Write-Host "Logging into Azure account..."
Login-AzAccount

Write-Host "Setting Azure subscription context..."
Set-AzContext -Subscription "YOUR SUB ID"

# Define variables. Keep the same name if you want to get rid of storage profile reference in VM view, or just change VM size, e.g. VM (with no local temp disk) -> VM (with local temp disk).
Write-Host "Defining variables for Resource Group and VM names..."
$resourceGroup = "RENAMERG"
$oldVmName = "BADNAME"
$newVmName = "GOODNAME"

Write-Host "Fetching the existing VM object..."
$vm = Get-AzVM -ResourceGroupName $resourceGroup -Name $oldVmName

Write-Host "Saving key properties from the VM object..."
$vmSize = $vm.HardwareProfile.VmSize #Change VM SKU Size here if needed, e.g Standard_B2ms
$osDisk = $vm.StorageProfile.OsDisk
$dataDisks = $vm.StorageProfile.DataDisks
$nic = $vm.NetworkProfile.NetworkInterfaces[0].Id
$osType = $vm.StorageProfile.OsDisk.OsType

Write-Host "Fetching extensions from the old VM..."
$vmExtensions = Get-AzVMExtension -ResourceGroupName $resourceGroup -VMName $oldVmName

Write-Host "Removing the old VM but retaining all attached resources..."
Remove-AzVM -ResourceGroupName $resourceGroup -Name $oldVmName -Force

Write-Host "Creating a new VM configuration..."
$vmConfig = New-AzVMConfig -VMName $newVmName -VMSize $vmSize

Write-Host "Setting the OS disk and type..."
if ($osType -eq 'Windows') {
    $vmConfig = Set-AzVMOSDisk -VM $vmConfig -CreateOption Attach -ManagedDiskId $osDisk.ManagedDisk.Id -Name $osDisk.Name -Windows
} else {
    $vmConfig = Set-AzVMOSDisk -VM $vmConfig -CreateOption Attach -ManagedDiskId $osDisk.ManagedDisk.Id -Name $osDisk.Name -Linux
}

Write-Host "Adding the network interface..."
$vmConfig = Add-AzVMNetworkInterface -VM $vmConfig -Id $nic

Write-Host "Checking and adding any data disks..."
foreach ($dataDisk in $dataDisks) {
    $disk = Get-AzDisk -ResourceGroupName $resourceGroup -DiskName $dataDisk.Name
    if ($disk.Id -eq $dataDisk.ManagedDisk.Id) {
        $vmConfig = Add-AzVMDataDisk -VM $vmConfig -Name $dataDisk.Name -ManagedDiskId $dataDisk.ManagedDisk.Id -Caching $dataDisk.Caching -Lun $dataDisk.Lun -DiskSizeInGB $dataDisk.DiskSizeGB -CreateOption Attach
    } else {
        Write-Host ("Disk name " + $dataDisk.Name + " does not match with given managed disk ID.")
    }
}

$vmConfig = Set-AzVMBootDiagnostic -VM $vmConfig -Disable

Write-Host "Creating the new VM..."
New-AzVM -ResourceGroupName $resourceGroup -Location $vm.Location -VM $vmConfig

Write-Host "Adding extensions to the new VM..."
$newVmName = $vmConfig.Name
foreach ($ext in $vmExtensions) {
    Set-AzVMExtension -ResourceGroupName $resourceGroup -VMName $newVmName -Name $ext.Name -Publisher $ext.Publisher -ExtensionType $ext.ExtensionType -TypeHandlerVersion $ext.TypeHandlerVersion -Settings $ext.Settings
}