nixy

Nixy

Simple, powerful Nix development environments without the complexity.

Why Nixy?

Nixy bridges the gap between Nix's powerful reproducibility and developer-friendly simplicity. Write a simple YAML file, get a fully reproducible development environment - no Nix knowledge required.

Quick Start

# Initialize a new project
nixy init

# Enter development shell
nixy shell

Auto Jump into nixy shell

Automatically enter the nixy shell when you navigate to a directory with a nixy.yml file.

Shell Integration

Add the following to your shell configuration file:

nixy shell:hook fish | source

eval "$(nixy shell:hook bash)"

eval "$(nixy shell:hook zsh)"

Features

• Supports auto-entering the nixy shell when nixy.yml is in the current directory
• Shows interactive prompt with 2-second timeout
• Press ENTER to launch, any other key to skip
• Auto-launches after timeout if no input
• Prevents duplicate activation when already in nixy shell
• Optional fancy styling with gum

Installation

Pre-built Binary (Recommended)

Download from releases page

From Source

go install github.com/nxtcoder17/nixy/cmd@latest

Using Nix

nix run github:nxtcoder17/nixy -- shell

Core Features

🎯 Simple YAML Configuration

No more complex Nix expressions. Just list what you need:

# Define multiple nixpkgs versions (default is required)
nixpkgs:
  default: abc123
  unstable: def456

packages:
  - nodejs           # Uses default nixpkgs
  - python3
  - unstable#go      # Uses unstable nixpkgs

libraries:      # System libraries
  - zlib
  - openssl

onShellEnter: |    # Shell initialization
  echo "Welcome to your dev environment!"

📦 Advanced Package Management

Nixpkgs Packages

# Define multiple nixpkgs versions
nixpkgs:
  default: dfb2f12e899db4876308eba6d93455ab7da304cd
  stable: abc123
  unstable: def456

packages:
  - nodejs                    # Latest from default nixpkgs
  - go_1_21                  # Specific version from default
  - stable#golang            # Package from stable nixpkgs
  - unstable#python314       # Package from unstable nixpkgs

URL Packages

Download and install packages directly from URLs with environment variable expansion:

packages:
  - name: kubectl
    sources:
      linux/amd64:
        url: https://dl.k8s.io/release/v1.28.0/bin/linux/amd64/kubectl
        sha256: "abc123..."  # Optional, auto-fetched if not provided
     
  - name: terraform
    sources:
      linux/amd64:
        url: https://releases.hashicorp.com/terraform/1.6.0/terraform_1.6.0_linux_amd64.zip
    # Automatically detects archive type and extracts
     
  # Environment variables are expanded in URLs
  - name: my-tool
    sources:
      linux/amd64:
        url: https://github.com/org/tool/releases/download/v${MY_VERSION}/tool-${NIXY_OS}-${NIXY_ARCH}.tar.gz
    # Uses MY_VERSION from env section and built-in NIXY_* vars

env:
  MY_VERSION: "1.2.3"  # Custom env vars can be used in URLs

Built-in environment variables available:

• NIXY_OS - Operating system (e.g., linux, darwin)
• NIXY_ARCH - Architecture (e.g., amd64, arm64)
• NIXY_ARCH_FULL - Full architecture string (e.g., x86_64)

🔧 Build System

Define reproducible runtime bundles that can be used outside nixy shell (for example in Docker images):

builds:
  runtime:
    dir: .
    command: |
      go build -o ./bin/my-app ./cmd/my-app
    packages:
      - python314
      - curl
      - nginx
    paths:
      - bin/my-app
      - scripts/
      - config/

Run a target:

nixy build runtime

Generate a target-specific Dockerfile while building:

nixy build runtime --dockerfile

Output layout:

• <dir>/.nixy/dist/app - symlink to built output in /nix/store
• <dir>/.nixy/dist/nix/store - copied recursive store closure for that output

dir is optional and defaults to .. It controls where the generated Dockerfile and .nixy/dist directory are written.

This makes it easy to copy the runtime bundle into container images and run the binaries without entering a nix shell.

Docker usage pattern:

1. Run nixy build <target> --dockerfile in your project.
2. Build the image using the target's dir as the Docker build context.
3. Add <copied-app>/bin to PATH.

