Book Image

Mastering Embedded Linux Programming - Third Edition

By : Frank Vasquez, Chris Simmonds
5 (3)
Book Image

Mastering Embedded Linux Programming - Third Edition

5 (3)
By: Frank Vasquez, Chris Simmonds

Overview of this book

If you’re looking for a book that will demystify embedded Linux, then you’ve come to the right place. Mastering Embedded Linux Programming is a fully comprehensive guide that can serve both as means to learn new things or as a handy reference. The first few chapters of this book will break down the fundamental elements that underpin all embedded Linux projects: the toolchain, the bootloader, the kernel, and the root filesystem. After that, you will learn how to create each of these elements from scratch and automate the process using Buildroot and the Yocto Project. As you progress, the book will show you how to implement an effective storage strategy for flash memory chips and install updates to a device remotely once it’s deployed. You’ll also learn about the key aspects of writing code for embedded Linux, such as how to access hardware from apps, the implications of writing multi-threaded code, and techniques to manage memory in an efficient way. The final chapters demonstrate how to debug your code, whether it resides in apps or in the Linux kernel itself. You’ll also cover the different tracers and profilers that are available for Linux so that you can quickly pinpoint any performance bottlenecks in your system. By the end of this Linux book, you’ll be able to create efficient and secure embedded devices using Linux.
Table of Contents (27 chapters)
1
Section 1: Elements of Embedded Linux
10
Section 2: System Architecture and Design Decisions
18
Section 3: Writing Embedded Applications
22
Section 4: Debugging and Optimizing Performance

Temporary filesystems

There are always some files that have a short lifetime or have no significance after a reboot. Many such files are put into /tmp, and so it makes sense to keep these files from reaching permanent storage.

The temporary filesystem, tmpfs, is ideal for this purpose. You can create a temporary RAM-based filesystem by simply mounting tmpfs:

# mount -t tmpfs tmp_files /tmp

As with procfs and sysfs, there is no device node associated with tmpfs, so you have to supply a placekeeper string, which is tmp_files in the preceding example.

The amount of memory used will grow and shrink as files are created and deleted. The default maximum size is half the physical RAM. In most cases, it would be a disaster if tmpfs grew to be that large, so it is a very good idea to cap it with the -o size parameter. The parameter can be given in bytes, KiB (k), MiB (m), or GiB (g), like this, for example:

# mount -t tmpfs -o size=1m tmp_files /tmp

In addition to /tmp, some...