Nix — Purely Functional Package Manager

Nix is a purely functional package manager that treats packages as values in a functional programming language — built by pure functions with no side effects, never overwritten after creation. This skill covers the complete Nix manual: language reference, store internals, command-line tools, and protocols.

Key properties:

• •Reproducible: Hermetic builds via pure function semantics — same inputs always produce the same outputs
• •Declarative: Package descriptions are Nix expressions, not imperative scripts
• •Reliable: Atomic upgrades/rollbacks, multiple versions coexist, garbage collection for unused paths
• •Multi-user: Unprivileged users can install packages securely without root

When to use this skill

Invoke when the user asks about:

• •Nix language syntax, builtins, derivations, or evaluation semantics
• •Nix store concepts (store paths, content addressing, file system objects)
• •Nix CLI commands (nix-build, nix-env, nix-store, nix-shell, etc.)
• •Package management (profiles, channels, garbage collection, binary caches)
• •Distributed/remote builds, build reproducibility, caching strategies
• •Nix protocols (NAR format, store path calculation, JSON formats)
• •Nix internals, architecture, or contributing to Nix development

Additional Resources

Overview

• •Introduction — What Nix is and its core features
• •Quick Start — Minimal getting-started guide (install, run, search, GC)
• •Glossary — Definitions of Nix terminology (derivation, store path, closure, etc.)
• •Table of Contents — Master hierarchical index of the entire manual

Installation

• •Installation Overview — Recommended installation methods
• •Installing a Binary Distribution — Install via official script (curl | sh)
• •Using Nix within Docker — Running Nix in Docker containers
• •Supported Platforms — Linux (i686, x86_64, aarch64) and macOS
• •Multi-User Mode — Shared store with build user isolation
• •Single-User Mode — Single-user store ownership
• •Security — Security models and threat prevention
• •Environment Variables — PATH setup and nix.sh sourcing
• •Upgrading — Version upgrades via channels
• •Uninstalling — Removal steps for Linux/macOS
• •Building from source: Prerequisites | Obtaining Source | Building | Installing

Nix Language

• •Language Overview — Domain-specific, declarative, pure, lazy, dynamically typed
• •Syntax — Expression syntax and semantics
• •Data Types — Integer, Float, Boolean, String, Path, Null, Attrset, List, Function
• •Variables — Variable binding and usage
• •Identifiers — Naming rules and reserved keywords
• •Scoping Rules — let, rec, with, and function scopes
• •String Literals — Quoted strings, indented strings, URI literals
• •String Interpolation — ${ } syntax in strings, paths, and attribute names
• •String Context — Derivation dependency tracking via string contexts
• •Operators — Full operator reference with precedence and associativity
• •Language Constructs — Expression forms and control flow
  • •Lookup Path — <name> resolution via builtins.nixPath
• •Derivations — The derivation builtin and store derivation creation
• •Evaluation — How expressions become values (lazy evaluation)
• •Import From Derivation — When expression values depend on build outputs
• •Advanced Attributes — Infrequent derivation attributes (exportReferencesGraph, etc.)
• •Built-in Functions — Reference for all builtins.* functions

Nix Store

• •Store Overview — Immutable file system abstraction for packages and dependencies
• •Store Object — FSO data + reference set forming a directed graph
• •Store Path — Opaque unique identifiers (e.g. /nix/store/a040m110...-git-2.38.1)
• •File System Object — Simplified FS model (files, directories, symlinks)
• •Building — How derivations are built (input normalization, builder execution)
• •Build Trace — Memoization table for content-addressed derivation outputs
• •Secrets — Why secrets must not be embedded in store objects
• •Derivation Resolution — Replacing inputs with simplest equivalent paths
• •Derivation outputs: Overview | Output Types | Content-Addressed | Input-Addressed
• •Content addressing: FSO | Store Object
• •Math Notation Appendix — Formal notation for store path grammar

