CODEWITHSUNDEEP
powershellwmi
Brian Duffy
Brian Duffy

Reputation: 162

Starting and stopping a remote service using WMI and Start-Job

Why does this work:

$bits = Get-WmiObject -Class win32_service -ComputerName computer -Credential $creds | 
? name -Like "bits*"

$bits.StopService()

but with this

$bits = Get-WmiObject -Class win32_service -ComputerName computer -Credential $creds | 
? name -Like "bits*"

$stopbits = Start-Job {$bits.StopService()}

I get an error "You cannot call a method on a null-valued expression"

I'm trying to write a script that will stop a set of services in a set order. I only have WMI available to me. By using Start-Job I want to then use 

$stopbits = Start-Job {$bits.StopService()}
Wait-Job -Id $stopbits.id

before going to the next service. I am a powershell beginner so I could be going about this all wrong. I would appreciate any help on getting this to work. Thank you!

Upvotes: 1

Views: 1565

Answers (3)

Sunny Chakraborty
Sunny Chakraborty

Reputation: 405

You need to invoke WMI Method called StopService to execute the job. Something like this.

$stopbits = Start-Job {
  $bits.InvokeMethod("StopService",$null)
}

On second thoughts, the above code won't work too as $bits object is not defined in the local scope. So you need to do this.

$global:creds = Get-credential
$stopbits = Start-Job {
  $bits = Get-WmiObject `
    -Class win32_service `
    -ComputerName $computer `
    -Credential $global:creds | 
      where name -Like "bits*"
  $bits.StopService()
}

Upvotes: 0

Dennis
Dennis

Reputation: 1790

In PowerShell 7.x, WMI isn't supported any more. In that case you'd need to use CIM instead. Besides, using CIM has a bunch of advantages (and some disadvantages).

$Creds = Get-Credential

$Bits = Get-CimInstance `
  -Class Win32_Service `
  -ComputerName 'computer' `
  -Credential $Creds `
  -Filter 'Name LIKE "bits%"' 

Start-Job {
  $Using:Bits | Invoke-CimMethod -MethodName StopService
} | Receive-Job -Wait

Ref 1: MS DevBlogs - Should I use CIM or WMI with Windows PowerShell?
Ref 2: MS Learn - Getting WMI objects with Get-CimInstance

Upvotes: 0

Mike Shepard
Mike Shepard

Reputation: 18176

The $bits variable isn't defined in the scope of the background job.

Upvotes: 0

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