hostsystem

A hostsystem is a computer or device that provides the operating environment for other software, services, or devices. In virtualization, the host system runs either a host operating system with a hypervisor or a bare-metal hypervisor, and it owns and manages the physical hardware. It allocates CPU, memory, storage, and I/O resources to one or more guest systems, which run as virtual machines on the host. The distinction between host and guest is common in virtualization technologies such as VMware, Hyper-V, KVM, or Xen.

In containerization, a host system runs a container runtime and provides the kernel and system resources shared by containers. Containers share the host's kernel and are isolated through namespaces and control groups, providing lightweight process isolation while retaining direct access to host resources. The host's resource controls, security boundaries, and storage subsystems influence container performance and security.

Beyond virtualization and containers, the term can refer to the machine that hosts network services or applications in a client-server setup. A host system typically includes capable CPUs, RAM, storage, and network interfaces, plus management software for monitoring, backups, patching, and security hardening.

Security considerations include keeping the host and its hypervisor or runtime up to date, segregating guest workloads, applying the principle of least privilege, and monitoring for abnormal I/O or performance changes. See also: guest system, hypervisor, container, virtualization.