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VMware Workstation VMware Workstation software consists of a virtual-machine suite for Intel x86- compatible computers. This software suite allows users to set up multiple x86 virtual computers and to use one or more of these virtual machines simultaneously. Each virtual machine instance can execute its own guest operating system, such as (but not limited to) Windows, Linux, and BSD variants. In simple terms, VMware Workstation allows one physical machine to run numerous operating systems simultaneously. Other VMware products help manage or migrate VMware virtual machines across multiple host machines. VMware Workstation has grown in popularity due to the large number of servers proliferating in the corporate market. Transferring workstations and servers to virtual-machine environments allows for easier systems management, a reduction in physical footprint and reduced need for hardware. Limitations (as of June 2006): VMware virtual machines do not support FireWire VMware virtual machines provide no direct USB 2.0 support, but make USB 2.0 devices in the host operating-system visible to the guest operating-system as USB 1.1 devices VMware virtual machines provide only experimental support for 3D hardware acceleration VMware Player installing Windows XP Professional under Windows XP  VMware Player VMware Player, which offers free software to host virtual machines, can run guest virtual machines produced by other VMware products, but cannot itself create new virtual machines. VMware's website provides many free virtual-disk images of preconfigured operating-systems and applications, many of them community- contributed. Freeware tools also exist for creating VMs, mounting, manipulating and converting VMware disks and floppies, so VMware Player users can create, run and maintain virtual machines for free (even for commercial use).  VMware Server (formerly VMware GSX Server) VMware Server running Microsoft Windows XP Professional under Ubuntu VMware released version 1.0 of VMware Server on July 12, 2006. VMware Server can create, edit, and play virtual machines. In addition to the ability to run virtual machines created by other VMware products, it can also run virtual machines created by Microsoft Virtual PC. VMware Inc makes VMware Server freely available in the hope that users will eventually upgrade to VMware ESX Server. VMware Inc. does not officially support VMware Server on Windows XP or on Windows 2000 Professional — unlike VMware Workstation — however, users have reported successfully installing and hosting VMware Server on Windows XP Professional, with some limitations. VMware Inc. provides a list of supported host operating-systems.  VMware ESX Server ESX Server uses a stripped-down proprietary kernel (based on Stanford University's SimOS) that replaces the Linux kernel after hardware-initialization. The Service Console (also known as "COS" or as "vmnix") for ESX Server 2.x is based on Red Hat Linux 7.2. The Service Console for ESX Server 3.0 derives from a modified version of RedHat 7.2 — it acts as a boot-loader for the vmkernel and provides management interfaces (CLI, Webpage MUI, Remote Console). This hypervisor- virtualization approach provides lower overhead and better control and granularity for allocating resources to virtual machines. It also increases security, thus positioning VMware ESX as an enterprise-grade product.  VMware Infrastructure VMware Infrastructure 3, a suite of virtualization products, includes VMware ESX Server Version 3, VMware Virtual Center Version 2, Virtual SMP (up to 4 way) and VMotion, as well as distributed services such as VMware HA, VMware DRS and VMware Consolidated Backup. VMware Inc. released VMware Infrastructure 3 in June 2006. The suite comes in three flavors: Starter, Standard and Enterprise.  Data-center products VMware Inc offers two main products for data centers: VMware ESX and VMware Server (formerly known as VMware GSX). VMware ESX server ranks as VMware's flagship product for running enterprise applications in data centers. ESX allows for a 60 to 80% increase in x86 utilization, since it loads on the bare metal level. Data centers can also use VMware Server, but it relies on a base operating- system in order to run. As such, machines incur additional overheads when running the extra layer of software. But VMware Server has an advantage over ESX in that it supports a wider array of devices, such as USB connectivity and certain PCI devices. Peripheral Component InterconnectE.) Note also the VMware ACE product.  Other products Three other products operate in conjunction with ESX - VirtualCenter, VMotion and P2V. VirtualCenter allows monitoring and management of multiple ESX or GSX servers. VMotion allows moving virtual machines between servers on the fly, with almost zero downtime. P2V allows users to image a physical server using imaging software, then creates a physical-to-virtual recreation of the machine. It replaces the physical driver-files with virtual driver files and creates the machine space within VMware data storage.  Description VMware Inc. refers to the computer and operating-system instance that executes the VMware Workstation process as the host machine, and identifies instances of operating systems running inside a virtual machine as guest virtual machines. Like an emulator, VMware Workstation provides a completely virtualized set of hardware to the guest operating system — for example, regardless of make and model of the physical network adapter, the guest machine will see an AMD PCnet network adapter. VMware virtualizes all devices within the virtual environment, including the video adapter, network adapter, and hard disk adapters. It also provides pass-through drivers for USB, serial, and parallel devices. Once all guest virtual machines use the same hardware drivers (regardless of the actual hardware on the host computer), virtual machine instances become highly portable between computers. For example, an operator running a virtual machine can pause it, copy it to another physical computer, and unpause it to resume execution exactly where it left off. With VMotion, a new feature in VMware's VirtualCenter, an administrator no longer even needs to pause virtual machines running on ESX servers while moving them — virtual machines can now continue running even while they migrate to different hosts — provided the source and target servers involved use the same processors and instruction-sets.  