Summary
Highlights
The hypervisor, or Virtual Machine Manager, is crucial for virtualization, managing the interaction between virtual and physical systems. It allocates resources like CPU cycles, memory, and networking, separating them across virtual machines (VMs). Modern hypervisors can leverage CPUs built with virtualization in mind.
Type 1 hypervisors (bare metal) run directly on hardware, acting as the primary OS, exemplified by VMware ESXi and Microsoft Hyper-V. Type 2 hypervisors (hosted) run on top of an existing operating system, like VMware Workstation or Oracle VirtualBox on a desktop. The primary difference is their underlying execution environment, not the VMs themselves.
Intel CPUs use Virtualization Technology (VT) and AMD processors use AMD-V for virtualization support. VMs require significant physical RAM and drive space to run their full operating systems, applications, and data. The hypervisor manages the allocation of these resources to ensure simultaneous operation.
Hypervisors offer granular control over VM network interactions. Virtual networks can be configured as shared (using network address translation), bridged (VMs act like physical devices on the local network), or private (VMs communicate only with themselves or specified devices) for enhanced security and isolation.
While hypervisor security breaches are rare, 'VM escape' is a significant concern where malware could exploit a hypervisor flaw to spread between VMs. It's crucial to apply traditional security controls (firewalls, anti-malware, OS hardening) to each VM. Users should be wary of pre-built VMs from untrusted sources, as they may contain embedded malware.
VDI allows desktops to run as virtual machines remotely (e.g., in the cloud), with users only needing a display, keyboard, and mouse locally. Also known as Desktop as a Service (DaaS), VDI reduces local hardware requirements and relies on network bandwidth to transmit screen updates, providing a seamless user experience despite remote execution.
Containerization virtualizes applications rather than entire operating systems, removing the OS overhead of VMs. Each application runs in a self-contained container, isolated from others. Containers are lightweight, portable, and share a single host operating system, simplifying management. Tools like Docker are popular for containerization. However, containers typically rely on the host OS, limiting cross-OS compatibility compared to VMs.