Open-source alternatives to Linux

NuttX is a POSIX-compliant real-time operating system designed for microcontrollers ranging from 8-bit to 64-bit architectures. It provides a deterministic execution environment with a real-time task scheduler and a POSIX embedded kernel to ensure portable code execution across diverse hardware targets. The project distinguishes itself through a comprehensive hardware abstraction layer that provides standardized drivers for I2C, SPI, CAN, and USB across various semiconductor chipsets. It also features an embedded networking stack supporting TCP, UDP, IPv4, and IPv6, alongside industrial proto

This project is a bare-metal operating system developed for ARM64 architecture. It serves as a low-level implementation of kernel engineering, focusing on the fundamental construction of an OS from the hardware level up. The system is distinguished by its comprehensive approach to ARM64 processor control, featuring a red-black tree task scheduler and a hierarchical page table system for virtual memory management. It implements a sophisticated privilege model that handles transitions between kernel and user modes, ensuring process isolation through address space splitting and exception level m

XNU is a hybrid operating system kernel that combines a microkernel architecture with a monolithic layer for system services. It provides a foundation for operating system development, incorporating standardized system-call interfaces, a modular device driver framework, and mandatory access control security. The architecture features a Mach-based microkernel and a BSD-based monolithic layer. It utilizes a message-passing inter-process communication bus for secure data exchange between isolated kernel components and user-space processes, alongside an object-oriented driver framework that decou

BCC is an eBPF development toolkit and tracing framework used for monitoring and analyzing the Linux kernel. It functions as a performance analysis tool and debugging utility to capture system events, measure kernel latency, and provide network observability. The project distinguishes itself by providing a build system that integrates with LLVM to compile C-like code into BPF bytecode at runtime. It utilizes BPF Type Format data for relocations to maintain cross-kernel compatibility and extracts kernel headers to ensure the generated programs match the specific kernel version. The toolkit co

bpftrace is a high-level eBPF tracing tool and kernel instrumentation framework for Linux. It provides a tracing language to instrument kernel and user-space events without recompiling the system, functioning as a dynamic system profiler and event aggregator. The project enables dynamic system tracing and Linux kernel observability by capturing tracepoints and dynamic probes in real time. It allows for kernel data inspection and runtime process debugging by accessing internal data structures and filtering specific process events. Its capability surface covers system performance analysis, inc

CppGuide is a curated collection of educational resources and practical guides focused on C++ server development, Linux kernel internals, concurrent programming, network protocols, and security exploitation. It provides structured learning paths for backend developers, covering everything from interview preparation to building high-performance network servers and understanding operating system fundamentals. The guide distinguishes itself by offering in-depth, hands-on tutorials that walk through real-world implementations, including building a Redis-like server from scratch, designing custom

FlameGraph is a performance profiling and visualization toolkit designed to identify bottlenecks in software execution. It functions as a processing engine that transforms raw stack trace samples into interactive, hierarchical diagrams. By representing aggregated execution frequency as nested rectangles, the tool allows developers to visualize hot code paths and analyze system behavior across both kernel and user-space environments. The project distinguishes itself through its ability to perform differential profile analysis, which highlights performance regressions or improvements by compari

This project is an educational curriculum designed to teach the fundamentals of operating system development and low-level systems programming. It provides a structured sequence of lessons and code samples that guide users through building a functional kernel and bootloader from scratch, enabling a practical understanding of how software interacts directly with computer hardware. The repository distinguishes itself by focusing on the core mechanics of bare-metal execution. It covers the implementation of essential system components, including assembly-based bootloaders that transition process

