A Full-Source Bootstrap for NixOS

Builds a NixOS installation fully from source. This code was created as part of my bachelor's thesis.
The presentation slides can be found here (or the extended version here).

Structure

The bootstrap chain consists of two largely independent parts:

• The inner bootstrap consists of a nixpkgs fork that has been modified so that the pre-build bootstrap seeds ususally used by nixpkgs are replaced with a version built from the bootstrapped packages built by Aux Foundation.
• The outer bootstrap is a modified fork of live-bootstrap that has been extended to build a full NixOS installation from source, using the modified nixpkgs from the inner bootstrap.

Usage

A computer running Linux is required to prepare the bootstrap. All needed dependencies are included in the Nix devShell. On a system that has Nix installed, it can be activated by running nix develop in the live-bootstrap directory.

The bootstrap itself works exclusively on 64-bit x86 based machines. It can be executed on physical hardware as well as in a QEMU-based virtual machine.

First of all, clone all submodules:

git submodule update --init --recursive

QEMU

cd live-bootstrap
make BOOTSTRAP_PLATFORM=qemu BOOTSTRAP_EXTS="nix nixos" bootstrap

The built system can be started with

make

Check live-bootstrap/Makefile for the possible configuration options

Physical Computer

To generate the bootstrap images, run:

cd live-bootstrap
make BOOTSTRAP_PLATFORM=bare-metal BOOTSTRAP_EXTS="nix nixos" target/seed

Then, write target/seed/init.img and target/seed/external.img to two separate drives, using your boot media creation tool of choice. Boot up the target system and select the init.img drive as the boot device.

Important: live-bootstrap expects the external disk to appear as /dev/sdb1 in Linux. If this is not true in your setup, change this in rootfs.py

Hardware requirements

• The external.img disk needs to have enough space to accomodate all needed files during the build process. I recommend at least 128GiB.
• The target computer needs to be able to boot in BIOS mode. Computers that only support UEFI are not compatible.

Backup Sources

In the (likely) event, that some of the needed sources are no longer available, a mirror is available. To use it, copy the replacement sources files from the backup-sources directory to the live-bootstrap directory like this:

cp -vr backup-sources/. live-bootstrap/
rm live-bootstrap/generate.sh

The included generate.sh script is used to generate the mirror sources files from the original ones.

To make sure that the bootstrap does not attempt to download the source files on-the-fly, enable the bootstrap's offline mode by adding BOOTSTRAP_OFFLINE=1 to the make commandline.