Manage pre and post-scripts

Pre-scripts and post-scripts let you run PowerShell runbooks in your Azure Automation account before (pre-task) and after (post-task) an update deployment. Pre and post-scripts run in the Azure context, not locally. Pre-scripts run at the beginning of the update deployment. Post-scripts run at the end of the deployment and after any reboots that are configured.

Runbook requirements

For a runbook to be used as a pre or post-script, the runbook must be imported into your Automation account and published. To learn more about this process, see Publish a runbook.

Using a pre-script or post-script

To use a pre-script or post-script in an update deployment, start by creating an update deployment. Select Pre-scripts + Post-Scripts. This action opens the Select Pre-scripts + Post-scripts page.

Select scripts

Select the script you want to use. In this example, we use the UpdateManagement-TurnOnVms runbook. When you select the runbook, the Configure Script page opens. Select Pre-Script, and then select OK.

Repeat this process for the UpdateManagement-TurnOffVms script. But when you choose the Script type, select Post-Script.

The Selected items section now shows both your scripts selected. One is a pre-script and the other is a post-script:

Selected items

Finish configuring your update deployment.

When your update deployment is complete, you can go to Update deployments to view the results. As you can see, the status is provided for the pre-script and post-script:

Update results

By selecting the update deployment run, you're shown additional details to the pre and post-scripts. A link to the script source at the time of the run is provided.

Deployment run results

Passing parameters

When you configure pre and post-scripts, you can pass in parameters just like scheduling a runbook. Parameters are defined at the time of update deployment creation. Pre and post-scripts support the following types:

  • [char]
  • [byte]
  • [int]
  • [long]
  • [decimal]
  • [single]
  • [double]
  • [DateTime]
  • [string]

If you need another object type, you can cast it to another type with your own logic in the runbook.

In addition to your standard runbook parameters, another parameter is provided: SoftwareUpdateConfigurationRunContext

This parameter is a JSON string, and if you define the parameter in your pre or post-script, it's automatically passed in by the update deployment. The parameter contains information about the update deployment, which is a subset of information returned by the SoftwareUpdateconfigurations API.

The following table shows you the properties that are provided in the variable.

SoftwareUpdateConfigurationRunContext properties

Property Description
SoftwareUpdateConfigurationName The name of the software update configuration.
SoftwareUpdateConfigurationRunId The unique ID for the run.
SoftwareUpdateConfigurationSettings A collection of properties related to the software update configuration.
SoftwareUpdateConfigurationSettings.operatingSystem The operating systems targeted for the update deployment.
SoftwareUpdateConfigurationSettings.duration The maximum duration of the update deployment run as PT[n]H[n]M[n]S as per ISO8601; also called the maintenance window.
SoftwareUpdateConfigurationSettings.Windows A collection of properties related to Windows computers.
SoftwareUpdateConfigurationSettings.Windows.excludedKbNumbers A list of KBs that are excluded from the update deployment.
SoftwareUpdateConfigurationSettings.Windows.includedUpdateClassifications Update classifications selected for the update deployment.
SoftwareUpdateConfigurationSettings.Windows.rebootSetting Reboot settings for the update deployment.
azureVirtualMachines A list of resourceIds for the Azure VMs in the update deployment.
nonAzureComputerNames A list of the non-Azure computers FQDNs in the update deployment.

The following example is a JSON string passed in to the SoftwareUpdateConfigurationRunContext parameter:

"SoftwareUpdateConfigurationRunContext":{
      "SoftwareUpdateConfigurationName":"sampleConfiguration",
      "SoftwareUpdateConfigurationRunId":"00000000-0000-0000-0000-000000000000",
      "SoftwareUpdateConfigurationSettings":{
         "operatingSystem":"Windows",
         "duration":"PT2H0M",
         "windows":{
            "excludedKbNumbers":[
               "168934",
               "168973"
            ],
            "includedUpdateClassifications":"Critical",
            "rebootSetting":"IfRequired"
         },
         "azureVirtualMachines":[
            "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myresources/providers/Microsoft.Compute/virtualMachines/vm-01",
            "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myresources/providers/Microsoft.Compute/virtualMachines/vm-02",
            "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myresources/providers/Microsoft.Compute/virtualMachines/vm-03"
         ],
         "nonAzureComputerNames":[
            "box1.contoso.com",
            "box2.contoso.com"
         ]
      }
   }

A full example with all properties can be found at: Get software update configuration by name.

Note

The SoftwareUpdateConfigurationRunContext object can contain duplicate entries for machines. This can cause pre and post-scripts to run multiple times on the same machine. To work around this behavior, use Sort-Object -Unique to select only unique VM names in your script.

Stopping a deployment

If you want to stop a deployment based on a pre-script, you must throw an exception. If you don't, the deployment and post-script will still run. The following code snippet shows how to throw an exception.