GitHub Actions (build + artifact)

name: Build runtime bundle

on:
  push:
    branches: [main]

jobs:
  build-runtime:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - uses: cachix/install-nix-action@v31

      - name: Install nixy
        run: |
          mkdir -p "$HOME/.local/bin"
          curl -fsSL -o "$HOME/.local/bin/nixy" \
            https://github.com/nxtcoder17/nixy/releases/latest/download/nixy-linux-amd64
          chmod +x "$HOME/.local/bin/nixy"
          echo "$HOME/.local/bin" >> "$GITHUB_PATH"

      - name: Build target
        working-directory: example/docker-build
        run: nixy build runtime --dockerfile

      - name: Build Docker image from runtime bundle
        run: |
          docker build \
            -f example/docker-build/Dockerfile \
            -t nixy-runtime:ci \
            example/docker-build

      - uses: actions/upload-artifact@v4
        with:
          name: nixy-runtime
          path: example/docker-build/.nixy/dist/

🏃 Multiple Execution Backends

Local (Default)

Uses your system's Nix installation and inherits host environment:

nixy shell

Local (Pure Environment)

Uses your system's Nix installation but creates a pure environment (ignores host environment variables):

NIXY_EXECUTOR=local-ignore-env nixy shell

Docker

Perfect for CI/CD pipelines:

NIXY_EXECUTOR=docker nixy shell

Bubblewrap (Sandboxed)

Strong isolation with automatic static nix binary download - no systemwide Nix installation required:

NIXY_EXECUTOR=bubblewrap nixy shell

[!NOTE] Read more at Enable kernel.unprivileged_userns_clone check output of sysctl kernel.unprivileged_userns_clone if it is not set to 1. Set it to 1, otherwise you won't be able to use bubblewrap

echo "1" > /proc/sys/kernel/sysrq 

### 👤 Profile Management

> [!NOTE]
> Profiles provide runtime isolation. Different dev shells within the same profile share runtime filesystems like nix-store and fake-home.
> Profile-level `nixy.yml` config is loaded only when `NIXY_USE_PROFILE=true`.

