Powershell security get-service different results interactive vs scheduled-task - powershell

Question

I've spent hours trying to pin down this problem. I'm running a PowerShell to verify if various services are running. I want to run it every 5 minutes from Windows Task Scheduler.
It checks services on other servers, and some on the same machine on which it is running. When I run it under task scheduler, under the same userid that I'm running interactive I get different results. Interactively, shows all the services on local machine are running. When run through task scheduler, it tells me that service is not found.
This is just a fragment of a larger program. I get the server/service names from a CSV file, then at the end it sends a nice HTML email. I added the Add-Content to create a trace file to prove this happening.
foreach ($line in $csv) {
$reportStatus = ""
$ServerCount = $ServerCount + 1
#$Service = (get-service -Name $line.ServiceName -ComputerName $line.ServerName)
#this is slower than above, but it gives us the processId which we can use to find out what time the service/process started
write-host "Verifying: " $line.ServerName $line.ServiceName
$myDate = Get-Date
Add-Content D:\scripts\ServiceMonitorTrace.txt "$myDate $($line.ServerName) $($line.ServiceName)"
$Service = (get-wmiobject win32_service -ComputerName $line.ServerName -filter "name = '$($line.ServiceName)'")
if ($Service -eq $null)
{
$reportStatus = "Service Not Found: name = '$($line.ServiceName)'"
$trColor = "Yellow"
$ErrorCount = $ErrorCount + 1
$CriticalErrorCount = $CriticalErrorCount + 1
$CreationDate = "NA"
Write-Host "----> $reportStatus "
Add-Content D:\scripts\ServiceMonitorTrace.txt "$myDate $reportStatus"
}
}
New Simpler Version (has exact same issue):
$Service = (get-wmiobject win32_service -ComputerName "DAL-BIZ-APP01" -filter "name = 'LanManServer'")
if ($Service -eq $null)
{
$reportStatus = "Service not found"
}
else
{
$reportStatus = "Service found"
}
$myDate = Get-Date
Write-Host $reportStatus
Add-Content D:\scripts\ServiceTestTrace.txt "$myDate $reportStatus"
Interactive Results:
10/31/2013 09:34:00 DAL-BIZ-APP01 MSDTC
10/31/2013 09:34:00 DAL-BIZ-APP01 BTSSvc$BizTalkHost_QT_Default
Scheduled Job Results:
10/31/2013 09:25:42 DAL-BIZ-APP01 MSDTC
10/31/2013 09:25:42 Service Not Found: name = 'MSDTC'
10/31/2013 09:25:42 DAL-BIZ-APP01 BTSSvc$BizTalkHost_QT_Default
I run it from a command file that contains this:
powershell -command "& 'D:\Scripts\ServerMonitor.ps1'" d:\Scripts\ServerMonitorConfig.csv
Running the command file from a non-admin command prompt window or the scheduler also seems to have different results.
New Simpler Version if someone want to try, just substitute two computer names:
$Service = (get-wmiobject win32_service -ComputerName "DAL-BIZ-APP01" -filter "name = 'LanManServer'")
if ($Service -eq $null)
{
$reportStatus = "Service not found"
}
else
{
$reportStatus = "Service found"
}
$myDate = Get-Date
Write-Host $reportStatus
Add-Content D:\scripts\ServiceTestTrace.txt "$myDate DAL-BIZ-APP01 $reportStatus"
$Service = (get-wmiobject win32_service -ComputerName "DAL-BIZ-APP02" -filter "name = 'LanManServer'")
if ($Service -eq $null)
{
$reportStatus = "Service not found"
}
else
{
$reportStatus = "Service found"
}
$myDate = Get-Date
Write-Host $reportStatus
Add-Content D:\scripts\ServiceTestTrace.txt "$myDate DAL-BIZ-APP02 $reportStatus"
Results:
10/31/2013 16:07:48 DAL-BIZ-APP01 Service found
10/31/2013 16:07:48 DAL-BIZ-APP02 Service found
10/31/2013 16:08:03 DAL-BIZ-APP01 Service not found
10/31/2013 16:08:03 DAL-BIZ-APP02 Service found
16:07:48 was from command prompt, 16:08:03 was from task scheduler.

Answer 1

I added this to code:
if ($error -ne $null)
{
Write-Host "----> $($error[0].Exception) "
Add-Content $TraceFilename "$myDate TRCE1 $($error[0].Exception)"
}
Now I'm able to see the reason that was getting swallowed:
11/13/2013 11:35:37 TRCE1 System.Management.ManagementException:
Access denied at System.Management.ManagementException.ThrowWithExtendedInfo(ManagementStatus
errorCode) at
System.Management.ManagementObjectCollection.ManagementObjectEnumerator.MoveNext()
at Microsoft.PowerShell.Commands.GetWmiObjectCommand.BeginProcessing()
I have not yet figured out the "Access Denied", but at least I'm happy I see the true error now, i.e. the reason the result of "get-wmiobject win32_service..." was null.
I'm following up with the "Access Denied" in a new thread here:
Access Denied - get-wmiobject win32_service (Powershell)