NixOS Environment

Overview

This host is a NixOS system with flakes enabled. This means package management and environment setup work differently than traditional Linux distributions.

Core Concepts

1. •Immutable System: Packages are not installed globally via traditional package managers (apt, yum, etc.). System packages are declared in Nix configuration files.
2. •Flakes Enabled: The system uses Nix flakes for reproducible configurations.
3. •Ephemeral Environments: Use nix-shell or nix shell to temporarily add packages without installing them permanently, or use nix run for one-off commands.

Running Scripts with Dependencies

When you need to run a script that requires packages (like Python, Node.js, Ruby, etc.) that may not be installed system-wide, use ephemeral environments:

Using nix run (flakes, preferred for single-package commands)

nix run nixpkgs#python3 -- script.py
nix run nixpkgs#nodejs -- script.js
nix run nixpkgs#bash -- script.sh

Using nix shell (flakes, for multiple packages or custom commands)

# When you need multiple packages (e.g., Python + libraries)
nix shell nixpkgs#python3 nixpkgs#python3Packages.requests -c python3 script.py

# When running non-default commands
nix shell nixpkgs#nodejs nixpkgs#yarn -c yarn install

Using nix-shell (legacy, still works)

nix-shell -p python3 --run "python3 script.py"
nix-shell -p python3 python3Packages.requests --run "python3 script.py"

Interactive Shells

# Drop into a shell with packages available
nix shell nixpkgs#python3 nixpkgs#python3Packages.requests
# Or legacy: nix-shell -p python3 python3Packages.requests

Common Patterns

• •Python scripts: nix run nixpkgs#python3 -- script.py
• •Python with libraries: nix shell nixpkgs#python3 nixpkgs#python3Packages.requests -c python3 script.py
• •Node.js scripts: nix run nixpkgs#nodejs -- script.js
• •Shell scripts with tools: nix shell nixpkgs#curl nixpkgs#jq -c bash script.sh
• •Compilation: nix shell nixpkgs#gcc nixpkgs#gnumake -c make

Key Rules

1. •Don't assume packages are installed: Always check if a command exists before running it, or wrap it with nix run or nix shell.
2. •Prefer nix run for single-package commands: Use nix run nixpkgs#python3 -- script.py when you only need one tool.
3. •Use nix shell for multiple dependencies: Use nix shell nixpkgs#python3 nixpkgs#python3Packages.requests -c python3 script.py when you need multiple packages.
4. •Check system packages first: Use which <command> or command -v <command> to check if a tool is already available.
5. •Package names: Use nix search nixpkgs <term> to find package names if unsure.

Examples

User: "Run this Python script that uses requests library"

Action:

1. •Check if Python is available: which python3
2. •If not, or if requests is needed: nix shell nixpkgs#python3 nixpkgs#python3Packages.requests -c python3 script.py

User: "Run this simple Python script"

Action: nix run nixpkgs#python3 -- script.py

User: "Install jq and use it"

Action: Don't permanently install. Instead: nix run nixpkgs#jq -- -r '.field' data.json

User: "I need to compile this C program"

Action: nix shell nixpkgs#gcc -c gcc -o program program.c