Apex is a real-time operating system (RTOS) designed for use in small to medium scale embedded systems. It aims to be a bridge between traditional RTOSes for small microcontrollers and Linux for larger embedded systems. Apex provides a Linux-compatible environment, making it easier for developers familiar with Linux. The RTOS is currently under heavy development and is not considered stable.


  • Implements a subset of the Linux syscall interface.
  • Uses the musl C library.
  • Monolithic architecture (as opposed to microkernel).
  • Open source & royalty-free.
  • Secure & reliable.
  • Small, efficient, and easy to understand.
  • Binary compatibility with Linux (using musl libc).
  • Development can focus on the kernel as userspace tools & libraries are provided by external projects.


  • Boot Loader: Responsible for initializing the system and loading the kernel.
  • CPU: Contains CPU-specific configurations and sources.
  • Libc: C library for the bootloader and kernel.
  • Libc++: C++ library for the bootloader and kernel.
  • Machine: Contains machine/board support files.
  • MK: Build system.
  • Sys: Apex kernel which includes:
    • Architecture support.
    • Device drivers.
    • File systems.
    • Kernel core.
    • Memory management.
    • Synchronization primitives.

Apex Platforms

  • ARM
  • RISC-V
  • QEMU

Apex Components

  • FileSystem
  • Shell