Globally Unique Identifiers - Creating GUIDs in Powershell

Powershell Pea...

New-Guid

I've been working more and more with Powershell, specifically with Azure Automation and scripting and wanted to share a useful Cmdlet for creating GUIDs. This link provides more detail, but ultimately this command will provide you with a unique ID that can be assigned to arbitrary objects that require a unique ID.

Bear in mind that this doesn't protect you from duplicates, but the probability of them occurring is small. So if you need GUIDs for relatively small record/object sets and your application can handle the prospect of duplicates, then this function is a quick way to generate a "unique" ID.

See this link for more details on GUIDs/UUIDs.

Azure Premium Storage Blob Snapshot Error - 409 Conflict

I've recently been working in more detail with Azure blob snapshots and (by trial and error) discovered that Premium storage imposes limitations on the number and frequency of snapshots that can be performed on a single blob.

If you create a snapshot of a Premium storage blob and then another in quick succession (within 60 seconds of each other), then you might get a 409/Conflict error message.

This article suggests that there are two possibilities for this error, either

• SnapshotCountExceeded - You've exceeded the limit of 100 snapshots per blob, or
• SnaphotOperationRateExceeded - You've exceeded the limit of snapshots within a time window (stated as 10 minutes, but I observed this as closer to 1 minute)

Whilst it's unlikely that these limits would cause a problem in practice, it's something to keep in mind when developing/testing solutions that make use of the blob snapshot facility.

Azure Automation Troubles

A recent venture into Azure Automation threw up some unexpected problems.

A simple script, run locally, that called Get-AzureRmVM was working to my subscription, but the same script did not work within an Azure Runbook.

I'd created the AzureRunAsConnection by default with the Azure Automation account and followed the same code as given in the AzureAutomationTutorialScript powershell runbook to login to the subscription and execute Cmdlets.

The problem came when executing the Get-AzureRmVM Cmdlet in the runbook, receiving the error:

Get-AzureRmVM : Run Login-AzureRmAccount to login.
+     $VM = Get-AzureRmVM | ? {$_.Name -eq $VMName}
+           ~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Get-AzureRmVM], PSInvalidOperationException
    + FullyQualifiedErrorId : InvalidOperation,Microsoft.Azure.Commands.Compute.GetAzureVMCommand

After several googles I found this post...
https://feedback.azure.com/forums/246290-automation/suggestions/16590229-get-azurermvm-failing-in-azure-automation

Therefore, if anyone else sees errors when running basic Cmdlets in a runbook (that work fine from PowerShell), try updating all the modules in the Automation account using a script like this one...
https://www.powershellgallery.com/packages/Update-ModulesInAutomationToLatestVersion/1.03/DisplayScript
(Note that the deploy to Azure button didn't work for me, so I had to import the script and run manually.)

Note also that (depending on when you created your Automation Account) the above may, or may not work, and you may have to create a new Automation Account and update the modules before starting to use the account. Microsoft suggest setting the script to run on a schedule in the automation account to keep the modules up to date.