Nested virtualization is a technology that allows hypervisors to run within virtual machines, enabling the creation of a layered virtualization environment. In other words, it is the ability to run a virtual machine inside another virtual machine.
This functionality is widely supported by the main hypervisors in the market, such as VMware ESXi, Microsoft Hyper-V, KVM, and Proxmox VE. However, for nested virtualization to work correctly, the underlying hardware, such as the processor, must support virtualization (Intel VT-x or AMD-V) and this functionality must be enabled in the BIOS/UEFI.
How Does Nested Virtualization Work?
To understand nested virtualization, it is important to know the two main levels:
- Level 0 Hypervisor (L0): This is the main hypervisor that runs directly on the server’s physical hardware. It manages physical resources and controls virtual machines.
- Level 1 Hypervisor (L1): This is the hypervisor that runs as a virtual machine within the L0 hypervisor. This hypervisor creates and manages additional virtual machines, called level 2 (L2) virtual machines.
For example, imagine you are using Proxmox VE as the L0 hypervisor. Within a virtual machine created in Proxmox (L1), you can install VMware ESXi. This ESXi, in turn, will be able to host additional virtual machines (L2).
Uses of Nested Virtualization
Nested virtualization may seem like an advanced concept, but it has several practical applications. Here are some of the most common use cases:
Study and Training Labs:
- Create lab environments to learn how to configure hypervisors like VMware ESXi, Hyper-V, or KVM without the need for additional physical hardware.
- Train teams in simulations of complex infrastructures.
Software Development and Testing:
- Test automations or scripts that interact with hypervisors and virtual machines, such as provisioning tools (Terraform, Ansible, etc.).
- Validate infrastructure as code implementations in simulated environments.
Production Environment Simulation:
- Create virtual replicas of complex infrastructures, such as clusters or hybrid environments, to test updates, migrations, or configuration changes.
DevOps and CI/CD:
- Simulate CI/CD pipelines in virtualized environments that reproduce multiple servers, clusters, or even private clouds.
Security Research and Development:
- Test exploits and vulnerabilities in isolated environments, creating labs for security analysis.
- Simulate malware or ransomware attacks without the risk of contaminating the physical environment.
Cloud Service Provisioning (IaaS):
- Cloud providers can offer customized environments where clients manage their own hypervisors and create personalized virtual machines.
Compatibility Testing:
- Verify the behavior of applications on different hypervisors, operating systems, or software combinations at multiple levels of virtualization.
Multi-Tenant Environments:
- Host multiple clients in separate layers of virtualization to increase security and isolate resources.
Network and High Availability Training:
- Configure scenarios with multiple hypervisors connected in clusters simulating networks with high availability (vSphere HA, Hyper-V Failover Clustering).
Exploration of New Technologies:
Test advanced hypervisor features, such as DRS, vMotion, or even new versions of virtualization tools, without impacting the physical environment.
These use cases make nested virtualization an essential tool for learning, development, and IT operations, offering flexibility and cost savings.
How to Enable Nested Virtualization in the BIOS
Access the BIOS:
- Restart your computer.
- During the startup process, press the appropriate key to access the BIOS. Common keys include F2, Delete, Esc, or F10. The exact key may vary depending on the manufacturer.
Locate the Virtualization Setting:
- Navigate to the tab that contains the processor settings, which may be under “Advanced”, “CPU Configuration” or similar.
- Look for an option called Intel Virtualization Technology, VT-x, AMD-V, or something similar.
Enable Virtualization:
- If the option is disabled, select it and change to Enabled.
- Some BIOS may have an additional option called Virtualization Extensions or Nested Virtualization; enable it as well if available.
Save Changes and Exit:
- After making the changes, look for the option to save and exit, usually by pressing F10 or selecting “Save Exit”.
- Confirm the changes when prompted.
Check if Virtualization is Enabled:
- After restarting the operating system, you can check if virtualization is enabled using the Task Manager in Windows. Go to the “Performance” tab and check if “Virtualization” is marked as “Enabled”.
Additional Tips
- Ensure that your processor supports virtualization. For Intel processors, you must have VT-x; for AMD, it is necessary to have AMD-V.
- If the virtualization option is not visible in the BIOS, it may be that your motherboard does not support this functionality or needs a firmware (BIOS) update 34.
- In some systems, especially laptops, virtualization may be disabled by default and must be enabled manually.
By following these steps, you should be able to enable nested virtualization in your computer’s BIOS.
Conclusion
Nested virtualization is a powerful tool that transforms the way we develop, test, and learn in IT environments. Its ability to create layers of virtualization allows you to explore and simulate complex infrastructures with a single physical server, reducing costs and increasing flexibility.
Whether to learn new technologies, test changes in a safe environment, or create innovative solutions, nested virtualization is an indispensable resource in the arsenal of those who work with infrastructure and virtualization. By mastering it, you will be better prepared to handle the challenges and demands of the modern IT market.
