Add build-flakes script for nix-cache

hosts/nix-cache01/default.nix

@@ -2,5 +2,6 @@
 {
   imports = [
     ./configuration.nix
+    ../../services/nix-cache
   ];
 }

services/monitoring/prometheus.nix

@@ -138,6 +138,7 @@
               "ns2.home.2rjus.net:9100"
               "http-proxy.home.2rjus.net:9100"
               "ha1.home.2rjus.net:9100"
+              "nix-cache01.home.2rjus.net:9100"
             ];
           }
         ];

services/nix-cache/build-flakes.nix

@@ -0,0 +1,42 @@
+{ pkgs, ... }:
+let
+  build-flake-script = pkgs.writeShellApplication {
+    name = "build-flake-script";
+    runtimeInputs = with pkgs; [
+      git
+      nix
+      nixos-rebuild
+      jq
+    ];
+    text = ''
+      cd /root/nixos-servers
+      git pull
+      echo "Starting nixos-servers builds"
+      for host in $(nix flake show --json| jq -r '.nixosConfigurations | keys[]'); do
+        echo "Building $host"
+        nixos-rebuild --verbose -L --flake ".#$host" build
+      done
+      echo "All nixos-servers builds complete"
+
+      echo "Building gunter"
+      cd /root/nixos
+      git pull
+      nixos-rebuild --verbose -L --flake ".#gunter" build
+    '';
+  };
+in
+{
+  systemd.services."build-flakes" = {
+    serviceConfig = {
+      Type = "oneshot";
+      ExecStart = "${build-flake-script}/bin/build-flake-script";
+    };
+  };
+  systemd.timers."build-flakes" = {
+    enable = true;
+    wantedBy = [ "timers.target" ];
+    timerConfig = {
+      OnCalendar = "Sun 06:00:00";
+    };
+  };
+}

services/nix-cache/default.nix

@@ -0,0 +1,6 @@
+{ ... }:
+{
+  imports = [
+    ./build-flakes.nix
+  ];
+}