Nix Environment Skills

Overview

This skill provides expertise in Nix-based environment management including flakes, home-manager, and cross-platform configurations.

Development Shell

Enter Environment

nom develop                           # Preferred (with progress UI)
nix develop                           # Standard
direnv allow                          # Automatic via direnv

Shell Commands (defined in devshell)

Command	Description
cb	colcon build --symlink-install
ct	colcon test
ctr	colcon test-result --verbose
ros2-env	Show ROS2 environment variables
update-deps	Run pixi update
ai	AI chat assistant (aichat)
pair	AI pair programming (aider)

Flake Operations

Check and Validate

nix flake check                       # Validate flake
nix flake check --no-build            # Quick syntax check
nix flake show                        # Show flake outputs

Update Dependencies

nix flake update                      # Update all inputs
nix flake lock --update-input nixpkgs # Update specific input

Build Outputs

nix build .#package                   # Build specific output
nix build -L                          # Build with logs
nix log /nix/store/...                # View build log

Package Management

Nix Profile

nix profile install nixpkgs#package   # Install package
nix profile remove package            # Remove package
nix profile list                      # List installed
nix profile upgrade '.*'              # Upgrade all

Search Packages

nix search nixpkgs package            # Search nixpkgs
nix search nixpkgs#python3Packages.X  # Search Python packages

Home Manager

Importing Modules

This flake exports home-manager modules that can be imported:

{
  inputs = {
    ripple-env.url = "github:FlexNetOS/ripple-env";
    home-manager.url = "github:nix-community/home-manager";
  };

  outputs = { self, nixpkgs, home-manager, ripple-env, ... }: {
    homeConfigurations.myuser = home-manager.lib.homeManagerConfiguration {
      pkgs = nixpkgs.legacyPackages.x86_64-linux;
      modules = [
        ripple-env.homeManagerModules.default
        # Your modules...
      ];
    };
  };
}

Available Exports

Export	Description
homeManagerModules.default	All modules (platform-detected)
homeManagerModules.common	Cross-platform modules only
homeManagerModules.linux	Linux-specific modules
homeManagerModules.macos	macOS-specific modules
nixosModules.default	NixOS system module
darwinModules.default	nix-darwin module
lib	Utility functions

Module Options

Each module supports enable/disable:

{
  ros2-env.shell.zsh.enable = true;
  ros2-env.shell.nushell.enable = true;
  ros2-env.editor.helix.enable = true;
  ros2-env.direnv.enable = true;
}

Pixi Integration

Package Management

pixi add <package>                    # Add package
pixi remove <package>                 # Remove package
pixi search <pattern>                 # Search packages
pixi update                           # Update lockfile
pixi install                          # Install from lockfile
pixi info                             # Environment info

ROS2 Packages

pixi add ros-humble-desktop           # Full desktop
pixi add ros-humble-rviz2             # Visualization
pixi search ros-humble-*              # List all ROS packages

direnv Configuration

Setup

direnv allow                          # Allow directory
direnv deny                           # Deny directory
direnv reload                         # Reload environment

.envrc File

# Standard flake integration
use flake

# With nix-direnv caching
use flake . --impure

Cross-Platform Support

Platform Detection in Nix

{ pkgs, lib, ... }:
let
  isLinux = pkgs.stdenv.isLinux;
  isDarwin = pkgs.stdenv.isDarwin;
in {
  config = lib.mkMerge [
    (lib.mkIf isLinux { /* Linux config */ })
    (lib.mkIf isDarwin { /* macOS config */ })
  ];
}

Windows/WSL2

• Use bootstrap.ps1 for automated setup
• NixOS-WSL provides full Nix experience
• See: .github/docs/self-hosted-runner-setup.md

Debugging

Flake Issues

nix flake check                       # Check for errors
nix flake show                        # Show structure
nix eval .#someOutput                 # Evaluate expression
nix repl                              # Interactive REPL

Build Issues

nix build -L                          # Verbose build output
nix log /nix/store/hash-name          # View stored log
nix-store -q --references /nix/store/path  # Show dependencies

Cache Issues

nix store gc                          # Garbage collect
nix store optimise                    # Deduplicate store
nix-collect-garbage -d               # Remove old generations

Module Structure

Creating a New Module

{ config, lib, pkgs, ... }:
{
  options.mymodule = {
    enable = lib.mkEnableOption "my module";

    setting = lib.mkOption {
      type = lib.types.str;
      default = "value";
      description = "Setting description";
    };
  };

  config = lib.mkIf config.mymodule.enable {
    # Implementation
    home.packages = [ pkgs.sometool ];
  };
}

Module Location

• Cross-platform: modules/common/
• Linux-specific: modules/linux/
• macOS-specific: modules/macos/

Best Practices

1. Lock dependencies - Commit flake.lock
2. Use mkIf - For conditional configuration
3. Type options - Use lib.types.* for validation
4. Document options - Add description to each option
5. Platform check - Use stdenv.isLinux/isDarwin

Related Skills

• ROS2 Development - Using the environment
• DevOps - CI/CD integration