add action

.editorconfig

@@ -0,0 +1,15 @@
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# Unix-style newlines with a newline ending every file
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 2
+indent_style = space
+insert_final_newline = true
+
+[LICENSE]
+indent_size = unset

.forgejo/dependabot.yml

@@ -0,0 +1,13 @@
+version: 2
+updates:
+
+- package-ecosystem: github-actions
+  directory: "/"
+  schedule:
+    interval: daily
+    time: '00:00'
+    timezone: UTC
+  open-pull-requests-limit: 10
+  commit-message:
+      prefix: "chore"
+      include: "scope"

.forgejo/workflows/test.yml

@@ -0,0 +1,152 @@
+name: "install-nix-action test"
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+
+env:
+  nixpkgs_channel: nixpkgs=channel:nixos-24.11
+  oldest_supported_installer: nix-2.8.0
+
+jobs:
+  simple-build:
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+        - ubuntu-latest
+        - ubuntu-24.04-arm
+        - macos-latest
+        - macos-13
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+    - name: Install Nix
+      uses: ./
+      with:
+        nix_path: ${{ env.nixpkgs_channel }}
+    - run: nix-env -iA cachix -f https://cachix.org/api/v1/install
+    - run: cat /etc/nix/nix.conf
+    # cachix should be available and be able to configure a cache
+    - run: cachix use cachix
+    - run: nix-build test.nix
+
+  custom-nix-path:
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+        - ubuntu-latest
+        - ubuntu-24.04-arm
+        - macos-latest
+        - macos-13
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+    - name: Install Nix
+      uses: ./
+      with:
+        nix_path: ${{ env.nixpkgs_channel }}
+    - run: test $NIX_PATH == '${{ env.nixpkgs_channel }}'
+    - run: nix-build test.nix
+
+  extra-nix-config:
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+        - ubuntu-latest
+        - ubuntu-24.04-arm
+        - macos-latest
+        - macos-13
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+    - name: Install Nix
+      uses: ./
+      with:
+        nix_path: ${{ env.nixpkgs_channel }}
+        extra_nix_config: |
+          sandbox = relaxed
+    - run: cat /etc/nix/nix.conf
+    - run: nix-build test.nix --arg noChroot true
+
+  flakes:
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+        - ubuntu-latest
+        - ubuntu-24.04-arm
+        - macos-latest
+        - macos-13
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+    - name: Install Nix
+      uses: ./
+    - run: nix flake show github:NixOS/nixpkgs
+
+  latest-installer:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-latest
+            system: x86_64-linux
+          - os: ubuntu-24.04-arm
+            system: aarch64-linux
+          - os: macos-latest
+            system: aarch64-darwin
+          - os: macos-13
+            system: x86_64-darwin
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+    - name: Run NAR server
+      run: |
+        curl --location https://github.com/cachix/nar-toolbox/releases/download/v0.1.0/nar-toolbox-${{ matrix.system }} -O
+        chmod +x ./nar-toolbox-${{ matrix.system }}
+        ./nar-toolbox-${{ matrix.system }} serve https://cache.nixos.org &
+    - name: Install Nix
+      uses: ./
+      with:
+        nix_path: ${{ env.nixpkgs_channel }}
+        install_url: https://hydra.nixos.org/job/nix/master/installerScript/latest-finished/download/1/install
+        install_options: "--tarball-url-prefix http://localhost:8080"
+    - run: nix-build test.nix
+
+  oldest-supported-installer:
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+        - ubuntu-latest
+        - ubuntu-24.04-arm
+        - macos-latest
+        - macos-13
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+    - name: Install Nix
+      uses: ./
+      with:
+        nix_path: ${{ env.nixpkgs_channel }}
+        install_url: https://releases.nixos.org/nix/${{ env.oldest_supported_installer }}/install
+    - run: nix-build test.nix
+
+  act-support:
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+    - run: curl https://raw.githubusercontent.com/nektos/act/master/install.sh | sudo bash
+    - run: docker pull ghcr.io/catthehacker/ubuntu:js-24.04
+    - run: |
+        ./bin/act push \
+          -P ubuntu-latest=ghcr.io/catthehacker/ubuntu:js-24.04 \
+          -j simple-build \
+          --matrix os:ubuntu-latest

.gitignore

@@ -0,0 +1,2 @@
+# dotenv environment variables file
+.env*

LICENSE

@@ -0,0 +1,225 @@
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+THE SOFTWARE.