Arthas is a Java diagnostic tool and runtime debugger designed for real-time troubleshooting of applications. It functions as a remote diagnostics agent that allows users to inspect the runtime state of a Java process, including its heap objects and classloader hierarchies, without requiring a process restart. The project distinguishes itself through advanced bytecode manipulation capabilities, enabling live class hotswapping and the modification of bytecode in running processes. It supports in-memory source compilation and runtime bytecode decompilation to verify and update logic instantly w

seL4 is a formally verified microkernel whose C implementation is backed by machine-checked mathematical proofs of correctness, confidentiality, integrity, and availability. It enforces strict isolation between processes through hardware-enforced address space separation and a capability-based access control system, where each process holds explicit rights only to the resources it has been granted. The kernel exposes hardware resources through a minimal API of system calls that manage threads, address spaces, and inter-process communication, with synchronous IPC supporting sender-identifying b

Firefox is a cross-platform web browser engine designed to render web content, execute JavaScript, and manage secure browsing sessions. It utilizes a multi-process isolation architecture that distributes browser tasks across independent operating system processes to ensure stability and prevent site-specific failures from impacting the entire application. The engine incorporates a sandboxed execution environment to restrict web content and untrusted scripts to isolated memory compartments, enforcing security policies that prevent unauthorized access to system resources. The project distinguis

Tinygrad is a deep learning framework and tensor computation engine designed for building and training neural networks. It functions as a hardware abstraction layer that manages device memory, command queues, and kernel dispatching across heterogeneous computing architectures. By utilizing a lazy-evaluation approach, the framework constructs computational graphs that defer execution until data is explicitly required, allowing it to process only the necessary operations for a given result. The project distinguishes itself through a just-in-time compilation layer that transforms abstract comput

This project provides a framework for managing multi-agent systems, designed to automate complex software development, infrastructure, and business workflows. It functions as a multi-agent workflow orchestrator that routes tasks to domain-specific workers while maintaining state persistence and infrastructure automation. By leveraging large language models, the system decomposes high-level objectives into actionable plans, ensuring that complex operations are executed with consistency and reliability. The framework distinguishes itself through its hierarchical agent registry and policy-driven

Excelize is a library for reading and writing spreadsheet files in the Office Open XML format. It provides a comprehensive suite of tools for programmatically creating, modifying, and analyzing workbooks, worksheets, and cell data, ensuring compatibility across various office software suites through structured XML serialization. The library distinguishes itself with a built-in formula calculation engine that evaluates complex mathematical and logical expressions directly against workbook data. It also features a memory-mapped streaming architecture, which allows for the efficient processing o

This project is a specialized toolset for profiling kernel latency, analyzing tracepoint frequency, and monitoring system-wide performance data. It functions as a kernel performance profiler, tracepoint analyzer, and a collection of utilities for the Linux ftrace and perf_events subsystems. The toolkit provides high-level abstractions via shell-scripted wrappers to manage complex kernel tracing interfaces. It distinguishes itself through the use of bucket-based event histograms to visualize the distribution of kernel events and the ability to identify functions exceeding specific latency thre

This project is a tutorial and framework for building a low-level, bare-metal operating system from scratch using the Rust language. It focuses on ARMv8 kernel development specifically for the Raspberry Pi 3, providing the resources necessary to implement a monolithic kernel that runs directly on hardware without an underlying operating system. The project distinguishes itself by providing a complete embedded cross-compilation suite within a containerized environment to ensure consistent builds. It includes a dedicated kernel deployer that uses a serial interface and chainloader to load and b

This project is an educational operating system kernel designed to demonstrate the fundamental architectural principles of memory paging and process management. It is implemented as a minimal kernel that serves as a practical reference for building a functioning system from the ground up. The implementation features a preemptive multitasking kernel that switches execution contexts between threads to share a single CPU. It includes an x86 virtual memory manager that uses paging to map virtual addresses to physical memory and isolate processes. The system covers low-level hardware interfacing

Gobot is a robotics framework for the Go programming language designed for developing robotics, drones, and IoT applications. It provides a hardware abstraction layer with standardized drivers to interact with GPIO, I2C, SPI, and PWM interfaces across various single-board computers and microcontrollers. The framework functions as an IoT device orchestrator and BLE device manager, enabling the coordination of multiple sensors, actuators, and Bluetooth Low Energy peripherals. It includes specialized interfaces for drone control, allowing for the management of flight maneuvers and video streams

