145 lines
5.9 KiB
ReStructuredText
145 lines
5.9 KiB
ReStructuredText
.. SPDX-FileCopyrightText: 2021 Andrius Štikonas <andrius@stikonas.eu>
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.. SPDX-FileCopyrightText: 2021 Paul Dersey <pdersey@gmail.com>
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.. SPDX-FileCopyrightText: 2021 fosslinux <fosslinux@aussies.space>
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.. SPDX-License-Identifier: CC-BY-SA-4.0
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live-bootstrap
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==============
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An attempt to provide a reproducible, automatic, complete end-to-end
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bootstrap from a minimal number of binary seeds to a supported fully
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functioning operating system.
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How do I use this?
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------------------
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Quick start:
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See ``./rootfs.py --help`` and follow the instructions given there.
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This uses a variety of userland tools to prepare the bootstrap.
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(*Currently, there is no way to perform the bootstrap without external
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preparations! This is a currently unsolved problem.*)
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Without using Python:
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1. ``git clone https://github.com/fosslinux/live-bootstrap``
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2. ``git submodule update --init --recursive``
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3. Consider whether you are going to run this in a chroot, in QEMU, or on bare
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metal. (All of this *can* be automated, but not in a trustable way. See
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further below.)
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a. **chroot:** Create a directory where the chroot will reside, run
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``./download-distfiles.sh``, and copy:
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* The entire contents of ``seed/stage0-posix`` into that directory.
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* All other files in ``seed`` into that directory.
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* ``steps/`` and ``distfiles/`` into that directory.
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* At least all files listed in ``steps/pre-network-sources`` must be
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copied in. All other files will be obtained from the network.
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* Run ``/bootstrap-seeds/POSIX/x86/kaem-optional-seed`` in the chroot.
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(Eg, ``chroot rootfs /bootstrap-seeds/POSIX/x86/kaem-optional-seed``).
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b. **QEMU:** Create two blank disk images.
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* On the first image, write
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``seed/stage0-posix/bootstrap-seeds/NATIVE/x86/builder-hex0-x86-stage1.img``
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to it, followed by ``kernel-bootstrap/builder-hex0-x86-stage2.hex0``,
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followed by zeros padding the disk to the next sector.
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* distfiles can be obtained using ``./download-distfiles.sh``.
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* See the list in part a. For every file within that list, write a line to
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the disk ``src <size-of-file> <path-to-file>``, followed by the contents
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of the file.
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* *Only* copy distfiles listed in ``steps/pre-network-sources`` into
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this disk.
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* Optionally (if you don't do this, distfiles will be network downloaded):
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* On the second image, create an MSDOS partition table and one ext3
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partition.
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* Copy ``distfiles/`` into this disk.
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* Run QEMU, with 4+G RAM, optionally SMP (multicore), both drives (in the
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order introduced above), a NIC with model E1000 (``-nic
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user,model=e1000``), and ``-machine kernel-irqchip=split``.
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c. **Bare metal:** Follow the same steps as QEMU, but the disks need to be
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two different *physical* disks, and boot from the first disk.
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Background
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----------
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Problem statement
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=================
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live-bootstrap's overarching problem statement is;
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> How can a usable Linux system be created with only human-auditable, and
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wherever possible, human-written, source code?
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Clarifications:
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* "usable" means a modern toolchain, with appropriate utilities, that can be
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used to expand the amount of software on the system, interactively, or
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non-interactively.
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* "human-auditable" is discretionary, but is usually fairly strict. See
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"Specific things to be bootstrapped" below.
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Why is this difficult?
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======================
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The core of a modern Linux system is primarily written in C and C++. C and C++
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are **self-hosting**, ie, nearly every single C compiler is written in C.
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Every single version of GCC was written in C. To avoid using an existing
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toolchain, we need some way to be able to compile a GCC version without C. We
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can use a less well-featured compiler, TCC, to do this. And so forth, until we
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get to a fairly primitive C compiler written in assembly, ``cc_x86``.
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Going up through this process requires a bunch of other utilities as well; the
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autotools suite, guile and autogen, etc. These also have to be matched
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appropriately to the toolchain available.
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Why should I care?
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------------------
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That is outside of the scope of this README. Here’s a few things you can
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look at:
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- https://bootstrappable.org
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- Trusting Trust Attack (as described by Ken Thompson)
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- https://guix.gnu.org/manual/en/html_node/Bootstrapping.html
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- Collapse of the Internet (eg CollapseOS)
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Specific things to be bootstrapped
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----------------------------------
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GNU Guix is currently the furthest along project to automate
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bootstrapping. However, there are a number of non-auditable files used
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in many of their packages. Here is a list of file types that we deem
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unsuitable for bootstrapping.
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1. Binaries (apart from seed hex0, kaem, builder-hex0).
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2. Any pre-generated configure scripts, or Makefile.in’s from autotools.
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3. Pre-generated bison/flex parsers (identifiable through a ``.y``
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file).
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4. Any source code/binaries downloaded within a software’s build system
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that is outside of our control to verify before use in the build
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system.
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5. Any non-free software. (Must be FSF-approved license).
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How does this work?
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-------------------
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**For a more in-depth discussion, see parts.rst.**
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Firstly, ``builder-hex0`` is launched. ``builder-hex0`` is a minimal kernel that is
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written in ``hex0``, existing in 3 self-bootstrapping stages.
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This is capable of executing the entirety of ``stage0-posix``, (see
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``seed/stage0-posix``), which produces a variety of useful utilities and a basic
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C language, ``M2-Planet``.
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``stage0-posix`` runs a file called ``after.kaem``. This is a shell script that
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builds and runs a small program called ``script-generator``. This program reads
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``steps/manifest`` and converts it into a series of shell scripts that can be
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executed in sequence to complete the bootstrap.
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From this point forward, ``steps/manifest`` is effectively self documenting.
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Each package built exists in ``steps/<pkg>``, and the build scripts can be seen
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there.
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