Chapter 4 Virtual Machines Parallels Workstation Parallels (its full name is Parallels Software International Inc.) can be considered a newcomer to the market of applications for creating virtual machines. Suffice it to say that at the end of 2005, only the second version of the Parallels package was released in beta

Why are labels needed? A special type of files are shortcuts. A shortcut only points to some file or folder that is itself located elsewhere. The fact that the file is a shortcut is indicated by a small arrow on its icon. It is convenient to place shortcuts on the Desktop. Double click on

Why do we need optimizers? The scheme described in the previous chapters covers almost all processes of creating and filling the portal, starting with the compilation of the semantic core and ending with the placement of finished texts. At the same time, until now we have had practically no work for

If you have ever installed any programs or conducted any experiments on your computer, then you know very well how much time it takes to restore it to its original state. Often, this requires completely reinstalling the system.

In order to avoid such serious consequences, users use all sorts of tricks: only from trusted sources, use the most powerful and high-quality antiviruses, and do this in case of problems. But ordinary ones are more reliable than all this.

What is a virtual machine?

Imagine that on your computer, in parallel with the first, a second operating system is installed, which simultaneously works with it. It is completely independent of the “real” OS; any risky experiments can be carried out on it.

Introduced? So, virtual machines allow all this, since they are special software “containers” in which you can run almost any operating system. Unlike the OS that is on your hard drive, it will not have direct access to the computer hardware, acting through the software shell.

As a result, you can run at least a whole brood of viruses in it: they will not be able to do any harm. An ideal example is the VMware virtual machine, which advanced users use to run new versions of operating systems and test dubious programs and drivers. In the realities of our country, it is used even more often to launch keygens to generate keys to programs. All this allows you not to needlessly spoil your system.

But you shouldn’t assume that virtual machines are the prerogative of Windows alone. They are used much more often by users of Linux-like systems, since in many cases they may need to run some small utility that only works on a Microsoft system. It is simply unjustified to bother with Wine for the sake of it, while the “virtual” easily eliminates such a need.

Users often look for comparisons of virtual machines, trying to choose the best one among them. It should be noted that VMware, which has a number of undoubted advantages, often comes up in disputes. The program developers constantly add support to their product for almost all existing operating systems, including those that have just come out. In particular, it was this application that at one time made it possible to launch Windows 8, while in the popular Virtual Box the system completely refused to start.

But the leader of the unspoken competition has one drawback. The program is paid. Of course, professionals who use its capabilities to test their programs do not have any difficulties, but I would still like to advise others not to mess with broken programs and use the free Virtual Box. Although these virtual machines are not particularly popular among professionals, their capabilities are more than enough for you.

The concept of a “virtual machine” was born several decades ago, back in the late 60s of the last century. But then virtual machines were used not on personal computers, but on “large” computers such as IBM/370 (or their Soviet analogue - ES Computers), and their tasks were somewhat different: to provide each of the numerous users with their own, independent “piece” » resources of a computing monster.

Today, virtual machines are experiencing a rebirth. One of the "fathers" of the modern generation of virtual machines, Professor Rosenblum, attributes their revival to two main reasons:

■ the emergence of a large number of different operating systems (OS), which impose specific requirements on the parameters of the computer hardware components used;

■ high administration costs and complexity of servicing computers on which several different operating systems are installed (including in terms of ensuring the required reliability and security of operation).

A modern virtual machine allows you to hide some parameters of the computer’s physical devices from the operating system installed on it and thereby ensure the mutual independence of the OS and the installed hardware.

This approach provides users (and/or computer system administrators) with a number of benefits. These include in particular:

■ the ability to install several operating systems on one computer without the need for corresponding configuration of physical hard drives;

■ work with several operating systems simultaneously with the ability to dynamically switch between them without rebooting the system (Fig. 1.1);

■ reducing the time required to change the composition of installed operating systems;

■ isolation of real hardware from the unwanted influence of software running in a virtual machine environment;

■ the ability to simulate a computer network on a single autonomous computer.

Rice. 1.1. Multiple virtual machines on one desktop

Thanks to these advantages, the range of tasks that the user can solve without rebooting the system and without fear of causing any damage to it or completely disabling it is significantly expanded. Here are just some examples of such tasks:

■ mastering a new OS;

■ launching applications designed to work in a specific OS environment;

■ testing one application running different operating systems;

■ installation and removal of evaluation or demo versions of programs;

■ testing potentially dangerous applications that are suspected of being infected with a virus;

■ managing user access rights to data and programs within a virtual machine.

