nix-installer

Install Nix - works on GitHub-hosted runners, self-hosted runners, and inside containers.

Features

• ✅ Smart detection - Skips install if Nix already present (container mode)
• ✅ Flakes enabled - nix-command and flakes enabled by default
• ✅ Universal - Works on ubuntu-latest, self-hosted, and nixos/nix containers
• ✅ Fast - No install needed when using containers

Usage

Basic

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: singularity-ng/nix-installer@v1
      - run: nix build

With Container (Fastest on self-hosted)

jobs:
  build:
    runs-on: self-hosted
    container: nixos/nix:latest
    steps:
      - uses: actions/checkout@v4
      - uses: singularity-ng/nix-installer@v1
      - run: nix build

Universal Matrix (Same workflow for all runner types)

jobs:
  build:
    strategy:
      matrix:
        include:
          - runner: self-hosted
            container: nixos/nix:latest
          - runner: ubuntu-latest
            container: nixos/nix:latest
          - runner: ubuntu-latest
            container: ''
    runs-on: ${{ matrix.runner }}
    container: ${{ matrix.container || null }}
    steps:
      - uses: actions/checkout@v4
      - uses: singularity-ng/nix-installer@v1
      - run: nix build

With Extra Configuration

- uses: singularity-ng/nix-installer@v1
  with:
    extra-conf: |
      substituters = https://cache.nixos.org https://nix-community.cachix.org
      trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs=

Inputs

Input	Description	Default
extra-conf	Extra lines to add to nix.conf	''
nix-version	Nix version to install (ignored in containers)	latest

Outputs

Output	Description
nix-path	Path to the Nix binary
already-installed	true if Nix was already installed (container mode)

How It Works

1. Detects if Nix is already installed (e.g., in nixos/nix container)
2. Skips installation if already present
3. Installs Nix if not found (using official installer)
4. Configures flakes and experimental features
5. Adds any extra configuration you provide

License

MIT