README.md

@@ -0,0 +1,232 @@
+# install-nix-action
+
+![GitHub Actions badge](https://github.com/cachix/install-nix-action/workflows/install-nix-action%20test/badge.svg)
+
+Installs [Nix](https://nixos.org/nix/) on GitHub Actions for the supported platforms: Linux and macOS.
+
+By default it has no nixpkgs configured, you have to set `nix_path`
+by [picking a channel](https://status.nixos.org/)
+or [pin nixpkgs yourself](https://nix.dev/reference/pinning-nixpkgs)
+(see also [pinning tutorial](https://nix.dev/tutorials/towards-reproducibility-pinning-nixpkgs)).
+
+# Features
+
+- Quick installation (~4s on Linux, ~20s on macOS)
+- Multi-User installation (with sandboxing enabled only on Linux)
+- [Self-hosted GitHub runner](https://docs.github.com/en/actions/hosting-your-own-runners/about-self-hosted-runners) support
+- Allows specifying Nix installation URL via `install_url` (the oldest supported Nix version is 2.3.5)
+- Allows specifying extra Nix configuration options via `extra_nix_config`
+- Allows specifying `$NIX_PATH` and channels via `nix_path`
+- Share `/nix/store` between builds using [cachix-action](https://github.com/cachix/cachix-action) for simple binary cache setup to speed up your builds and share binaries with your team
+- Enables KVM on supported machines: run VMs and NixOS tests with full hardware-acceleration
+
+## Usage
+
+Create `.github/workflows/test.yml` in your repo with the following contents:
+
+```yaml
+name: "Test"
+on:
+  pull_request:
+  push:
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: cachix/install-nix-action@v31
+      with:
+        nix_path: nixpkgs=channel:nixos-unstable
+    - run: nix-build
+```
+
+## Usage with Flakes
+
+```yaml
+name: "Test"
+on:
+  pull_request:
+  push:
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: cachix/install-nix-action@v31
+      with:
+        github_access_token: ${{ secrets.GITHUB_TOKEN }}
+    - run: nix build
+    - run: nix flake check
+```
+
+To install Nix from any commit, go to [the corresponding installer_test action](https://github.com/NixOS/nix/runs/2219534360) and click on "Run cachix/install-nix-action@XX" step and expand the first line.
+
+## Inputs (specify using `with:`)
+
+- `extra_nix_config`: append to `/etc/nix/nix.conf`
+
+- `github_access_token`: configure Nix to pull from GitHub using the given GitHub token. This helps work around rate limit issues. Has no effect when `access-tokens` is also specified in `extra_nix_config`.
+
+- `install_url`: specify URL to install Nix from (useful for testing non-stable releases or pinning Nix, for example https://releases.nixos.org/nix/nix-2.3.7/install)
+
+- `install_options`: additional installer flags passed to the installer script.
+
+- `nix_path`: set `NIX_PATH` environment variable, for example `nixpkgs=channel:nixos-unstable`
+
+- `enable_kvm`: whether to enable KVM for hardware-accelerated virtualization on Linux. Enabled by default if available.
+
+- `set_as_trusted_user`: whether to add the current user to `trusted-users`. Enabled by default.
+
+
+## Differences from the default Nix installer
+
+Some settings have been optimised for use in CI environments:
+
+- `nix.conf` settings. Override these defaults with `extra_nix_config`:
+
+  - The experimental `flakes` and `nix-command` features are enabled. Disable by overriding `experimental-features` in `extra_nix_config`.
+
+  - `max-jobs` is set to `auto`.
+
+  - `show-trace` is set to `true`.
+
+  - `$USER` is added to `trusted-users`.
+
+  - `$GITHUB_TOKEN` is added to `access_tokens` if no other `github_access_token` is provided.
+
+  - `always-allow-substitutes` is set to `true`.
+
+  - `ssl-cert-file` is set to `/etc/ssl/cert.pem` on macOS.
+
+- KVM is enabled on Linux if available. Disable by setting `enable_kvm: false`.
+
+- `$TMPDIR` is set to `$RUNNER_TEMP` if empty.
+
+---
+
+## FAQ
+
+### How do I print nixpkgs version I have configured?
+
+```yaml
+- name: Print nixpkgs version
+  run: nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'
+```
+
+### How do I run NixOS tests?
+
+With the following inputs:
+
+```yaml
+- uses: cachix/install-nix-action@vXX
+  with:
+    enable_kvm: true
+    extra_nix_config: "system-features = nixos-test benchmark big-parallel kvm"
