Flakes: Difference between revisions

@@ Line 385: / Line 385: @@
 </syntaxHighlight>
 should make a package accessible through <syntaxHighlight>pkgs.unstable.package</syntaxHighlight>
+For example, a NixOS config flake skeleton could be as follows:
+<syntaxHighlight lang=nix>
+{
+  description = "NixOS configuration with two or more channels";
+  inputs = {
+    nixpkgs.url = "nixpkgs/nixos-21.11";
+    nixpkgs-unstable.url = "nixpkgs/nixos-unstable";
+  };
+  outputs = { self, nixpkgs, nixpkgs-unstable }:
+    let
+      overlay-unstable = final: prev: {
+        unstable = nixpkgs-unstable.legacyPackages.${prev.system};
+      };
+    in {
+      nixosConfigurations.<hostname> = nixpkgs.lib.nixosSystem {
+        system = "x86_64-linux";
+        modules = [
+          # Overlays-module makes "pkgs.unstable" available in configuration.nix
+          ({ config, pkgs, ... }: { nixpkgs.overlays = [ overlay-unstable ]; })
+          ./configuration.nix
+        ];
+      };
+    };
+}
+# NixOS configuration.nix, can now use "pkgs.app" or "pkgs.unstable.app"
+{ config, pkgs, ... }: {
+  environment.systemPackages = [pkgs.firefox pkgs.unstable.chromium];
+  # ...
+}
+</syntaxHighlight>
 Same can be done with the NURs, as it already has an ''overlay'' attribute in the flake.nix of the project, you can just add <syntaxHighlight>nixpkgs.overlays = [ nur.overlay ];</syntaxHighlight>