nixos/modules/system/boot/shutdown.nix

   1 {
   2   config,
   3   lib,
   4   pkgs,
   5   ...
   6 }:
   7
   8 with lib;
   9
  10 {
  11
  12   # This unit saves the value of the system clock to the hardware
  13   # clock on shutdown.
  14   systemd.services.save-hwclock = {
  15     description = "Save Hardware Clock";
  16
  17     wantedBy = [ "shutdown.target" ];
  18
  19     unitConfig = {
  20       DefaultDependencies = false;
  21       ConditionPathExists = "/dev/rtc";
  22       ConditionPathIsReadWrite = "/etc/";
  23     };
  24
  25     serviceConfig = {
  26       Type = "oneshot";
  27       ExecStart = "${pkgs.util-linux}/sbin/hwclock --systohc ${
  28         if config.time.hardwareClockInLocalTime then "--localtime" else "--utc"
  29       }";
  30     };
  31   };
  32
  33   boot.kernel.sysctl."kernel.poweroff_cmd" = "${config.systemd.package}/sbin/poweroff";
  34
  35 }