The reader himself will probably easily add two or three situations to the above list when having a virtual machine on the computer would be very useful.

Which users would like to learn how to work with virtual machines? Perhaps everyone who has more than one OS installed on their computer. And also for those who want to master a new operating system, but do not dare to immediately abandon the previous one. Virtual machines are very useful for teachers of various computer courses and disciplines, as well as developers of multi-platform software products. They are of particular interest to web designers: after all, the pages they create should look equally attractive to users working on a variety of systems and platforms. With the ability to quickly switch from one environment to another using a virtual machine system, the “right” web designer is unlikely to miss the chance to test the results of his work in different web browsers.

All of the listed advantages of virtual machines are common to many of them. In addition to these general properties, a specific software product usually has individual features designed to increase its attractiveness in comparison with competing products.

On the websites of virtual machine developers you can find numerous examples of the use of virtual machine technology by various well-known companies. Thus, VMware virtual machines are used by Symantec to test network antivirus packages; Programmers of the popular Google search engine use VMware virtual machines to evaluate the performance of Google with different web browsers and on different platforms.

Let's start by clarifying the terms.

From the user's point of view, virtual machine (VM) - This is a specific instance of a certain virtual computing environment (“virtual computer”), created using a special software tool. Typically, such tools allow you to create and run an arbitrary number of virtual machines, limited only by the physical resources of a real computer.

The actual tool for creating VMs (sometimes called virtual machine application, or FDA) is a regular application installed, like any other, on a specific real operating system. This real OS is called the "host" or host, OS (from the English term host - “main”, “base”, “master”).

All tasks for managing virtual machines are solved by a special module as part of the VM application - Virtual Machine Monitor (VMM). The monitor plays the role of an intermediary in all interactions between virtual machines and the underlying hardware, supporting the execution of all created VMs on a single hardware platform and ensuring their reliable isolation. The user does not have direct access to the VMM. In most software products, it is provided only with a graphical interface for creating and configuring virtual machines (Fig. 1.2). This interface is usually called virtual machine console.

Rice. 1.2. Example of a virtual machine console

“Inside” the virtual machine, the user installs the operating system he needs, just like on a real computer. Such an OS belonging to a specific VM is called guest(guest OS). The list of supported guest operating systems is one of the most important characteristics of a virtual machine. The most powerful modern virtual machines (presented in this book) provide support for about a dozen popular versions of operating systems from the Windows, Linux and MacOS families.

Once the virtual machine is created and running, the user may have the complete illusion that he is working with a standalone computer, which has its own processor, RAM, video system and (usually) a “standard” set of external devices, including a floppy drive and CD reader /DVD.

In fact, the virtual machine does not have access to the physical resources of the real computer. Working with them is assigned to the previously mentioned VMM, as well as to another utility program - the virtual machine driver.

In a simplified form, the architecture of the system that uses virtual machines is as follows (Fig. 1.3):

■ the host OS and the virtual machine monitor share rights to manage the computer’s hardware components; at the same time, the host OS distributes resources between its own applications (including the VM console);

■ the VM monitor controls the distribution of resources between running virtual machines, creating for them the illusion of direct access to the hardware level (this mechanism is called virtualization);

■ guest operating systems, within the resources allocated to them, manage the operation of “their” applications.

Rice. 1.3. Virtual machine system architecture

The architecture shown is very general. However, the virtual machine systems on the market today have significant differences. They are determined primarily by the virtualization mechanism used in a particular system.

A virtual machine system can be built on various platforms and using different technologies. The virtualization scheme used depends both on the hardware platform and on the characteristics of the “relationship” between the host OS and the supported guest OS. Some architectures provide virtualization capabilities at the hardware level, while others require additional software tricks.

Currently, three virtualization schemes are widespread:

■ guest OS API emulation;

■ full emulation of the guest OS;

■ quasi-emulation of the guest OS.

Typically, applications operate in an isolated address space and interact with hardware using the Application Programming Interface (API) provided by the operating system. If two operating systems are compatible in their APIs (for example, Windows 98 and Windows ME), then applications developed for one will work on the other. If two operating systems are incompatible in their API interfaces (for example, Windows 2000 and Linux), then it is necessary to intercept application calls to the guest OS API and imitate its behavior using the host OS. With this approach, you can install one operating system and work simultaneously with both its applications and applications of another operating system.

