Virtuozzo, from Parallels (formerly SWSoft), gives every application its own sandbox to play in.

Virtuozzo 4.0 is a virtual machine hosting platform that provides application partitioning services. These Virtual Environments operate in a way that's similar to the way Red Hat's SELinux and Sun's Containers provide operating-system-instance isolation for applications.

Virtuozzo 4.0 (we tested the final RC version), hosts a single operating system (either Windows or Linux, we tested it on machines running Windows XP SP2, Win 2003 Server Standard Edition and CentOS4), then creates independent virtual environment instances that can be setup to run designated applications temporarily, permanently or on an as-needed basis. The Virtual Environments (depending on the operating system host used) have separate administrative controls, registry instances, domain users, Active Directory instances, and can run processes or applications with either unique or shared files.

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Virtuozzo's Virtual Environments are superficially similar to Microsoft Terminal Services or Citrix Systems' Metaframe sessions, but provide instance controls that are more closely related to the application isolation provided through Red Hat's SELinux session/user system file and permissions controls.

The applications are captive to the specific host kernel, meaning that a hardware server platform offers only the host operating system instance, rather than a number of hosted operating system instances. This also fits the common profile of other VM products that usually have one variety of operating system running aside each other atop a hypervisor or paravirtulized host VM management kernel. Virtuozzo is therefore a hybrid between sophisticated VM hosts such as VMware's ESX or Citrix's XenSource, and application instance hosting environments such as Microsoft's Terminal Services or RedHat's SELinux.

All the user and application provisioning controls needed are easily found within the product's excellent GUI, Virtuozzo Control Center (VZCC), or its remote access alternative, Virtuozzo Management Console.

VZCC provides strong and clear control of the Virtual Environments, and makes Virtuozzo approachable by several technical levels of administrators from systems engineers to savvy users, and controls user Virtual Environments administrative behavior. This degree of control isn't usually available in other virtualization environments, although Microsoft's Virtual Manager System Center proposes this capability in the betas we've seen of Microsoft's upcoming virtual services for Windows 2008 Server editions.