virtual appliance

A virtual appliance is a minimalistic virtual machine image designed to run under Parallels, VMWare, Xen, Microsoft Virtual PC, Virtual Iron or other virtualization technologies. Virtual appliances are a subset of the broader class of software appliances. Like software appliances, virtual appliances are aimed to eliminate the installation, configuration and maintenance costs associated with running complex stacks of software. A key concept that differentiates a virtual appliance from a virtual machine is that a virtual appliance is a fully pre-installed and pre-configured machine and operating system environment, whereas a virtual machine stands alone, without any application software.Typically, a virtual appliance has a web interface or an external system to configure the inner workings of the appliance. For example, StoneGate Management Center acts as an external system while StoneGate Firewall and IPS are virtual appliances. A virtual appliance is usually built to host a single application, thus representing a new way of deploying network applications.