hypervisoriin

A hypervisor, also known as a virtual machine monitor (VMM), is software, firmware, or hardware that creates and runs virtual machines (VMs). It provides abstraction of the physical hardware, allowing multiple VMs to share CPU, memory, storage, and I/O resources while remaining isolated from each other. The hypervisor sits between the hardware and the guest operating systems, controlling and mediating their access to physical resources.

There are two main types: Type 1 (bare-metal) hypervisors run directly on the host hardware and are common in data centers and clouds; Type 2 (hosted) hypervisors run on top of a general-purpose operating system and are frequently used for desktop virtualization or testing. Modern hypervisors often use hardware-assisted virtualization features (such as Intel VT-x or AMD-V) to reduce overhead and improve security.

Key features include VM scheduling, memory management, virtual NICs and disks, live migration, snapshots, and resource controls to enforce quotas and isolation. Hypervisors enable capabilities such as high availability, fault tolerance, and disaster recovery.

Use cases include server consolidation, private and public cloud infrastructure, software development and testing, and training. Compared with containers, hypervisors provide stronger isolation by virtualizing hardware and running separate kernels; containers share the host OS kernel and can be lighter-weight but offer different security and management models.

Notable examples include VMware ESXi, Microsoft Hyper-V, KVM (often used with QEMU), Xen, and Oracle VM VirtualBox.