A hypervisor, also known as a virtual machine monitor (VMM), is software, firmware, or hardware that creates and manages virtual machines (VMs). It allows multiple operating systems to share a single hardware host. Each operating system runs in its own virtualized environment and operates as if it’s running on its own physical machine. The hypervisor keeps the activities of each VM separate, ensuring they do not interfere with one another.

There are two main types of hypervisors:

Type 1 (Bare Metal Hypervisor):

  • Runs directly on the host’s hardware to control the hardware and manage guest operating systems.
  • Examples: VMware vSphere/ESXi, Microsoft Hyper-V, Oracle VM Server for x86, and Xen.
  • This type of hypervisor is generally considered more efficient because it has direct access to physical hardware without any middle layer.

Type 2 (Hosted Hypervisor):

  • Runs on a conventional operating system (OS) just like any other software application. The underlying OS is called the host OS.
  • Examples: VMware Workstation, Oracle VirtualBox, and Parallels Desktop.
  • While it’s less efficient than a Type 1 hypervisor, it’s typically easier for users to install and manage.

Advantages of using a hypervisor:

  • Resource Efficiency: Multiple VMs can run on a single physical machine, utilizing the hardware more effectively.
  • Isolation: VMs are isolated from each other. If one VM crashes, it doesn’t affect the others.
  • Flexibility: VMs can be easily created, modified, and moved between host servers.
  • Hardware Independence: VMs can run on any compatible physical server, irrespective of the underlying hardware.

Use Cases:

  • Data Centers and Cloud Computing: Hypervisors are foundational in these environments, allowing for server virtualization, maximizing hardware usage, and segmenting workloads.
  • Development and Testing: Developers can use VMs to run multiple environments on a single machine.
  • Desktop Virtualization: Allows users to run multiple OS on a single machine, useful for compatibility, testing, or specialized requirements.

Security Considerations:
While hypervisors add a layer of security due to the isolation of VMs, they are not immune to vulnerabilities or attacks. Proper configuration, regular patching, and adherence to best practices are crucial for maintaining a secure virtualized environment.