Create Azure Resources with Azure PowerShell using a script

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Complex or repetitive tasks can be time-consuming and error-prone when performed manually. Organizations prefer to automate these tasks to reduce costs and avoid mistakes.

Automation is essential in the Customer Relationship Management (CRM) example, where you're testing your software on multiple Linux virtual machines (VMs) that need to be continuously deleted and re-created. Using a PowerShell script to automate VM creation is much more efficient and reliable than manually creating them each time.

Beyond the core operation of creating a VM, your script needs to meet a few other requirements:

• Create multiple VMs: Use New-AzVM to create multiple uniquely named VMs.
• Resource group parameter: Allow the script to accept the name of the resource group as a parameter.

In this unit, you learn how to write and execute a PowerShell script that meets these requirements.

What is a PowerShell script?

A PowerShell script is a text file containing commands and control constructs. The commands are invocations of cmdlets, and the control constructs are programming features like loops, variables, parameters, comments, etc. supplied by PowerShell.

PowerShell script files have a .ps1 file extension. You can create and save these files using any text editor.

Tip

If you're writing PowerShell scripts, consider using Visual Studio Code (VS Code), which is free and supported on Windows, Linux, and macOS. The PowerShell extension for VS Code offers features like syntax highlighting and a list of available cmdlets.

The following screenshot is an example of VS Code with a sample script to connect to Azure and create a virtual machine:

Once you create a script, you can execute it from the PowerShell command line by passing the name of the file preceded by a dot for the current directory and a backslash:

.\myScript.ps1

PowerShell techniques

PowerShell includes features commonly found in programming languages. You can define variables, use branches and loops, capture command-line parameters, write functions, add comments, and more. For the script you're focusing on, you need three key features: variables, loops, and parameters.

Variables

In PowerShell, variables are declared using the dollar sign ($) and assigned values using the equals (=) operator. For example:

$location = 'eastus'

To determine the value stored in a variable, use the $ prefix and its name:

$location

Variables can hold objects. For example, the following definition sets the $adminCredential variable to the object returned by the Get-Credential cmdlet:

$adminCredential = Get-Credential

Loops

PowerShell has several loop structures, including For, Foreach, Do-Until, Do-While, and While. The Foreach loop is a good choice for scenarios where you need to execute a loop over a set of values in a collection.

$items = 'web','app','sql'
foreach ($item in $items) {
    $item
}

Parameters

When you create a PowerShell script, you can add parameters to the script and then specify values for these parameters when executing the script. For example:

.\setupEnvironment.ps1 -Name 'web','app','sql' -Location eastus

Inside the script, capture the values into variables. In this example, the parameters are Name and Location:

param (
    [string[]]$Name,
    [string]$Location
)

You can use these parameters as input and a loop to create a set of VMs based on the given parameters. This approach keeps the script generic and avoids repeating the same code.

Combining techniques

The combination of PowerShell language features and Azure PowerShell cmdlets provides all the tools you need to automate Azure tasks. In the CRM example, you can create multiple Linux VMs using a parameterized script and a loop to streamline the process. This script allows you to perform a complex operation in a single step.

Example script

Here's an example script that demonstrates using variables, loops, and parameters to create multiple VMs:

param (
    [string[]]$Name = 'web','app','sql',
    [string]$ResourceGroupName,
    [string]$Location = 'eastus'
)

$adminCredential = Get-Credential

foreach ($vm in $Name) {
    $azVmParams = @{
        ResourceGroupName   = $ResourceGroupName
        Name                = $vm
        Credential          = $adminCredential
        Location            = $Location
        Image               = 'Canonical:0001-com-ubuntu-server-jammy:22_04-lts:latest'
        OpenPorts           = 22
        PublicIpAddressName = $vm
    }
    New-AzVM @azVmParams
}

Executing the script

Save the script as CreateVMs.ps1 and run it from the PowerShell command line, providing the required parameters:

.\CreateVMs.ps1 -ResourceGroupName <resource-group-name>

Using this script, you can efficiently create multiple VMs in different resource groups, automating repetitive tasks and ensuring consistency across your Azure environment.