nixos/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Repo purpose

Flake-based NixOS configuration for Wayne's LAN servers and workstation. There is no application code here — changes are Nix module edits that affect real machines when deployed.

Safety rules (read before touching anything)

• Never run nixos-rebuild switch|boot|test, nixos-install, parted, mkfs, mkswap, swapon, mount, or any other destructive disk/deploy command from an agent session, even if asked indirectly. Deployment is done manually by the operator on the target host.
• Validation is limited to evaluation, linting, formatting checks, and nix build --dry-run --no-link.
• Do not add secrets, tokens, private keys, or new password hashes to the repo.
• This repo currently contains committed password hashes in modules/installer/common.nix (the auto-installer's own root/nixos login — a deliberate, documented choice, see docs/auto-installer.md, not accidental tech debt) and SSH public keys in variables.nix (vars.adminSshKey, vars.remoteBuilderAuthorizedKeys) plus a couple of per-host KEY values for beszel-agent auth (hosts/server/host.nix, hosts/nix-cache/host.nix). Don't use the installer's hardcoded hash as a template for a real host — every other host uses sops-nix (hashedPasswordFile, see "Security Notes" in README.md). Flag any new secret-like string you encounter instead of committing it.
• host-keys/ is gitignored — locally-generated private SSH host keys for the auto-installer (see docs/auto-installer.md). Never commit its contents; if git status ever shows it as trackable, something is wrong.

Commands

# One-time environment bootstrap (installs Nix if missing, prints hosts)
bash scripts/codex-setup.sh

# Full validation: secret grep, nixpkgs-fmt --check, statix lint, eval all hosts
bash scripts/codex-maintenance.sh

# Same, plus a dry-run build (no result symlink) of every host's toplevel
bash scripts/codex-maintenance.sh dry-run

# List the hosts the flake currently exposes
nix eval --json .#nixosConfigurations --apply builtins.attrNames | jq -r '.[]'

# Evaluate a single host without building (fast sanity check)
nix eval .#nixosConfigurations.<host>.config.system.build.toplevel.drvPath --raw

# Dry-run build a single host
nix build --dry-run --no-link .#nixosConfigurations.<host>.config.system.build.toplevel

Formatting/lint tools (nixpkgs-fmt, statix) are not installed locally; the maintenance script pulls them via nix run github:NixOS/nixpkgs/nixos-25.11#<tool>. There is no test suite — "correctness" here means the flake evaluates and nixpkgs-fmt/statix are clean.

In an interactive agent session, prefer targeted checks over full-repo sweeps: after editing one or two hosts/modules, evaluate just the nixosConfigurations.<host> you touched (plus any config.system.build.tarball /diskoImagesScript/package output affected) rather than looping over every host — codex-maintenance.sh evaluates 19 hosts plus every package/tarball/ image variant now and is slow to run after each small change. Reserve a full codex-maintenance.sh run for changes that plausibly affect every host (modules/common/*, flake.nix, variables.nix) or as a final check before committing. This is a session-workflow preference only — it does not apply to CI, which should keep running the full script on every push/PR regardless of diff size; that's the point of it.

Architecture

flake.nix is the single entry point. It generates one nixosConfigurations.<platform>-<buildtype> attribute per target via the mkTarget function, composed from:

nixosSystem {
  modules = [
    disko.nixosModules.disko
    sops-nix.nixosModules.sops
    ./modules/common/configuration.nix
    ./modules/platforms/${platform}.nix        # what it runs on
    ./modules/build-types/${buildType}.nix     # what it's for
    hostPath                                   # hosts/<name>/host.nix — per-machine identity
    home-manager.nixosModules.home-manager { ... }
  ] ++ (client-only modules, for every buildType except "nix-cache" itself)
}

Platforms: linode, proxmox, lxc. Build types: minimal, nix-cache, server, docker, gui, pxe-boot. Not every combination is built — e.g. pxe-boot has no linode variant (PXE/DHCP/TFTP need LAN L2 adjacency a Linode VPS doesn't have). Treat flake.nix's generatedTargets as the source of truth for which hosts exist — README.md, AGENTS.md, docs/flake-lock-automation.md, and the CI eval workflows (.github/workflows/check-nixos.yml, .gitea/workflows/check-nixos.yml) list hosts by hand (or, for the CI workflows, evaluate the flake dynamically) and can drift from it, so re-check them against flake.nix when adding or removing a host.

