How to remove custom script extension for a particular VMSS instance

Question

I am using the below code to remove a custom script extension using powershell for a particular VMSS instance. However, my code fails when retrieving the instance view with Get-AzVmssVM, as the instance ID is alphanumeric rather than numeric.Could you please assist me in obtaining the instance ID in numeric format

# Input Parameters
$ResourceGroupName = "MyResourceGroup" # Replace with your resource group name
$VMScaleSetName = "MyVMSS"            # Replace with your VMSS name
$ExtensionName = "CustomScriptExtension" # Replace with the name of the extension to remove

# Get all VMSS instances
$instances = Get-AzVmssVM -ResourceGroupName $ResourceGroupName -VMScaleSetName $VMScaleSetName

# Loop through each instance
foreach ($instance in $instances) {
    $InstanceId = $instance.InstanceId # InstanceId is often alphanumeric
    $InstanceName = $instance.Name

    Write-Output "Processing Instance ID: $InstanceId, Instance Name: $InstanceName"

    try {
        # Get the instance view to check extensions
        $instanceView = Get-AzVmssVM -ResourceGroupName $ResourceGroupName -VMScaleSetName $VMScaleSetName -InstanceId $InstanceId -InstanceView
        $extensionExists = $instanceView.Extensions | Where-Object { $_.Name -eq $ExtensionName }

        if ($extensionExists) {
            Write-Output "Removing extension '$ExtensionName' from Instance ID: $InstanceId"
            # Remove the extension
            Remove-AzVmssVMExtension -ResourceGroupName $ResourceGroupName -VMScaleSetName $VMScaleSetName -InstanceId $InstanceId -Name $ExtensionName -Force
            Write-Output "Extension '$ExtensionName' removed successfully from Instance ID: $InstanceId"
        } else {
            Write-Output "Extension '$ExtensionName' not found on Instance ID: $InstanceId"
        }
    } catch {
        Write-Output "Error processing Instance ID: $InstanceId. Details: $_"
    }

    Write-Output "--------------------------------------------"
}

I would like to get the instance view using instance Id but Get-AzVmssVM expecting numeric value but I am getting alphanumeric instance Id

Error Msg:Instance view with instance Id

Answer 1

The command Remove-AzVmssVMExtension you are trying for removing the extension is invalid. The correct cmdlet is Remove-AzVmssExtension.You can check MS Doc: Remove-AzVmssExtension

I have a CustomScriptExtension in VMSS before running the script.

Here is the updated PowerShell script to remove the CustomScriptExtension in VMSS.

Note: In flexible mode, each instance has a unique string identifier(venkat-vmss_3d929c9a). This is different from the uniform orchestration mode, where the InstanceId is an integer (starting from 0 and increasing for each instance)

$RGName = "venkat-rg"
$vmssName= "venkatvmss" 
$vmssExtensionName= "CustomScriptExtension"

# Get all VMSS instances
$instances = Get-AzVmssVM -ResourceGroupName $ResourceGroupName -VMScaleSetName $VMScaleSetName

# Loop through each instance
foreach ($instance in $instances) {
    $InstanceId = $instance.InstanceId # InstanceId is often alphanumeric
    $InstanceName = $instance.Name

    Write-Output "Processing Instance ID: $InstanceId, Instance Name: $InstanceName"

    try {
        # Get the instance view to check extensions
        $instanceView = Get-AzVmssVM -ResourceGroupName $ResourceGroupName -VMScaleSetName $VMScaleSetName -InstanceId $InstanceId -InstanceView
        $extensionExists = $instanceView.Extensions | Where-Object { $_.Name -eq $ExtensionName }

        if ($extensionExists) {
            Write-Output "Removing extension '$ExtensionName' from Instance ID: $InstanceId"
            # Remove the extension
            Remove-AzVmssExtension -VirtualMachineScaleSet $vmss -Name $vmssExtensionName 
            Write-Output "Extension '$ExtensionName' removed successfully from Instance ID: $InstanceId"

            Write-Host "Updating the VMSS to reflect the removal of the extension..."

            Update-AzVmss -ResourceGroupName $RGName -Name $vmssName -VirtualMachineScaleSet $vmss
        } else {
            Write-Output "Extension '$ExtensionName' not found on Instance ID: $InstanceId"
        }
    } catch {
        Write-Output "Error processing Instance ID: $InstanceId. Details: $_"
    }

    Write-Output "--------------------------------------------"
}

Output

After running the script, the extension has been uninstalled in VMSS.

Reference: Remove an instance from within a VMSS