You're reading from Mastering Embedded Linux Programming - Third Edition

Product type Book

Published in May 2021

Publisher Packt

ISBN-13 9781789530384

Pages 758 pages

Edition 3rd Edition

Languages

Concepts

Embedded Systems

Authors (2):

Frank Vasquez

Chris Simmonds

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Table of Contents (27) Chapters

Preface

1. Section 1: Elements of Embedded Linux

2. Chapter 1: Starting Out

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

System V init

This init program was inspired by the one from Unix System V and so dates back to the mid-1980s. The version most often found in Linux distributions was written initially by Miquel van Smoorenburg. Until recently, it was the init daemon for almost all desktop and server distributions and a fair number of embedded systems as well. However, in recent years, it has been replaced by systemd, which I will describe in the next section.

The BusyBox init daemon I have just described is just a trimmed-down version of System V init. Compared to BusyBox init, System V init has two advantages:

Firstly, the boot scripts are written in a well-known, modular format, making it easy to add new packages at build time or runtime.
Secondly, it has the concept of runlevels, which allow a collection of programs to be started or stopped in one go when switching from one runlevel to another.

There are eight runlevels, numbered from 0 to 6, plus S: