1 files changed, 178 insertions, 0 deletions
diff --git a/nixos/modules/services/networking/ntp/chrony.nix b/nixos/modules/services/networking/ntp/chrony.nix
new file mode 100644
index 00000000000..34728455a21
--- /dev/null
+++ b/nixos/modules/services/networking/ntp/chrony.nix
@@ -0,0 +1,178 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.chrony;
+  chronyPkg = cfg.package;
+
+  stateDir = cfg.directory;
+  driftFile = "${stateDir}/chrony.drift";
+  keyFile = "${stateDir}/chrony.keys";
+
+  configFile = pkgs.writeText "chrony.conf" ''
+    ${concatMapStringsSep "\n" (server: "server " + server + " " + cfg.serverOption + optionalString (cfg.enableNTS) " nts") cfg.servers}
+
+    ${optionalString
+      (cfg.initstepslew.enabled && (cfg.servers != []))
+      "initstepslew ${toString cfg.initstepslew.threshold} ${concatStringsSep " " cfg.servers}"
+    }
+
+    driftfile ${driftFile}
+    keyfile ${keyFile}
+    ${optionalString (cfg.enableNTS) "ntsdumpdir ${stateDir}"}
+
+    ${optionalString (!config.time.hardwareClockInLocalTime) "rtconutc"}
+
+    ${cfg.extraConfig}
+  '';
+
+  chronyFlags = "-n -m -u chrony -f ${configFile} ${toString cfg.extraFlags}";
+in
+{
+  options = {
+    services.chrony = {
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether to synchronise your machine's time using chrony.
+          Make sure you disable NTP if you enable this service.
+        '';
+      };
+
+      package = mkOption {
+        type = types.package;
+        default = pkgs.chrony;
+        defaultText = literalExpression "pkgs.chrony";
+        description = ''
+          Which chrony package to use.
+        '';
+      };
+
+      servers = mkOption {
+        default = config.networking.timeServers;
+        defaultText = literalExpression "config.networking.timeServers";
+        type = types.listOf types.str;
+        description = ''
+          The set of NTP servers from which to synchronise.
+        '';
+      };
+
+      serverOption = mkOption {
+        default = "iburst";
+        type = types.enum [ "iburst" "offline" ];
+        description = ''
+          Set option for server directives.
+
+          Use "iburst" to rapidly poll on startup. Recommended if your machine
+          is consistently online.
+
+          Use "offline" to prevent polling on startup. Recommended if your
+          machine boots offline or is otherwise frequently offline.
+        '';
+      };
+
+      enableNTS = mkOption {
+        type = types.bool;
+        default = false;
+        description = ''
+          Whether to enable Network Time Security authentication.
+          Make sure it is supported by your selected NTP server(s).
+        '';
+      };
+
+      initstepslew = {
+        enabled = mkOption {
+          type = types.bool;
+          default = true;
+          description = ''
+            Allow chronyd to make a rapid measurement of the system clock error
+            at boot time, and to correct the system clock by stepping before
+            normal operation begins.
+          '';
+        };
+
+        threshold = mkOption {
+          type = types.either types.float types.int;
+          default = 1000; # by default, same threshold as 'ntpd -g' (1000s)
+          description = ''
+            The threshold of system clock error (in seconds) above which the
+            clock will be stepped. If the correction required is less than the
+            threshold, a slew is used instead.
+          '';
+        };
+      };
+
+      directory = mkOption {
+        type = types.str;
+        default = "/var/lib/chrony";
+        description = "Directory where chrony state is stored.";
+      };
+
+      extraConfig = mkOption {
+        type = types.lines;
+        default = "";
+        description = ''
+          Extra configuration directives that should be added to
+          <literal>chrony.conf</literal>
+        '';
+      };
+
+      extraFlags = mkOption {
+        default = [];
+        example = [ "-s" ];
+        type = types.listOf types.str;
+        description = "Extra flags passed to the chronyd command.";
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    meta.maintainers = with lib.maintainers; [ thoughtpolice ];
+
+    environment.systemPackages = [ chronyPkg ];
+
+    users.groups.chrony.gid = config.ids.gids.chrony;
+
+    users.users.chrony =
+      { uid = config.ids.uids.chrony;
+        group = "chrony";
+        description = "chrony daemon user";
+        home = stateDir;
+      };
+
+    services.timesyncd.enable = mkForce false;
+
+    systemd.services.systemd-timedated.environment = { SYSTEMD_TIMEDATED_NTP_SERVICES = "chronyd.service"; };
+
+    systemd.tmpfiles.rules = [
+      "d ${stateDir} 0755 chrony chrony - -"
+      "f ${driftFile} 0640 chrony chrony -"
+      "f ${keyFile} 0640 chrony chrony -"
+    ];
+
+    systemd.services.chronyd =
+      { description = "chrony NTP daemon";
+
+        wantedBy = [ "multi-user.target" ];
+        wants    = [ "time-sync.target" ];
+        before   = [ "time-sync.target" ];
+        after    = [ "network.target" "nss-lookup.target" ];
+        conflicts = [ "ntpd.service" "systemd-timesyncd.service" ];
+
+        path = [ chronyPkg ];
+
+        unitConfig.ConditionCapability = "CAP_SYS_TIME";
+        serviceConfig =
+          { Type = "simple";
+            ExecStart = "${chronyPkg}/bin/chronyd ${chronyFlags}";
+
+            ProtectHome = "yes";
+            ProtectSystem = "full";
+            PrivateTmp = "yes";
+          };
+
+      };
+  };
+}