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Virtualization in Cloud Computing, Virtualization is a process that makes the use of physical computer hardware more effective and forms the basis for cloud computing., Virtualization uses software to create a layer of abstraction over computer hardware, enabling multiple virtual computers, usually referred to as VMs, to split the hardware elements from a single computer ., Every VM performs its own OS and acts like an autonomous computer given the fact that it runs on only a portion of the underlying computer hardware., Software called hypervisor is used for hardware virtualization. With the help of a virtual machine hypervisor, software is incorporated into the server hardware component. The role of hypervisor is to control the physical hardware that is shared between the client and the provider., The machine on which the virtual machine is going to create is known as Host Machine and that virtual machine is referred as a Guest MachineC, Different approaches to virtualization, 1. Full Virtualization :, Full Virtualization was introduced by IBM in the year 1966. It is the first software solution of server virtualization and uses binary translation and direct approach technique. In full virtualization, guest OS is completely isolated by the virtual machine from the virtualization layer and hardware. Microsoft and Parallels systems are examples of full virtualization., 2. Paravirtualization :, Paravirtualization is the category of CPU virtualization which uses hypercalls(A call by a user process or the operating system for the hypervisor to perform some service required by the operating system of process. ) for operations to handle instructions at compile time. In paravirtualization, guest OS is not completely isolated but it is partially isolated by the virtual machine from the virtualization layer and hardware. VMware and Xen are some examples of paravirtualization., 3.partial virtualization, In Partial virtualization multiple instances of an underlying hardware environment are simulated. It is not mandatory that in para virtualization, it simulates hardware. It may provide an API, which can be exceptionally used by altering the guest operating systems., Types of Virtualization:, Desktop Virtualization – In desktop virtualization, one OS (operating system) is run over another OS. For example, a Windows 7 virtual machine running over Windows XP PC., Application Virtualization – Application virtualization allows software and other apps to be incorporated into a “single and executable” package that can be run anywhere., Storage Virtualization – Storage virtualization is when you group several physical resource and make it look like a . The combined storage can then be further divided when required., Network Virtualization – In network virtualization, a  is decoupled from the main network. This means, there can exist several networks that will use the same network hardware., Server Virtualization – Like every other virtualization, the virtualization of server is the process of creating  that behave independently despite sharing the same underlying hardware., HYPERVISER(virtual machine manager), A hypervisor is a key software piece which enables virtualization. It abstracts from the actual hardware, the guest machines and the operating system they use., Hypervisors create the CPU / Processor, RAM and other physical resources virtualized layer that separates you from the virtual devices you are creating., The hypervisor on which we install the machine is called a host machine. Hypervisors emulate resources available for guest machines to use., There are two types of hypervisor:, • Type 1 Hypervisor (also called bare metal or native), • Type 2 Hypervisor (also known as hosted hypervisors), Type 1 Hypervisor, A bare-metal hypervisor (type 1) is a software layer which is installed directly above a physical server and its underlying hardware., Examples of Type 1 hypervisors include VMware ESXi, Citrix XenServer and Microsoft Hyper-V hypervisor., There is no intermediate software or operating system, therefore bare-metal hypervisor is the name., In enterprise environments, type 1 hypervisors are mostly found, Type 2 Hypervisor, This type of hypervisor runs within a physical host operating system., Example of Type 2 hypervisor include VMware Player or Parallels Desktop., Hosted hypervisors have one underlying layer of the software., Type 2 hypervisor include the following:, • A physical machine., • An installed hardware operating system (Windows, Linux, macOS)., • Software for the type 2 hypervisor in this operating system., • The current instances of virtual guest machines., VIRTUAL MACHINE, A virtual machine (VM) is a software-based computer that exists within another computer’s operating system, often used for the purposes of testing, backing up data, or running  applications., It is possible to run multiple operating systems on one computer. This can be achieved through a process called virtualization. In virtualization, a piece of software behaves as if it were an independent computer. This piece of software is called a virtual machine, also known as a ‘guest’ computer. (The computer on which the VM is running is called the ‘host’.) The guest has an OS as well as its own virtual hardware., Common use cases for virtual machines on single computers include:, Testing - Software developers often want to test their applications in different environments. They can use virtual machines to run their applications in various OSes on one computer. This is simpler and more cost-effective than testing on several different physical machines., Running software designed for other OSes - Although certain software applications are only available for a single platform, a VM can run software designed for a different OS. For example, a Mac user who wants to run software designed for Windows can run a Windows VM on their Mac host., Running outdated software - Some pieces of older software can’t be run in modern OSes. Users who want to run these applications can run an old OS on a virtual machine., Browser isolation -  is the practice of 'isolating' web browser activity away from the rest of a computer's operating system to keep malware from affecting the computer's other files and programs. Some browser isolation tools use VMs to establish this isolation — though this approach can slow down browsing activity., Virtual Machine Images, A virtual machine image is a template for creating new instances. You can choose images from a catalogue to create images or save your own images from running instances. Specialists in those platforms often create catalogue images, making sure that they are created with the proper patches and that any software is installed and configured with good default settings. The images can be plain operating systems or can have software installed on them, such as databases, application servers, or other applications. Images usually remove some data related to runtime operations, such as swap data and configuration files with embedded IP addresses or host names. Many users share clouds, the cloud helps you track information about images, such as ownership, history, and so on.