Virtual machines (VM) can be very helpful if you need to use multiple operating systems on a daily basis. That said, as easy as they are to use, they come in many different types, and picking the right one can be tricky.
One particular type of virtualization that we don’t see that often is called nested virtualization. It’s exactly what it sounds like and is a bit tricky to set up, but can be massively helpful if that’s the kind of thing you’re looking for.
What Is Nested Virtualization?
In its simplest form, nested virtualization involves running a virtual machine inside another virtual machine. That means you’ve got a host computer and operating system running a virtual machine with its own set of virtualized hardware and software, in which another VM is running.
It essentially adds another layer of virtualization to your hypervisor and can isolate the VM from the host machine by two separate layers. This has many use cases, especially in development applications where you might need an isolated environment to test out software frameworks, apps, codebases, and the like.
What Requirements Do You Need to Use Nested Virtualization?
Based on the hypervisor you’re using, the software and hardware requirements for running a nested virtualization environment can be different. That said, hardware requirements are going to be more or less the same across the board. As for software, different programs will have their own versions that support nested virtualization.
In the case of VMware VirtualBox, support for nested virtualization arrived with version 6.0 for AMD CPUs. Intel CPUs were added later with version 6.1. So all you really need to do is ensure you’re running the latest version of VirtualBox, and you should be good to go.
Why Would You Need to Use Nested Virtualization?
As mentioned above, nested virtualization is mostly used in development scenarios to test software frameworks and codebases in an isolated environment. However, their use cases aren’t limited to just that.
Nested VMs can be quite cost-efficient as you don’t need to add additional physical equipment for more machines. They’re also easy to move about, so if you (or your organization) are moving machines from your local server to the cloud, the process can be as simple asexporting the VM files and uploading them to another computeror a cloud hypervisor.
Other than this, the flexibility that nested VMs provide also gives users the option to run multiple hypervisors. Not all hypervisors are built the same, and you might need to pick one over the other at times. For example, it’s possible to run Windows Hyper-V on a Windows VM hosted on VMware’s VirtualBox—running two hypervisors at the same time.
Last but not least, they’re also rather easy to scale up according to your needs. All you need to do is add more storage, RAM, or a stronger CPU to your host machine, and the VMs, as well as nested VMs, will be able to use the additional resources in just a few clicks.
How to Set Up a Nested VM
Setting up a nested VM can actually be tricky based on the hypervisor you’re using. For VirtualBox, though, the process is as simple as clicking a checkbox.
On some systems, you might notice that theEnable Nested VT-x/AMD-Vcheckbox is greyed out. You can override this by using theVBoxManagetool. Here’s how.
The process for enabling nested virtualization works the same way whether you’re using Windows, Linux, or macOS, including the terminal commands as they’re installed along with VirtualBox. Additionally,VBoxManagecan do more than just enable nested virtualization. We’ve coveredsix useful VirtualBox commands you may use to manage your VMs here.
Additional Troubleshooting Steps for Enabling Nested Virtualization on Windows
Sometimes Windows' inbuilt virtualization features can cause issues with nested virtualization. In case the GUI and command line methods fail to enable nested virtualization on your system, you’re going to have to disable theVirtual Machine Platformfeature.
You might be asked to restart your PC. Once done, you may try the Command Prompt commands mentioned above to enable nested virtualization in your VM. Keep in mind that you might run into specific issues based on your operating system and processor. As you’d expect, these require solutions specific to your host environment and hardware.
That said, most common issues have either been fixed via updates or have been discussed enough for you to find a solution easily. That’s not to say that you shouldn’t be deterred from trying out nested VMs just because you run into a problem while configuring them because resolving such issues in most cases will only take a little research and experimentation. Once again, you can also simply avoid a lot of such issues if you’re using the latest version of VirtualBox and are on newer CPUs, whether they’re Intel or AMD.
Nested VMs Can Be Useful
Not only is it possible to create nested VMs, but it can actually be rather beneficial if done properly. Sure, it’s more suitable for specific, niche workloads, but for the right user, the flexibility and scalability, as well as the convenience they provide, are well worth the slight drop in performance.