Keep separate development profiles:
```bash
# Create profiles
nixy profile create work
nixy profile create personal

# Use a profile
NIXY_PROFILE=work nixy shell

# List profiles
nixy profile list

# Edit profile config
nixy profile edit work

Advanced Features

🌐 Mixed Package Sources

Combine packages from different nixpkgs versions:

nixpkgs:
  default: dfb2f12e899db4876308eba6d93455ab7da304cd
  older: 9d1fa9fa266631335618373f8faad570df6f9ede

packages:
  - nodejs                    # From default nixpkgs
  - older#python311           # Python from older nixpkgs version
  - name: custom-tool
    sources:
      linux/amd64:
        url: https://example.com/tool.tar.gz

🗂️ Smart Archive Packages Handling

Automatically detects and extracts from various archive formats:

• .tar, .tar.gz, .tar.xz, .tar.bz2
• .zip, .7z, .rar
• .gz, .xz, .bz2

🔒 Pure Environments

All execution backends provide pure, reproducible environments with:

• Isolated dependencies
• Consistent behavior across machines
• No global state pollution

⚡ Intelligent Caching

• Configuration change detection via SHA256
• Rebuilds only when necessary
• Fast subsequent shells

🔎 Inspectable Generated Files

Nixy writes generated workspace files to the project-local .nixy/ directory:

• .nixy/flake.nix - generated Nix flake used for the shell/build environment
• .nixy/flake.lock - generated lock file for the workspace flake
• .nixy/shell-enter.sh - generated script from onShellEnter
• .nixy/shell-env.sh - generated environment from nix print-dev-env
• .nixy/build.<target>.sh - generated build script for a target (/ and : are replaced with _)
• .nixy/config.hash - hash used to decide when generated files need refreshing

Build outputs remain under each build target directory, for example <build.dir>/.nixy/dist. .nixy/ should be gitignored because these files are regenerated from nixy.yml.

🎨 Environment Customization

onShellEnter: |
  export EDITOR=vim
  alias ll='ls -la'
  echo "Environment ready!"

env:
  NODE_ENV: development
  DATABASE_URL: postgresql://localhost/myapp
  # Use $$ for literal dollar signs
  MY_VAR: "some-value-$$-with-dollar"
  # Reference other env vars (expands at runtime)
  PATH: "$PATH:/custom/bin"

# Mount additional directories (Docker/Bubblewrap only)
mounts:
  - source: /host/path
    dest: /container/path
    readonly: true

Commands

Core Commands

• nixy init - Initialize a new nixy.yml
• nixy shell - Enter development shell
• nixy build [target] - Build defined targets
• nixy shell:hook <shell> - Output shell hook script for auto-activation (supports: bash, zsh, fish)

Profile Commands

• nixy profile create <name> - Create a profile namespace
• nixy profile edit [name] - Edit profile-level config
• nixy profile list - List all profiles

Examples

Full-Stack Development

nixpkgs:
  default: dfb2f12e899db4876308eba6d93455ab7da304cd

packages:
  # Backend
  - nodejs
  - postgresql_15

  # Frontend
  - pnpm
  - cypress

  # Tools
  - name: stripe-cli
    sources:
      linux/amd64:
        url: https://github.com/stripe/stripe-cli/releases/download/v1.19.1/stripe_1.19.1_linux_x86_64.tar.gz

libraries:
  - postgresql

Python Data Science

nixpkgs:
  default: dfb2f12e899db4876308eba6d93455ab7da304cd
  cuda: abc123                                  # Specific version for CUDA

packages:
  - python311
  - poetry
  - jupyter
  - cuda#cudaPackages.cudatoolkit              # CUDA from cuda nixpkgs

libraries:
  - zlib
  - blas
  - lapack

env:
  JUPYTER_ENABLE_LAB: "true"

Go with Kubernetes

packages:
  - go_1_21
  - golangci-lint
  - gopls
  
  # Kubernetes tools
  - name: kubectl
    sources:
      linux/amd64:
        url: https://dl.k8s.io/release/v1.28.0/bin/linux/amd64/kubectl
  - name: helm
    sources:
      linux/amd64:
        url: https://get.helm.sh/helm-v3.13.0-linux-amd64.tar.gz
  - name: k9s
    sources:
      linux/amd64:
        url: https://github.com/derailed/k9s/releases/download/v0.27.4/k9s_Linux_amd64.tar.gz

onShellEnter: |
  export KUBECONFIG=$HOME/.kube/config

Configuration Reference

nixy.yml

# Define nixpkgs versions (default is required)
nixpkgs:
  default: <commit-hash>              # Required
  stable: <commit-hash>               # Optional
  unstable: <commit-hash>             # Optional

# Package list
packages:
  - <package-name>                    # Simple package (uses default)
  - <key>#<package>                   # From specific nixpkgs key
  - name: <name>                      # URL package
    sources:
      linux/amd64:
        url: <url>
        sha256: <hash>                # Optional
    binPaths:
      - <relative-bin-dir>            # Optional
    installHook: |                    # Optional
      <shell commands>

# System libraries
libraries:
  - <library-name>

# Environment variables
env:
  KEY: value                          # Static value
  PATH: "$PATH:/custom"               # Variable expansion
  ESCAPED: "value-$$-literal"         # Use $$ for literal $

# Additional mounts (Docker/Bubblewrap only)
mounts:
  - source: /host/path
    dest: /container/path
    readonly: true                    # Optional, defaults to false

# Shell initialization
onShellEnter: |
  <bash commands>

# Build targets
builds:
  <target>:
    dir: .                              # Optional Docker/output context directory, defaults to .
    command: |                          # Optional command run before packaging paths
      <shell commands>
    packages:                            # Optional nix packages in output
      - <package>
    paths:
      - <file-path-1>                    # Optional project paths to include
      - <file-path-2>

Environment Variables

• NIXY_EXECUTOR - Execution backend (local, local-ignore-env, docker, bubblewrap)
• NIXY_PROFILE - Profile namespace to use
• NIXY_USE_PROFILE - Load profile-level config when set to true or 1

Troubleshooting

"No Nix installation found"

• Install Nix, or use NIXY_EXECUTOR=bubblewrap for automatic Nix download

"Package not found"

• Check package name at search.nixos.org
• Try updating nixpkgs commit hash

"Archive extraction failed"

• Verify URL is accessible
• Check if SHA256 matches
• Ensure archive isn't corrupted

Performance Issues

• Use local executor for fastest performance

Contributing

We welcome contributions! See CONTRIBUTING.md for guidelines.

License

MIT

Acknowledgments

Built with ❤️ using:

• Nix - The powerful package manager
• Go - The programming language
• bubblewrap - Unprivileged Sandboxing tool

Making Nix accessible to everyone, one YAML at a time.