Azure - Resize Virtual Machines (Parallel).ps1

<#
Written with PowerShell v7.0.1 - install available here https://github.com/PowerShell/powershell/releases
Written with version 4.2.0 of the Az PowerShell Module 
available from here https://github.com/Azure/azure-powershell/releases/tag/v4.2.0-June2020 or run: Install-Module -Name Az -RequiredVersion 4.2.0 -AllowClobber
Migration instructions Azure.RM to Az - https://azure.microsoft.com/en-au/blog/how-to-migrate-from-azurerm-to-az-in-azure-powershell/
#>

##########################################################################################
############################    Logon to Microsoft Azure     #############################
##########################################################################################

$AzContextPath = "$($env:TEMP)\$(Get-Date -Format yyyyMMdd)AzEnv.json"

#region Logon to Azure | @marckean
Connect-AzAccount -Tenant '72f988bf-86f1-41af-91ab-2d7cd011db47'

##################### Subscription Select #####################
$subscriptions = Get-AzSubscription
$cnt = 1
Write-Host "ID    Subscription Name"
Write-Host "-----------------------"

foreach ($sub in $subscriptions){
    Write-Host "$cnt   $($sub.name)"
    $cnt++
}
$selection = Read-Host -Prompt "Select a subscription to deploy to"
$subSelect = $subscriptions[$selection - 1] # Revert 1-index to 0-index

Select-AzSubscription $subSelect.SubscriptionId
Save-AzContext -Path $AzContextPath -Force

#endregion

##########################################################################################
################################    List of VM sizes     #################################
##########################################################################################

# Get a list of VM sizes, so you know exactly the format of the name:
(Get-AzVMSize -Location 'Australia East').Name | Select-String 'DS14'

##########################################################################################
#############################    List of VMs to re-size     ##############################
##########################################################################################
#region List of VMs to re-size | @marckean

###########       Only do one of two options here       ###########

# Option 1: Pull VMs from a .CSV file - two columns, headers (vmname,targetsize) | @marckean
$VMs_to_resize = Import-Csv -Path 'W:\VMs_to_resize.csv'

# Option 2: Pull VMs from a comma separated here string - this is practically a mini CSV file anyway | @marckean
$VMs = @'
vmname,targetsize
Hadoop01,Standard_DS14_v2
Hadoop02,Standard_DS14_v2
'@
$VMs_to_resize = $VMs | ConvertFrom-Csv

#endregion

##########################################################################################
################################     Resize the VMs     ###################$##############
##########################################################################################

$VMs_to_resize | ForEach-Object -Parallel {

    Import-AzContext -Path $using:AzContextPath

    # Set private IP address to static to not loose it
    $NicID = ((Get-AzVM -Name $_.vmname).NetworkProfile.NetworkInterfaces[0].Id)
    $Nic = Get-AzNetworkInterface -ResourceId $NicID
    $PrivateIpAllocationMethod = $Nic.IpConfigurations[0].PrivateIpAllocationMethod # Remember original Private IP Allocation Method
    If($PrivateIpAllocationMethod -eq 'Dynamic'){ # only change the IP addess to static it's Dynamic
    $Nic.IpConfigurations[0].PrivateIpAllocationMethod = 'Static'
    Set-AzNetworkInterface -NetworkInterface $Nic}
    Write-Output "$($_.vmname) is currently set as $PrivateIpAllocationMethod"

    # Stop deallocate, resize the VM
    $vm = Get-AzVM -Name $_.vmname
    $VMsize = $_.targetsize
    Write-Output "Change $($_.vmname) to $VMsize"
    $vm | Stop-AzVM -Force
    $vm.HardwareProfile.VmSize = $VMsize
    Update-AzVM -VM $vm -ResourceGroupName $vm.ResourceGroupName
    $vm | Start-AzVM

    # Changing the Private IP address allocation method of a running VM to Dynamic using PowerShell doesn't cause a restart
    If($PrivateIpAllocationMethod -eq 'Dynamic'){ # only change the IP addess back to Dynamic it was Dynamic in the first instance
    $Nic = Get-AzNetworkInterface -ResourceId ((Get-AzVM -Name $_.vmname).NetworkProfile.NetworkInterfaces[0].Id)
    $Nic.IpConfigurations[0].PrivateIpAllocationMethod = 'Dynamic'
    Set-AzNetworkInterface -NetworkInterface $Nic}

  }