RUMPKERNEL(7) | Miscellaneous Information Manual | RUMPKERNEL(7)

# NAME

`rump kernel` — The Anykernel and Rump Kernels

# DESCRIPTION

Rump kernels provide portable, componentized, kernel quality drivers such as file systems, POSIX system call handlers, PCI device drivers, a SCSI protocol stack, virtio and a TCP/IP stack. The fundamental enabling technology is the anykernel architecture of NetBSD, which enables the use of unmodified NetBSD kernel drivers. The minimalistic rumpuser(3) interface integrates a rump kernel to the host platform. Suitable and readily supported platforms include for example POSIX userspace (such as NetBSD), hypervisors (such as Xen and KVM), and bare metal hardware.

Rump kernels are component-oriented, which means that they consist of libraries which are linked together to form runtime images. If the platform supports it, dynamic linking may be used to load components at runtime, allowing the creation of services where the runtime component configuration is specified when the service is run (see rump_server(1) for an example).

A rump kernel provides its own set of namespaces, such as a file system hierarchy and TCP ports, that are independent of the ones on the host and of any other rump kernel instances. It should be noted that the presence of the provided namespaces depends on the components that the rump kernel was constructed with. For example, networking and file systems are components, and it is possible to construct a rump kernel which supports neither.

A rump kernel accepts the following bootstrap parameters. The exact way of specifying the parameters depends on the host platform; for example in POSIX userspace the parameters are environment variables.

`RUMP_NCPU`
  If set, the value indicates the number of virtual cores configured into a rump kernel, i.e. the number of threads which can be concurrently executing code inside the rump kernel.

  The special value "host" can be used to specify the number of of host cores available (note: not available on all platforms). If this parameter is unset, two cores will be configured.

`RUMP_VERBOSE`
  If set to non-zero, causes bootstrap messages to be displayed on the console.
`RUMP_MEMLIMIT`
  If set, indicates the maximum amount of memory that a rump kernel will attempt to allocate from the host. If this parameter is unset, the rump kernel attempt to allocate host memory until allocation fails. When the rump kernel is close to the allocation limit, or when host allocation fails, the rump kernel will attempt to make more memory available by invoking its internal pagedaemon to flush caches.

# SEE ALSO

https://rumpkernel.github.io

Antti Kantee and Justin Cormack, Rump Kernels: No OS? No Problem!, USENIX, ;login:, No. 5, Vol. 39, October 2014.

Antti Kantee, Flexible Operating System Internals: The Design and Implementation of the Anykernel and Rump Kernels, Aalto University Doctoral Dissertations, 2012.

Antti Kantee, Rump Device Drivers: Shine On You Kernel Diamond, Proceedings of AsiaBSDCon 2010, pp. 75-84, March 2010.

Arnaud Ysmal and Antti Kantee, Fs-utils: File Systems Access Tools for Userland, EuroBSDCon 2009, September 2009.

Antti Kantee, Rump File Systems: Kernel Code Reborn, Proceedings of the 2009 USENIX Annual Technical Conference, pp. 201-214, June 2009.

Antti Kantee, Kernel Development in Userspace - The Rump Approach, BSDCan 2009, May 2009.

Antti Kantee, Environmental Independence: BSD Kernel TCP/IP in Userspace, Proceedings of AsiaBSDCon 2009, pp. 71-80, March 2009.

# HISTORY

An experimental concept for the anykernel and rump kernels was first seen during the NetBSD 5.0 development cycle. A stable concept was ready for NetBSD 6.0.

July 15, 2023 | NetBSD 10.99