Buildroot: a Firmware Generator for Embedded Systems Training Course

Overview

Buildroot is an open-source project that contains scripts that produce a cross-compilation toolchain, a customizable root filesystem image, and a Linux kernel for embedded devices. During this practical course, participants will learn how to use it:

• How to select software that goes into the root filesystem.
• How to add new packages and modify existing ones.
• How to add support for new embedded boards.

During the course, bootable filesystem images will be produced. Remote courses are delivered using the QEMU emulator, while in the classroom it is possible to use either QEMU or real embedded boards of the trainer’s choice.

Other projects with similar goals include the Yocto project and OpenWRT. Please use these presentations to determine which one is the right choice for your needs.

Requirements

• The participant must have built a kernel at least once for a traditional desktop (non-embedded) Linux system.
• Knows what components the Linux userspace on a desktop system is composed of.
• Knows how to generate and use patches.
• Must be able to explain what is GNU Make, Autotools, what other build systems exist.
• Ideally, maintains at least one Linux package, either as an upstream author, or in any traditional Linux desktop distribution.
• Prior experience with embedded development is not required, and is not a substitute for the knowledge about traditional Linux desktops specified above.

Course Outline

1. Getting started
   1. Obtaining Buildroot
   2. Build system requirements
   3. Cross-compiler terminology: build, host, target, sysroot
   4. Choosing the correct target
   5. Building a minimal embedded system and booting it
   6. Contents of the resulting filesystem image
   7. Parallel builds
   8. Full and partial rebuilds
2. Design goals of Buildroot
3. Choices to be made
   1. C library: glibc or uClibc or musl?
   2. Init system: busybox vs sysVinit vs systemd
   3. Managing device nodes in /dev
   4. Selecting other packages
4. Understanding the build instructions
   1. Syntax of Kconfig (Confog.in) files
   2. Features of GNU Make used by Buidroot Makefiles
   3. Style guide for Config.in and *.mk files
   4. How to add a simple Autotools-based package
   5. The difference between staging and target directories
   6. The need for host packages
   7. How to express dependencies and optional features
   8. Support for languages other than C and build systems other than Autotools
   9. Debugging Makefiles
   10. Rebuilding a single package
5. Analyzing the build results
   1. What took so much build time?
   2. What took so much disk space?
   3. Why has this package been built?
6. Organizing external package trees
7. Workflow for application developers
   1. How to use a local source directory
   2. Overriding build instructions
   3. Debugging your application
   4. Speeding up rebuilds
   5. Viewing build logs
8. Dealing with common cross-compilation issues
   1. How to write your own software so that it is friendly to cross-compilers
9. Workflow for kernel developers
   1. How the kernel boots on an embedded system
   2. Changing configuration options and adding patches
   3. Module loading mechanisms
10. Making a finished product
    1. Running daemons at startup
    2. Providing custom configuration files
    3. Available firmware update mechanisms
    4. Upgrading to a new Buildroot version
    5. Complying with open-source licenses