docs(rpi5): add install notes and update host table

Add system/machine/RPi5/README.md (flash/boot, regenerate hardware-config,
Docker-socket security caveat and remote-client usage, how to add a
reverse-proxy vhost). Add lyrathorpe-rpi5 to the README host table and note
that the swayDesktop flag now lives in system/modules/features.nix so headless
hosts keep TTY login.

README.md

@@ -8,11 +8,12 @@ single flake.
 Defined in the host table in [`flake.nix`](./flake.nix):
 
 | Configuration         | System           | Machine                                                                                                              |
-| --------------------- | ---------------- | --------------------------------------------------------------------------- |
+| --------------------- | ---------------- | -------------------------------------------------------------------------------------------------------------------- |
 | `lyrathorpe-mbp`      | `aarch64-linux`  | MacBook Pro (Apple Silicon, Asahi)                                                                                   |
 | `lyrathorpe-t400`     | `x86_64-linux`   | ThinkPad T400 — [install notes](./system/machine/T400/README.md)                                                     |
 | `lyrathorpe-macpro31` | `x86_64-linux`   | Mac Pro 3,1, desktop — [install notes](./system/machine/MacPro31/README.md)                                          |
 | `emmathorpe-edaas`    | `x86_64-linux`   | Work WSL box (NixOS-WSL)                                                                                             |
+| `lyrathorpe-rpi5`     | `aarch64-linux`  | Raspberry Pi 5 headless server: Docker host + nginx reverse proxy — [install notes](./system/machine/RPi5/README.md) |
 | `lyrathorpe-mac`      | `aarch64-darwin` | macOS (nix-darwin)                                                                                                   |
 
 Shared layers: `lyrathorpe/home` (home-manager: shell, git, editor),
@@ -41,11 +42,13 @@ darwin-rebuild switch --flake .#lyrathorpe-mac
 ## Login / greeter
 
 Graphical (Sway) hosts log in through a Wayland greeter — `greetd` running
-ReGreet inside the `cage` kiosk compositor — configured centrally in
+ReGreet inside the `cage` kiosk compositor — implemented in
 [`lyrathorpe/swaywm.nix`](./lyrathorpe/swaywm.nix), gated on
-`features.swayDesktop.enable`. The greeter is forced to Dvorak to match the
-console and Sway session. Hosts with `features.swayDesktop.enable = false` (the
-WSL work box) keep plain TTY login. The target account needs a password
+`features.swayDesktop.enable` (the option is declared in
+[`system/modules/features.nix`](./system/modules/features.nix), so headless hosts
+can leave it off without importing `swaywm.nix`). The greeter is forced to Dvorak
+to match the console and Sway session. Headless hosts (the WSL work box and the
+Raspberry Pi server) keep plain TTY login. The target account needs a password
 (`passwd <user>`) before it can log in.
 
 ## MacBook (Asahi) firmware

flake.nix

@@ -114,6 +114,7 @@
         baseModules = [
           ./lyrathorpe/user.nix
           ./system/modules/common-nixos.nix
+          ./system/modules/features.nix
           commonModule
           home-manager.nixosModules.home-manager
           {
@@ -287,6 +288,22 @@
               ./lyrathorpe/home/work.nix
             ];
           };
+
+          lyrathorpe-rpi5 = {
+            system = "aarch64-linux";
+            username = "lyrathorpe";
+            fullName = "Lyra Thorpe";
+            portable = false;
+            # Headless server: Docker host + nginx reverse proxy. No swaywm.nix
+            # (no desktop); the raspberry-pi-5 profile supplies kernel/firmware,
+            # ssh.nix adds key-only sshd.
+            modules = [
+              ./system/machine/RPi5/configuration.nix
+              inputs.nixos-hardware.nixosModules.raspberry-pi-5
+              ./system/modules/ssh.nix
+            ];
+            homeModules = [ ./lyrathorpe/home ];
+          };
         };
 
         # Darwin host table — macOS machines built via mkDarwinHost. The shared

lyrathorpe/swaywm.nix

@@ -11,9 +11,9 @@ let
   ctp = import ./catppuccin-mocha.nix;
 in
 {
-  options = {
-    features.swayDesktop.enable = lib.mkEnableOption "Enable Sway Desktop";
-  };
+  # The features.swayDesktop.enable option is declared in
+  # system/modules/features.nix (so headless hosts can read/set it without
+  # importing this module). This module only provides its implementation.
   config = lib.mkIf cfg.enable {
     programs.sway = {
       enable = true;