Since all application code runs without emulation, and only API calls are emulated, this virtualization scheme results in a negligible loss in virtual machine performance. However, due to the fact that many applications use undocumented API functions or access the operating system bypassing the API, even very good API emulators have compatibility problems and only allow to run no more than 70% of the total number of applications. In addition, maintaining API emulation of a rapidly evolving operating system (such as Windows) is not easy, and most API emulators remain emulators of a specific version of the operating system. Thus, Windows NT/2000 still has a built-in emulator for OS/2 version 1.x applications. But the biggest drawback of a VM with guest OS API emulation is its focus on a specific operating system.

Examples of products made using guest OS API emulation technology:

■ open source project Wine (Wine Is Not an Emulator, “Wine is not an emulator”), which allows you to run DOS, Win16 and Win32 applications running the Linux and Unix operating systems;

■ Netraverse's Win4Lin product, which allows you to run Windows operating systems running the Linux operating system;

■ open source project DOSEMU, which allows you to run DOS applications running the Linux operating system;

■ open source project User Mode Linux (UML), which allows you to run multiple copies of the Linux operating system on one computer (currently the Linux kernel version 2.6 is built in);

■ Virtuozzo technology, developed by the Russian company SWsoft, which allows you to run multiple copies of the Linux operating system on one computer.

Projects that support full emulation technology work on the principle of interpreting instructions from the guest OS command system. Since this completely emulates the behavior of both the processor and all external devices, it is possible to emulate a computer with Intel x86 architecture on computers with a completely different architecture, for example, on Mac workstations or on Sun servers with RISC processors. The main disadvantage of full emulation is a significant loss of performance of the guest operating system (the speed of “guest” applications can drop by 100-1000 times). Therefore, until recently, VMs with full emulation were most often used as low-level debuggers for examining and tracing operating systems. However, thanks to the significant increase in computing power, even “desktop” computers, VMs with full emulation have now become quite competitive. The most prominent representative of this type of VM is the Virtual PC product from Connectix (now purchased by Microsoft), which is described in detail in Chapter 2 of the book. Other examples of projects implemented using full emulation technology include the following:

■ Bochs open source project, which allows you to run various Intel x86 operating systems under Linux, Windows, BeOS and Mac OS;

■ Simics product from Virtutech, which allows you to run and debug various Intel x86 operating systems running Windows and other operating systems;

■ Qemu project - an emulator of various architectures on PC,

Guest OS quasi-emulation technology is based on the fact that not all guest OS instructions need to be emulated using the host operating system. Many of the instructions needed for guest applications to run correctly can be addressed directly to the host OS. The exception is instructions for controlling devices such as a video card, IDE controller, timer, and some others.

Thus, during RM operation with quasi-emulation, selective emulation of guest OS instructions occurs. Obviously, the performance of such a VM should be higher than that of a VM with full emulation. However, as mentioned, at the achieved levels of performance of personal computers, the difference is not so noticeable.

Examples of projects made using quasi-emulation technology:

■ Virtual Platform technology, on the basis of which VMware offers four products: VMware Workstation for Windows NT/2000/XP, VMware Workstation for Linux, VMware GSX Server (group server) and VMware LSX Server (enterprise server);

■ virtual machine Serenity Virtual Station (SVISTA) (formerly twoOStwo), developed by the Russian company Parallels for the German company NetSys GmbH;

■ Plex86 open source project, which allows you to run various Intel x86 operating systems running Linux.

■ open source project L4Ka, which uses a microkernel;

■ open source project Xen, which allows you to run modified Linux, FreeBSD, NetBSD and Windows XP operating systems running Linux, FreeBSD, NetBSD and, subject to certain conditions, even providing a performance increase.

The subsequent chapters of the book examine the most popular representatives of various types of virtual machines today: Virtual PC 2004 from Microsoft, VMware Workstation from VMware and a relatively “fresh” product - Parallels Workstation, created by Parallels. Moreover, the description of all competing programs is built according to the same scheme, so that it is easier for the reader to compare them with each other and make an informed choice.

Notes:

Mendel Rosenblum(mendel@ cs.stanford.edu) is a professor of computer science at Stanford University and one of the founders and chief scientist of VMware. Chapter 3 of the book is devoted to working with this company’s virtual machine, VMware Workstation.

Currently, Parallels has split into two independent companies. The first of them, which retained the same name, promotes its product under the Parallels brand; the second, called Serenity Systems International (http://www.serenityvirtual.com), on the contrary, uses the previous name of the product - SVISTA - and its logo; both versions of virtual machines can run on Windows NT/2000/XP and Linux.