+```
+
+### How do I install packages via nix-env from the specified `nix_path`?
+
+```
+nix-env -i mypackage -f '<nixpkgs>'
+```
+
+### How do I add a binary cache?
+
+If the binary cache you want to add is hosted on [Cachix](https://cachix.org/) and you are
+using [cachix-action](https://github.com/cachix/cachix-action), you
+should use their `extraPullNames` input like this:
+
+```yaml
+- uses: cachix/cachix-action@vXX
+   with:
+     name: mycache
+     authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+     extraPullNames: nix-community
+```
+
+Otherwise, you can add any binary cache to nix.conf using
+install-nix-action's own `extra_nix_config` input:
+
+```yaml
+- uses: cachix/install-nix-action@v31
+  with:
+    extra_nix_config: |
+      trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
+      substituters = https://hydra.iohk.io https://cache.nixos.org/
+```
+
+### How do I pass environment variables to commands run with `nix develop` or `nix shell`?
+
+Nix runs commands in a restricted environment by default, called `pure mode`.
+In pure mode, environment variables are not passed through to improve the reproducibility of the shell.
+
+You can use the `--keep / -k` flag to keep certain environment variables:
+
+```yaml
+- name: Run a command with nix develop
+  run: nix develop --ignore-environment --keep MY_ENV_VAR --command echo $MY_ENV_VAR
+  env:
+    MY_ENV_VAR: "hello world"
+```
+
+Or you can disable pure mode entirely with the `--impure` flag:
+
+```
+nix develop --impure
+```
+
+### How do I pass AWS credentials to the Nix daemon?
+
+In multi-user mode, Nix commands that operate on the Nix store are forwarded to a privileged daemon. This daemon runs in a separate context from your GitHub Actions workflow and cannot access the workflow's environment variables. Consequently, any secrets or credentials defined in your workflow environment will not be available to Nix operations that require store access.
+
+There are two ways to pass AWS credentials to the Nix daemon:
+  - Configure a default profile using the AWS CLI
+  - Install Nix in single-user mode
+
+#### Configure a default profile using the AWS CLI
+
+The Nix daemon supports reading AWS credentials from the `~/.aws/credentials` file.
+
+We can use the AWS CLI to configure a default profile using short-lived credentials fetched using OIDC:
+
+```yaml
+job:
+  build:
+    runs-on: ubuntu-latest
+    # Required permissions to request AWS credentials
+    permissions:
+      id-token: write
+      contents: read
+    steps:
+      - uses: actions/checkout@v4
+      - uses: cachix/install-nix-action@v31
+      - name: Assume AWS Role
+        uses: aws-actions/configure-aws-credentials@v4.1.0
+        with:
+          aws-region: us-east-1
+          role-to-assume: arn:aws-cn:iam::123456789100:role/my-github-actions-role
+      - name: Make AWS Credentials accessible to nix-daemon
+        run: |
+          sudo -i aws configure set aws_access_key_id "${AWS_ACCESS_KEY_ID}"
+          sudo -i aws configure set aws_secret_access_key "${AWS_SECRET_ACCESS_KEY}"
+          sudo -i aws configure set aws_session_token "${AWS_SESSION_TOKEN}"
+          sudo -i aws configure set region "${AWS_REGION}"
+```
+
+#### Install Nix in single-user mode
+
+In some environments it may be possible to install Nix in single-user mode by passing the `--no-daemon` flag to the installer.
+This mode is normally used on platforms without an init system, like systemd, and in containerized environments with a single user that can own the entire Nix store.
+
+This approach is more generic as it allows passing environment variables directly to Nix, including secrets, proxy settings, and other configuration options.
+
+However, it may not be suitable for all environments. [Consult the Nix manual](https://nix.dev/manual/nix/latest/installation/nix-security) for the latest restrictions and differences between the two modes.
+
+For example, single-user mode is currently supported on hosted Linux GitHub runners, like `ubuntu-latest`.
+It is not supported on macOS runners, like `macos-latest`.
+
+```yaml
+- uses: cachix/install-nix-action@v31
+  with:
+    install_options: --no-daemon
+```

