Richard Siddaway's Blog

It’s not often I come across soemthing brand new in PowerShell but yesterday when I was investigating New-CimInstance I discovered 2 cmdlets in the CimCmdlets module I hadn’t noticed before. These are:

Export-BinaryMiLog

Import-BinaryMiLog

 

The cmdlets are used to export, or import, CIM instances as a binary encoded file.  Think of them as  Export-Clixml and Import-Clixml but for CIM instances.

Their usage is very simple:

Get-CimInstance -ClassName Win32_OperatingSystem |
Export-BinaryMiLog -Path testfile.bmil

 

This creates a   30 KB binary file – its definitely not human readable!

You don’t need to use a bmil extension (its the one in the help file) and you can use a CIM instance object instead of the pipeline

$os = Get-CimInstance -ClassName Win32_OperatingSystem
Export-BinaryMiLog -InputObject $os -Path testfile2.stuff

 

Getting the data back is performed by Import-BinaryMiLog

$os1 = Import-BinaryMiLog -Path .\testfile.bmil
$os2 = Import-BinaryMiLog -Path .\testfile2.stuff

 

The results appear to be a standard CIM object

Compare-Object -ReferenceObject $os -DifferenceObject $os1 -IncludeEqual
Compare-Object -ReferenceObject $os -DifferenceObject $os2 -IncludeEqual
Compare-Object -ReferenceObject $os1 -DifferenceObject $os2 –IncludeEqual

 

These cmdlets give you way to persist CIM objects to disk so that they can be referenced at a later date. If you need to test for changes to a system this could be a useful technique

I was asked a question about the –Key parameter on New-CimInstance today. I wasn’t sure of the answer so I’ve done some experimentation.

 

I tend to avoid New-CimInstance if I can preferring to use the Create method on the CIM class – however not all CIM classes have a create method so need to fall back on New-CimInstance.

 

I started by looking at the documentation. The help file for New-CimInstance says:

-Key<String[]>

Specifies the properties that are used as keys. CimSession and ComputerName cannot be used when Key is specified.

 

That then leads to the question how do I discover the Key or Keys of a CIM class.  You can’t use the –Qualifier parameter in Get-CimClass because that works at the class level and Key is a property qualifier.  Means you need to use some code

function Get-CimClassKey { 

    param (
   
        [string]$CIMnamespace = 'ROOT/cimv2',
       
        [string]$CIMclass
   
    )

    $class = Get-CimClass -Namespace $CIMnamespace -ClassName $CIMclass

    foreach ($property in $class.CimClassProperties) {
 
        $property | Select-Object -ExpandProperty Qualifiers |
        foreach {
            if ($_.Name -eq 'key'){
                $property
            }
        }

    }
}

 

The Key property of a class HAS to be given a value when a new instance of the class is created.

 

The New-CimInstance help file shows an example using Win32_Environment.  Adapring the example:

PS> New-CimInstance -ClassName Win32_Environment @{Name='RStest1'; VariableValue='test1'; UserName='RSSURFACEPRO2\Richard'}

Name             UserName                                            VariableValue
----             --------                                            -------------
RStest1          RSSURFACEPRO2\Richard                               test1

Using our function to discover the Keys of Win32_Environment

PS> Get-CimClassKey -CIMclass Win32_Environment

Name               : Name
Value              :
CimType            : String
Flags              : Property, Key, NullValue
Qualifiers         : {read, key, MappingStrings, Override...}
ReferenceClassName :

Name               : UserName
Value              :
CimType            : String
Flags              : Property, Key, ReadOnly, NullValue
Qualifiers         : {key, MappingStrings, MaxLen, read}
ReferenceClassName :

 

Adding the –Key parameter

PS> New-CimInstance -ClassName Win32_Environment @{Name='RStest2'; VariableValue='test2'; UserName='RSSURFACEPRO2\Richard'} -Key 'Name', 'UserName'

Name             UserName                                            VariableValue
----             --------                                            -------------
RStest2          RSSURFACEPRO2\Richard                               test2

 

Using Win32_Environment you can use the Key parameter, or not, as long as you define values for the Name and Username properties.

