Making a micro Linux distro (2023)

Uros Popovic’s article, 'Making a micro Linux distro (2023)', offers an engaging, hands-on journey into the foundational elements of a Linux operating system. Targeting the RISC-V architecture within QEMU, the piece meticulously guides readers through the process of building a bare-bones Linux distribution from the ground up, emphasizing clarity and practical understanding over exhaustive detail. It’s designed to help beginners grasp the intricate interplay between the kernel, user space, and initial system processes.

• Kernel Fundamentals: Explains the core responsibilities of an OS kernel, including hardware abstraction, resource management, and providing a programming model, with Linux as a prime example.
• Distribution Defined: Clarifies that a Linux distribution comprises the kernel plus layers of 'infrastructure on top of infrastructure' running in user space, contrasting it with the bare kernel.
• The init Process: Details the crucial role of the init process (PID 1) as the first user-space program launched by the kernel, acting as the ancestor for all other processes.
• Building a Custom Kernel: Provides a step-by-step guide to cross-compiling a Linux kernel for RISC-V, including configuration using menuconfig.
• initramfs and First Boot: Demonstrates overcoming the "Kernel panic" by building a minimalist initramfs (initial RAM filesystem) containing a simple C-based init program.
• Advanced initramfs with Go: Evolves the initramfs to include a more interactive Go-based "little shell," illustrating process forking and execution.
• Utilizing u-root: Introduces u-root as a powerful tool to quickly generate a functional initramfs with a comprehensive set of Go-based user-space utilities, enabling a more useful micro-distribution capable of networking.
• Networking a Micro-Distro: Guides through configuring QEMU with network devices and using dhclient and wget within the custom distro to connect to the internet, showcasing its functional capabilities.
• Beyond the Basics: Briefly touches upon package managers and the complexity of real-world init systems, encouraging further exploration.

By walking through the tangible steps of kernel compilation, initramfs creation, and user-space tooling, the article successfully demystifies the structure of a Linux system. It provides a solid pedagogical foundation for anyone looking to understand what truly happens from the moment a Linux kernel boots up to the point of running user applications and even browsing the web.