Riot OS

RIOT is a small operating system for networked, memory-constrained systems with a focus on low-power wireless IoT devices. It is open-source software, released under the GNU Lesser General Public License (LGPL). Due to its large independent community RIOT is often referred to as the Linux of the Internet of Things.

RIOT is an operating system designed for the particular requirements of Internet of Things (IoT) scenarios. These requirements comprise a low memory footprint, high energy efficiency, real-time capabilities, a modular and configurable communication stack, and support for a wide range of low-power devices. RIOT provides a microkernel, utilities like cryptographic libraries, data structures (bloom filters, hash tables, priority queues), a shell, various network stacks, and support for various microcontrollers, radio drivers, sensors, and configurations for entire platforms, e.g. TelosB or STM32 Discovery Boards.

The microkernel itself comprises thread management, a priority-based scheduler, a powerful API for inter-process communication (IPC), a system timer, and mutexes. Read more

Wikipedia and The Verge