Implementation of virtual processing Conventional emulators like Bochs emulate the microprocessor, executing each guest- CPU instruction by calling a software subroutine on the host machine that simulates the function of that CPU instruction. This abstraction allows the guest machine to run on host machines with a different type of microprocessor, but also operates very slowly. Dynamic recompilation offers an improvement on this approach: it dynamically compiles blocks of machine instructions the first time they are executed, and later uses the translated code directly when the code runs a second time. This approach is taken by Microsoft's Virtual PC for Mac OS X. VMware Workstation takes an even more optimized approach and uses the CPU to run code directly whenever possible. This is the case for user mode and virtual 8086 mode code on x86. When direct execution is not possible, code is rewritten dynamically. This is the case for kernel-level and real mode code. In VMware's case, the translated code is put into a spare area of memory, typically at the end of the address space, which can then be protected and made invisible using the segmentation mechanisms. For these reasons, VMware is dramatically faster than emulators, running at more than 80% of the speed that the virtual guest OS would run on hardware. VMware boasts an overhead as small as 3%-6% for computationally intensive applications. Although VMware virtual machines run in user mode, VMware Workstation itself requires installing various drivers in the host operating system, notably in order to dynamically switch the GDT and the IDT tables. One final note: many people erroneously believe that virtualization products like VMware or Virtual PC replace offending instructions or simply run kernel code in user mode. Neither of these approaches can work on x86. Replacing instructions means that if the code reads itself it will be surprised not to find the expected content; it is not possible to protect code against reading and at the same time allow normal execution; replacing in place is complicated. Running the code unmodified in user mode is not possible either, as most instructions which just read the machine state do not cause an exception and will betray the real state of the program, and certain instructions silently change behavior in user mode. A rewrite is always necessary; a simulation of the current program counter in the original location is performed when necessary and notably hardware code breakpoints are remapped.  Features Besides bridging to network adapters, CD-ROM readers, hard-disk drives, and USB devices, VMware Workstation also provides the ability to simulate some hardware. For example, it can mount an ISO file as a CDROM, and .vmdk files as hard disks; and the network adapter driver can be configured to use network address translation through the host machine rather than bridging through it (which would require an IP address for each guest OS on the host network). VMware Workstation also allows the testing of LiveCDs without first burning them onto physical discs or rebooting the computer. You can also take snapshots of an OS running under VMware Workstation. Each snapshot allows you to roll back the virtual machine to the saved status at any time. The Multiple snapshots feature makes VMware Workstation very popular as a tool for sales people to demonstrate complex software products, and for developers to create virtual development and test environments. VMware Workstation includes the ability to designate multiple virtual machines as a team, which can then be powered on and off, suspended and resumed as one object—making it particularly useful for testing client-server environments. New enterprise-grade servers and tools from VMware, Inc. have started to popularise the migration of older production servers into virtual machines so that many legacy servers can be consolidated onto a single new host machine with little effort. The VMware Tools package enhances graphics and mouse performance in virtual machines. It adds various drivers and utilities which support different capabilities in different guest operating systems: features like shared folders, clock-synchronisation and plug-and-play devices. The VMware product line can also utilize different operating-systems on a dual-boot system simultaneously by booting one partition natively while using the other as a guest operating-system within VMware Workstation. Installers must take care, however to reconfigure the guest partition to accept the new hardware configuration, as the VMware virtual machine presents a different set of hardware than the guest may expect. Failure to re-configure the guest operating-system can result in the "Blue Screen of Death" on Microsoft Windows-based operating systems, or a "kernel panic" on Unix and Linux-based systems. Microsoft Windows users can use hardware profiles, while Linux (as of August 2006) has no known method of changing hardware-configurations quickly without recompiling the kernel. (Note: most Linux distros have for years shipped with InitRD-based kernel-packages which allows at run-time/startup time loading of appropriate drivers matching the hardware it is running on top of)  Issues Older versions of VMware seem unable to run newer versions of Linux (kernel 2.4 series seem to panic when run on VMware 2.x; and 2.6 series kernels, when run on VMware 3.x, give a protection error). VMware Workstation has now reached version 5.5.1, which supports these newer operating systems and kernels. However, the latest versions of the 2.6.x kernel require a patch to use all the VMware features — even when using VMware Workstation 5.0 or 5.5. This patch, freely available as vmware- any-any-updatexxx ([[as of 2006 | as of 17 August 2006: update103) comes via the Czech Technical University Additionally, when using VMware Workstation in an environment using Media Access Control (MAC) addresses as unique identifiers (UID), one should (and often must) manually configure the MAC address for each virtual machine in order to ensure uniqueness. For example, an environment in which switches implement MAC security; or an environment in which Altiris products use the MAC address as the UID. If you find yourself in such a situation, simply disable all networks/adapters other than "bridged" and edit each virtual machine's .vmx file to change "ethernet0.address" to a unique MAC, and "ethernet0.addresstype" to "static". Make sure also to remove the "ethernet0.generatedaddress" entry entirely.