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VMware Workstation


									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[citation needed]. 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

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


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

        VirtualCenter allows monitoring and management of multiple ESX or GSX
        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.


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

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.

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)


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.

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