Nix flake templates

For more details, please check my blog post.

Here are the templates I often use for my projects. They works perfectly with nix develop command and nix-direnv.

Systems

When we start using flake, we must specify which system this flake is targeting to. Honestly I never really care about the targeting system, I am using both Linxu and MacOS, I just want the same flake to be working on all systems.

    allSystems = [
      "x86_64-linux" # 64-bit Intel/AMD Linux
      "aarch64-linux" # 64-bit ARM Linux
      "x86_64-darwin" # 64-bit Intel macOS
      "aarch64-darwin" # 64-bit ARM macOS
    ];

flake-utils is a popular solution to this problem. After reading Why you don't need flake-utils, I've opted to use nix-systems instead.

Templates

Currently I have 5 templates to cover my daily needs.

default / shell

This template generates a flake that enables you to initiate the CLI exclusively for the project. For instance, if I solely require Terraform for my infrastructure projects, I can use this template to launch the opentofu CLI.

nix flake init -t github:liyangau/flake-templates

nur

This template leverages packages accessible from NUR. I've uploaded several packages I use daily onto NUR. With this template, I can easily access the CLI on a per-project basis.

nix flake init -t github:liyangau/flake-templates#nur

local

This template reads a local default.nix file, built the package and create shell environment with the package. It is useful when the package isn't accessible via nixpkgs or NUR. Typically, I use nix-init to generate the default.nix file automatically, which I subsequently integrate into my local project.

nix flake init -t github:liyangau/flake-templates#local

python

This template gives you a shell with Python 3.12 along with certain libraries to my needs.

nix flake init -t github:liyangau/flake-templates#python

docker

This template is a starting point to built docker images for x86_64 and ARM64 linux systems. You can find more examples here and the docs here.

unfree App

Sometimes, you might encounter errors similar to the following when attempting to use the flake. This typically occurs due to one of the packages being non-free, such as terraform.

       a) To temporarily allow unfree packages, you can use an environment variable
          for a single invocation of the nix tools.

            $ export NIXPKGS_ALLOW_UNFREE=1

          Note: When using `nix shell`, `nix build`, `nix develop`, etc with a flake,
                then pass `--impure` in order to allow use of environment variables.

       b) For `nixos-rebuild` you can set
         { nixpkgs.config.allowUnfree = true; }
       in configuration.nix to override this.

       Alternatively you can configure a predicate to allow specific packages:
         { nixpkgs.config.allowUnfreePredicate = pkg: builtins.elem (lib.getName pkg) [
             "terraform"
           ];
         }

       c) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
         { allowUnfree = true; }
       to ~/.config/nixpkgs/config.nix.

To solve the issue, you need to add config.allowUnfree = true; to forEachSystem as below.

    let
      forEachSystem =
        f:
        nixpkgs.lib.genAttrs (import systems) (
          system:
          f {
            pkgs = import nixpkgs {
              config.allowUnfree = true;
              inherit system;
            };
          }
        );
    in