仮想マシン

A virtual machine (VM) is a software-based emulation of a physical computer system. It operates as a self-contained environment that runs its own operating system (guest OS) and applications, independent of the underlying hardware (host machine). Virtualization technology allows multiple VMs to run concurrently on a single physical host, each with its own virtualized hardware resources such as CPU, memory, storage, and network interfaces. This abstraction is managed by a hypervisor, which is a layer of software (Type 1 runs directly on hardware, Type 2 runs on top of a host OS) responsible for creating, running, and managing the VMs. VMs provide numerous benefits, including hardware independence, allowing applications to run on different hardware configurations without modification; resource isolation, preventing issues in one VM from affecting others or the host; and efficient resource utilization, by consolidating multiple workloads onto fewer physical servers. They are widely used for server consolidation, testing and development environments, disaster recovery, running legacy applications, and creating isolated security sandboxes. Trade-offs include performance overhead compared to bare-metal execution due to the hypervisor layer, and the need for sufficient host resources to support multiple VMs effectively. Managing VM lifecycles, storage, and networking also requires specialized expertise.