The Determinate Nix Installer Action

The fast, friendly, and reliable GitHub Action to install [Determinate Nix][det-nix] with [flakes]. The Determinate Nix Installer Action is based on [Determinate Nix Installer][installer], which is responsible for tens of thousands of installs daily.

Supports

• ✅ Accelerated KVM on open source projects and larger runners. See GitHub's announcement for more info.
• ✅ Linux (x86_64 and aarch64)
• ✅ macOS (aarch64)
• ✅ Windows Subsystem for Linux (WSL) (x86_64 and aarch64)
• ✅ Containers
• ✅ Valve's SteamOS
• ✅ GitHub Enterprise Server
• ✅ GitHub Hosted, self-hosted, and long running Actions Runners

Usage

on:
  pull_request:
  push:
    branches: [main]

jobs:
  lints:
    name: Build
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
      - uses: DeterminateSystems/nix-installer-action@main
      - run: nix build .

[!NOTE] This Action installs [Determinate Nix][det-nix] by default. You can, however, use it to install upstream Nix until January 1, 2026.

With FlakeHub

To fetch private flakes from FlakeHub and Nix builds from FlakeHub Cache, update the permissions block and use [determinate-nix-action][determinate-nix-action] instead of this Action:

on:
  pull_request:
  push:
    branches: [main]

jobs:
  lints:
    name: Build
    runs-on: ubuntu-latest
    permissions:
      id-token: "write"
      contents: "read"
    steps:
      - uses: actions/checkout@v6
      - uses: DeterminateSystems/determinate-nix-action@v3
      - run: nix build .

See .github/workflows/ci.yml for a full example.

Pinning the version

This GitHub Action uses the most recent version of Determinate Nix Installer, even when the Action itself is pinned. If you wish to pin your CI workflows to a specific Determinate Nix version, use the [determinate-nix-action][determinate-nix-action]. That Action is updated and tagged for every Determinate release.

The DeterminateSystems/determinate-nix-action@v3.5.2 reference, for example, always installs Determinate Nix v3.5.2.

Additionally, an extra tag on the major version is kept up to date with the current release. The DeterminateSystems/determinate-nix-action@v3 reference, for example, installs the most recent release in the v3.x.y series.

If you do tag to a specific version, please [use Dependabot to update your actions][dependabot-actions].

Advanced Usage

• If KVM is available, the installer sets up KVM so that Nix can use it ,and exports the DETERMINATE_NIX_KVM environment variable set to 1. If KVM is not available, DETERMINATE_NIX_KVM is set to 0. This can be used in combination with GitHub Actions' if syntax for turning on and off steps.

Installation Differences

Differing from the upstream Nix installer scripts:

• In nix.conf:
• the nix-command and flakes features are enabled
• bash-prompt-prefix is set
• auto-optimise-store is set to true (On Linux only)
• extra-nix-path is set to nixpkgs=flake:nixpkgs
• max-jobs is set to auto
• KVM is enabled by default.
• an installation receipt (for uninstalling) is stored at /nix/receipt.json as well as a copy of the install binary at /nix/nix-installer
• nix-channel --update is not run, ~/.nix-channels is not provisioned
• ssl-cert-file is set in /etc/nix/nix.conf if the ssl-cert-file argument is used.

Configuration