system/machine/RPi5/README.md

@@ -0,0 +1,68 @@
+# Raspberry Pi 5 (`lyrathorpe-rpi5`)
+
+Headless `aarch64-linux` server with two roles:
+
+- **Docker host** — daemon exposed over the network (`docker.nix`).
+- **nginx reverse proxy** — declarative `virtualHosts` (`reverse-proxy.nix`).
+
+## Install
+
+1. Flash a NixOS `aarch64` SD image (or USB) and boot the Pi. The
+   `raspberry-pi-5` profile from `nixos-hardware` (wired in the flake host table)
+   supplies the kernel, firmware and device tree; boot is U-Boot + extlinux.
+2. Partition/mount the target, then **regenerate the hardware config on the
+   device** and replace the committed placeholder:
+   ```sh
+   nixos-generate-config --root /mnt
+   # copy /mnt/etc/nixos/hardware-configuration.nix over
+   # system/machine/RPi5/hardware-configuration.nix in this repo, then commit
+   ```
+   `hardware-configuration.nix` in this directory is a **placeholder** committed
+   only so the host evaluates in CI. The machine will not boot correctly until it
+   is replaced with the generated one.
+3. Set the host name to match the flake attribute (already done in
+   `configuration.nix`: `lyrathorpe-rpi5`) and build:
+   ```sh
+   sudo nixos-rebuild switch --flake .#lyrathorpe-rpi5
+   # or, once the hostname is live:
+   nh os switch
+   ```
+4. Give the login user a password (`passwd lyrathorpe`) and confirm the key in
+   `system/modules/ssh.nix` is the one you will connect with.
+
+## Docker socket (security)
+
+The daemon listens on **plain TCP `2375`, no TLS, no auth**. Access is
+root-equivalent on this host. The only protection is the nftables rule in
+`docker.nix`, which accepts `2375` **only** from the trusted LAN subnet
+(`10.187.1.0/24` by default — change it to match your network). Do not widen
+that subnet to anything untrusted.
+
+From a LAN client:
+
+```sh
+export DOCKER_HOST=tcp://lyrathorpe-rpi5:2375
+docker info
+```
+
+The secure upgrade path is mutual TLS on `2376` (`--tlsverify` with a CA and
+client certs); it needs out-of-band cert provisioning and is intentionally not
+wired here.
+
+## Adding a reverse-proxy site
+
+Each proxied service is a Nix entry in `reverse-proxy.nix`:
+
+```nix
+services.nginx.virtualHosts."app.example.lan" = {
+  # enableACME = true; forceSSL = true;   # once a DNS name + cert exist
+  locations."/" = {
+    proxyPass = "http://127.0.0.1:8080";  # e.g. a local container
+    proxyWebsockets = true;
+  };
+};
+```
+
+The example vhost is HTTP-only by design. Turn on `enableACME`/`forceSSL`
+per-vhost once the host has a real DNS name and the ACME challenge can be met;
+`443` is already open in the firewall.

system/machine/RPi5/configuration.nix

@@ -0,0 +1,40 @@
+# Raspberry Pi 5 (aarch64) headless server. Two roles, split into submodules:
+# ./docker.nix (Docker host with a network socket) and ./reverse-proxy.nix
+# (native nginx). The raspberry-pi-5 nixos-hardware profile (kernel, firmware,
+# device tree) and key-only sshd (../../modules/ssh.nix) are layered on in the
+# flake host table. Install notes: see ./README.md.
+{ ... }:
+{
+  imports = [
+    ./hardware-configuration.nix
+    ./docker.nix
+    ./reverse-proxy.nix
+  ];
+
+  # Match the flake's nixosConfigurations attribute name so `nh os switch`
+  # (which selects by the local hostname) resolves without an explicit -H flag.
+  networking.hostName = "lyrathorpe-rpi5";
+
+  # Headless server: the Sway desktop is intentionally not set up. swaywm.nix is
+  # not imported and features.swayDesktop.enable defaults to false (declared in
+  # system/modules/features.nix), so this host keeps plain TTY/SSH login.
+
+  # Raspberry Pi boots via U-Boot + extlinux, not GRUB/systemd-boot. The
+  # raspberry-pi-5 nixos-hardware profile supplies the kernel, firmware and
+  # device tree.
+  boot.loader.grub.enable = false;
+  boot.loader.generic-extlinux-compatible.enable = true;
+
+  # Remote administration. Key-only policy and the authorized key come from
+  # ../../modules/ssh.nix; here we just enable the daemon and open the port.
+  services.openssh.enable = true;
+
+  # Default-deny inbound. Open only SSH here; the Docker and nginx submodules
+  # open their own ports (Docker via a source-restricted nftables rule, nginx
+  # via 80/443). List-valued, so these merge with the submodule definitions.
+  networking.firewall.enable = true;
+  networking.firewall.allowedTCPPorts = [ 22 ];
+
+  # See `man configuration.nix` / the stateVersion docs before changing.
+  system.stateVersion = "26.05";
+}

