Group shared system settings

system/shared/services/oomd.nix

@@ -0,0 +1,20 @@
+{ lib, ... }: {
+  systemd = {
+    # OOMd: Out Of Memory daemon
+    # By default, this will only kill cgroups. So either systemd services
+    # marked for killing uder OOM or (non-default, but enabled here) the entire user slice.
+    oomd = {
+      enable = true;
+      enableSystemSlice = true;
+      enableRootSlice = true;
+      enableUserSlices = true;
+      extraConfig = {
+        "DefaultMemoryPressureDurationSec" = "20s";
+      };
+    };
+
+    # Make nix builds more likely to get killed than other important services.
+    # The default for user slices is 100, and systemd-coredumpd is 500
+    services.nix-daemon.serviceConfig.OOMScoreAdjust = lib.mkDefault 350;
+  };
+}