Nix Install

Nix Install

Install the Nix package manager and prepare it for development use. Handles platform detection, installer selection, installation, post-install verification, and flake enablement.

What this skill does

1. Detects the platform (OS, distro, WSL2, container).
2. Checks for an existing Nix installation.
3. Selects an installer (Determinate Systems or upstream nixos.org).
4. Installs Nix using the appropriate command for the platform.
5. Verifies the installation, daemon, and flake support.

Platform detection

Detect the environment before selecting an install method. Unlike Tailscale, Nix runs inside WSL2 cleanly — no host bridging needed.

1. Check WSL2 (informational — install path is unchanged)
   ├─ grep -qi microsoft /proc/version 2>/dev/null
   └─ AND [ ! -f /.dockerenv ]

2. Check OS
   ├─ uname -s → Linux  → continue
   ├─ uname -s → Darwin → macOS (DetSys handles APFS automatically)
   └─ Windows native    → STOP. Nix requires WSL2 on Windows.

3. Confirm prerequisites
   ├─ curl, sudo, xz are required by both installers
   ├─ bash is required (Alpine: install bash before running installer)
   └─ Fedora/RHEL: SELinux may need adjustment (see error handling)

Existing install check

Before installing, check whether Nix is already present:

nix --version 2>/dev/null

If installed: report the version, check daemon status (multi-user only, systemctl status nix-daemon), check flakes (nix flake --help >/dev/null), and run a functional test (nix-shell -p hello --run hello). Stop here unless the user requests reinstall or repair. If not installed, proceed to installer selection.

Installer selection

Two installers are supported. Default to Determinate Systems unless the user explicitly asks for the upstream installer or has a compliance constraint.

Determinate Systems installer (default)

Enables flakes by default, supports clean uninstall via /nix/receipt.json, and produces actionable error messages.

curl --proto '=https' --tlsv1.2 -sSf -L \
  https://install.determinate.systems/nix | sh -s -- install

For unattended runs, add --no-confirm after install.

Upstream nixos.org installer

Use when an organization requires the canonical Nix installer (audit, compliance) or when the Determinate installer is unavailable.

# Multi-user (recommended for shared machines)
sh <(curl -L https://nixos.org/nix/install) --daemon

# Single-user (only when sudo is unavailable)
sh <(curl -L https://nixos.org/nix/install) --no-daemon

For installer trade-offs, see references/installer-comparison.md.

Installation

Run the chosen installer command (above) for the platform. The same command works across Linux distros, macOS, and WSL2 — the installers handle platform specifics internally (APFS on macOS, daemon setup on Linux). After install, start a new shell so the Nix profile is sourced. For per-distro prerequisites and uninstall commands, see references/platform-install-commands.md.

Post-install verification

After installation, verify four things in order. Stop and remediate if any check fails.

1. Binary is available

nix --version

If not found, the shell has not sourced the Nix profile. Open a new terminal or run:

. /etc/profile.d/nix.sh    # multi-user
# or
. ~/.nix-profile/etc/profile.d/nix.sh    # single-user

2. Daemon is running (multi-user only)

# Linux
systemctl status nix-daemon

# macOS
sudo launchctl print system/org.nixos.nix-daemon

Single-user installs do not have a daemon — skip this check.

3. Flakes are enabled

nix flake --help >/dev/null && echo "flakes enabled" || echo "flakes NOT enabled"

The Determinate installer enables flakes by default. The upstream installer does not — see "Enabling flakes" below.

4. Functional test

nix-shell -p hello --run hello
# Expected output: "Hello, world!"

This verifies the substituter (cache.nixos.org) is reachable, signature verification works, and the store is writable.

Enabling flakes

If flakes are not enabled (upstream installer default):

mkdir -p ~/.config/nix
echo "experimental-features = nix-command flakes" \
  >> ~/.config/nix/nix.conf

For system-wide flake enablement on multi-user installs, use /etc/nix/nix.conf — see references/post-install-checklist.md.

Error handling

Do not silently skip a failed installation. Report the error with a specific remediation step.

• Permission denied — multi-user install requires sudo. Re-run with privileges or use --no-daemon for single-user.
• xz: command not found (Alpine, minimal containers) — install xz-utils (Debian/Ubuntu) or xz (Alpine/Arch) before retrying.
• SELinux denials on Fedora/RHEL — the Determinate installer handles this; the upstream installer may need setenforce 0 temporarily, then re-enable.
• macOS APFS volume creation failed — use the Determinate installer, which handles this. With the upstream installer on macOS, see references/platform-install-commands.md for manual volume setup.
• nix --version not found after install — shell not yet sourcing the Nix profile. Open a new terminal or source /etc/profile.d/nix.sh.
• Substituter unreachable (unable to download cache.nixos.org) — check network, proxy, and corporate TLS interception. Test with curl -fI https://cache.nixos.org.
• Existing /nix directory — a previous install left state. Use /nix/nix-installer uninstall (Determinate) or follow references/installer-comparison.md for upstream uninstall.

References

• references/installer-comparison.md — Determinate Systems vs upstream installer trade-offs and migration notes.
• references/platform-install-commands.md — exhaustive per-platform install and uninstall commands for both installers.
• references/post-install-checklist.md — flakes config, channels, substituters, trusted-users, and first-run troubleshooting.