User-mode Linux is the port of the Linux kernel to userspace. It runs
a Linux virtual machine in a set of processes on a Linux host. A UML
virtual machine is capable of running nearly the same set of processes
as the host. It lends itself to a variety of applications, such as
kernel development, security applications like sandboxing and jailing,
and virtual networking. This paper describes the design and implementation
of UML, current and future applications for it, and future work.