.nix
   ./services/misc/gammu-smsd.nix
   ./services/misc/geoip-updater.nix
   #./services/misc/gitit.nix

nixos/modules/services/misc/fstrim.nix

@@ -0,0 +1,45 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.services.fstrim;
+
+in {
+
+  options = {
+
+    services.fstrim = {
+      enable = mkEnableOption "periodic SSD TRIM of mounted partitions in background";
+
+      interval = mkOption {
+        type = types.string;
+        default = "weekly";
+        description = ''
+          How often we run fstrim. For most desktop and server systems
+          a sufficient trimming frequency is once a week.
+
+          The format is described in
+          <citerefentry><refentrytitle>systemd.time</refentrytitle>
+          <manvolnum>7</manvolnum></citerefentry>.
+        '';
+      };
+    };
+
+  };
+
+  config = mkIf cfg.enable {
+
+    systemd.packages = [ pkgs.utillinux ];
+
+    systemd.timers.fstrim = {
+      timerConfig = {
+        OnCalendar = cfg.interval;
+      };
+      wantedBy = [ "timers.target" ];
+    };
+
+  };
+
+}