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VIRTUALIZATION

Virtualization is a technology that enables a software platform, called a hypervisor, to run processes that contain a fully emulated computer system.

Types of Hypervisors

Xen

  • Type: Type-1 Hypervisor (Bare-Metal Hypervisor)
  • Description: Xen is an open-source hypervisor that does not rely on an underlying operating system. It boots directly into the hypervisor, making it a bare-metal hypervisor.

KVM (Kernel Virtual Machine)

  • Type: Type-1 and Type-2 Hypervisor
  • Description: KVM is a Linux kernel module for virtualization. It integrates with a running Linux installation, allowing it to function as both a Type-1 and Type-2 hypervisor. Virtual machines deployed with KVM use the libvirt daemon and associated utilities for management.

VirtualBox

  • Type: Type-2 Hypervisor
  • Description: VirtualBox is a popular desktop application for creating and managing virtual machines. It is cross-platform, supporting Linux, macOS, and Windows. As it requires an underlying operating system, it is classified as a Type-2 hypervisor.

Migration

Migration is the process of moving a virtual machine from one hypervisor installation to another.

Types of Virtual Machines

1. Fully Virtualized

  • Description: All instructions executed by the guest operating system run within a fully virtualized environment. The guest is unaware it is running in a virtual machine (HardwareVM).
  • Use Case: Ideal for unmodified guest operating systems.

2. Paravirtualized

  • Description: The guest operating system is aware it is running in a virtual machine (PVM). It uses a modified kernel and guest drivers to optimize resource utilization.
  • Use Case: Offers better performance than fully virtualized guests.

3. Hybrid

  • Description: Combines full virtualization with paravirtualized drivers to overcome hardware-assisted full virtualization limitations.
  • Use Case: Balances performance and compatibility.

Virtual Machine Hard Disk Image Location

Virtual machine hard disk images are typically stored at: 

/var/lib/libvirt/images/

The D-Bus Machine ID

The D-Bus Machine ID is a unique identification number generated during installation.

Why It’s Important

  • If a virtual machine is cloned, a new D-Bus Machine ID must be generated to ensure proper resource allocation.
  • No two Linux systems on a hypervisor should share the same D-Bus Machine ID.

Generate a New D-Bus Machine ID

dbus-uuidgen --get

Containerization

Containerization is a form of operating-system–level virtualization that allows software applications to run in isolated user spaces called containers.

Key Points

  • Lightweight and portable.
  • Can run in any cloud or non-cloud environment.

Containers

Containers are lightweight software packages that include all necessary dependencies to run an application in any environment.