RIKEN Advanced Institute for Computation Science is in charge of leading the development of Japan’s next generation flagship supercomputer, the successor of the K. Part of this effort is to design and develop a system software stack that suits the needs of future extreme scale computing. In this talk, we focus on operating system (OS) requirements for HPC and discuss IHK/McKernel, a multi-kernel based operating system framework. IHK/McKernel runs Linux with a light-weight kernel (LWK) side-by-side on compute nodes with the primary motivation of providing scalable, consistent performance for large scale HPC simulations, but at the same time to retain a fully Linux compatible execution environment. We provide an overview of the project and discuss the status of its support for Arm architecture.