feat: setup base

modules/nixos/core/nix.nix

@@ -0,0 +1,83 @@
+{
+  flake.modules.nixos.core =
+    { userName, ... }:
+    {
+      nix = {
+        channel.enable = false;
+
+        gc = {
+          automatic = true;
+          options = "--delete-older-than 7d";
+          dates = "weekly";
+          persistent = true;
+        };
+
+        optimise.automatic = true;
+
+        settings = {
+          experimental-features = [
+            "nix-command"
+            "flakes"
+          ];
+
+          max-jobs = "auto";
+
+          # Make legacy nix commands use the XDG base directories instead of creating directories in $HOME.
+          use-xdg-base-directories = true;
+
+          # The maximum number of parallel TCP connections used to fetch files from binary caches and by other downloads.
+          # It defaults to 25. 0 means no limit.
+          http-connections = 128;
+
+          # This option defines the maximum number of substitution jobs that Nix will try to run in
+          # parallel. The default is 16. The minimum value one can choose is 1 and lower values will be
+          # interpreted as 1.
+          max-substitution-jobs = 128;
+
+          # The number of lines of the tail of the log to show if a build fails.
+          log-lines = 25;
+
+          # When free disk space in /nix/store drops below min-free during a build, Nix performs a
+          # garbage-collection until max-free bytes are available or there is no more garbage.
+          # A value of 0 (the default) disables this feature.
+          min-free = 128000000; # 128 MB
+          max-free = 1000000000; # 1 GB
+
+          # Prevent garbage collection from altering nix-shells managed by nix-direnv
+          # https://github.com/nix-community/nix-direnv#installation
+          keep-outputs = true;
+          keep-derivations = true;
+
+          # If set to true, Nix will keep building derivations even if some fail. The default is false.
+          keep-going = true;
+
+          # Automatically detect files in the store that have identical contents, and replaces
+          # them with hard links to a single copy. This saves disk space.
+          auto-optimise-store = true;
+
+          # Whether to warn about dirty Git/Mercurial trees.
+          warn-dirty = false;
+
+          # The timeout (in seconds) for establishing connections in the binary cache substituter.
+          # It corresponds to curl’s –connect-timeout option. A value of 0 means no limit.
+          connect-timeout = 5;
+
+          # Allow the use of cachix
+          trusted-users = [
+            "root"
+            "${userName}"
+          ];
+          allowed-users = [
+            "root"
+            "${userName}"
+          ];
+
+          builders-use-substitutes = true;
+
+          # If set to true, Nix will fall back to building from source if a binary substitute
+          # fails. This is equivalent to the –fallback flag. The default is false.
+          fallback = true;
+        };
+      };
+    };
+}