install-nix.sh

#!/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 for user
add_config "trusted-users = root ${USER:-}"
# Add a GitHub access token.
# Token-less access is subject to lower rate limits.
if [[ -n "${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
  --darwin-use-unencrypted-nix-store-volume
  --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-2.25.2/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::"