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

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:

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:

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:

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:

cd secrets
agenix -r

Edit secrets

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:

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

If you only know the IP:

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

That script:

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

Files written on the Pi

The deploy script creates:

• /opt/noisebell/releases/<timestamp>/noisebell
• /opt/noisebell/current -> current release symlink
• /etc/noisebell/pi-to-cache-key
• /etc/noisebell/cache-to-pi-key
• /etc/noisebell/tailscale-auth-key
• /etc/noisebell/noisebell.env
• /etc/systemd/system/noisebell.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:

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_SECS	5	Debounce delay in seconds
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

API

All endpoints require Authorization: Bearer <token>.

GET /

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