To have several operating systems with separate workspace and applications at hand, you don’t need to buy a second (third, fourth, etc.) computer. Because it all fits into your single PC. How? Thanks to virtual machines (VMs) - special programs that create (emulate) imaginary (virtual) computers inside the main operating system.

A virtual PC is almost like a real one. It has its own processor, memory, hard drive, network adapter and everything else. Of course, these are not physical devices, but they are made in such a way that operating systems consider them to be just that - real.

Several virtual computers can work simultaneously on one physical computer. Exactly how much depends on the hardware resources: the faster the processor, the larger the RAM, the more spacious the storage, the more. A typical average-performance home PC running Windows 10 can handle three to five lightweight operating systems simultaneously (for example, Windows XP, Android and Lubuntu + the main system). Or two or three relatively heavy ones (for example, the main Windows 10 + virtual Windows 7 and Mac OS X). As you already understand, virtual computer emulator applications allow you to install and run a variety of operating systems on them.

General purpose virtual machines (as opposed to specialized ones, such as the Java VM) use:

• To run applications that the main system does not support.
• To protect the system from potential harm from untested programs.
• As an additional barrier against viruses when visiting dubious web resources.
• To create an isolated environment for studying the activities of malware.
• As a testing ground for debugging your own developments.
• To master network construction technologies.
• For double authorization on some gaming portals and much more.

And of course, virtual machines are widely used to distribute server work resources.

Today we will not touch on the industrial use of VMs, but will only consider what can be useful to home users of Windows OS.

Oracle Virtualbox

Let's look at the process of creating a new virtual machine and starting to install Windows 10 on it.

• Click the “Create” button in the top panel.

• In the first window of the VM creation wizard, we will indicate the name of the OS (it will be displayed in the list of guest systems), its type (Windows, Linux, etc.) and version. In our example, this is Windows 10 32 bit (you can install 64 bit, but it will require more resources). To move to the next step, click Next.

• Next, we will indicate the size of the VM RAM. By default, Windows 10 x86 is allocated 1 GB, but you can increase this amount by moving the slider to the right. If your PC does not have a lot of RAM, do not give the VM more than 2-3 GB, otherwise the main system will slow down due to lack of memory.

• Next we create a virtual hard disk. If you are installing the system for the first time, select the “Create new” option.

• Leave the virtual disk type as default.

• A storage format is an area on your computer's physical drive that is allocated to a VM. It can have a constant or dynamically expanding volume within the limits that you define further. To save space, we will choose a dynamic format.

• Next we indicate the name of the volume (virtual disk C) and its size. The default is 32 GB.

• After clicking the “Create” button in the last window, a new virtual machine will appear in the list. Its parameters are shown in the frame on the right.
• To proceed to installing Windows, click the “Run” button in the top panel.

• In the window that opens after this, the “Select boot disk” window will appear. Click on the folder icon and specify the path to the system distribution. This can be an image in .iso format or physical media (DVD, flash drive). After selecting your distribution, click Continue.

• The further course of installing the OS into a virtual machine is no different from installing it on a physical computer.

Some VM and guest system settings

Clicking on the virtual machine window will capture the mouse cursor (i.e. it will only move within the virtual screen). To return the cursor to the main OS, press the Ctrl+Alt combination.

To access the full range of features of the guest OS, you need to install special add-ons. Go to the "Devices" menu, click "Mount Guest Additions Disk Image" and follow the further instructions.

To connect a folder to the guest system for exchanging files with the main one, click the “Shared Folders” item in the “Devices” menu. Click on the “folder+” icon in the window that opens and use the “path to folder” field to specify it in Explorer (it shows the directories of the main system).

If you want the setting to work permanently, check “Auto-connect” and “Create permanent folder”. The shared folder will be accessible from the virtual machine explorer as a network folder.

To change the order in which boot devices are polled (for example, to boot a virtual machine from a DVD), shut down the guest OS, open its settings (in the main Virtualbox window) and go to the first tab of the “System” section. In the "Load Order" list, select the desired media and press the arrow buttons to move it to the top.

VMware Workstation Pro

Some Hyper-V virtual machine options

To take a snapshot of a running guest OS, open the top menu of its Action window and click Checkpoint. Or press the combination Ctrl+N.

Access to the settings of an individual virtual machine is opened from its context menu in the list of the main manager window and hidden behind the “Settings” button.

Other features of the program are also very simple and can be mastered without much difficulty.