nixos/timesyncd: migrate to RFC 42-style settings

Replace `services.timesyncd.extraConfig` with a freeform `services.timesyncd.settings.Time` submodule, rendered via `utils.systemdUtils.lib.settingsToSections`. `extraConfig` is removed via `mkRemovedOptionModule`.

`servers` and `fallbackServers` are kept as typed wrappers; they now bridge into `settings.Time.NTP` / `settings.Time.FallbackNTP` via `mkDefault` so users can still override them through `settings.Time`.

Adds `nixos/tests/systemd-timesyncd` to assert the rendered `timesyncd.conf` contents.

nixos/doc/manual/release-notes/rl-2611.section.md

@@ -23,6 +23,8 @@
   no longer sets `programs.pqos-wrapper.enable = true`
   as the corresponding module has been deleted.
 
+- `services.timesyncd.extraConfig` has been removed in favor of the structured [](#opt-services.timesyncd.settings.Time) option. Use `services.timesyncd.settings.Time` to set any `timesyncd.conf(5)` option directly. For example, replace `services.timesyncd.extraConfig = "PollIntervalMaxSec=180";` with `services.timesyncd.settings.Time.PollIntervalMaxSec = 180;`.
+
 ## Other Notable Changes {#sec-release-26.11-notable-changes}
 
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->

nixos/modules/system/boot/timesyncd.nix

@@ -1,10 +1,23 @@
-{ config, lib, ... }:
+{
+  config,
+  lib,
+  utils,
+  ...
+}:
 
 let
   cfg = config.services.timesyncd;
 in
 {
 
+  imports = [
+    (lib.mkRemovedOptionModule [
+      "services"
+      "timesyncd"
+      "extraConfig"
+    ] "Use services.timesyncd.settings.Time instead.")
+  ];
+
   options = {
 
     services.timesyncd = {
@@ -43,15 +56,17 @@ in
           See {manpage}`timesyncd.conf(5)` for details.
         '';
       };
-      extraConfig = lib.mkOption {
-        default = "";
-        type = lib.types.lines;
-        example = ''
-          PollIntervalMaxSec=180
-        '';
+      settings.Time = lib.mkOption {
+        default = { };
+        type = lib.types.submodule {
+          freeformType = lib.types.attrsOf utils.systemdUtils.unitOptions.unitOption;
+        };
+        example = {
+          PollIntervalMaxSec = 180;
+        };
         description = ''
-          Extra config options for systemd-timesyncd. See
-          {manpage}`timesyncd.conf(5)` for available options.
+          Settings for systemd-timesyncd. See {manpage}`timesyncd.conf(5)` for
+          available options.
         '';
       };
     };
@@ -74,16 +89,17 @@ in
       environment.LD_LIBRARY_PATH = config.system.nssModules.path;
     };
 
-    environment.etc."systemd/timesyncd.conf".text = ''
-      [Time]
-    ''
-    + lib.optionalString (cfg.servers != null) ''
-      NTP=${lib.concatStringsSep " " cfg.servers}
-    ''
-    + lib.optionalString (cfg.fallbackServers != null) ''
-      FallbackNTP=${lib.concatStringsSep " " cfg.fallbackServers}
-    ''
-    + cfg.extraConfig;
+    services.timesyncd.settings.Time = lib.mkMerge [
+      (lib.mkIf (cfg.servers != null) {
+        NTP = lib.mkDefault (lib.concatStringsSep " " cfg.servers);
+      })
+      (lib.mkIf (cfg.fallbackServers != null) {
+        FallbackNTP = lib.mkDefault (lib.concatStringsSep " " cfg.fallbackServers);
+      })
+    ];
+
+    environment.etc."systemd/timesyncd.conf".text =
+      utils.systemdUtils.lib.settingsToSections cfg.settings;
 
     users.users.systemd-timesync = {
       uid = config.ids.uids.systemd-timesync;

nixos/tests/all-tests.nix

@@ -1653,6 +1653,7 @@ in
   systemd-sysusers-immutable = runTest ./systemd-sysusers-immutable.nix;
   systemd-sysusers-mutable = runTest ./systemd-sysusers-mutable.nix;
   systemd-sysusers-password-option-override-ordering = runTest ./systemd-sysusers-password-option-override-ordering.nix;
+  systemd-timesyncd = runTest ./systemd-timesyncd.nix;
   systemd-timesyncd-nscd-dnssec = runTest ./systemd-timesyncd-nscd-dnssec.nix;
   systemd-user-linger = runTest ./systemd-user-linger.nix;
   systemd-user-linger-purge = runTest ./systemd-user-linger-purge.nix;

nixos/tests/systemd-timesyncd-nscd-dnssec.nix

@@ -50,9 +50,7 @@ in
       # Configure systemd-timesyncd to use our NTP hostname
       services.timesyncd.enable = lib.mkForce true;
       services.timesyncd.servers = [ ntpHostname ];
-      services.timesyncd.extraConfig = ''
-        FallbackNTP=${ntpHostname}
-      '';
+      services.timesyncd.settings.Time.FallbackNTP = ntpHostname;
 
       # The debug output is necessary to determine whether systemd-timesyncd successfully resolves our NTP hostname or not
       systemd.services.systemd-timesyncd.environment.SYSTEMD_LOG_LEVEL = "debug";

nixos/tests/systemd-timesyncd.nix

@@ -0,0 +1,31 @@
+{
+  name = "systemd-timesyncd";
+  meta = {
+    maintainers = [ ];
+  };
+
+  nodes.machine =
+    { lib, ... }:
+    {
+      services.timesyncd = {
+        enable = lib.mkForce true;
+        servers = [ "ntp.example.com" ];
+        fallbackServers = [ "fallback.example.com" ];
+        settings.Time = {
+          PollIntervalMaxSec = "180";
+          RootDistanceMaxSec = "5";
+        };
+      };
+    };
+
+  testScript = ''
+    machine.wait_for_unit("multi-user.target")
+
+    with subtest("settings.Time renders timesyncd.conf"):
+      machine.succeed("grep -F '[Time]' /etc/systemd/timesyncd.conf")
+      machine.succeed("grep -F 'NTP=ntp.example.com' /etc/systemd/timesyncd.conf")
+      machine.succeed("grep -F 'FallbackNTP=fallback.example.com' /etc/systemd/timesyncd.conf")
+      machine.succeed("grep -F 'PollIntervalMaxSec=180' /etc/systemd/timesyncd.conf")
+      machine.succeed("grep -F 'RootDistanceMaxSec=5' /etc/systemd/timesyncd.conf")
+  '';
+}