Skip to content

23 – Bootstrapping a System with Cosmos

This guide walks through how to build a working root filesystem using Cosmos alone. It assumes you have a Cosmos binary, a Galaxy source (HTTP, file, or USB), and a directory to install into.

This process works from live ISOs, recovery images, or even inside minimalist containers. If you can run the Cosmos binary, you can build a system.

TL;DR Use this guide to go from zero to rootfs using Cosmos and a local Galaxy—no shell, no dynamic linking, no nonsense.

🌜 What Is Bootstrapping?

Bootstrapping is the act of building a usable system from near-zero. With Cosmos, this means:

  • No shell
  • No package manager
  • No userland
  • Just a tarball or static binary and a goal

Cosmos enables you to go from "nothing but libc" to a minimal, functional user environment.

✅ Requirements

  • Statically compiled cosmos binary (no interpreter or dynamic libs)
  • Galaxy source (USB, HTTP, Git clone, etc.)
  • Writable mount point (e.g. /mnt/wombat)

🔨 Install Process

# Optional: create target root
mkdir -p /mnt/wombat

# somewhere earlier, you add a local/mounted Galaxy

# Install base system
cosmos install --root /mnt/wombat core-stack

# Bind system dirs for chroot
mount --bind /dev /mnt/wombat/dev
mount --bind /proc /mnt/wombat/proc
mount --bind /sys /mnt/wombat/sys

# Optional: copy /etc/passwd or minimal shadow configs
cp -r /etc/skel /mnt/wombat/etc/

# Chroot in
chroot /mnt/wombat /bin/sh

# Optional: validate install
which sh
ls /

🔄 What to Install First

cosmos install core-stack
cosmos install net-tools
cosmos install busybox

core-stack is a placeholder for your base system. It can be a Nebula (metapackage). The goal is to get a minimal system up and running.

A full Constellation file (e.g. bootstrap.toml) can define this list.

name = "bootstrap"
description = "Minimal system bootstrap"

members = [
  "core-stack",
  "net-tools",
  "busybox",
]

🌐 Use Cases

  • Minimal Linux from scratch builds
  • Custom distro bootstrapping
  • Initramfs builds
  • Embedded rescue environments

🚫 What Cosmos Does Not Do

  • Partition drives
  • Configure bootloaders
  • Handle systemd or runit setup

Cosmos installs files and packages—nothing more. It is your tool for building a system, not for booting one.

🫰 Pro Tips

  • Test bootstrap flows inside a container or VM before bare metal
  • Keep a Galaxy synced to USB in case your network goes down
  • Use a Nebula to define your base stack for repeatable installs
  • Use cosmos freeze (future) to snapshot what you just installed

With Cosmos, you can go from a blank directory to a bootable rootfs with only a few commands—no interpreters, no curl, no Python, no tears.