A virtual machine (VM) is a software-based emulation of a physical computer that can run different operating systems (OS) and applications. VMs are widely used for various purposes, such as testing, development, security, and cloud computing. In this article, you will learn what is the purpose of a virtual machine and how it works.
A VM consists of two main components: the host and the guest. The host is the physical machine that provides the hardware resources, such as CPU, memory, disk, and network, to the VM. The guest is the virtual machine that runs on top of the host, using a portion of its resources. The guest has its own OS and applications, which are isolated from the host and other VMs. To enable the communication between the host and the guest, a software layer called the hypervisor or the virtual machine monitor (VMM) is required. The hypervisor manages the allocation and sharing of resources among the VMs and handles the requests from the guest OS.
In layman's terms, a virtual machine (VM) is like a computer within a computer. Its main purpose is to allow you to run different operating systems and software on a single physical computer, as if you had multiple separate machines. Imagine you have one powerful computer, and you want to do different things that require different operating systems or setups. With a VM, you can create multiple "virtual computers" inside your real computer. Each virtual machine can run its own operating system and software independently, without affecting the others. This is useful for testing software, isolating different tasks, or running older programs on modern hardware. It helps you make the most of your computer's resources and flexibility.
A virtual machine (VM) is no different than any other physical computer like a laptop, smart phone, or server. It has a CPU, memory, disks to store your files. Virtualization is the process of creating a "virtual" version of a computer, with dedicated amounts of CPU, memory, and storage that are "borrowed" from a physical host computer. Hypervisor on top of the physical host computer helps you run different operating systems on different virtual machines at the same time. VMs are independent of each other, they're also extremely portable. You can move a VM on a hypervisor to another hypervisor on a completely different machine.
A virtual machine is to create an isolated and virtualized environment that abstracts hardware from the operating system and applications, offering numerous benefits, including resource efficiency, isolation, flexibility, and improved management of computing resources. We can add a bit more into it like DR, Legacy software Support, Testing purpose, Sandboxing and much more.
the purpose of using Virtual Machines, is to run multiple OS instances on a single piece of hardware, saving a company time, management costs and physical space. Another advantage is that VMs can support legacy apps, reducing or eliminating the need and cost of migrating an older app to an updated or different operating system.
A virtual machine (VM) operates like a computer within a computer, where the host provides the actual hardware and the guest is like a tenant, living in a slice of that hardware's capabilities. The hypervisor is the landlord, coordinating resource sharing and ensuring each VM plays nicely without interfering with others. With its own operating system and apps, a guest VM functions independently, while the hypervisor keeps the peace and maintains order on the host's resources. This setup allows for safe experimentation, efficient resource use, and flexible system management.
One of the main benefits of a VM is that it allows you to run multiple OS and applications on a single physical machine, without affecting each other. This can save you time, money, and space, as you do not need to buy or maintain separate hardware for each OS or application. Another benefit of a VM is that it provides flexibility and portability, as you can easily create, copy, move, and delete VMs as needed. You can also adjust the resources allocated to each VM according to the workload and performance requirements. A third benefit of a VM is that it enhances security and reliability, as you can isolate and protect your VMs from external threats and internal errors. You can also backup and restore your VMs easily, in case of any disaster or failure.
This is only partially correct. You're only as secure as your network and OS posture set you up to be; there's really no additional security that you buy being a VM slice. For all practical purposes, a fully virtual machine is as protected or not protected as a standalone server. I cannot speak about paravirtual machines, however.
IT Service Manager & IT Administrator at EASA - European Union Aviation Safety Agency
IMHO, the VM does not enhance security per se, but the technology makes it easier to split applications and application components to many VMs/OS instances allowing for segregation and control of the communication between the apps and app components on network layer
VMs are the Swiss Army knives in IT. They're about doing more with less, running multiple systems on one machine. It's like having a team of superheroes, each with different powers and all working from a single headquarters. They're not just about saving space and money; VMs are agents for your data, providing a secure, isolated environment. And they're shape-shifters, morphing resources to fit the task at hand
Virtual machines (VMs) offer many benefits, including: Consolidating servers to reduce costs and improve efficiency Isolating applications to improve security and reliability Creating a variety of computing environments to improve flexibility Easily moving applications from one environment to another for portability Scaling up or down as needed to meet demand Improving security by isolating applications and protecting data Creating disaster recovery plans to quickly switch to a backup environment in case of failure VMs are a valuable tool for businesses of all sizes to improve their computing environments.
