Book Image

Mastering Embedded Linux Programming - Second Edition

By : Chris Simmonds
Book Image

Mastering Embedded Linux Programming - Second Edition

By: Chris Simmonds

Overview of this book

Embedded Linux runs many of the devices we use every day, from smart TVs to WiFi routers, test equipment to industrial controllers - all of them have Linux at their heart. Linux is a core technology in the implementation of the inter-connected world of the Internet of Things. The comprehensive guide shows you the technologies and techniques required to build Linux into embedded systems. You will begin by learning about the fundamental elements that underpin all embedded Linux projects: the toolchain, the bootloader, the kernel, and the root filesystem. You’ll see how to create each of these elements from scratch, and how to automate the process using Buildroot and the Yocto Project. Moving on, you’ll find out how to implement an effective storage strategy for flash memory chips, and how to install updates to the device remotely once it is deployed. You’ll also get to know the key aspects of writing code for embedded Linux, such as how to access hardware from applications, the implications of writing multi-threaded code, and techniques to manage memory in an efficient way. The final chapters show you how to debug your code, both in applications and in the Linux kernel, and how to profile the system so that you can look out for performance bottlenecks. By the end of the book, you will have a complete overview of the steps required to create a successful embedded Linux system.
Table of Contents (17 chapters)

Transferring the root filesystem to the target

After having created a skeleton root filesystem in your staging directory, the next task is to transfer it to the target. In the sections that follow, I will describe three possibilities:

  • initramfs: Also known as a ramdisk, this is a filesystem image that is loaded into RAM by the bootloader. Ramdisks are easy to create and have no dependencies on mass storage drivers. They can be used in fallback maintenance mode when the main root filesystem needs updating. They can even be used as the main root filesystem in small embedded devices, and they are commonly used as the early user space in mainstream Linux distributions. Remember that the contents of the root filesystem are volatile, and any changes you make in the root filesystem at runtime will be lost when the system next boots. You would need another storage type to store permanent...