From ab076fc22ddb751249a518de8b3217e1097bcb82 Mon Sep 17 00:00:00 2001
From: Jamie Magee <jamie.magee@gmail.com>
Date: Sun, 3 May 2026 14:27:49 -0700
Subject: [PATCH] nixos/coredump: migrate to RFC 42-style settings

Replace the free-form `systemd.coredump.extraConfig` option with a structured `systemd.coredump.settings.Coredump` submodule rendered via `utils.systemdUtils.lib.settingsToSections`, in line with RFC 42. A `mkRemovedOptionModule` entry points existing users at the new option, and the systemd-coredump NixOS test now exercises the new settings option by asserting the rendered `coredump.conf` contents.
---
 .../manual/release-notes/rl-2605.section.md   |  2 ++
 .../modules/system/boot/systemd/coredump.nix  | 29 ++++++++++++-------
 nixos/tests/systemd-coredump.nix              | 18 ++++++++++--
 3 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/nixos/doc/manual/release-notes/rl-2605.section.md b/nixos/doc/manual/release-notes/rl-2605.section.md
index a652c7a3657c..e2eff27bc5ec 100644
--- a/nixos/doc/manual/release-notes/rl-2605.section.md
+++ b/nixos/doc/manual/release-notes/rl-2605.section.md
@@ -160,6 +160,8 @@
 
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
 
+- `systemd.coredump.extraConfig` has been removed in favor of the structured [](#opt-systemd.coredump.settings.Coredump) option. Use `systemd.coredump.settings.Coredump` to set any `coredump.conf(5)` option directly. For example, replace `systemd.coredump.extraConfig = "Storage=journal";` with `systemd.coredump.settings.Coredump.Storage = "journal";`.
+
 - `opentrack`, `slushload`, `synthesia`, `vtfedit`, `winbox`, `wineasio`, and `yabridge` use wineWow64Packages instead of wineWowPackages as wine versions >= 11.0 have deprecated wineWowPackages. As such, the prefixes for these packages are NOT backwards compatible and need to be regenerated with potential for data loss.
 
 - []{#sec-release-26.05-incompatibilities-profiles-hardened-removed} `profiles/hardened` has been removed, because:
diff --git a/nixos/modules/system/boot/systemd/coredump.nix b/nixos/modules/system/boot/systemd/coredump.nix
index c70e0004ca25..2241876baf7f 100644
--- a/nixos/modules/system/boot/systemd/coredump.nix
+++ b/nixos/modules/system/boot/systemd/coredump.nix
@@ -11,6 +11,14 @@ let
   systemd = config.systemd.package;
 in
 {
+  imports = [
+    (lib.mkRemovedOptionModule [
+      "systemd"
+      "coredump"
+      "extraConfig"
+    ] "Use systemd.coredump.settings.Coredump instead.")
+  ];
+
   options = {
     systemd.coredump.enable = lib.mkOption {
       default = true;
@@ -22,13 +30,17 @@ in
       '';
     };
 
-    systemd.coredump.extraConfig = lib.mkOption {
-      default = "";
-      type = lib.types.lines;
-      example = "Storage=journal";
+    systemd.coredump.settings.Coredump = lib.mkOption {
+      default = { };
+      type = lib.types.submodule {
+        freeformType = lib.types.attrsOf utils.systemdUtils.unitOptions.unitOption;
+      };
+      example = {
+        Storage = "journal";
+      };
       description = ''
-        Extra config options for systemd-coredump. See {manpage}`coredump.conf(5)` man page
-        for available options.
+        Settings for systemd-coredump. See {manpage}`coredump.conf(5)` for
+        available options.
       '';
     };
   };
@@ -42,10 +54,7 @@ in
       ];
 
       environment.etc = {
-        "systemd/coredump.conf".text = ''
-          [Coredump]
-          ${cfg.extraConfig}
-        '';
+        "systemd/coredump.conf".text = utils.systemdUtils.lib.settingsToSections cfg.settings;
 
         # install provided sysctl snippets
         "sysctl.d/50-coredump.conf".source =
diff --git a/nixos/tests/systemd-coredump.nix b/nixos/tests/systemd-coredump.nix
index 9ab7555279d1..58db509535ff 100644
--- a/nixos/tests/systemd-coredump.nix
+++ b/nixos/tests/systemd-coredump.nix
@@ -21,10 +21,19 @@ in
     maintainers = [ ];
   };
 
-  nodes.machine1 = { pkgs, lib, ... }: commonConfig;
+  nodes.machine1 =
+    { pkgs, lib, ... }:
+    {
+      imports = [ commonConfig ];
+      systemd.coredump.settings.Coredump = {
+        Storage = "journal";
+        ProcessSizeMax = "0";
+      };
+    };
   nodes.machine2 =
     { pkgs, lib, ... }:
-    lib.recursiveUpdate commonConfig {
+    {
+      imports = [ commonConfig ];
       systemd.coredump.enable = false;
       systemd.package = pkgs.systemd.override {
         withCoredump = false;
@@ -39,6 +48,11 @@ in
       machine1.wait_until_succeeds("coredumpctl list | grep crasher", timeout=10)
       machine1.fail("stat /var/lib/crasher/core*")
 
+    with subtest("settings.Coredump renders coredump.conf"):
+      machine1.succeed("grep -F '[Coredump]' /etc/systemd/coredump.conf")
+      machine1.succeed("grep -F 'Storage=journal' /etc/systemd/coredump.conf")
+      machine1.succeed("grep -F 'ProcessSizeMax=0' /etc/systemd/coredump.conf")
+
     with subtest("systemd-coredump disabled"):
       machine2.systemctl("start crasher");
       machine2.wait_until_succeeds("stat /var/lib/crasher/core*", timeout=10)