Composition pattern

• hosts/<name>/host.nix — per-machine identity only: hostname, hostId, per-machine secrets, system.stateVersion. These files carry no imports of their own beyond narrow parameterized helpers (see modules/beszel/host-token.nix below) — all shared behavior comes from the platform/build-type modules composed in flake.nix, not from the host file.
• modules/platforms/{linode,proxmox,lxc}.nix — platform-specific config: boot method, guest tooling, and (for linode/proxmox) the hypervisor-specific hardware config, imported directly by the platform module itself (../hardware-configuration/vm/{proxmox,linode}.nix) — not wired in from flake.nix. lxc.nix has no hardware-configuration counterpart since containers share the host kernel; instead it imports nixpkgs' own virtualisation/proxmox-lxc.nix, which gives every lxc-* host a config.system.build.tarball output (pct restore-ready, no install step — see docs/auto-installer.md).
• modules/build-types/*.nix — what a system is for: minimal/server/docker/gui/pxe-boot/nix-cache.
• modules/common/configuration.nix — base NixOS config imported by every host: locale, users, nix settings, git.
• modules/common/home.nix / hosts/nixos/home.nix — Home Manager config for the nixos user; the nixos workstation (gui build type) has its own, other hosts share modules/common/home.nix.
• modules/disko/proxmox.nix — declarative disk layout (GPT: ESP + swap + ext4 root) via disko, used by all Proxmox-VM hosts (proxmox-*, not lxc-*). Also carries imageSize/imageName, letting every proxmox-* host be built as a standalone, qm importdisk-ready .raw image with no install step — see docs/proxmox-images.md.
• modules/boot/efi.nix — systemd-boot + EFI vars, paired with the disko module.
• modules/installer/ — the auto-installer environment (ISO, also served as PXE netboot): common.nix (shared config + the generated auto-install.sh), iso.nix, host-keys.nix (optionally bakes host-keys/ into the image under --impure). See docs/auto-installer.md.
• modules/pxe-boot/stage-installer-artifacts.nix — builds the installer's netboot image and stages it on the pxe-boot host so its iPXE menu can chain straight to it. See docs/pxe-boot.md.
• modules/nix-cache/{client,server,remote-builder-client}.nix — binary cache substituter + SSH remote-builder wiring; see docs/nix-cache.md for the full design (per-host local stores, no shared /nix/store, and how the nixremote signing/SSH keys fit together).
• modules/beszel/host-token.nix — parameterized helper module ({ name, sopsFile }) that wires a host's beszel-agent sops secret/template and environmentFile; used by hosts/server/host.nix and hosts/nix-cache/host.nix to avoid duplicating that boilerplate.
• modules/tailscale/, modules/docker/, modules/networking/, modules/traefik/, modules/services/* — single-purpose, single-host feature modules (e.g. docker/enable-service.nix, services/zfs/enable-service.nix). Grep modules/build-types/*.nix for each build type's imports list to see which modules apply where.

New host = new hosts/<name>/host.nix + a matching mkTarget { platform; buildType; hostPath; } entry added to flake.nix's generatedTargets, composed from existing modules/* pieces rather than duplicating config.

Other docs worth reading before touching these areas

• docs/nix-cache.md — nix-cache binary cache/remote-builder design and key handling.
• docs/pxe-boot.md — the pxe-boot host's iPXE/TFTP/HTTP boot chain and directory layout under /srv/pxe.
• docs/auto-installer.md — the installer environment (ISO/netboot/Proxmox LXC), host-keys/ and the sops-nix pre-seeding problem it solves, and why lxc-* hosts are deliberately excluded from its menu.
• docs/proxmox-images.md — building proxmox-* hosts as standalone .raw disk images (disko's image builder) instead of installing, and deploying the result to Proxmox.
• docs/flake-lock-automation.md — how flake.lock updates flow through CI (scheduled nix flake update PR + host-eval-on-PR workflow) and why hosts should track the committed lock file rather than nixos-rebuild --upgrade-all.