You're reading from Mastering Embedded Linux Programming Create fast and reliable embedded solutions with Linux 5.4 and the Yocto Project 3.1 (Dunfell)

Product type Paperback

Published in May 2021

Publisher Packt

ISBN-13 9781789530384

Length 758 pages

Edition 3rd Edition

Languages

C++

Tools

Linux

Concepts

Embedded Systems

Authors (2):

Frank Vasquez

Mr. Chris Simmonds

View More author details

Table of Contents (27) Chapters

Preface

1. Section 1: Elements of Embedded Linux

2. Chapter 1: Starting Out FREE CHAPTER

3. Chapter 2: Learning about Toolchains

4. Chapter 3: All about Bootloaders

5. Chapter 4: Configuring and Building the Kernel

6. Chapter 5: Building a Root Filesystem

7. Chapter 6: Selecting a Build System

8. Chapter 7: Developing with Yocto

9. Chapter 8: Yocto Under the Hood

10. Section 2: System Architecture and Design Decisions

11. Chapter 9: Creating a Storage Strategy

12. Chapter 10: Updating Software in the Field

13. Chapter 11: Interfacing with Device Drivers

14. Chapter 12: Prototyping with Breakout Boards

15. Chapter 13: Starting Up – The init Program

16. Chapter 14: Starting with BusyBox runit

17. Chapter 15: Managing Power

18. Section 3: Writing Embedded Applications

19. Chapter 16: Packaging Python

20. Chapter 17: Learning about Processes and Threads

21. Chapter 18: Managing Memory

22. Section 4: Debugging and Optimizing Performance

23. Chapter 19: Debugging with GDB

24. Chapter 20: Profiling and Tracing

25. Chapter 21: Real-Time Programming

26. Other Books You May Enjoy

The init program

Running a shell, or even a shell script, at boot time is fine for simple cases, but really you need something more flexible. Normally, Unix systems run a program called init that starts up and monitors other programs. Over the years, there have been many init programs, some of which I will describe in Chapter 13, Starting Up – The init Program. For now, I will briefly introduce the init program from BusyBox.

The init program begins by reading the configuration file, /etc/inittab. Here is a simple example that is adequate for our needs:

::sysinit:/etc/init.d/rcS
::askfirst:-/bin/ash

The first line runs a shell script, rcS, when init is started. The second line prints the message Please press Enter to activate this console to the console and starts a shell when you press Enter. The leading - before /bin/ash means that it will become a login shell, which sources /etc/profile and $HOME/.profile before giving the shell prompt. One of the advantages of launching...