init nix-os configuraion files

modules/nixos/core.nix

@@ -0,0 +1,70 @@
+{ lib, ... }:
+{
+  programs = {
+    git.enable = true;
+    dconf.enable = true;
+    vim = {
+      defaultEditor = true;
+    };
+  };
+
+
+  # This setups a SSH server. Very important if you're setting up a headless system.
+  # Feel free to remove if you don't need it.
+  services.openssh = {
+    enable = true;
+    # Forbid root login through SSH.
+    # Use keys only. Remove if you want to SSH using password (not recommended)
+    settings = {
+      # permitRootLogin = "no";
+      # passwordAuthentication = false;
+    };
+  };
+
+
+  # networking.firewall.allowedTCPPorts = [ ... ];
+  # networking.firewall.allowedUDPPorts = [ ... ];
+  # Or disable the firewall altogether.
+  networking.firewall.enable = lib.mkDefault false;
+
+  # Select internationalisation properties.
+  i18n.defaultLocale = "en_US.UTF-8";
+
+  i18n.extraLocaleSettings = {
+    LC_ADDRESS = "zh_CN.UTF-8";
+    LC_IDENTIFICATION = "zh_CN.UTF-8";
+    LC_MEASUREMENT = "zh_CN.UTF-8";
+    LC_MONETARY = "zh_CN.UTF-8";
+    LC_NAME = "zh_CN.UTF-8";
+    LC_NUMERIC = "zh_CN.UTF-8";
+    LC_PAPER = "zh_CN.UTF-8";
+    LC_TELEPHONE = "zh_CN.UTF-8";
+    LC_TIME = "zh_CN.UTF-8";
+  };
+
+  time.timeZone = "Asia/Shanghai";
+
+  nix = {
+    settings = {
+      # Enable flakes and new 'nix' command
+      experimental-features = "nix-command flakes";
+      # Deduplicate and optimize nix store
+      auto-optimise-store = true;
+      substituters = [
+        "https://mirrors.ustc.edu.cn/nix-channels/store"
+        "https://nixos-cn.cachix.org"
+        "https://nix-community.cachix.org"
+        "https://cache.nixos.org/"
+      ];
+      trusted-public-keys = [
+        "nixos-cn.cachix.org-1:L0jEaL6w7kwQOPlLoCR3ADx+E3Q8SEFEcB9Jaibl0Xg="
+        "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+      ];
+    };
+    gc = {
+      automatic = true;
+      dates = "daily";
+      options = "--delete-older-than 7d";
+    };
+  };
+}