PowerShell for Windows Admins

Jul 11 2014   12:39PM GMT

CIM or WMI – – accessing remote machines

Richard Siddaway Richard Siddaway Profile: Richard Siddaway

Tags:
CIM
WMI

I much prefer the CIM cmdlets for accessing remote machines. The WMI cmdlets use DCOM which is firewall unfriendly and can often be unavailable of a server – cue the dreaded RPC server is unavailable error messages.

By contrast the CIM cmdlets use WSMAN.

For one off access to a remote machine use the computername parameter

Get-CimInstance -ClassName Win32_OperatingSystem -ComputerName RSSURFACEPRO2

 

If you want to access a machine multiple times in the session create a CIM session – analagous to a remoting session

 

$cs = New-CimSession -ComputerName RSSURFACEPRO2
Get-CimInstance -ClassName Win32_OperatingSystem -CimSession $cs

 

By default a CIM session uses WSMAN

£> $cs
Id           : 1
Name         : CimSession1
InstanceId   : 30c2b530-4ff7-448e-b68d-1f1282890e6a
ComputerName : RSSURFACEPRO2
Protocol     : WSMAN

 

though you can configure them to use DCOM if need be

$opt = New-CimSessionOption -Protocol DCOM
$csd = New-CimSession -ComputerName RSSURFACEPRO2 -SessionOption $opt
Get-CimInstance -ClassName Win32_OperatingSystem -CimSession $csd

 

When would you need to use DCOM – if you are accessing a machine with PowerShell 2 installed. The CIM cmdlets want to use WSMAN 3 and will error if you access a machine with WSMAN 2 installed however if you include a –Filter they will work

So

Get-CimInstance -ClassName Win32_OperatingSystem -ComputerName computer1

will fail if computer1 is running WSMAN 2 (PowerShell 2)

However, if you change the command to include a filter

Get-CimInstance -ClassName Win32_OperatingSystem -Filter “Manufacturer LIKE ‘Microsoft%'” -ComputerName computer1

 

Even if, as in this case, the filter doesn’t actually do anything

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