IREE is an MLIR-based compiler toolchain and runtime designed to translate machine learning models from various frameworks into optimized binaries for execution across diverse hardware targets. It provides a unified pipeline to ingest models from PyTorch, TensorFlow, JAX, and ONNX, lowering them into a common intermediate representation for deployment on CPUs, GPUs, and bare-metal embedded systems. The project distinguishes itself through a bytecode virtual machine and a hardware abstraction layer that decouple high-level model logic from specific hardware instruction sets. It supports sophis

OpenTabletDriver is a user-mode graphics tablet driver and USB HID input manager that translates raw USB input from digitizer hardware into system cursor and pen events. It serves as a hardware abstraction layer that normalizes input from various tablet brands into a consistent API, providing a cross-platform pen interface with pressure and tilt sensitivity. The project distinguishes itself through a plugin-based architecture and a profile-based configuration system, allowing for custom filters, interpolators, and persistent hardware setups. It includes specialized tools for hardware driver d

TinyGo is a specialized compiler and development toolkit designed to bring the Go programming language to resource-constrained microcontrollers and WebAssembly environments. It provides a bare-metal runtime environment that enables high-level code execution without the need for a traditional operating system, utilizing an LLVM-based backend to generate efficient machine instructions. The project distinguishes itself through aggressive optimization techniques tailored for small hardware, including a static memory allocation strategy and whole-program dead code elimination that significantly re

This repository provides the original source code and binaries for legacy disk operating systems. It serves as a historical software archive and a reference implementation for early personal computer operating systems. The project is designed for software archaeology, legacy operating system research, and the study of foundational kernel design. It allows for the technical analysis of historical software architecture and implementation. The codebase covers several core system areas, including monolithic kernel design, segmented memory addressing, and file allocation table indexing. It also i

NuttX is a POSIX-compliant real-time operating system designed for resource-constrained embedded environments. It functions as a scalable microcontroller OS that provides a Unix-like environment for managing hardware and running applications across architectures ranging from 8-bit to 64-bit. The system ensures high software portability by implementing a kernel that follows POSIX and ANSI standards. This allows developers to create portable embedded applications using standardized API calls across diverse hardware architectures. The project includes a modular kernel architecture and a hardwar

This project is an educational resource and technical reference for building operating systems from scratch. It provides a comprehensive guide to mastering x86 architecture and implementing core kernel components by writing code that executes directly on hardware without the support of standard libraries or operating system abstractions. The materials focus on low-level systems engineering, teaching users how to interpret technical datasheets to manage hardware resources. It covers the fundamental mechanics of bare-metal programming, including the use of assembly language to define execution

liquidctl is a command line interface and set of Python drivers used to monitor and control liquid cooling hardware. It functions as a liquid cooler controller, hardware telemetry tool, and RGB lighting controller, providing a unified way to manage temperatures, fan speeds, and pump rates for all-in-one and custom loop cooling systems. The project provides a Python hardware driver that enables programmatic control and telemetry collection without relying solely on the command line. It allows for the configuration of device lighting using standard RGB, HSV, and HSL formats. The system include

This project provides an open-source firmware platform and complete build environment for portable multi-tool hardware. It functions as an embedded operating system designed to manage radio, infrared, and physical interface components, enabling users to develop custom applications and system logic for specialized hardware devices. The firmware distinguishes itself through a modular architecture that organizes system functionality into isolated units, allowing for the development of custom user interfaces and logic. It includes a comprehensive collection of low-level drivers and applications s

ReactOS is an open-source operating system designed to be binary compatible with Windows applications and drivers. It consists of a low-level system kernel that manages hardware resources and a binary compatibility layer that enables the execution of software designed for the Windows binary interface. The project implements a cross-platform build system and toolchain for compiling and deploying bootable operating system images across different hardware architectures. This includes the use of cross-compilation toolchains and a hardware-abstraction layer to support various processor and motherb