Book Image

Mastering Embedded Linux Programming

By : Chris Simmonds
Book Image

Mastering Embedded Linux Programming

By: Chris Simmonds

Overview of this book

Mastering Embedded Linux Programming takes you through the product cycle and gives you an in-depth description of the components and options that are available at each stage. You will begin by learning about toolchains, bootloaders, the Linux kernel, and how to configure a root filesystem to create a basic working device. You will then learn how to use the two most commonly used build systems, Buildroot and Yocto, to speed up and simplify the development process. Building on this solid base, the next section considers how to make best use of raw NAND/NOR flash memory and managed flash eMMC chips, including mechanisms for increasing the lifetime of the devices and to perform reliable in-field updates. Next, you need to consider what techniques are best suited to writing applications for your device. We will then see how functions are split between processes and the usage of POSIX threads, which have a big impact on the responsiveness and performance of the final device The closing sections look at the techniques available to developers for profiling and tracing applications and kernel code using perf and ftrace.
Table of Contents (22 chapters)
Mastering Embedded Linux Programming
About the Author
About the Reviewers

BusyBox init

BusyBox has a minimal init program that uses a configuration file, /etc/inittab, to define rules to start programs at boot up and to stop them at shutdown. Usually, the actual work is done by shell scripts which, by convention, are placed in the /etc/init.d directory.

init begins by reading the configuration file, /etc/inittab. This contains a list of programs to run, one per line, with this format:


The role of these parameters is as follows:

  • id: The controlling terminal for the command

  • action: The conditions to run this command, as shown in the following paragraph

  • program: The program to run

The actions are as follows:

  • sysinit: Run the program when init starts, before any of the other types of actions.

  • respawn: Run the program and restart it if it terminates. It is used to run a program as a daemon.

  • askfirst: This is the same as respawn, but prints the message Please press Enter to activate this console to the console and runs the program after...