Tuesday, March 22, 2011

Scheduling Tasks in PowerShell for Windows Server 2008 -- Part 3: Daily Tasks

In my previous blog posts, "Scheduling Tasks in PowerShell for Windows Server 2008 -- Part 1: Monthly Task" and "Scheduling Tasks in PowerShell for Windows Server 2008 -- Part 2: Weekly Tasks", I explored the various settings required for scheduled tasks for those given date ranges. This post deals with the daily reoccurring tasks that administrators need to schedule, sometimes more than once a day. In the code sample below, I schedule a fictitious log cleanup PowerShell script to run three times a day; midnight, 8 am and 4 pm. For security reasons, after running this script, you should close the PowerShell command window as the password submitted for the Task Security Principal will remain in the command buffer allowing anyone with access to your keyboard to "up arrow" and reveal it.
# Parameters to modify
$taskName = "Start-TriDailyLogCleanup"
$taskWorkingDirectory = "C:\PowerShell"
$taskPath = "%SystemRoot%\system32\WindowsPowerShell\v1.0\powershell.exe"
$taskArguments = "-command `"$taskWorkingDirectory\$taskName.ps1`""
$taskAuthor = "ad\myaccount"
$taskDescription = "The Tri-Daily Log Cleanup on the servers."
$taskSecurityPrincipal = "ad\maintenance"
$taskShedulerTaskFolder = "\MyTasks"
$startTimes = @((Get-Date "03/23/2011 00:00:00" -Format s),(Get-Date "03/23/2011 08:00:00" -Format s),(Get-Date "03/23/2011 16:00:00" -Format s))

# Would like to use -asSecureString but RegisterTaskDefinition does not accept it
# Look over your shoulder before typing
$password = Read-Host -prompt "$taskSecurityPrincipal Password"

# The meaty parts

$taskService = New-Object -ComObject Schedule.Service

$rootFolder = $taskService.GetFolder($taskShedulerTaskFolder)

$taskDefinition = $taskService.NewTask(0)

$registrationInformation = $taskDefinition.RegistrationInfo
$registrationInformation.Description = $taskDescription
$registrationInformation.Author = $taskAuthor

$taskPrincipal = $taskDefinition.Principal
$taskPrincipal.LogonType = 1
$taskPrincipal.UserID = $taskSecurityPrincipal
$taskPrincipal.RunLevel = 0

$taskSettings = $taskDefinition.Settings
$taskSettings.StartWhenAvailable = $true
$taskSettings.RunOnlyIfNetworkAvailable = $true
$taskSettings.Priority = 7
$taskSettings.ExecutionTimeLimit = "PT2H"

$taskTriggers = $taskDefinition.Triggers

foreach($startTime in $startTimes) {
	$executionTrigger = $taskTriggers.Create(2) 
	$executionTrigger.StartBoundary = $startTime

$taskAction = $taskDefinition.Actions.Create(0)
$taskAction.Path = $taskPath
$taskAction.Arguments = $taskArguments
$taskAction.WorkingDirectory = $taskWorkingDirectory

# 6 == Task Create or Update
# 1 == Password must be supplied at registration
$rootFolder.RegisterTaskDefinition($taskName, $taskDefinition, 6, $taskSecurityPrincipal, $password, 1)

# Since we captured this in plain text I am going to nuke the value
# Not 100% security. Close the PowerShell command window to increase security.
Clear-Variable -name password

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