noisebell/pi/README.md

# Pi

Rust service and deployment workflow for the Raspberry Pi at Noisebridge.

The current recommended setup is:

1. run Raspberry Pi OS Lite on the Pi
2. keep the Pi itself free of Nix
3. build a static `aarch64` Noisebell binary on your laptop with Nix
4. copy the binary, secrets, and systemd service to the Pi over SSH

This avoids the Raspberry Pi Zero 2 W NixOS boot issues while still keeping the application build reproducible.

## What stays on Raspberry Pi OS

- bootloader
- kernel
- firmware
- Wi-Fi and local networking
- SSH base access
- Tailscale package/runtime
- Avahi package/runtime

## What Nix manages

- building a static `noisebell` binary for `aarch64-linux`
- the exact app binary you deploy
- encrypted secrets in the repo
- repeatable deployment from your laptop

## Initial Pi OS setup

### 1. Flash Raspberry Pi OS Lite

```sh
curl -L "https://downloads.raspberrypi.org/raspios_lite_arm64_latest" | xz -d -c | sudo dd of=/dev/sdb bs=16M conv=fsync status=progress && sync
```

### 2. Configure the flashed SD card

Configure it for:

- Wi-Fi on `Noisebridge`
- SSH enabled
- serial enabled if you want a recovery console

The helper script is:

```sh
sudo scripts/configure-pios-sd.sh /run/media/jet/bootfs /run/media/jet/rootfs
```

This setup expects SSH key login for user `pi`; it does not configure a password.

### 3. Boot the Pi and verify SSH

After boot, verify SSH works:

```sh
ssh pi@noisebell-pi.local
```

## Add the Pi host key to age recipients

The deploy flow decrypts secrets locally on your laptop, but the Pi host key should still be a recipient for the Pi-facing secrets so the repo stays accurate.

Grab the Pi host key:

```sh
ssh-keyscan noisebell-pi.local 2>/dev/null | grep ed25519
```

Add that key to `secrets/secrets.nix` for:

- `pi-to-cache-key.age`
- `cache-to-pi-key.age`
- `tailscale-auth-key.age`

Then refresh recipients if needed:

```sh
cd secrets
agenix -r
```

## Edit secrets

```sh
cd secrets
agenix -e pi-to-cache-key.age
agenix -e cache-to-pi-key.age
agenix -e tailscale-auth-key.age
```

These stay encrypted in git. The deploy script decrypts them locally on your laptop and copies the plaintext files to the Pi as root-only files.

## Deploy to Raspberry Pi OS

From your laptop:

```sh
scripts/deploy-pios-pi.sh pi@noisebell-pi.local
```

If you only know the IP:

```sh
scripts/deploy-pios-pi.sh pi@10.21.x.x
```

That script:

1. builds `.#packages.aarch64-linux.noisebell-static` locally
2. builds `.#packages.aarch64-linux.noisebell-relay-static` locally
3. decrypts the Pi-facing secrets locally with `agenix`
4. uploads the binaries and secrets to the Pi
5. installs Tailscale and Avahi if needed
6. writes `/etc/noisebell/noisebell.env`
7. writes `/etc/noisebell/noisebell-relay.env`
8. installs `noisebell.service` and `noisebell-relay.service`
9. enables and starts both services
10. runs `tailscale up` with the decrypted auth key

## Files written on the Pi

The deploy script creates:

- `/opt/noisebell/releases/<timestamp>/noisebell`
- `/opt/noisebell/releases/<timestamp>/noisebell-relay`
- `/opt/noisebell/current` -> current release symlink
- `/etc/noisebell/pi-to-cache-key`
- `/etc/noisebell/cache-to-pi-key`
- `/etc/noisebell/relay-webhook-secret`
- `/etc/noisebell/homeassistant-webhook-id`
- `/etc/noisebell/tailscale-auth-key`
- `/etc/noisebell/noisebell.env`
- `/etc/noisebell/noisebell-relay.env`
- `/etc/systemd/system/noisebell.service`
- `/etc/systemd/system/noisebell-relay.service`

All secret files are root-only.

## Tailscale

Tailscale is kept on Raspberry Pi OS rather than NixOS.

The deploy script:

- installs the Tailscale package if missing
- enables `tailscaled`
- runs `tailscale up --auth-key=... --hostname=noisebell-pi`

So Tailscale stays part of the base OS, while its auth key is still managed as an encrypted `age` secret in this repo.

## Later updates

Normal iteration is just rerunning the deploy script:

```sh
scripts/deploy-pios-pi.sh pi@noisebell-pi.local
```

That rebuilds the binary locally, uploads a new release, refreshes secrets, and restarts the service.

## Service configuration

The deployed service uses these environment variables:

| Variable | Default | Description |
|---|---|---|
| `NOISEBELL_GPIO_PIN` | `17` | GPIO pin number |
| `NOISEBELL_DEBOUNCE_MS` | `50` | Debounce delay in milliseconds |
| `NOISEBELL_PORT` | `80` | HTTP server port |
| `NOISEBELL_ENDPOINT_URL` | required | Webhook URL to POST state changes to |
| `NOISEBELL_RETRY_ATTEMPTS` | `3` | Webhook retry count |
| `NOISEBELL_RETRY_BASE_DELAY_SECS` | `1` | Exponential backoff base delay |
| `NOISEBELL_HTTP_TIMEOUT_SECS` | `10` | Outbound request timeout |
| `NOISEBELL_BIND_ADDRESS` | `0.0.0.0` | HTTP bind address |
| `NOISEBELL_ACTIVE_LOW` | `true` | Low GPIO = door open |

## Relay service configuration

The optional relay service accepts authenticated webhooks from cache-service and forwards them to Home Assistant on the local network.

| Variable | Default | Description |
|---|---|---|
| `NOISEBELL_RELAY_PORT` | `8090` | HTTP port for the relay webhook endpoint |
| `NOISEBELL_RELAY_BIND_ADDRESS` | `0.0.0.0` | HTTP bind address |
| `NOISEBELL_RELAY_TARGET_BASE_URL` | `http://homeassistant.local:8123` | Base URL for Home Assistant |
| `NOISEBELL_RELAY_TARGET_WEBHOOK_ID` | required | Home Assistant webhook ID |
| `NOISEBELL_RELAY_INBOUND_API_KEY` | required | Bearer token expected from cache-service |
| `NOISEBELL_RELAY_RETRY_ATTEMPTS` | `3` | Forward retry count |
| `NOISEBELL_RELAY_RETRY_BASE_DELAY_SECS` | `1` | Exponential backoff base delay |
| `NOISEBELL_RELAY_HTTP_TIMEOUT_SECS` | `10` | Outbound request timeout |

Example cache target for the relay:

```nix
{
  services.noisebell-cache.outboundWebhooks = [
    {
      url = "http://noisebell-pi.local:8090/webhook";
      secretFile = /run/agenix/noisebell-relay-webhook-secret;
    }
  ];
}
```

## API

All endpoints require `Authorization: Bearer <token>`.

**`GET /`**

```json
{"status": "open", "timestamp": 1710000000}
```