RELEASE.md

@@ -0,0 +1,44 @@
+# Release
+
+As of v31, releases of this action follow Semantic Versioning.
+
+### Publishing a new release
+
+#### Publish the release
+
+Draft [a new release on GitHub](https://github.com/cachix/install-nix-action/releases):
+
+- In `Choose a tag`, create a new tag, like `v31.2.1`, following semver.
+- Click `Generate release notes`.
+- `Set as the latest release` should be selected automatically.
+- Publish release
+
+#### Update the major tag
+
+The major tag, like `v31`, allows downstream users to opt-in to automatic non-breaking updates.
+
+This process follows GitHub's own guidelines:
+https://github.com/actions/toolkit/blob/main/docs/action-versioning.md
+
+##### Fetch the latest tags
+
+```
+git pull --tags --force
+```
+
+##### Move the tag
+
+```
+git tag -fa v31
+```
+```
+git push origin v31 --force
+```
+
+#### Update the release notes for the major tag
+
+Find the release on GitHub: https://github.com/cachix/install-nix-action/releases
+
+Edit the release and click `Generate release notes`.
+Edit the formatting and publish.
+

action.yml

@@ -0,0 +1,39 @@
+name: 'Install Nix'
+description: 'Installs Nix on GitHub Actions for the supported platforms: Linux and macOS.'
+author: 'Domen Kožar'
+inputs:
+  extra_nix_config:
+    description: 'Gets appended to `/etc/nix/nix.conf` if passed.'
+  github_access_token:
+    description: 'Configure Nix to pull from GitHub using the given GitHub token.'
+  install_url:
+    description: 'Installation URL that will contain a script to install Nix.'
+  install_options:
+    description: 'Additional installer flags passed to the installer script.'
+  nix_path:
+    description: 'Set NIX_PATH environment variable.'
+  enable_kvm:
+    description: 'Enable KVM for hardware-accelerated virtualization on Linux, if available.'
+    required: false
+    default: true
+  set_as_trusted_user:
+    description: 'Add current user to `trusted-users`.'
+    required: false
+    default: true
+branding:
+  color: 'blue'
+  icon: 'sun'
+runs:
+  using: 'composite'
+  steps:
+    - run : ${GITHUB_ACTION_PATH}/install-nix.sh
+      shell: bash
+      env:
+        INPUT_EXTRA_NIX_CONFIG: ${{ inputs.extra_nix_config }}
+        INPUT_GITHUB_ACCESS_TOKEN: ${{ inputs.github_access_token }}
+        INPUT_INSTALL_OPTIONS: ${{ inputs.install_options }}
+        INPUT_INSTALL_URL: ${{ inputs.install_url }}
+        INPUT_NIX_PATH: ${{ inputs.nix_path }}
+        INPUT_ENABLE_KVM: ${{ inputs.enable_kvm }}
+        INPUT_SET_AS_TRUSTED_USER: ${{ inputs.set_as_trusted_user }}
+        GITHUB_TOKEN: ${{ github.token }}

