tiny-kernel

Small Linux boot experiment built around a tiny kernel config, a minimal BusyBox-based initramfs, and a local QEMU boot script.

What this repo does

This repository keeps the pieces needed to boot a very small Linux userspace:

• a kernel .config
• a minimal initramfs/ tree
• a start.sh helper that triggers a GitHub Actions build, downloads the released bzImage and initrd.img, and boots them with QEMU

The default init mounts /proc, /sys, and /dev, installs BusyBox applets, and then drops into /bin/sh. If the kernel was built without CONFIG_DEVTMPFS, it falls back to creating the minimum /dev nodes needed for an interactive rescue shell on the serial console.

Inspiration

This project is directly inspired by blinry's article, Building a tiny Linux from scratch, which walks through assembling a minimal Linux system from a tiny kernel, BusyBox, and an initramfs.

Usage

Prerequisites:

• gh
• qemu-system-x86_64
• tar
• GitHub CLI authenticated with access to trigger Actions in the target repo

Run:

./start.sh

What happens:

1. start.sh triggers the build-linux-tinyconfig.yml workflow.
2. GitHub Actions builds bzImage from the repository .config.
3. GitHub Actions packs initramfs/ into initrd.img.
4. The script downloads the release artifact and boots it with QEMU in serial mode.

If needed, override the branch used for the workflow dispatch:

RUN_REF=my-branch ./start.sh

Repo layout

• .config: Linux kernel configuration used by CI
• initramfs/init: PID 1 inside the initramfs
• initramfs/bin/busybox: static BusyBox binary used by the initramfs
• start.sh: fetch-and-boot helper for local testing
• .github/workflows/build-linux-tinyconfig.yml: CI build and release pipeline

Notes

• The local boot path expects prebuilt artifacts from GitHub Actions rather than compiling the kernel on your machine.
• QEMU is started with -nographic, so interaction happens through the terminal.