Package Management

• •Package Management Overview — Obtaining, installing, upgrading, and erasing packages
• •Profiles — Per-user configurations with atomic upgrades/rollbacks
• •Garbage Collection — Removing unused packages
• •Garbage Collector Roots — Symlinks protecting store paths from GC
• •Binary Cache (HTTP) — Serving a Nix store as a binary cache
• •SSH Substituter — Fetching binaries from remote stores via SSH
• •Sharing Packages — Copying packages between machines

Command Reference

• •Command Reference Overview — Index of all Nix commands
• •Common Options — Universal CLI options (--help, etc.)
• •Common Environment Variables — NIX_PATH, IN_NIX_SHELL, etc.
• •Configuration File (nix.conf) — Settings and format
• •Build Failure Exit Codes — Exit codes 100 (generic), 101 (timeout), etc.

Main Commands

• •nix-build — Build a Nix expression
• •nix-shell — Interactive shell from Nix expression
• •nix-store — Manipulate/query the store
• •nix-env — Manage user environments
• •nix-channel — Manage Nix channels
• •nix-collect-garbage — Delete unreachable store objects
• •nix-instantiate — Instantiate store derivations from expressions
• •nix-hash — Compute cryptographic hashes
• •nix-prefetch-url — Download URL to store and print hash
• •nix-copy-closure — Copy closures to/from remote machines
• •nix-daemon — Multi-user support daemon

nix-env Subcommands

• •install | uninstall | upgrade | query | set | set-flag | rollback | switch-generation | switch-profile | list-generations | delete-generations

nix-store Subcommands

• •realise | gc | delete | query | add | add-fixed | verify | verify-path | repair-path | dump | dump-db | restore | export | import | optimise | read-log | print-env | generate-binary-cache-key | serve | load-db

Files

• •

  Profiles | Channels | Default Nix Expression | manifest.json | manifest.nix

• •

  Experimental Commands — Unstable commands subject to change

• •

  Utilities — Additional utility tools

Advanced Topics

• •Advanced Topics Overview — Build performance and advanced build features
• •Tuning Cores and Jobs — Configuring cores and max-jobs for CPU utilization
• •Verifying Build Reproducibility — Using diff-hook to compare builds
• •Remote/Distributed Builds — Forwarding builds to other machines
• •Evaluation Profiler — Flamegraph-compatible profiling of Nix evaluation
• •Post-Build Hook — Auto-running scripts after builds (e.g. upload to cache)

Protocols

• •Protocols Overview — Developer-facing interfaces provided by Nix
• •Store Path Calculation — Full EBNF spec for computing store paths
• •Derivation ATerm Format — On-disk serialization (Derive(...))
• •Tarball Fetcher Protocol — Lockable HTTP tarball serving via Link header
• •Nix Archive (NAR) Format — EBNF spec for FSO tree serialization
• •JSON formats: Index | Build Result | Store Path | Store | Store Object Info | Content Address | Hash | Deriving Path | FSO | Build Trace Entry | Derivation | Derivation Options

Architecture

• •Architecture — Internal component hierarchy and concept map

Development (Contributing to Nix)

• •Development Overview — Entry points for contributing
• •Building Nix — Cloning and building from source
• •Testing — Coverage analysis and test execution
• •Debugging — Debug symbols and debugging in tests
• •Contributing — Release note format and PR conventions
• •CLI Guideline — UX design guidelines for nix commands
• •JSON Guideline — Consistent JSON interface practices
• •C++ Style Guide — C++ conventions and *-impl.hh pattern
• •Documentation — Contributing docs, building the manual
• •Experimental Features — Feature flag system for unstable functionality
• •Benchmarking — Google Benchmark framework usage

C API

• •C API — In-development stable C API with auto-generated documentation

Release Notes

• •Release Notes Index — All release notes from Nix 0.5 through 2.33

Assets

• •figures/user-environments.png — User environments diagram
• •figures/user-environments.sxd — Source for user environments diagram