install-nix.sh

@@ -0,0 +1,124 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+if nix_path="$(type -p nix)" ; then
+  echo "Aborting: Nix is already installed at ${nix_path}"
+  exit
+fi
+
+if [[ ($OSTYPE =~ linux) && ($INPUT_ENABLE_KVM == 'true') ]]; then
+  enable_kvm() {
+    echo 'KERNEL=="kvm", GROUP="kvm", MODE="0666", OPTIONS+="static_node=kvm"' | sudo tee /etc/udev/rules.d/99-install-nix-action-kvm.rules
+    sudo udevadm control --reload-rules && sudo udevadm trigger --name-match=kvm
+  }
+
+  echo '::group::Enabling KVM support'
+  enable_kvm && echo 'Enabled KVM' || echo 'KVM is not available'
+  echo '::endgroup::'
+fi
+
+# GitHub command to put the following log messages into a group which is collapsed by default
+echo "::group::Installing Nix"
+
+# Create a temporary workdir
+workdir=$(mktemp -d)
+trap 'rm -rf "$workdir"' EXIT
+
+# Configure Nix
+add_config() {
+  echo "$1" >> "$workdir/nix.conf"
+}
+add_config "show-trace = true"
+# Set jobs to number of cores
+add_config "max-jobs = auto"
+if [[ $OSTYPE =~ darwin ]]; then
+  add_config "ssl-cert-file = /etc/ssl/cert.pem"
+fi
+# Allow binary caches specified at user level
+if [[ $INPUT_SET_AS_TRUSTED_USER == 'true' ]]; then
+  add_config "trusted-users = root ${USER:-}"
+fi
+# Add a GitHub access token.
+# Token-less access is subject to lower rate limits.
+if [[ -n "${INPUT_GITHUB_ACCESS_TOKEN:-}" ]]; then
+  echo "::debug::Using the provided github_access_token for github.com"
+  add_config "access-tokens = github.com=$INPUT_GITHUB_ACCESS_TOKEN"
+# Use the default GitHub token if available.
+# Skip this step if running an Enterprise instance. The default token there does not work for github.com.
+elif [[ -n "${GITHUB_TOKEN:-}" && $GITHUB_SERVER_URL == "https://github.com" ]]; then
+  echo "::debug::Using the default GITHUB_TOKEN for github.com"
+  add_config "access-tokens = github.com=$GITHUB_TOKEN"
+else
+  echo "::debug::Continuing without a GitHub access token"
+fi
+# Append extra nix configuration if provided
+if [[ -n "${INPUT_EXTRA_NIX_CONFIG:-}" ]]; then
+  add_config "$INPUT_EXTRA_NIX_CONFIG"
+fi
+if [[ ! $INPUT_EXTRA_NIX_CONFIG =~ "experimental-features" ]]; then
+  add_config "experimental-features = nix-command flakes"
+fi
+# Always allow substituting from the cache, even if the derivation has `allowSubstitutes = false`.
+# This is a CI optimisation to avoid having to download the inputs for already-cached derivations to rebuild trivial text files.
+if [[ ! $INPUT_EXTRA_NIX_CONFIG =~ "always-allow-substitutes" ]]; then
+  add_config "always-allow-substitutes = true"
+fi
+
+# Nix installer flags
+installer_options=(
+  --no-channel-add
+  --nix-extra-conf-file "$workdir/nix.conf"
+)
+
+# only use the nix-daemon settings if on darwin (which get ignored) or systemd is supported
+if [[ (! $INPUT_INSTALL_OPTIONS =~ "--no-daemon") && ($OSTYPE =~ darwin || -e /run/systemd/system) ]]; then
+  installer_options+=(
+    --daemon
+    --daemon-user-count "$(python3 -c 'import multiprocessing as mp; print(mp.cpu_count() * 2)')"
+  )
+else
+  # "fix" the following error when running nix*
+  # error: the group 'nixbld' specified in 'build-users-group' does not exist
+  add_config "build-users-group ="
+  sudo mkdir -p /etc/nix
+  sudo chmod 0755 /etc/nix
+  sudo cp "$workdir/nix.conf" /etc/nix/nix.conf
+fi
+
+if [[ -n "${INPUT_INSTALL_OPTIONS:-}" ]]; then
+  IFS=' ' read -r -a extra_installer_options <<< "$INPUT_INSTALL_OPTIONS"
+  installer_options=("${extra_installer_options[@]}" "${installer_options[@]}")
+fi
+
+echo "installer options: ${installer_options[*]}"
+
+# There is --retry-on-errors, but only newer curl versions support that
+curl_retries=5
+while ! curl -sS -o "$workdir/install" -v --fail -L "${INPUT_INSTALL_URL:-https://releases.nixos.org/nix/nix-2.28.3/install}"
+do
+  sleep 1
+  ((curl_retries--))
+  if [[ $curl_retries -le 0 ]]; then
+    echo "curl retries failed" >&2
+    exit 1
+  fi
+done
+
+sh "$workdir/install" "${installer_options[@]}"
+
+# Set paths
+echo "/nix/var/nix/profiles/default/bin" >> "$GITHUB_PATH"
+# new path for nix 2.14
+echo "$HOME/.nix-profile/bin" >> "$GITHUB_PATH"
+
+if [[ -n "${INPUT_NIX_PATH:-}" ]]; then
+  echo "NIX_PATH=${INPUT_NIX_PATH}" >> "$GITHUB_ENV"
+fi
+
+# Set temporary directory (if not already set) to fix https://github.com/cachix/install-nix-action/issues/197
+if [[ -z "${TMPDIR:-}" ]]; then
+  echo "TMPDIR=${RUNNER_TEMP}" >> "$GITHUB_ENV"
+fi
+
+# Close the log message group which was opened above
+echo "::endgroup::"

test.nix

@@ -0,0 +1,18 @@
+# Realizes <num>> of derivations with size of <size>MB
+{ size ? 1 # MB
+, num ? 10 # count 
+, currentTime ? builtins.currentTime
+, noChroot ? false
+}:
+
+with import <nixpkgs> {};
+
+let
+  drv = i: runCommand "${toString currentTime}-${toString i}" {
+    __noChroot = noChroot;
+  } ''
+    dd if=/dev/zero of=$out bs=${toString size}MB count=1
+  '';
+in writeText "empty-${toString num}-${toString size}MB" ''
+  ${lib.concatMapStringsSep "" drv (lib.range 1 num)}
+''