Xenomai is a software framework cooperating with the Linux kernel to provide interface-agnostic, hard real-time computing support to user space application software seamlessly integrated into the Linux environment.

Any number of RTOS personalities called “skins” can then be built over the nucleus, providing their own specific interface to the applications, by using the services of a single generic core to implement it.

[1] Many differences exist between Xenomai and RTAI, though both projects share a few ideas and support the RTDM (Real Time Data Monitoring) layer.

While RTAI is focused on lowest technically feasible latencies, Xenomai also considers clean extensibility (RTOS skins), portability, and maintainability as very important goals.

Xenomai's path towards Ingo Molnár's PREEMPT_RT support is another major difference compared to RTAI's objectives.