Virtual machines (VMs) are like slicing up a single powerful physical computer into multiple isolated virtual computers. The physical hardware acts as the host, while each VM is a guest virtual machine. The host hardware is partitioned so that each VM has its own CPU, memory, storage, and networking resources allocated to it. This allows multiple VMs to run simultaneously on the same physical server, each executing specific tasks independently. From the perspective of software running inside each VM, it appears to have a complete computer to itself. In essence, VMs provide the functionality and isolation of separate physical machines, even though they share the same underlying physical hardware.
There are two main types of VMs: full virtualization and paravirtualization. Full virtualization means that the guest OS is unaware that it is running on a virtual machine, and does not need any modification to run on the hypervisor. The hypervisor emulates the hardware devices and intercepts the instructions from the guest OS, which may cause some overhead and performance loss. Paravirtualization means that the guest OS is aware that it is running on a virtual machine, and has some modifications to cooperate with the hypervisor. The hypervisor does not need to emulate the hardware devices and can directly access them, which may improve the performance and efficiency.
Virtual machines (VMs) come in two main types: System VMs (SVMs) provide a complete virtual hardware environment for running an operating system and its applications. Process VMs (PVMs) provide a lightweight virtual environment for running a single process. VMs can also be classified by their hypervisor type: Hosted hypervisors run on top of an existing operating system. Bare-metal hypervisors run directly on the physical hardware. VMs offer a number of benefits, including consolidation, isolation, flexibility, scalability, security, and disaster recovery.
Virtual machines come in several types: Full Virtualization, which emulates complete hardware; Para-Virtualization, where guest OS is modified to collaborate with the hypervisor; Hardware-assisted Virtualization, using specific CPU features to enhance VM performance; Container-based Virtualization, enabling multiple isolated user-space instances within a single OS; and Emulation-based VMs, which emulate hardware for running incompatible software. Each type serves different purposes, from running diverse operating systems on one server to isolating applications within containers, catering to various computing needs and optimization strategies.
Three types of virtual machines are: System Virtual Machines: These provide a complete system platform that supports the execution of a full operating system (OS). They replicate a real physical computer's functionality. Process Virtual Machines: They are designed to execute a single program and can be created when the process starts and deleted when it ends. They provide a platform-independent programming environment. Hardware Virtualization: This type uses the physical hardware directly to run a guest OS on top of the host OS, giving direct hardware access for high performance.
There are many examples of VMs that you can use for different purposes and scenarios, such as VirtualBox, VMware, Hyper-V, and QEMU. VirtualBox is a free and open-source VM software that supports various OS, including Windows, Linux, MacOS, and Solaris. VMware is a commercial VM software used to create and manage VMs for development, testing, deployment, and security. Hyper-V is a built-in VM feature in Windows 10 and Windows Server that allows you to create and run VMs on your Windows machine. Lastly, QEMU is a free and open-source VM software that can emulate various CPU architectures like x86, ARM, MIPS, and PowerPC. All of these VMs can be used to test and run different OS and applications on your desktop or laptop, access remote VMs on Azure cloud, or run OS and applications that are not compatible with your host machine.
System VMs: -VMware vSphere ESXi -Microsoft Hyper-V Server -Citrix XenServer -Red Hat Virtualization -Nutanix AHV Process VMs: -Java Virtual Machine (JVM) -Common Language Runtime (CLR) -Node.js Virtual Machine (V8) -Android Runtime (ART) -Erlang Virtual Machine (BEAM) VMs are used in a wide variety of environments, including: Data centers: VMs are used to consolidate servers, isolate applications, and create test and development environments. Cloud computing: VMs are used to provide scalable and elastic computing resources. Desktop computers: VMs are used to run multiple operating systems on a single computer, or to isolate applications from each other.
