If you are here with the below error, and you are trying to install Hyper-V on a VM for testing purpose, you are at the right place.
Hyper-V can not be installed: The hypervisor is already running
We know that it is not recommended to run Hyper-V inside a VM, and it is not supported by Microsoft.
Okey, what if you want to do some test, say Azure Site Recovery with an Hyper-V?
Let’s see how we can ignore this warning and install HyperV on your Windows Server 2012 R2 VM and proceed with the Lab or testing purpose.
Open the PowerShell on your Windows VM.
Run the below command,
Enable-WindowsOptionalFeature –Online -FeatureName Microsoft-Hyper-V –All -NoRestart
Once it is finished, run the 2nd command.
Install-WindowsFeature RSAT-Hyper-V-Tools -IncludeAllSubFeature
Now you will be able to see Hyper-V Manager in your VM.