Windows Server 2008 Hyper-V: Insiders Guide to Microsoft's Hypervisor by John Kelbley & Mike Sterling & Allen Stewart

Author:John Kelbley & Mike Sterling & Allen Stewart
Language: eng
Format: epub
Publisher: Wiley Publishing, Inc.
Published: 2011-01-06T16:00:00+00:00

Figure 9-4: WMI virtualization provider

Accessing WMI

The key to unlocking the value of WMI is to understand where relevant information may lie. Windows offers more than 100 providers to access system components, including the event log, the Registry, performance counters, and so on. Software developers—including Microsoft—can add new providers, and that is what has been done for Hyper-V. The virtualization WMI provider exposes a rich interface that lets you monitor and control Hyper-V and the virtual environment.

WMI organizes information on a given computer into namespaces. Information about the computer’s hard disk, operating system, hotfixes, and so on, are found in the root\cimV2 namespace. Hyper-V uses the root\virtualization namespace.

Properties of objects that are accessible through WMI (like a VM name) are organized into groups called classes. Hotfixes have a class, processors have a class, and VMs have a class named MSVM_ComputerSystem. There may be one or more instances of an object class. For example, on a system with four VMs, there are four instances of the MSVM_ComputerSystem object, one for each VM (and a fifth for the parent partition).

WMI classes for a provider are commonly accessed via the corresponding namespace. The namespace that corresponds to the classes made available by the virtualization provider is \root\virtualization. Scripting tools access WMI through a WMI scripting library. The WMI scripting library provides the set of script-enabling objects to access the WMI infrastructure.

WMI Security

WMI uses Windows security to validate logon information on local computers and for remote access. WMI enforces security for resources at the level of individual namespaces. For the purposes of all WMI-related examples in this book, it’s assumed that you’ll execute them with full administrative access to the parent partition and the underlying WMI namespaces.

NOTE The security check for WMI occurs only when a user logs in. Changes to user access (including access revocation) take effect the next time a user logs on.

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