Virtual operating systems, virtual machines
Sit tight, Linux Users. User Mode Linux will soon have the same capabilities as Xen in the virtualization arena -- like live migration, says Jeff Dike, author of User Mode Linux. Operating out of the Linux kernel port, UML enables the port to host multiple virtual operating systems.
Speaking with SearchOpenSource.com, Dike described the pros and cons of virtual machines versus virtual operating systems and offers some advice on whether to opt for UML, Xen or VMware.
SearchOpenSource.com: You mentioned that User Mode Linux differs from other virtualization technologies because it's more of a virtual operating system than a virtual machine. How does a virtual operating system compare with a virtual machine?
Jeff Dike: A virtual operating system has greater contact with the host operating system. This allows interactions between guest and host, which would be difficult or impossible with a virtual machine. For example, UML has two file systems [with somewhat different properties], which allow a host directory to be mounted as a UML file system.