Azure Powershell script fails when run through task scheduler - powershell

Question

I have a powershell script that I wrote to backup a local sqlserver to an azure blob. Its based on one I took from MSDN, but I added an extra feature to delete any old backups that are over 30 days old. When I run this as a user, it works fine. When I added this to task scheduler, set to run as me, and I manually ask for it to run, it works fine. (All output is captured in a log file, so I can see that its all working). When run from the task scheduler at night when I'm not logged in (the task scheduler is set to run the script as me) it fails. Specifically, it claims my azure subscription name is not know when I call Set-AzureSubscription. Then, fails when trying to delete the blob with:
Get-AzureStorageBlob : Can not find your azure storage credential. Please set current storage account using "Set-AzureSubscription" or set the "AZURE_STORAGE_CONNECTION_STRING" environment variable.
The script in question:
import-module sqlps
import-module azure
$storageAccount = "storageaccount"
$subscriptionName = "SubName"
$blobContainer = "backup"
$backupUrlContainer = "https://$storageAccount.blob.core.windows.net/$blobContainer/"
$credentialName = "creds"
Set-AzureSubscription -CurrentStorageAccountName $storageAccount -SubscriptionName $subscriptionName
$path = "sqlserver:\sql\servername\SQLEXPRESS\databases"
$alldatabases = get-childitem -Force -path $path | Where-object {$_.name -eq "DB0" -or $_.name -eq "DB1"}
foreach ($db in $alldatabases)
{
Backup-SqlDatabase -BackupContainer $backupUrlContainer -SqlCredential $credentialName $db
}
$oldblobs = Get-AzureStorageBlob -container backup | Where-object { $_.name.Contains("DB") -and (-((($_.LastModified) - $([DateTime]::Now)).TotalDays)) -gt $(New-TimeSpan -Days 30).TotalDays }
foreach($blob in $oldblobs)
{
Write-Output $blob.Name
Remove-AzureStorageBlob -Container "backup" -Blob $blob.Name
}
The backup part of the script works, just not the blob deletion parts. It would appear that something is being done to the environment when I log in that allows the azure powershell scripts to work but that isn't being done when I run the command at night when I'm not logged in.
Any one have any idea what that might be?
Task scheduler is set to run the command with a
Powershell -Command "C:\Scripts\BackupDatabases.ps1" 2>&1 >> "C:\Logs\backup.log"

Answer 1

The Azure PowerShell environment just needs to understand what Azure subscription to work with by default. You probably did this for your own environment, but the task scheduler is running in a different environment.
You just need to add an additional command to the beginning of your script to set the Azure subscription. Something like this:
Set-AzureSubscription -SubscriptionName
The documentation for this command is here. You can also set by SubscriptionID etc. instead of SubscriptionName.
In addition, this article walks through how to connect your Azure subscription to the PowerShell environment.
UPDATE: I messed around and got it working. Try adding a "Select-AzureSubscription" before your Set-AzureSubscription command.
Select-AzureSubscription $subscriptionName
Set-AzureSubscription -SubscriptionName $subscriptionName -CurrentStorageAccountName $storageAccount
The documentation for Select-AzureSubscription is here. If you aren't relying on that storage account being set, you may be able to remove the Set-AzureSubscription command.

Answer 2

I was never able to make the powershell script work. I assume I could have made it work if I had set the credentials in the environment variable, as it said, but I instead wrote a little program to do the work for me.
Visit https://github.com/sillyotter/BackupDBToAzure if you need a tool to backup things to azure blobs and delete old leftover backups.
Thanks for the help!