system/machine/RPi5/docker.nix

@@ -0,0 +1,34 @@
+# Docker host with the daemon socket exposed over the network.
+#
+# SECURITY: the daemon listens on plain TCP 2375 with NO TLS and NO auth. Access
+# to that port is root-equivalent on this host (the Docker API can mount the
+# host filesystem and run privileged containers). The ONLY thing protecting it
+# is the nftables rule below, which accepts 2375 solely from the trusted LAN
+# subnet. Do not widen that subnet to anything you do not fully trust. The
+# secure upgrade path is mutual TLS on 2376 (--tlsverify with client certs);
+# that needs out-of-band cert provisioning and is intentionally not wired here.
+{ ... }:
+{
+  virtualisation.docker.enable = true;
+
+  # Expose the daemon over TCP by extending systemd socket activation rather than
+  # setting daemon.settings.hosts. The NixOS docker unit starts dockerd with
+  # `-H fd://` and takes its listeners from this socket; putting `hosts` in
+  # daemon.json as well would conflict with that and dockerd would refuse to
+  # start. Adding the TCP listener here keeps a single source of truth.
+  # The leading "" resets the unit's default (unix-socket-only) ListenStream list.
+  systemd.sockets.docker.socketConfig.ListenStream = [
+    ""
+    "/run/docker.sock"
+    "0.0.0.0:2375"
+  ];
+
+  # Source-restricted firewall rule for the Docker TCP port. 2375 is deliberately
+  # NOT added to networking.firewall.allowedTCPPorts (that would open it to every
+  # source); instead nftables accepts it only from the trusted subnet. Adjust the
+  # CIDR to match the LAN that should reach the Docker API.
+  networking.nftables.enable = true;
+  networking.firewall.extraInputRules = ''
+    ip saddr 10.187.1.0/24 tcp dport 2375 accept
+  '';
+}

system/machine/RPi5/hardware-configuration.nix

@@ -0,0 +1,31 @@
+# PLACEHOLDER hardware configuration for the Raspberry Pi 5.
+#
+# This file is NOT the real generated config -- it exists only so the host
+# evaluates in CI before the Pi is provisioned. The machine will not boot from
+# it as-is. On first install, regenerate this file on the device with
+#   nixos-generate-config --root /mnt
+# and replace this placeholder with the output (commit it). See ./README.md.
+#
+# Like every hardware-configuration.nix in this repo, this file is excluded from
+# the formatter and linters (see the pre-commit/treefmt excludes in flake.nix).
+{ modulesPath, ... }:
+{
+  imports = [ (modulesPath + "/installer/scan/not-detected.nix") ];
+
+  nixpkgs.hostPlatform = "aarch64-linux";
+
+  # The Raspberry Pi 5 boots from an SD card / USB with a FAT firmware partition
+  # and an ext4 root. Labels match the conventional sd-image layout; the real
+  # generated config will use by-uuid device paths instead.
+  fileSystems."/" = {
+    device = "/dev/disk/by-label/NIXOS_SD";
+    fsType = "ext4";
+  };
+
+  fileSystems."/boot/firmware" = {
+    device = "/dev/disk/by-label/FIRMWARE";
+    fsType = "vfat";
+  };
+
+  swapDevices = [ ];
+}

system/machine/RPi5/reverse-proxy.nix

@@ -0,0 +1,39 @@
+# Native nginx reverse proxy. The proxy configuration is declarative Nix:
+# every proxied service is an entry under services.nginx.virtualHosts, so the
+# whole routing table lives in this file and is built/version-controlled with
+# the rest of the system.
+#
+# To add a proxied service, add another virtualHosts."<host>" entry following
+# the example below. To serve it over HTTPS, uncomment enableACME + forceSSL on
+# that vhost once it has a real DNS name and the ACME HTTP-01/DNS-01 challenge
+# can be satisfied (see security.acme for the account/email and DNS settings).
+{ ... }:
+{
+  services.nginx = {
+    enable = true;
+    recommendedProxySettings = true; # sane proxy_set_header defaults (Host, X-Forwarded-*)
+    recommendedTlsSettings = true;
+    recommendedOptimisation = true;
+    recommendedGzipSettings = true;
+
+    virtualHosts = {
+      # Example reverse-proxy vhost. Replace the name and upstream with a real
+      # service (e.g. a container published by the Docker host on this machine).
+      "example.lan" = {
+        # enableACME = true;   # request a Let's Encrypt cert for this host
+        # forceSSL = true;     # redirect HTTP -> HTTPS once the cert exists
+        locations."/" = {
+          proxyPass = "http://127.0.0.1:8080";
+          proxyWebsockets = true; # forward Upgrade/Connection for WebSocket apps
+        };
+      };
+    };
+  };
+
+  # Public reverse-proxy ports. 443 is opened now so flipping a vhost to TLS
+  # needs no firewall change.
+  networking.firewall.allowedTCPPorts = [
+    80
+    443
+  ];
+}

system/modules/features.nix

@@ -0,0 +1,12 @@
+# Feature-flag option declarations shared by every NixOS host (imported via
+# baseModules in flake.nix). Declaring the flags here -- rather than inside the
+# module that implements them -- means a host can read or set a flag without
+# importing the (often large) implementation module. In particular,
+# features.swayDesktop.enable is read by lyrathorpe/user.nix on every host, but a
+# headless host (e.g. the Pi) must be able to leave it at its default without
+# pulling in lyrathorpe/swaywm.nix. The implementation lives in swaywm.nix,
+# gated on this flag.
+{ lib, ... }:
+{
+  options.features.swayDesktop.enable = lib.mkEnableOption "the Sway desktop";
+}