Another example in the New-CimInstance help file uses the Win32_Process class.  The key for that class is the Handle property

PS> Get-CimClassKey -CIMclass Win32_process

Name               : Handle
Value              :
CimType            : String
Flags              : Property, Key, ReadOnly, NullValue
Qualifiers         : {key, MaxLen, read}
ReferenceClassName :

 

the Handle is appears to be identical to the ProcessId in value as far as I can determine

 

This now gets  messy:

 

Just the Handle.  BTW exmple 3 in the documentation has an error as Handle is a string not an integer

PS> New-CimInstance -ClassName Win32_Process -Property @{Handle='0'}
New-CimInstance : Provider is not capable of the attempted operation
At line:1 char:1
+ New-CimInstance -ClassName Win32_Process -Property @{Handle='0'}
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (Win32_Process:CimInstance) [New-CimInstance], CimException
    + FullyQualifiedErrorId : HRESULT 0x80041024,Microsoft.Management.Infrastructure.CimCmdlets.NewCimInstanceCommand

 

Add the Key parameter

PS> New-CimInstance -ClassName Win32_Process -Property @{Handle='0'} -Key Handle
New-CimInstance : Provider is not capable of the attempted operation
At line:1 char:1
+ New-CimInstance -ClassName Win32_Process -Property @{Handle='0'} -Key ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (Win32_Process (Handle = "0"):CimInstance) [New-CimInstance], CimException
    + FullyQualifiedErrorId : HRESULT 0x80041024,Microsoft.Management.Infrastructure.CimCmdlets.NewCimInstanceCommand

 

The only way it works is if you use –ClientOnly to make an in memory CIM instance that only exists in your PowerShell session

PS> New-CimInstance -ClassName Win32_Process -Property @{Handle='0'} -Key Handle -ClientOnly

Handle PSComputerName
------ --------------
0

 

You can remove the –Key parameter

PS> New-CimInstance -ClassName Win32_Process -Property @{Handle='0'} -ClientOnly

Handle PSComputerName
------ --------------
0

 

Win32_Process has a Create method that takes these parameters

PS> $class.CimClassMethods['Create'].Parameters

Name                       CimType Qualifiers                                 ReferenceClassName
----                                 ------- ----------                                 ------------------
CommandLine                 String {ID, In, MappingStrings}
CurrentDirectory            String {ID, In, MappingStrings}
ProcessStartupInformation Instance {EmbeddedInstance, ID, In, MappingStrings}
ProcessId                   UInt32 {ID, MappingStrings, Out}

 

Using Invoke-CimMethod

PS> Invoke-CimMethod -ClassName Win32_Process -MethodName Create -Arguments @{CommandLine='notepad.exe'}

ProcessId ReturnValue PSComputerName
--------- ----------- --------------
     2648           0

 

Now trying New-CimInstance

PS> New-CimInstance -ClassName Win32_Process -Property @{Handle='0'; CommandLine='notepad.exe'} -Key Handle
New-CimInstance : Provider is not capable of the attempted operation
At line:1 char:1
+ New-CimInstance -ClassName Win32_Process -Property @{Handle='0'; Comm ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (Win32_Process (Handle = "0"):CimInstance) [New-CimInstance], CimException
    + FullyQualifiedErrorId : HRESULT 0x80041024,Microsoft.Management.Infrastructure.CimCmdlets.NewCimInstanceCommand

 

Other variants of not including the Handle property and changing the handle value all fail with same error

 

Botton line is that New-CimInstance is a bit of a mess to use – with or without the –Key parameter (which doesn’t seem to do much).

 

If the CIM class hasa create method Id recommend that you use that as a lot of CIm classes (or their providers) don’t work with New-cimInstance. In reality given that many of the CIM classes are effectively read only – you can’t create a new instance of Win32_ComputerSystem for example – it probably doesn’t matter.