Intro to mkroot, Rob Landley, https://landley.net/toybox
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This outline: https://landley.net/talks/txlf-2024.txt

Quickstart:
  https://github.com/landley/toybox/blob/master/mkroot/mkroot.sh
  3 parts: setup, root filesystem, kernel and packaging
  https://github.com/landley/toybox/blob/master/mkroot/README
  toolchain, build

use
  wget, run, cat /init, zcat /proc/config.gz, cat run-qemu.sh
    -hda (becomes /mnt), KARGS
    test wrapper
    native compiler

design
  AOSP self-hosting, base scales up, used
    https://landley.net/toybox/about.html
  Countering "trusting trust"
    http://lists.landley.net/pipermail/toybox-landley.net/2020-July/011898.html
    one langauge, no dependencies
    recent xz, rust making it worse
    Students should be able to binary re-audit entire base as exercise
      Binary reverse engineering/auditing is an industry, veracode etc
  If you can't reproduce it from scratch, you're not doing science.
    Minimal native development environment
      - rebuild itself
      - build linux from scratch (and now AOSP)
    Simple, auditable, dependency free
      4 packages (kernel, libc, cmdline, compiler), circular dependencies

  backstory; aboriginal busybox
    https://youtu.be/MkJkyMuBm3g https://landley.net/aboriginal/history.html
    - FWL replaced 20 LFS packages (aboriginal/old)
    - aboriginal was 7: linux, uclibc, busybox, gcc, binutils, make, bash
      https://landley.net/aboriginal/about.html
      - build linux from scratch under result
        https://github.com/landley/control-images/tree/master/images/lfs-bootstrap
        - then gentoo/debian/fedora...
      - Aboriginal EOL in 2017, Alpine Linux took this ball and ran with it

build
  simple chroot
    alpine has musl, glibc sucks
  var=, packages
  CROSS=
  LINUX=

script walkthrough
  setup, root filesystem, kernel and packaging
  1) setup: vars, dirs, airlock (hermetic build)
  2) chroot: mkdir, init, other files
  3) kernel (config be->csv->mini->full)
       I build with kernel patches
     initramfs.cpio.gz (static vs dynamic, modules)

packages
  plumbing
  dropbear
  busybox
  overlay

toybox vs busybox
  drop in file, adds commands
  0BSD
  If you prefer: mkroot/packages/busybox, NOTOYBOX=1
  (bzip2 dependency) vs scripts/prereq/build.sh

mkroot/testroot.sh