Add initial installer

nixos/installer.nix

@@ -0,0 +1,43 @@
+{ lib, modulesPath, config, ... }:
+let
+  inherit (lib) mkDefault mkForce;
+in
+{
+  imports = [
+    # Lots of kernel modules and firmware
+    "${modulesPath}/profiles/all-hardware.nix"
+    # Useful tools to have
+    "${modulesPath}/profiles/base.nix"
+  ];
+
+  # Some of this is yoinked from modules/profiles/installation-device.nix
+  config = {
+    my = {
+      # Whatever installer mechanism is chosen will provied an appropriate `/`
+      tmproot.enable = false;
+      firewall.nat.enable = false;
+      server.enable = true;
+    };
+
+    # Good to have docs in the installer!
+    documentation.enable = mkForce true;
+    documentation.nixos.enable = mkForce true;
+
+    # Enable wpa_supplicant, but don't start it by default.
+    networking.wireless.enable = mkDefault true;
+    networking.wireless.userControlled.enable = true;
+    systemd.services.wpa_supplicant.wantedBy = mkForce [];
+
+    # Tell the Nix evaluator to garbage collect more aggressively.
+    # This is desirable in memory-constrained environments that don't
+    # (yet) have swap set up.
+    environment.variables.GC_INITIAL_HEAP_SIZE = "1M";
+
+    # Make the installer more likely to succeed in low memory
+    # environments.  The kernel's overcommit heustistics bite us
+    # fairly often, preventing processes such as nix-worker or
+    # download-using-manifests.pl from forking even if there is
+    # plenty of free memory.
+    boot.kernel.sysctl."vm.overcommit_memory" = "1";
+  };
+}