about_WMI_Cmdlets | Easy Powershell 2.0 Reference

TOPIC
about_WMI_Cmdlets

SHORT DESCRIPTION
Provides background information about Windows Management Instrumentation
(WMI) and Windows PowerShell.

LONG DESCRIPTION
    This topic provides information about WMI technology, the WMI cmdlets for
    Windows PowerShell, WMI-based remoting, WMI accelerators,
    and WMI troubleshooting. This topic also provides links to more information
    about WMI.

About WMI

     Windows Management Instrumentation (WMI) is the Microsoft implementation
     of Web-Based Enterprise Management (WBEM), which is an industry
     initiative to develop a standard technology for accessing management
     information in an enterprise Environment. WMI uses the Common Information
     Model (CIM) industry standard to represent systems, applications,
     networks, devices, and other managed components. CIM is developed and
     maintained by the Distributed Management Task Force (DMTF). You can use
     WMI to manage both local and remote computers. For example, you can use
     WMI to do the following:

— Start a process on a remote computer.

— Restart a computer remotely.

— Get a list of the applications that are installed on a local or
remote computer.

— Query the Windows event logs on a local or remote computer.

The WMI Cmdlets for Windows PowerShell

     Windows PowerShell implements WMI Functionality through a set of cmdlets
     that are available in Windows PowerShell by default. You can use these
     cmdlets to complete the end-to-end tasks necessary to manage local and
     remote computers.

The following WMI cmdlets are included.

     Cmdlet                 Description
     ——————     ———————————————-
     Get-WmiObject         Gets instances of WMI classes or information
                             about the available classes.

Invoke-WmiMethod Calls WMI methods.

Remove-WmiObject Deletes WMI classes and instances.

Set-WmiInstance Creates or modifies instances of WMI classes.

Sample Commands

The following command displays the BIOS information for the local
computer.

C:\PS> Get-WmiObject win32_bios | Format-List *

The following command displays information about the WinRM service
for three remote computers.

C:\PS> Get-WmiObject -query “select * from win32_service where name=’WinRM'” -computername server01, server01, server03

The following more complex command exits all instances of a program.

         C:\PS> notepad.exe
         C:\PS> $np = Get-WmiObject -query “select * from win32_process where name=’notepad.exe'”
         C:\PS> $np | Remove-WmiObject

WMI-Based Remoting

     While the ability to manage a local system through WMI is useful, it is
     the remoting capabilities that make WMI a powerful administrative tool.
     WMI uses Microsoft’s Distributed Component Object Model (DCOM) to
     connect to and manage systems. You might have to configure some systems
     to allow DCOM connections. Firewall settings and locked-down DCOM
     permissions can block WMI’s ability to remotely manage systems.

WMI Type Accelerators

     Windows PowerShell includes WMI type accelerators. These WMI type
     accelerators (shortcuts) allow more direct access to a WMI objects
     than a non-type accelerator approach would allow.

The following type accelerators are supported with WMI:

[WMISEARCHER] – A shortcut for searching for WMI objects.

[WMICLASS] – A shortcut for accessing the static properties
and methods of a class.

[WMI] – A shortcut for getting a single instance of a class.

     [WMISEARCHER] is a type accelerator for a ManagementObjectSearcher.
     It can take a string constructor to create a searcher that you can then
     do a GET() on.

For example:

PS> $s = [WmiSearcher]’Select * from Win32_Process where Handlecount > 1000′
PS> $s.Get() |sort handlecount |ft handlecount,__path,name -auto

     handlecount __PATH                                             name
     ———– ——                                             —-
     1105         \\SERVER01\root\cimv2:Win32_Process.Handle=”3724″ powershell…
     1132         \\SERVER01\root\cimv2:Win32_Process.Handle=”1388″ winlogon.exe
     1495         \\SERVER01\root\cimv2:Win32_Process.Handle=”2852″ iexplore.exe
     1699         \\SERVER01\root\cimv2:Win32_Process.Handle=”1204″ OUTLOOK.EXE
     1719         \\SERVER01\root\cimv2:Win32_Process.Handle=”1912″ iexplore.exe
     2579         \\SERVER01\root\cimv2:Win32_Process.Handle=”1768″ svchost.exe

     [WMICLASS] is a type accelerator for ManagementClass. This has a
     string constructor that takes a local or absolute WMI path to a WMI
     class and returns an object that is bound to that class.

For example:

     PS> $c = [WMICLASS]”root\cimv2:WIn32_Process”
     PS> $c |fl *
     Name             : Win32_Process
     __GENUS         : 1
     __CLASS         : Win32_Process
     __SUPERCLASS     : CIM_Process
     __DYNASTY        : CIM_ManagedSystemElement
     __RELPATH        : Win32_Process
     __PROPERTY_COUNT : 45
     __DERIVATION     : {CIM_Process, CIM_LogicalElement, CIM_ManagedSystemElement}
     __SERVER         : SERVER01
     __NAMESPACE     : ROOT\cimv2
     __PATH         : \\SERVER01\ROOT\cimv2:Win32_Process

     [WMI] is a type accelerator for ManagementObject. This has a string
     constructor that takes a local or absolute WMI path to a WMI instance
     and returns an object that is bound to that instance.

For example:

     PS> $p = [WMI]’\\SERVER01\root\cimv2:Win32_Process.Handle=”1204″‘
     PS> $p.Name
     OUTLOOK.EXE

WMI Troubleshooting

The following problems are the most common problems that might occur
when you try to connect to a remote computer.

Problem 1: The remote computer is not online.

If a computer is offline, you will not be able to connect to it by
using WMI. You may receive the following error message:

“Remote server machine does not exist or is unavailable”

If you receive this error message, verify that the computer is online.
Try to ping the remote computer.

Problem 2: You do not have local administrator rights on the remote
computer.

To use WMI remotely, you must have local administrator rights on the
remote computer. If you do not, access to that computer will be denied.

To verify namespace security:

a. Click Start, right-click My Computer, and then click Manage.

b. In Computer Management, expand Services and Applications,
right-click WMI Control, and then click Properties.

c. In the WMI Control Properties dialog box, click the Security tab.

Problem 3: A firewall is blocking access to the remote computer.

     WMI uses the DCOM (Distributed COM) and RPC (Remote Procedure Call)
     protocols to traverse the network. By default, many firewalls block
     DCOM and RPC traffic. If your firewall is blocking these protocols,
     your connection will fail. For example, Windows Firewall in Microsoft
     Windows XP Service Pack 2 is configured to automatically block all
     unsolicited network traffic, including DCOM and WMI. In its default
     configuration, Windows Firewall rejects an incoming WMI request, and
     you receive the following error message:

“Remote server machine does not exist or is unavailable”

More Information about WMI

For more information about WMI, see the following topics in the MSDN
(Microsoft Developer Network) library:

“About WMI:
http://go.microsoft.com/fwlink/?LinkId=142212

“WMI Troubleshooting”
http://go.microsoft.com/fwlink/?LinkId=142213

And, see “Secrets of Windows Management Instrumentation – Troubleshooting
and Tips” in the Microsoft TechNet Script Center:

http://go.microsoft.com/fwlink/?LinkId=142214

SEE ALSO
    Online version: http://go.microsoft.com/fwlink/?LinkId=142219
    Get-WmiObject
    Invoke-WmiMethod
    Register-WmiEvent
    Remove-WmiObject
    Set-WmiInstance