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Exploiting Virtual PC - II

VPC architecture

VPC consists of the following components:

• The base VPC User Interface Window in which the VPC runs.
• The configuration file (.VMC) file
• The file containing the actual VPC data. This file is VHD or Virtual Hard Disk. This file contains the OS, the applications and data.
• All peripherals and devices are emulated. Real drivers are loaded but the devices themselves are emulated.

VPC emulates the following base hardware:

The processor is not emulated. The host PC processor is used.

The network adapter emulation is important. It always emulates DEC network card, irrespective of which card is physically present.

OS Installation options

There are two ways of loading an OS:

• Using a Startup CD

This option allows you to perform the installation using a bootable CD. This is a common method.

In some cases, there is an ISO file which contains the base installation. If you have the file, you can simply drag the file from the host machine and drop it onto the CD icon in the status bar of the virtual machine window.

• Using a System Disk

It is also possible to setup an OS on a VPC using a network installation. This requires a remote boot disk to be prepared.

Virtual Machine additions

Additions are a set of features that are loaded on top of the base VPC. Additions primarily increase the integration between the virtual and host machines.

1. Drag-and-drop operations
2. Folder sharing
3. Copy-and-paste operations
4. Integrated mouse support: Pointer integration is a good feature. As virtual machine is a PC within the host UI, this feature decides what happens when you move the pointer over the VPC window. There are two methods. The mouse pointer is “captured” by VPC when it moves within its bounds (or optionally you click inside it). A captured pointer then only moves within the VPC. To release the pointer so that it is available for the Host UI, you have to press the Host key (Right Alt by default)
5. International keyboard support
6. Dock Start Menu (Virtual PC versions 6.0 and 6.1)
7. Dock proxy applications (Virtual PC versions 6.0 and 6.1)
8. Optimised video drivers
9. Virtual PC Helper (includes SyncTime)
10. Dynamic resizing of the virtual machine window, which automatically adjusts the size of the guest operating system desktop

To load these, load the base Virtual Machine and then choose “Install or Update Virtual Machine Additions” option. If this menu is disabled, it indicates that the additions are already loaded.

Networking with VPC

You can have upto 4 emulated network adapters on a VPC. Each of the adapters can be mapped to a single or multiple host adapters.

• Local network

This establishes a network between multiple VPCs running.

• Shared Networking (NAT)

The Shared Networking (NAT) networking option uses the Virtual PC Network Address Translation (NAT) and Port Address Translation (PAT) service to provide networking support for the guest PC. When you use this option, one or more guest PCs can share the IP address of the host computer. The Shared Networking (NAT) networking option is suited for typical network activities such as browsing the Web, accessing e-mail, accessing FTP sites, or accessing shared printers and files. This networking option is not suitable for more advanced networking scenarios, such as running a Web or FTP server on the guest PC. For these advanced networking scenarios, it is best to use the Virtual Switch option.

• Virtual Switch

The Virtual Switch networking option addresses both typical and advanced networking requirements, such as a running server program that has predefined port numbers, remote login (RLOGIN), network performance analysis (NETPERF), or remote shell (RSH) support. This networking option permits the highest degree of compatibility and control. When you use the Virtual Switch networking option, a guest PC can use the following network protocols:

- TCP/IP

- IPX/SPX

- NetBEUI

It is best to use the Virtual Switch networking option if the guest PC is connected to a Microsoft or Novell network and if it must be authenticated on the network. Virtual Switch networking option is the default networking option in Virtual PC 5.x.

• Network availability

VPC can be configured like another node with distinct networked computer.

Accessing a network and network resources requires that the operating system on the virtual machine be configured as a part of the network. If, for example, you have a virtual machine running on a physical computer that is a member of an Active Directory domain, to access both the physical computer and any resources in the Active Directory domain you must join the virtual machine to the Active Directory domain. If the operating system on the virtual machine is appropriately configured, the network should recognise the virtual machine as a networked computer, so the virtual machine is subject to the same policy settings as every other computer on the network.

Data and Folder Sharing

Folder sharing allows VPC to recognise a folder on host PC like a network share. This share can be shared by multiple VPCs (for read only operations). For writing to the file, only one VPC can participate at a time.

On the other hand, we can make a folder on the virtual machine shareable from the host PC. To configure this, follow these steps:

1. Open the VPC console.
2. Run the required VPC and start the required virtual machine.
3. Now choose settings from the console for the virtual machine.
4. Click on Share folder… option.
5. Select the folder. That’s it.

Configuration options

VPC console Settings button allows you to configure many options for the selected VPC. Here are the options:

Some important ones are explained below.

• Memory

Usually VPC recommends a specific amount of RAM. However, you can override the setting. This setting should be increased only after confirming that the host PC has adequate amount of RAM for supporting the host applications as well as the additional VPC requirements.

• Display

By default, ‘Allow any screen resolution’ is selected. You can change this configuration to various options. You can make the guest resolution to change as per the VPC setting or vice versa. You can also specify that the VPC will start in full screen mode.

• Hard disks

Upto three hard disks can be configured. Hard disks can be of various types.

- Fixed size does not grow automatically

- Dynamically expanding.

- Linked to Hard disk which uses a physical disk

- Differencing disk is a type of virtual disk which is associated with another virtual disk. This is a very nice feature. There is a parent disk and the differencing (child) disk. Parent disk is ideally write protected. The differencing disk records all the changes happening to data on the parent disk. This allows very complex setup scenarios to be connected without repeated loading of the entire VPC.

For example, let us consider we want to test an application on different service pack levels of SQL Server. You can first create a parent disk with Windows 2000 and SQL Server 2000. Now you create separate differencing disks with separate service packs applied to the base parent disk. This way, you don’t need to create multiple full featured VPCs. This is some kind of chaining of the VPC itself.

Performance management

You can improve the performance of the VPC in various ways:

1. Provide maximum possible amount of RAM, without jeopardising the host PC operation.

2. In some cases, the VPC hogs the processor so much the host OS slows down. This can be controlled from VPC Console – File menu – Options – Performance options. Choose “Give processes on Host OS priority” option. The opposite option is to choose “Run VPC at maximum speed” which could be dangerous. You need to test the VPC with this option enabled to ensure that the host pc performance is not hampered.

3. You can also increase the amount of processor time which the active VPC gets compared to the inactive ones.

Summary

As you can see, VPC is a very sophisticated piece of software, not just a utility. I suggest you seriously look at this software when you require a quick setup, multi-configuration testing, or a similar task to be performed.

There are many more areas that I cannot explain due to space constraints. But spend some time on VPC and believe me, it will not be wasted.

About the Author:Dr Nitin Paranjape is the Chairman and MD of Maestros (Mediline). He is a consultant with many organisations, covering appropriate technology utilisation, business application of relevant technology, application architecture and audit as well as knowledge transfer. He has authored more than 650 articles on various technology-related subjects. He can be contacted at nitin@mediline.co.in