nh

nh (Nix Helper) Skill

nh is a CLI tool that simplifies Nix operations, providing a cleaner interface for builds, switches, and garbage collection.

Core Commands

System Updates (NixOS)

Use nh os for managing NixOS configurations. Prefix local paths with path:.

# Build and switch to a configuration (equivalent to nixos-rebuild switch)
nh os switch path:.

# Build and test a configuration (equivalent to nixos-rebuild test)
nh os test path:.

# Build a configuration without switching (equivalent to nixos-rebuild build)
nh os build path:.

# Make configuration the boot default without activating
nh os boot path:.

# Rollback to a previous generation
nh os rollback

# List available generations
nh os info

# Build a NixOS VM image
nh os build-vm path:.

# Load system configuration in a REPL (use tmux for interactive)
tmux new -d -s nh-repl 'nh os repl path:.'

Home Manager Updates

Use nh home for managing Home Manager configurations.

# Build and switch Home Manager configuration
nh home switch path:.

# Build Home Manager configuration without switching
nh home build path:.

# Load Home Manager configuration in a REPL (use tmux for interactive)
tmux new -d -s hm-repl 'nh home repl path:.'

Nix-Darwin (macOS)

Use nh darwin for managing nix-darwin configurations on macOS.

# Build and switch darwin configuration
nh darwin switch path:.

# Build darwin configuration without switching
nh darwin build path:.

Package Search

Search for packages using search.nixos.org:

# Search for packages
nh search ripgrep

Maintenance and Cleanup

nh clean provides a more intuitive way to manage the Nix store and generations.

# Clean all profiles (system + user)
nh clean all --keep-since 7d

# Clean only current user's profiles
nh clean user --keep 5

# Clean a specific profile
nh clean profile /nix/var/nix/profiles/system --keep 3

# Run garbage collection on the Nix store
nh clean all

Common Options

• --ask: Ask for confirmation before performing actions (Avoid in headless/automated scripts).
• --dry: Show what would happen without making changes.
• --update: Update flake inputs before building.

Best Practices

• Headless Usage: Avoid using the --ask flag in scripts or automated environments as it requires user interaction.
• Path Inference: nh automatically looks for a flake.nix in the current directory if no path is provided.
• Visuals: nh provides a more readable "Nom-like" output by default, which is helpful for monitoring build progress in a terminal.

Related Skills

• nix: Use Nix for running applications without installation and evaluating Nix expressions.
• nix-flakes: Leverage Nix Flakes for reproducible builds and project isolation with nh.