VMware Workstation VirtualBox Microsoft Hyper-V Parallels Desktop KVM (Kernel-based Virtual Machine) Xen QEMU Oracle VM Server Red Hat Virtualization Citrix Hypervisor (formerly XenServer)
Full virtualization: Emulates complete hardware resources to run multiple operating systems on one machine (e.g., VMware ESXi, Microsoft Hyper-V). Para-virtualization: Modified guest operating systems for better performance (e.g., Xen). Operating system-level virtualization: Virtualizes the OS, allowing multiple containers on the same host OS (e.g., Docker, LXC). Hardware-assisted virtualization: Uses special hardware features to improve performance (e.g., Intel VT-x, AMD-V). Desktop virtualization: Runs multiple virtual desktops on a single machine (e.g., VMware Horizon, Citrix Virtual Apps and Desktops).
Virtual machine software includes VMware (offering products like VMware Workstation, vSphere), Oracle VM VirtualBox, Microsoft Hyper-V, KVM for Linux, Xen (an open-source hypervisor), and Docker for container-based virtualization. Each of these tools enables users to create, manage, and run virtual machines or containers, catering to a wide array of needs, from simultaneous operation of multiple OSs on a single machine to isolated application deployments across diverse operating systems.
While a VM has many advantages, it also has some challenges and limitations that you need to consider. Performance is one of the main challenges, as VMs have to share resources with the host and other VMs, and rely on the hypervisor to handle instructions and requests. The performance may vary depending on the type and configuration of the VM, the workload and demand of applications, and the optimization and tuning of the hypervisor. Additionally, compatibility can be an issue since VMs depend on the hypervisor to emulate or access hardware devices or software applications. Some devices or applications may require specific drivers or protocols that are not supported by the hypervisor, or may have licensing or security restrictions that prevent them from running on a VM. Lastly, managing a VM can be more complex than managing a physical machine since it involves more layers and components that need to be updated, monitored, and secured. It’s important to manage resources and policies for each VM separately to avoid conflicts or interference with each other or the host.
Debugging software opens executables in virtual machine space for analysis and execution. Some malware is able to detect that it is running in a virtual environment (called a red pill) and then trigger counter analysis measures. This can be bypassed by setting up specific registers to simulate bare metal.
VMs offer many benefits, including consolidation, isolation, flexibility, scalability, security, and disaster recovery. However, they also come with some challenges, such as performance overhead, complexity, security, and licensing costs. To overcome these challenges, you should choose the right hypervisor, use a VM management tool, properly isolate your VMs, keep your VMs up to date, and back up your VMs regularly. Despite the challenges, VMs can be a valuable tool for businesses of all sizes.
Snapshots are a powerful feature of VMs allowing you to save the state of a VM at a given point in time. Poor management of snapshots may lead to storage space issues. They are used for short-term purposes. Some hypervisors have limits on disk space or the number of snapshots as snapshots can grow large and consume significant disk space.
Performance: VMs can have a slight performance overhead compared to physical machines, but this is often manageable. Resource allocation: Managing resources among multiple VMs can be complex, requiring careful planning and monitoring. Compatibility: Some hardware and software may not be fully compatible with virtualization, which can limit certain applications. Backup and recovery: Managing backups and recovery for VMs can be more complex than for physical machines. Licensing: VMs can introduce licensing complexities, as some software vendors have specific requirements for virtualized environments. Security risks: If not properly configured and managed, VMs can introduce security risks.
Virtual machines present challenges such as performance overhead due to resource abstraction, potential security vulnerabilities at the hypervisor level, complex resource allocation, issues related to compatibility and interoperability, intricacies in backup and recovery, licensing costs, and a need for specialized expertise. Balancing resource allocation, ensuring security measures, and managing costs while maintaining compatibility across different virtualization platforms are critical factors in addressing these challenges and optimizing the efficiency and security of virtualized environments.
Resource-saving and maintenance effectiveness Virtual machines are also used for resource-saving and for reducing the costs of maintaining servers and service infrastructure. Compared to hardware costs, VMs are cheap and almost unlimited. They are also much easier to maintain and to restart or return to some state that we have saved snapshots.
Hardware: Ensure your host machine meets the hardware requirements for running VMs. Backup and recovery: Develop a plan to regularly back up VMs and data for disaster recovery. Monitoring and optimization: Monitor VM performance and optimize resource allocation for efficiency. Network configuration: Configure network settings for secure and efficient communication between VMs and other devices. Patch management: Keep VMs up to date with the latest patches and security updates.
VMs are widely used for their flexibility. They allow for testing software on different operating systems without needing multiple physical computers, provide secure environments for testing new programs or configurations without risking the main system, and facilitate the running of applications that require different operating systems or configurations.