nix: modify nix configurations

darwin/default.nix

@@ -6,5 +6,6 @@
     ./packages
     ./main.nix
     ./input.nix
+    ./nix
   ];
 }

darwin/main.nix

@@ -14,18 +14,10 @@
 
   # List packages installed in system profile. To search by name, run:
   # $ nix-env -qaP | grep wget
-  environment.systemPackages = with pkgs; [
-    #neovim
-    #vscode
-  ];
-
-  # Auto upgrade nix package and the daemon service.
-  services.nix-daemon.enable = true;
-  nix.package = pkgs.nix;
-
-  # Necessary for using flakes on this system.
-  #nix.settings.experimental-features = "nix-command flakes";
-  nix.settings.experimental-features = [ "nix-command" "flakes" ];
+  #environment.systemPackages = with pkgs; [
+  #  neovim
+  #  vscode
+  #];
 
   # Create /etc/zshrc that loads the nix-darwin environment.
   programs.zsh.enable = true;  # default shell on catalina
@@ -154,8 +146,4 @@
 
   # Set Git commit hash for darwin-version.
   #system.configurationRevision = self.rev or self.dirtyRev or null;
-
-  # Used for backwards compatibility, please read the changelog before changing.
-  # $ darwin-rebuild changelog
-  system.stateVersion = 4;
 }

darwin/nix/default.nix

@@ -0,0 +1,9 @@
+{ ... }:
+
+{
+  imports = [
+    ./flake.nix
+    ./nix.nix
+    ./gc.nix
+  ];
+}

darwin/nix/flake.nix

@@ -0,0 +1,5 @@
+{ ... }:
+
+{
+  nix.settings.experimental-features = [ "nix-command" "flakes" ]; # enable flakes
+}

darwin/nix/gc.nix

@@ -0,0 +1,16 @@
+{ ... }:
+
+{
+  nix = {
+    ### optimiser
+    settings = {
+      auto-optimise-store = true;
+    };
+
+    ### auto delete older NixOS builds
+    gc = {
+      automatic = true;
+      options = "--delete-older-than 7d";
+    };
+  };
+}

darwin/nix/nix.nix

@@ -0,0 +1,29 @@
+{ pkgs, ... }:
+
+{
+  nix.settings = {
+    trusted-users = [ "@admin" ];
+    substituters = [
+      "https://mirrors.ustc.edu.cn/nix-channels/store"            # USTC - 中国科学技术大学 Mirror
+      "https://mirrors.tuna.tsinghua.edu.cn/nix-channels/store"   # TUNA - 清华大学 Mirror
+      "https://mirrors.bfsu.edu.cn/nix-channels/store"            # BFSU - 北京外国语大学 Mirror
+      "https://mirror.sjtu.edu.cn/nix-channels/store"             # SJTU - 上海交通大学 Mirror
+
+      "https://nix-community.cachix.org"
+      "https://cache.garnix.io"
+    ];
+    trusted-public-keys = [
+      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+      "cache.garnix.io:CTFPyKSLcx5RMJKfLo5EEPUObbA78b0YQ2DTCJXqr9g="
+    ];
+    use-xdg-base-directories = true;
+  };
+
+  # Auto upgrade nix package and the daemon service.
+  services.nix-daemon.enable = true;
+  nix.package = pkgs.nix;
+
+  # Used for backwards compatibility, please read the changelog before changing.
+  # $ darwin-rebuild changelog
+  system.stateVersion = 4;
+}

nixos/nix/gc.nix

@@ -2,15 +2,19 @@
 
 {
   nix = {
-    # hard linking
-    settings.auto-optimise-store = true;
+    ### optimiser
+    settings = {
+      auto-optimise-store = true;
+    };
 
-    # auto delete older NixOS builds
+    ### auto delete older NixOS builds
     gc = {
       automatic = true;
       dates = "weekly";
       options = "--delete-older-than 7d";
     };
+
+    ### optimiser
     optimise = {
       automatic = true;
       dates = [ "03:45" ];

nixos/nix/nix.nix

@@ -2,13 +2,13 @@
 
 {
   nix.settings = {
-    allowed-users = [ "@wheel" ];
+    trusted-users = [ "@wheel" ];
     substituters = [
-      "https://mirrors.ustc.edu.cn/nix-channels/store"
-      "https://mirrors.tuna.tsinghua.edu.cn/nix-channels/store"
-      "https://mirror.sjtu.edu.cn/nix-channels/store"
+      "https://mirrors.ustc.edu.cn/nix-channels/store"            # USTC - 中国科学技术大学 Mirror
+      "https://mirrors.tuna.tsinghua.edu.cn/nix-channels/store"   # TUNA - 清华大学 Mirror
+      "https://mirrors.bfsu.edu.cn/nix-channels/store"            # BFSU - 北京外国语大学 Mirror
+      "https://mirror.sjtu.edu.cn/nix-channels/store"             # SJTU - 上海交通大学 Mirror
 
-      # TODO: actually figure out what is Cachix
       "https://nix-community.cachix.org"
       "https://berberman.cachix.org"
       "https://hyprland.cachix.org"