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Mastering Embedded Linux Development

Mastering Embedded Linux Development

By : Frank Vasquez, Mr. Chris Simmonds
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Mastering Embedded Linux Development

Mastering Embedded Linux Development

By: Frank Vasquez, Mr. Chris Simmonds

Overview of this book

Mastering Embedded Linux Development' is designed to be both a learning resource and a reference for your embedded Linux projects. The book starts by breaking down the fundamental elements that underpin all embedded Linux projects: the toolchain, the bootloader, the kernel, and the root filesystem. First, you will download and install a pre-built toolchain. After that, you will cross-compile each of the remaining three elements from scratch and learn to automate the process using Buildroot and the Yocto Project. The book progresses with coverage of over-the-air software updates and rapid prototyping with add-on boards. Two new chapters tackle modern development practices including Python packaging and deploying containerized applications. These are followed by a chapter on writing multithreaded code and another on techniques to manage memory in an efficient way. The final chapters demonstrate how to debug your code, whether it resides in user space or in the Linux kernel itself. In addition to GDB, the book also covers 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 book, you will be able to create efficient and secure embedded devices with Linux that will delight your users.
Table of Contents (28 chapters)
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1
Part 1: Elements of Embedded Linux
7
Part 2: Building Embedded Linux Images
11
Part 3: System Architecture and Design Decisions
18
Part 4: Developing Applications
23
Part 5: Debugging and Optimizing Performance

Configuring user accounts

As I already said, it is bad practice to run all programs as root because if one program is compromised by an outside attack then the whole system is at risk. It is better to create unprivileged user accounts and use them where full root is not necessary.

Usernames are configured in /etc/passwd. There is one line per user with seven fields of information separated by colons. These are, in order:

  • The login name
  • The hash code used to verify the password or, more usually, an x to indicate that the password is stored in /etc/shadow
  • The UID or user ID
  • The GID or group ID
  • The comment field (often left blank)
  • The user’s home directory
  • The shell this user will use (optional)

Here is a simple example in which we have the user root with UID 0 and the user daemon with UID 1:

root:x:0:0:root:/root:/bin/sh
daemon:x:1:1:daemon:/usr/sbin:/bin/false

Setting the shell for the user daemon as /bin/false...

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