nixos: systemd-coredump: improve disabled state

The systemd-coredump module required systemd to be built with
withCoredump=true, even if the module was disabled.

- allow systemd to be missing systemd-coredump if the module is disabled
- switch to mkDefault for the sysctl config to allow user overrides when
  the module is disabled
- add nixos tests for both the enabled and disabled cases

2 files changed, 45 insertions, 0 deletions

diff --git a/nixos/tests/all-tests.nix b/nixos/tests/all-tests.nix
index ff54a327424e8..06210095cfce3 100644
--- a/nixos/tests/all-tests.nix
+++ b/nixos/tests/all-tests.nix
@@ -537,6 +537,7 @@ in {
   systemd-binfmt = handleTestOn ["x86_64-linux"] ./systemd-binfmt.nix {};
   systemd-boot = handleTest ./systemd-boot.nix {};
   systemd-confinement = handleTest ./systemd-confinement.nix {};
+  systemd-coredump = handleTest ./systemd-coredump.nix {};
   systemd-cryptenroll = handleTest ./systemd-cryptenroll.nix {};
   systemd-escaping = handleTest ./systemd-escaping.nix {};
   systemd-initrd-btrfs-raid = handleTest ./systemd-initrd-btrfs-raid.nix {};
diff --git a/nixos/tests/systemd-coredump.nix b/nixos/tests/systemd-coredump.nix
new file mode 100644
index 0000000000000..62137820878bd
--- /dev/null
+++ b/nixos/tests/systemd-coredump.nix
@@ -0,0 +1,44 @@
+import ./make-test-python.nix ({ pkgs, ... }:
+
+let
+
+  crasher = pkgs.writeCBin "crasher" "int main;";
+
+  commonConfig = {
+    systemd.services.crasher.serviceConfig = {
+      ExecStart = "${crasher}/bin/crasher";
+      StateDirectory = "crasher";
+      WorkingDirectory = "%S/crasher";
+      Restart = "no";
+    };
+  };
+
+in
+
+{
+  name = "systemd-coredump";
+  meta = with pkgs.lib.maintainers; {
+    maintainers = [ squalus ];
+  };
+
+  nodes.machine1 = { pkgs, lib, ... }: commonConfig;
+  nodes.machine2 = { pkgs, lib, ... }: lib.recursiveUpdate commonConfig {
+    systemd.coredump.enable = false;
+    systemd.package = pkgs.systemd.override {
+      withCoredump = false;
+    };
+  };
+
+  testScript = ''
+    with subtest("systemd-coredump enabled"):
+      machine1.wait_for_unit("multi-user.target")
+      machine1.wait_for_unit("systemd-coredump.socket")
+      machine1.systemctl("start crasher");
+      machine1.wait_until_succeeds("coredumpctl list | grep crasher", timeout=10)
+      machine1.fail("stat /var/lib/crasher/core")
+
+    with subtest("systemd-coredump disabled"):
+      machine2.systemctl("start crasher");
+      machine2.wait_until_succeeds("stat /var/lib/crasher/core", timeout=10)
+  '';
+})