Rump kernels provide a full stack of mature and stable drivers for running off-the-Internet applications as Xen Project guests. Examples of supported drivers include POSIX'y system calls, TCP/IP networking (incl. firewalls, IPv6, etc.), file systems, encryption of block storage, a SCSI stack and PCI device drivers. Rump kernels are component-oriented, and stack builders can choose which components are necessary for their applications. Since rump kernels use unmodified NetBSD kernel drivers, maturity and stability is excellent. Traditional OS functions such as virtual memory and multiprocess management are not included, thereby avoiding unnecessary overhead for a cloud environment.