Hybrid benefit in Azure means that you are purchasing the Windows license elsewhere, instead of “pay-as-you-go” with the VM consumption. The reason to do this is either your organization already owns licenses or purchased licensese to save cost (there is a brake even when it makes sense to buy the license outside of Azure).
To retrofit this to existing subscription, it is quite straight forward with Powershell. It is just a metadata for the virtual machine, so there is no down time required (reference https://docs.microsoft.com/en-us/azure/virtual-machines/windows/hybrid-use-benefit-licensing#convert-an-existing-vm-using-azure-hybrid-benefit-for-windows-server) .
The following Powershell code takes your current logged in Azure subscription context, get all Windows machines that does not have Hybrid benefit enabled and loops thru them, enabling Hybrid benefit.
[Cmdletbinding()]
Param
(
)
$nonehbvm = Get-AzVM -Status | where{$_.StorageProfile.OsDisk.OsType -eq "Windows" -and (!($_.LicenseType))} | Select-Object Name,ResourceGroupName,Licensetype
foreach($i in $nonehbvm)
{
$vm = Get-AzVM -ResourceGroup $($i.ResourceGroupName) -Name $($i.Name)
Write-Verbose "Setting hybrid benefit on VM $($i.Name) "
$vm.LicenseType = "Windows_Server"
Update-AzVM -ResourceGroupName $($i.ResourceGroupName) -VM $vm
}
