Tutorial: Building the Simplest Possible Linux System - Rob Landley, se-instruments.com
This tutorial walks you through building and booting the simplest possible Linux system, first under QEMU and then on real hardware. We cover kernel configuration and building, native vs cross compiling, initramfs creation (and other root filesystem options), installing and booting, the init process and system bringup, running an app, adding an example server (sshd), and finally we'll add a native toolchain to compile "hello world" on the target.
Rob Landley
I used to maintain busybox and a tinycc fork, currently maintain toybox and aboriginal linux, was briefly linux-kernel documentation maintainer, made initramfs use tmpfs, co-founded Penguicon, inexplicably wrote stock market investment columns for The Motley Fool for a few years long ago, youtube video of me throwing liquid nitrogen into a swimming pool has been viewed over 10 million times... you know, the usual.