Adeos (Adaptive Domain Environment for Operating Systems) is a nanokernel hardware abstraction layer (HAL), or hypervisor, that operates between computer hardware and the operating system (OS) that runs on it. It is distinct from other nanokernels in that it is not only a low level layer for an outer kernel. Instead, it is intended to run several kernels together, which makes it similar to full virtualization technologies. It is free and open-source software released under a GNU General Public License (GPL).