Install another version of hercules-ci-agent using Flakes

Whereas the setup guides assume you want to install the version bundled with Nixpkgs, a specific version of hercules-ci-agent can be installed using a Nix flake.

The hercules-ci-agent flake offers the following attributes:

  • nixosModules.agent-service: a module that replaces the Nixpkgs agent module

  • nixosModules.agent-profile: a similar module that has opinionated defaults for Nix garbage collection

  • darwinModules.agent-service: a module that replaces the nix-darwin agent module

  • darwinModules.agent-profile: a similar module that has opinionated defaults for Nix garbage collection

  • packages.<system>.hercules-ci-agent: just the agent package

  • packages.<system>.hercules-ci-agent-<variant>: variants of the agent package, such as different Nix versions

While Flakes allows you to append a path and import files from within the flake, the /module.nix file and other files do not work in Nix version 2.4, because it does not allow these files to open the flake, for apparently no good reason. Similarly, regressions have broken flake-compat.

hercules-ci.cachix.org provides binaries to accompany the flake.

Example NixOS configuration

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    hercules-ci-agent.url = "github:hercules-ci/hercules-ci-agent/stable";
    # or to pin a specific version, for example:
    # hercules-ci-agent.url = "github:hercules-ci/hercules-ci-agent/hercules-ci-agent-0.8.4";
  };

  outputs = [email protected]{ self, nixpkgs, ... }: {

    nixosConfigurations.default = nixpkgs.lib.nixosSystem {
      system = "x86_64-linux";
      modules = [
        ({ config, lib, pkgs, ... }: {
          imports = [
            inputs.hercules-ci-agent.nixosModules.agent-service
            # ... other imports if you have them
          ];

          services.hercules-ci-agent.enable = true;

          # ... other option value definitions
        })
      ];
    };
  };
}

Install an agent variant; different Nix version

Add to the NixOS or nix-darwin configuration:

# Make sure your module starts with at least the parameters
{ lib, pkgs, ... }: {

  services.hercules-ci-agent.package =
    let inherit (pkgs.stdenv.hostPlatform) system;
    in inputs.hercules-ci-agent.package.${system}.hercules-ci-agent-nix_2_4;
}

Install an agent variant using a separate module file

If your flake references a separate file for the module, for example using imports, you can wire up inputs along as follows:

Make sure you bind inputs where you define the flake outputs:

  outputs = [email protected]{ self, nixpkgs, ... }: {

Pass inputs along to all modules.

    nixpkgs.lib.nixosSystem {
      system = "x86_64-linux";
      specialArgs = { inherit inputs; };

      # ...
    }

Make your module ask for the inputs argument:

{ inputs, ... }: {
  services.hercules-ci-agent.package =
    let inherit (pkgs.stdenv.hostPlatform) system;
    in inputs.hercules-ci-agent.package.${system}.hercules-ci-agent-nix_2_4;
}