flake: add commonModules and enable nixos-exporter on all hosts

Refactor flake.nix to use a commonModules list for modules shared by
all hosts (overlays, sops-nix, nixos-exporter). This simplifies adding
new modules that apply to all hosts.

Move nixos-exporter configuration to system/monitoring/metrics.nix
alongside node-exporter and systemd-exporter.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

flake.nix

@@ -47,6 +47,17 @@
         alerttonotify.overlays.default
         labmon.overlays.default
       ];
+      # Common modules applied to all hosts
+      commonModules = [
+        (
+          { config, pkgs, ... }:
+          {
+            nixpkgs.overlays = commonOverlays;
+          }
+        )
+        sops-nix.nixosModules.sops
+        nixos-exporter.nixosModules.default
+      ];
       allSystems = [
         "x86_64-linux"
         "aarch64-linux"
@@ -63,15 +74,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/ns1
-            sops-nix.nixosModules.sops
           ];
         };
         ns2 = nixpkgs.lib.nixosSystem {
@@ -79,15 +83,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/ns2
-            sops-nix.nixosModules.sops
           ];
         };
         ha1 = nixpkgs.lib.nixosSystem {
@@ -95,15 +92,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/ha1
-            sops-nix.nixosModules.sops
           ];
         };
         template1 = nixpkgs.lib.nixosSystem {
@@ -111,15 +101,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/template
-            sops-nix.nixosModules.sops
           ];
         };
         template2 = nixpkgs.lib.nixosSystem {
@@ -127,15 +110,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/template2
-            sops-nix.nixosModules.sops
           ];
         };
         http-proxy = nixpkgs.lib.nixosSystem {
@@ -143,15 +119,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/http-proxy
-            sops-nix.nixosModules.sops
           ];
         };
         ca = nixpkgs.lib.nixosSystem {
@@ -159,15 +128,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/ca
-            sops-nix.nixosModules.sops
           ];
         };
         monitoring01 = nixpkgs.lib.nixosSystem {
@@ -175,17 +137,9 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/monitoring01
-            sops-nix.nixosModules.sops
             labmon.nixosModules.labmon
-            nixos-exporter.nixosModules.default
           ];
         };
         jelly01 = nixpkgs.lib.nixosSystem {
@@ -193,15 +147,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/jelly01
-            sops-nix.nixosModules.sops
           ];
         };
         nix-cache01 = nixpkgs.lib.nixosSystem {
@@ -209,15 +156,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/nix-cache01
-            sops-nix.nixosModules.sops
           ];
         };
         pgdb1 = nixpkgs.lib.nixosSystem {
@@ -225,15 +165,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/pgdb1
-            sops-nix.nixosModules.sops
           ];
         };
         nats1 = nixpkgs.lib.nixosSystem {
@@ -241,15 +174,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/nats1
-            sops-nix.nixosModules.sops
           ];
         };
         testvm01 = nixpkgs.lib.nixosSystem {
@@ -257,15 +183,8 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/testvm01
-            sops-nix.nixosModules.sops
           ];
         };
         vault01 = nixpkgs.lib.nixosSystem {
@@ -273,33 +192,19 @@
           specialArgs = {
             inherit inputs self sops-nix;
           };
-          modules = [
+          modules = commonModules ++ [
-            (
-              { config, pkgs, ... }:
-              {
-                nixpkgs.overlays = commonOverlays;
-              }
-            )
             ./hosts/vault01
-            sops-nix.nixosModules.sops
           ];
         };
-      vaulttest01 = nixpkgs.lib.nixosSystem {
+        vaulttest01 = nixpkgs.lib.nixosSystem {
-        inherit system;
+          inherit system;
-        specialArgs = {
+          specialArgs = {
-          inherit inputs self sops-nix;
+            inherit inputs self sops-nix;
+          };
+          modules = commonModules ++ [
+            ./hosts/vaulttest01
+          ];
         };
-        modules = [
-          (
-            { config, pkgs, ... }:
-            {
-              nixpkgs.overlays = commonOverlays;
-            }
-          )
-          ./hosts/vaulttest01
-          sops-nix.nixosModules.sops
-        ];
-      };
       };
       packages = forAllSystems (
         { pkgs }:

hosts/monitoring01/configuration.nix

@@ -99,23 +99,6 @@
     ];
   };
 
-  # NixOS metrics exporter
-  services.prometheus.exporters.nixos = {
-    enable = true;
-    flake = {
-      enable = true;
-      url = "git+https://git.t-juice.club/torjus/nixos-servers.git";
-    };
-  };
-
-  # Register nixos-exporter as a Prometheus scrape target
-  homelab.monitoring.scrapeTargets = [
-    {
-      job_name = "nixos-exporter";
-      port = 9971;
-    }
-  ];
-
   labmon = {
     enable = true;
 

system/monitoring/metrics.nix

@@ -18,4 +18,21 @@
       "--systemd.collector.enable-ip-accounting"
     ];
   };
+
+  services.prometheus.exporters.nixos = {
+    enable = true;
+    # Default port: 9971
+    flake = {
+      enable = true;
+      url = "git+https://git.t-juice.club/torjus/nixos-servers.git";
+    };
+  };
+
+  # Register nixos-exporter as a Prometheus scrape target
+  homelab.monitoring.scrapeTargets = [
+    {
+      job_name = "nixos-exporter";
+      port = 9971;
+    }
+  ];
 }