MSDN Documentation

Debugging Azure PowerShell Scripts

This guide provides essential techniques and tools for debugging your Azure PowerShell scripts, ensuring efficient development and reliable deployment.

Common Debugging Scenarios

• Authentication Issues: Errors related to connecting to Azure subscriptions.
• Resource Not Found: Scripts failing because a specified resource does not exist or is misspelled.
• Permission Denied: Insufficient rights to perform an operation on an Azure resource.
• Parameter Mismatches: Incorrect or missing parameters for cmdlets.
• Logic Errors: Bugs in the script's flow control or data manipulation.

Debugging Techniques

1. Verbose Output and Error Messages

Leverage the built-in verbosity of Azure PowerShell cmdlets. Many cmdlets have parameters like -Verbose, -Debug, and -ErrorAction.

• -Verbose: Provides detailed information about what the cmdlet is doing.
• -Debug: Offers even more detailed debugging output, often useful for understanding internal cmdlet behavior.
• -ErrorAction SilentlyContinue: Suppresses non-terminating errors, allowing the script to continue. Use with caution.
• -ErrorAction Stop: Treats non-terminating errors as terminating errors.
• $ErrorActionPreference: A preference variable that controls the default error action for cmdlets. You can set it to Continue, Stop, Ignore, etc.

# Example of verbose output
            Get-AzResourceGroup -Name "MyResourceGroup" -Verbose
            

2. Using the PowerShell Debugger

PowerShell has a powerful built-in debugger that allows you to step through your script line by line, inspect variables, and set breakpoints.

• `Set-PSBreakpoint`: Allows you to set breakpoints at specific lines, conditions, or variable values.
• `Enable-PSBreakpoint` / Disable-PSBreakpoint: Control whether breakpoints are active.
• `Remove-PSBreakpoint`: Delete breakpoints.
• `Get-PSBreakpoint`: List current breakpoints.

Once a breakpoint is hit, you'll enter the debugger prompt. Common commands include:

• `l` (list): Show the current code context.
• `s` (step): Execute the current line and move to the next.
• `c` (continue): Continue script execution until the next breakpoint or the end.
• `q` (quit): Exit the debugger.
• `p` (print): Display the value of a variable.

# Setting a breakpoint on line 5
            Set-PSBreakpoint -ScriptPath ".\MyScript.ps1" -LineNumber 5

            # Then run your script
            .\MyScript.ps1
            

3. Logging and Tracing

For complex scripts or long-running operations, logging can be invaluable for tracking execution flow and identifying issues after the fact.

• `Out-File`: Redirect cmdlet output to a file.
• `Add-Content`: Append output to a file.
• `Start-Transcript` / Stop-Transcript: Records a complete session to a text file, including all input and output.

# Start transcript
            Start-Transcript -Path ".\MyScriptLog.txt" -Append

            # ... your script commands ...

            # Stop transcript
            Stop-Transcript
            

4. Variable Inspection

At any point during debugging, you can inspect the values of variables. You can do this within the debugger prompt or by adding Write-Host or Write-Output statements in your script.

# Example of checking a variable
            $resourceGroupName = "MyRG"
            Write-Host "Resource Group Name is: $resourceGroupName"
            

5. Using `Invoke-WebRequest` and `Invoke-RestMethod`

When interacting with Azure APIs directly, ensure your requests are correctly formatted. Use -Verbose with these cmdlets to see the HTTP requests and responses.

Advanced Debugging Tips

• Modularize your script: Break down complex scripts into smaller, reusable functions. This makes it easier to isolate and debug individual components.
• Use `try-catch` blocks: Gracefully handle errors and provide more informative messages.
• Check Azure Activity Logs: For operations that are failing at the Azure platform level, the Azure Activity Log can provide critical insights.

Troubleshooting Common Azure PowerShell Errors

When you encounter an error, carefully read the error message. It often contains clues about the cause. Common error codes and their potential meanings:

• ResourceNotFound: The specified resource does not exist or you don't have permissions to see it.
• UnauthorizedOperation: Your service principal or user account lacks the necessary permissions.
• BadRequest: The request syntax or parameters are invalid.

For more detailed troubleshooting, refer to the official Azure PowerShell troubleshooting guide.