Book Image

Raspberry Pi for Secret Agents - Third Edition

Book Image

Raspberry Pi for Secret Agents - Third Edition

Overview of this book

This book is for all mischievous Raspberry Pi owners who’d like to see their computer transform into a neat spy gadget to be used in a series of practical pranks and projects. No previous skills are required to follow along, and if you’re completely new to Linux, you’ll pick up much of the basics for free. We’ll help you set up your Raspberry Pi Zero, Raspberry Pi 2 and Raspberry Pi 3 and guide you through a number of pranks and secret agent techniques that are so inconspicuous yet high on mischief. You’ll learn how to configure your operating system for maximum mischief and start exploring audio, video, or Wi-Fi techniques. We’ll show you how to record, listen, or talk to people from a distance and how to set up your own phone network. Then, you’ll plug in your webcam and set up a motion detector with an alarm and find out what the other computers on your Wi-Fi network are up to. Once you’ve mastered the techniques, we’ll combine them with a battery pack and GPS for the ultimate off-road spy kit.
Table of Contents (7 chapters)

Scheduling your audio actions

In this section, we'll be looking at different techniques for triggering a recording or a playback, and optionally how to make it stop after a certain period of time.

Start on power up

The first method we'll cover is also the bluntest: how to start a recording or playback directly when powering up the Raspberry Pi. There isn't really a standardized way of auto-starting regular user applications on boot, so we'll have to improvise a bit to come up with our own way of doing what we want.

The Raspbian boot process is basically a collection of shell scripts being run one after the other, with each script performing some important task. One of the last scripts to run is /etc/rc.local, which is a good starting point for our custom auto-run solution. Right now, the script doesn't do much, it just prints out the IP address of the Pi.

You can try running the script any time using the following command:

pi@raspberrypi ~ $ /etc/rc.local

We could just jam our list of commands...