Linux /RK stands for Linux/Resource Kernel, which incorporates real-time extensions to the Linux kernel to support the abstractions of a resource kernel.
A resource kernel is a real-time kernel (operating system) that provides timely, guaranteed and enforced access to system resources for applications.
preview:
http://www.cs.cmu.edu/%7Erajkumar/linux-rk.html
11/25/2005