Googulator / live-bootstrap

Use of a Linux initramfs to fully automate the bootstrapping process

live-bootstrap

An attempt to provide a reproducible, automatic, complete end-to-end bootstrap from a minimal number of binary seeds to a supported fully functioning operating system.

How do I use this?

Quick start:

See ./rootfs.py --help and follow the instructions given there. This uses a variety of userland tools to prepare the bootstrap.

(Currently, there is no way to perform the bootstrap without external preparations! This is a currently unsolved problem.)

Without using Python:

1. git clone https://github.com/fosslinux/live-bootstrap
2. git submodule update --init --recursive
3. Consider whether you are going to run this in a chroot, in QEMU, or on bare metal. (All of this can be automated, but not in a trustable way. See further below.) a. chroot: Create a directory where the chroot will reside, run ./download-distfiles.sh, and copy: * The entire contents of seed/stage0-posix into that directory. * All other files in seed into that directory. * steps/ and distfiles/ into that directory. * At least all files listed in steps/pre-network-sources must be copied in. All other files will be obtained from the network. * Run /bootstrap-seeds/POSIX/x86/kaem-optional-seed in the chroot. (Eg, chroot rootfs /bootstrap-seeds/POSIX/x86/kaem-optional-seed).
   2. QEMU: Create two blank disk images.
      • On the first image, write seed/stage0-posix/bootstrap-seeds/NATIVE/x86/builder-hex0-x86-stage1.img to it, followed by kernel-bootstrap/builder-hex0-x86-stage2.hex0, followed by zeros padding the disk to the next sector.
      • distfiles can be obtained using ./download-distfiles.sh.
      • See the list in part a. For every file within that list, write a line to the disk src <size-of-file> <path-to-file>, followed by the contents of the file.
        • Only copy distfiles listed in steps/pre-network-sources into this disk.
      • Optionally (if you don't do this, distfiles will be network downloaded):
        • On the second image, create an MSDOS partition table and one ext3 partition.
        • Copy distfiles/ into this disk.
      • Run QEMU, with 4+G RAM, optionally SMP (multicore), both drives (in the order introduced above), a NIC with model E1000 (-nic user,model=e1000), and -machine kernel-irqchip=split.
   c. Bare metal: Follow the same steps as QEMU, but the disks need to be two different physical disks, and boot from the first disk.

Background

Problem statement

live-bootstrap's overarching problem statement is;

> How can a usable Linux system be created with only human-auditable, and wherever possible, human-written, source code?

Clarifications:

• "usable" means a modern toolchain, with appropriate utilities, that can be used to expand the amount of software on the system, interactively, or non-interactively.
• "human-auditable" is discretionary, but is usually fairly strict. See "Specific things to be bootstrapped" below.

Why is this difficult?

The core of a modern Linux system is primarily written in C and C++. C and C++ are self-hosting, ie, nearly every single C compiler is written in C.

Every single version of GCC was written in C. To avoid using an existing toolchain, we need some way to be able to compile a GCC version without C. We can use a less well-featured compiler, TCC, to do this. And so forth, until we get to a fairly primitive C compiler written in assembly, cc_x86.

Going up through this process requires a bunch of other utilities as well; the autotools suite, guile and autogen, etc. These also have to be matched appropriately to the toolchain available.

Why should I care?

That is outside of the scope of this README. Here’s a few things you can look at:

• https://bootstrappable.org
• Trusting Trust Attack (as described by Ken Thompson)
• https://guix.gnu.org/manual/en/html_node/Bootstrapping.html
• Collapse of the Internet (eg CollapseOS)

Specific things to be bootstrapped

GNU Guix is currently the furthest along project to automate bootstrapping. However, there are a number of non-auditable files used in many of their packages. Here is a list of file types that we deem unsuitable for bootstrapping.

1. Binaries (apart from seed hex0, kaem, builder-hex0).
2. Any pre-generated configure scripts, or Makefile.in’s from autotools.
3. Pre-generated bison/flex parsers (identifiable through a .y file).
4. Any source code/binaries downloaded within a software’s build system that is outside of our control to verify before use in the build system.
5. Any non-free software. (Must be FSF-approved license).

How does this work?

For a more in-depth discussion, see parts.rst.

Firstly, builder-hex0 is launched. builder-hex0 is a minimal kernel that is written in hex0, existing in 3 self-bootstrapping stages.

This is capable of executing the entirety of stage0-posix, (see seed/stage0-posix), which produces a variety of useful utilities and a basic C language, M2-Planet.

stage0-posix runs a file called after.kaem. This is a shell script that builds and runs a small program called script-generator. This program reads steps/manifest and converts it into a series of shell scripts that can be executed in sequence to complete the bootstrap.

From this point forward, steps/manifest is effectively self documenting. Each package built exists in steps/<pkg>, and the build scripts can be seen there.