Building a small Raspberry Pi System from Scratch

What you are looking at right now is a collection of instructions on how to bootstrap a tiny system for a Raspberry Pi 3 board.

We will bootstrap the system by building our own cross compiler toolchain and then using it to cross compile everything we need for a working Linux based OS.

In contrast to similar guides, I try to explain why we are doing the things the way we are doing them, instead of just throwing a bunch of copy-paste command lines around (I'm looking at you, LFS).

This guide is divided into the following parts:

• Basic Setup. Lists some tools that you should have installed and walks through the steps of setting up the directory tree that we work in, as well as a few handy environment variables.
• Building a cross compiler toolchain.
• Cross compiling a statically linked BusyBox and the kernel. The BusyBox is packaged into a small initramfs. We will make it boot on the Rapsberry Pi and explore some parts of the Linux boot process.
• Building a simple userland. Mostly a Linux-From-Scratch-Style walkthrough to building some packages for a simple GNU userland. The userland is packed into a SquashFS image. The BusyBox based initrd is modified to mount it and switch into it.