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Raspberry Pi network configuration

This document describes the design principles and operational behaviour of the Raspberry Pi network setup for the Automator system.

For the full step-by-step implementation (UUIDs, nmcli commands, scripts, and service files) see HandOver.md sections 4.8–4.10 and Raspberry_Pi_Direct_Ethernet_Access_from_MacBook_UPDATED.md.

Scope and audience

This guide is intended as:

  • A design reference
  • An architecture overview
  • A reusable pattern that can be adapted to other environments

It is not a copy-and-paste configuration for external networks.

High-Level design

The Raspberry Pi uses two network interfaces managed by NetworkManager.

Network roles

Wi-Fi (wlan0)

  • Primary Internet access
  • Default route under normal operation
  • Used for system updates and web interfaces
  • Active profile: IOT

Ethernet (eth0)

  • Direct MacBook access only — the Pi assigns the MacBook a 192.168.50.x address automatically via DHCP when a cable is connected directly
  • Active profile: mac-direct-auto (192.168.50.2/24)
  • Do not connect the Ethernet cable to the institute or instrument network

The auto-switch script (/usr/local/sbin/eth0-auto-switch.sh) activates mac-direct-auto and starts the DHCP service (automator-direct-dhcp.service) whenever an Ethernet cable is detected. The script is triggered at boot, on cable events, and every 15 seconds by a systemd timer.

Traffic behaviour summary

Traffic Type Interface
Internet Wi-Fi
Controller web UI Direct MacBook Ethernet for users; Pi desktop browser for admins
QR PDF download Browser path used for the controller web UI

Key design principles

  • Routing decisions are made at the OS level
  • Route metrics determine preference and fallback
  • Configuration is persistent, auditable, and aligned with enterprise IT practices

Controller access

URL When it works
http://192.168.50.2:8080/ MacBook connected by direct Ethernet cable
http://automator.local:8080/ mDNS hostname — works from a connected MacBook and from the Pi desktop browser
http://127.0.0.1:8080/ Pi desktop browser only
  • The MacBook USB-C Ethernet adapter must be set to Using DHCP (the default); the Pi assigns a 192.168.50.x address automatically in direct mode
  • The Pi boots into a full-screen kiosk at http://127.0.0.1:8080/ when a monitor, keyboard, and mouse are connected — no MacBook needed. Use only one access method at a time to avoid latency
  • Admins exit kiosk with Ctrl+Alt+A to reach the Pi desktop browser; Windows+K returns to kiosk
  • Terminal, NetworkManager, service, and desktop access is for technical/admin maintenance only

QR PDF printing

  • The controller generates QR sheets as downloadable PDF files
  • Printing is handled by the user's own computer after download
  • The Raspberry Pi does not need an application-level network printer path for the Automator QR workflow

File access

  • Images are stored locally on the Pi at /home/pi/Automator/data/
  • Image retrieval is via the web UI file browser (when connected by MacBook Ethernet or kiosk) or USB export

Time synchronisation

  • NTP server: ntp.nbi.ac.uk (NBI IT policy — public NTP pools are not used)
  • Config file: /etc/systemd/timesyncd.conf.d/nbi-ntp.conf
  • Time synchronisation persists across reboots; synchronises over Wi-Fi
  • Verify: timedatectl timesync-status / timedatectl status

Failure behaviour (intentional)

Scenario Internet Controller UI File Access
Wi-Fi up, MacBook Ethernet active Wi-Fi Yes Yes (local)
Wi-Fi down, MacBook Ethernet active None Yes Yes (local)
Ethernet cable disconnected, Wi-Fi up Wi-Fi Yes, if reachable over Wi-Fi/local hostname Yes (local)

This behaviour is intentional.

Summary

This architecture provides:

  • Clear separation of network roles
  • Automatic direct MacBook Ethernet access
  • User access through http://192.168.50.2:8080/
  • IT-approved time synchronisation via Wi-Fi
  • A maintainable Raspberry Pi deployment model

Public overview; internal details intentionally excluded.

Document updated on 23/06/2026 Rohan R.