TIL: Using Stable And Unstable Nix/NixOS Channels Together

content/til/using-stable-and-unstable-nix-channels-together

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++++
+title =  "Using Stable And Unstable Nix/NixOS Channels Together"
+date =  2025-05-03
+
+[taxonomies]
+tags = ["Nix", "NixOS"]
+categories = [ "TIL" ]
+
+[extra]
+toc = true
+keywords = ["Nix", "NixOS"]
++++
+
+For one of my servers that is running NixOS I have been using the stable channel for all packages. However I wanted for one package to use the version of the package that the unstable channel had and had to learn how to do it.
+
+I am using flakes and this is what I originally had as my input:
+
+```nix
+inputs = {
+    nixpkgs = {
+      url = "github:NixOS/nixpkgs/nixos-24.11";
+    };
+  };
+```
+
+I added the unstable channel as an input:
+
+```nix
+inputs = {
+    nixpkgs = {
+      url = "github:NixOS/nixpkgs/nixos-24.11";
+    };
+    nixpkgs-unstable = { # <-- added this !
+      url = "github:NixOS/nixpkgs/nixos-unstable";
+    };
+  };
+```
+
+I changed my output to make sure my system is configured with both channels as follows (see comments in code snippet for what I added):
+
+```nix
+outputs =
+    {
+      self,
+      nixpkgs,
+      nixpkgs-unstable, # <--- added this
+    }:
+    let
+      system = "x86_64-linux";
+
+      # Define the pkgs from both stable and unstable channels
+      pkgs = import nixpkgs {
+        inherit system;
+      };
+
+      unstablePkgs = import nixpkgs-unstable {
+        inherit system;
+      };
+    in
+    {
+      nixosConfigurations = {
+        myserver = nixpkgs.lib.nixosSystem {
+          inherit system;
+          modules = [
+            ./configuration.nix
+          ];
+          specialArgs = {
+            inherit pkgs unstablePkgs;   # <--- inheriting both!
+          };
+        };
+      };
+    };
+```
+
+Now where ever I define a nix function I include both `pkgs` and `unstablePkgs` as arguments and am able to chose what package from which channel to use.
+
+For example when choosing what system packages I want to install:
+
+```nix
+environment.systemPackages = with pkgs; [
+    eza
+    unstablePkgs.ripgrep
+];
+```
+
+Happy Days!