devos/nix: add nix module

modules/devos/nix.nix

@@ -0,0 +1,65 @@
+{ channel, inputs, pkgs, lib, ... }:
+with lib;
+{
+  nix = {
+    package = pkgs.nixUnstable;
+
+    systemFeatures = [ "nixos-test" "benchmark" "big-parallel" "kvm" ];
+
+    autoOptimiseStore = true;
+
+    gc.automatic = true;
+
+    optimise.automatic = true;
+
+    useSandbox = true;
+
+    allowedUsers = [ "@wheel" ];
+
+    trustedUsers = [ "root" "@wheel" ];
+
+    extraOptions = ''
+      min-free = 536870912
+      keep-outputs = true
+      keep-derivations = true
+      fallback = true
+    '';
+
+    nixPath = [
+      "nixpkgs=${channel.input}"
+      "nixos-config=${../../lib/compat/nixos}"
+      "home-manager=${inputs.home}"
+    ];
+  };
+
+  nixpkgs.config = {
+    allowUnfree = true;
+  };
+
+
+  environment = {
+    systemPackages = with pkgs; [ nix-index nixfmt nixpkgs-fmt ];
+
+    shellAliases =
+      let ifSudo = mkIf config.security.sudo.enable;
+      in
+      {
+        # nix
+        n = "nix";
+        np = "n profile";
+        ni = "np install";
+        nr = "np remove";
+        ns = "n search --no-update-lock-file";
+        nf = "n flake";
+        nepl = "n repl '<nixpkgs>'";
+        srch = "ns nixos";
+        nrb = ifSudo "sudo nixos-rebuild";
+        mn = ''
+          manix "" | grep '^# ' | sed 's/^# \(.*\) (.*/\1/;s/ (.*//;s/^# //' | sk --preview="manix '{}'" | xargs manix
+        '';
+
+        # fix nixos-option
+        nixos-option = "nixos-option -I nixpkgs=${self}/lib/compat";
+      };
+  };
+}