#In this case, we want to terminate the patch job if any run fails.
#This logic might not hold for all cases - you might want to allow success as long as at least 1 run succeeds
foreach($summary in $finalStatus)
{
    if ($summary.Type -eq "Error")
    {
        #We must throw in order to fail the patch deployment.
        throw $summary.Summary
    }
}

Samples

Samples for pre and post-scripts can be found in the Script Center Gallery and the PowerShell Gallery, or you can import them through the Azure portal. To do that, in your Automation account, under Process Automation, select Runbooks Gallery. Use Update Management for the filter.

Gallery list

Or you can search for them by their script name, as shown in the following list:

  • Update Management - Turn On VMs
  • Update Management - Turn Off VMs
  • Update Management - Run Script Locally
  • Update Management - Template for Pre/Post Scripts
  • Update Management - Run Script with Run Command

Important

After you import the runbooks, you must publish them before they can be used. To do that, find the runbook in your Automation account, select Edit, and then select Publish.

The samples are all based on the basic template that's defined in the following example. This template can be used to create your own runbook to use with pre and post-scripts. The necessary logic for authenticating with Azure and handling the SoftwareUpdateConfigurationRunContext parameter is included.

<#
.SYNOPSIS
 Barebones script for Update Management Pre/Post

.DESCRIPTION
  This script is intended to be run as a part of Update Management pre/post-scripts.
  It requires a RunAs account.

.PARAMETER SoftwareUpdateConfigurationRunContext
  This is a system variable which is automatically passed in by Update Management during a deployment.
#>

param(
    [string]$SoftwareUpdateConfigurationRunContext
)
#region BoilerplateAuthentication
#This requires a RunAs account
$ServicePrincipalConnection = Get-AutomationConnection -Name 'AzureRunAsConnection'

Add-AzureRmAccount `
    -ServicePrincipal `
    -TenantId $ServicePrincipalConnection.TenantId `
    -ApplicationId $ServicePrincipalConnection.ApplicationId `
    -CertificateThumbprint $ServicePrincipalConnection.CertificateThumbprint

$AzureContext = Select-AzureRmSubscription -SubscriptionId $ServicePrincipalConnection.SubscriptionID
#endregion BoilerplateAuthentication

#If you wish to use the run context, it must be converted from JSON
$context = ConvertFrom-Json  $SoftwareUpdateConfigurationRunContext
#Access the properties of the SoftwareUpdateConfigurationRunContext
$vmIds = $context.SoftwareUpdateConfigurationSettings.AzureVirtualMachines | Sort-Object -Unique
$runId = $context.SoftwareUpdateConfigurationRunId

Write-Output $context

#Example: How to create and write to a variable using the pre-script:
<#
#Create variable named after this run so it can be retrieved
New-AzureRmAutomationVariable -ResourceGroupName $ResourceGroup –AutomationAccountName $AutomationAccount –Name $runId -Value "" –Encrypted $false
#Set value of variable
Set-AutomationVariable –Name $runId -Value $vmIds
#>

#Example: How to retrieve information from a variable set during the pre-script
<#
$variable = Get-AutomationVariable -Name $runId
#>

Interacting with machines

Pre and post-tasks run as a runbook in your Automation account and not directly on the machines in your deployment. Pre and post-tasks also run in the Azure context and don't have access to non-Azure machines. The following sections show how you can interact with the machines directly, whether they're Azure VMs or non-Azure machines.

Interacting with Azure machines

Pre and post-tasks are run as runbooks and don't natively run on your Azure VMs in your deployment. To interact with your Azure VMs, you must have the following items:

  • A Run As account
  • A runbook you want to run

To interact with Azure machines, you should use the Invoke-AzureRmVMRunCommand cmdlet to interact with your Azure VMs. For an example of how to do this, see the runbook example Update Management – run script with Run command.

Interacting with non-Azure machines

Pre and post-tasks run in the Azure context and don't have access to non-Azure machines. To interact with the non-Azure machines, you must have the following items:

  • A Run As account
  • Hybrid Runbook Worker installed on the machine
  • A runbook you want to run locally
  • A parent runbook

To interact with non-Azure machines, a parent runbook is run in the Azure context. This runbook calls a child runbook with the Start-AzureRmAutomationRunbook cmdlet. You must specify the -RunOn parameter and provide the name of the Hybrid Runbook Worker for the script to run on. For more info, see the runbook example Update Management – run script locally.

Abort patch deployment

If your pre-script returns an error, you might want to abort your deployment. To do that, you must throw an error in your script for any logic that would constitute a failure.

if (<My custom error logic>)
{
    #Throw an error to fail the patch deployment.
    throw "There was an error, abort deployment"
}

Known issues

  • You can't pass a boolean, objects, or arrays to parameters when you're using pre and post-scripts. If you do, the runbook fails. For a complete list of supported types, see Passing parameters.

Next steps

Go on to the following tutorial to learn how to manage updates for your Windows virtual machines: