Red or blue pill

If you are in the same rabbit-hole as I was of setting up a Windows Service of any form of looping script, there’s two pills you can choose from:

1. Red Pill: Create a program that abide to the law of the fearsome Service Control Manager.

2. Blue Pill: Write a PowerShell script, 8 lines of XML, and download WinSW.exe

WinSW describes itself as following:

A wrapper executable that can run any executable as a Windows service, in a permissive license.

Naturally as someone who enjoys coding with hand grenades, I took the Blue Pill and here’s how that story went:

The Blue Pill

1. Create a new working directory and save it to a variable

$DirParams = @{
    ItemType    = 'Directory'
    Name        = "PowerShell_Service"
    OutVariable = 'WorkingDirectory'
}
New-Item @DirParams

2. Download the latest WinSW-x64.exe to the working directory

# Get the latest WinSW 64-bit executable browser download url
$ExecutableName = 'WinSW-x64.exe'
$LatestURL = Invoke-RestMethod 'https://api.github.com/repos/winsw/winsw/releases/latest'
$LatestDownloadURL = ($LatestURL.assets | Where-Object {$_.Name -eq $ExecutableName}).browser_download_url
$FinalPath = "$($WorkingDirectory.FullName)\$ExecutableName"

# Download it to the newly created working directory
Invoke-WebRequest -Uri $LatestDownloadURL -Outfile $FinalPath -Verbose

3. Create the PowerShell script which the service runs

This loop checks for notepad every 5 sec and kills it if it finds it

while ($true) {
    $notepad = Get-Process notepad -ErrorAction SilentlyContinue
    if ($notepad) {
        $notepad.Kill()
    }
    Start-Sleep -Seconds 5
}

4. Construct the .XML file

Just edit the id, name, description and startarguments

<service>
  <id>PowerShellService</id>
  <name>PowerShellService</name>
  <description>This service runs a custom PowerShell script.</description>
  <executable>C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe</executable>
  <startarguments>-NoLogo -file C:\Path\To\Script\Invoke-PowerShellServiceScript.ps1</startarguments>
  <log mode="roll"></log>
</service>

Save the .xml, in this example I saved it as PowerShell_Service.xml

# if not already, step into the workingdirectory
cd $WorkingDirectory.FullName

# Install the service
.\WinSW-x64.exe install .\PowerShell_Service.xml

# Make sure powershell.exe's executionpolicy is Bypass
Set-ExecutionPolicy -ExecutionPolicy Bypass -Scope LocalMachine

# As an administrator
Get-Service PowerShellService | Start-Service

Conclusion

Running a PowerShell script as a service on any windows machine isn’t that complicated thanks to WinSW. It’s a great choice if you don’t want to get deeper into the process of developing windows services (it’s kind of a fun rabbit-hole though).

I recommend reading docs of WinSW.

Some things to consider:

• The service will run PowerShell 5.1 as System
• Meaning the executionpolicy must be supporting that usecase (bypass as local machine will do)
• The script in this example is just a demo of a loop, but anything you can think of that loops will do here
• Starting the Service requires elevated rights in this example
• If you get the notorious The service did not respond to the start or control request in a timely fashion, you have my condolences (This is a very general error msg that has no clear answer by itself it seems)

Good luck have fun, happy coding

/Emil