Operating system virtualization is an implementation variant of server virtualization. In contrast to other models such as full virtualization or paravirtualization, the operating system itself is virtualized. The solutions are based on a single operating system instance or kernel, hence the synonym Single Kernel Image (SKI).
The operating system forms instances of itself that are isolated from each other, with the system assigning "private" resources such as file systems, IP addresses, host names, user namespaces, etc. to the virtual machines (often referred to as containers in this context). In this context, all virtual machines (VM) are necessarily of the same operating system type and release level, at least with respect to the kernel.Linux vServer, SUN Zones, BSD Jails.