Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
One of the features that was introduced a year ago into Ubuntu 7.04 "Feisty Fawn" was support for KVM, which is the Kernel-based Virtual Machine. The Kernel-based Virtual Machine provides full virtualization support for Linux when running on x86 hardware with either Intel's VT or AMD-V technology, which means you can run unmodified guest operating systems such as Linux or Microsoft Windows within your Linux host operating system.
As we had shared in benchmarks, KVM -- even back to its infancy -- has been quite fast at virtualization when compared to Xen or kqemu. However, the KVM virtualization support found in Ubuntu hasn't been the most user-friendly. Installing and then managing these guest operating systems in Ubuntu 7.04 and Ubuntu 7.10 has required using the command-line interface and thus requiring the user to be familiar with the various QEMU options. However, in Ubuntu 8.04 this has all changed for the better now that virt-manager and libvirt are available from the main Ubuntu repository.
KVM support had premiered in Fedora 7 "Moonshine" around the same time as Ubuntu 7.04, but this virtualization support was accompanied by two new Red Hat innovations: virt-manager and libvirt. Virt-manager is the Virtual Machine Manager and is a GUI for managing virtual machines while at its foundation is libvirt, which is a virtualization API for not only interfacing with KVM but also Xen, QEMU, and OpenVZ. Virt-manager goes beyond just providing a user interface for facilitating the installation and basic management of the guest operating systems, but also provides a detailed analysis of the guest performance/resource usage and modifying the virtual system details (CPU cores, disk size, network devices, and memory capacity).