Running Proxmox Inside a VM Sounds Ridiculous. That's Why People Love It.

Proxmox VE can run inside another virtual machine when the outer hypervisor exposes the required CPU virtualization features. Nested virtualization is useful for classes, cluster practice and experiments, but it is not a sensible default for workloads that require predictable performance and recovery.

The example that prompted this discussion was playful rather than a production benchmark. Enthusiasts recognized a valuable laboratory trick; one participant also described trouble when a nested setup affected a normal daily-use VM.

Can Proxmox VE run inside another VM?

Proxmox can run as a guest when the outer environment provides hardware-assisted nested virtualization.

Virtualization has a way of turning ordinary computer rules into suggestions. A single physical machine can behave like several independent computers. Each virtual machine gets an operating system, its own settings, and the impression that it is running on hardware of its own. Once that idea feels normal, the next question almost asks itself: what happens when the operating system inside one of those machines is itself a hypervisor? For someone meeting the concept for the first time, it sounds like putting a box inside a box, then asking the smaller box to manufacture more boxes. For a seasoned tinkerer, it sounds like a perfectly acceptable way to spend an evening.

The QEMU and KVM explanation provides a useful model of what the outer and inner virtualization layers actually do.

That contrast was the entire charm of the exchange. A commenter answered the implied question with two words: "Nested virtualization." Another responded that of course it was possible. The explanation is simple enough to name, even if implementing it well can be much less simple. One virtualization layer hosts another, and the inner environment may then host its own virtual machines. It is a concept that can feel absurd and technically ordinary at the same time. The post did not contain a full tutorial, benchmark, or claim that this was a sensible everyday setup. It contained delight, and the replies supplied the technical framing.

The humor also came from recognition. In homelabs, achieving a result is sometimes only half the reward. The other half is discovering an unexpected route to it. A comment consisting of "Yo dawg" captured that self aware absurdity without needing a diagram. Yet humor should not be mistaken for universal approval, and laughter is not proof of stability. The people reacting to the post were not all making the same argument. Some saw a clever toy. Some saw a teaching tool. At least one saw a painful memory. The same experiment can be funny from a distance and expensive in time when it shares resources with something somebody actually needs.

Why do people build nested Proxmox labs?

Nested Proxmox is most useful for learning clusters, administration and failure scenarios without buying a separate physical server.

One of the most revealing replies came from someone who had once asked a teacher whether the idea was possible. According to that commenter, the teacher thought the question was crazy and laughed. Seeing the experiment gave the person a sense that an old ambition had finally been validated. It is easy to dismiss that response as enthusiasm over a technical trick, but there is something familiar underneath it. Beginners often ask questions that sound foolish only because they have not yet learned which restrictions are real. They are testing the boundaries of a system.

Before trying to virtualize another hypervisor, work through the basic Proxmox installation steps so host-network mistakes are easier to diagnose.

Another commenter challenged the novelty of the whole thing. In college infrastructure courses, they said, students had used classroom PCs running VirtualBox to host Proxmox or ESXi, then connected the resulting environments. The detail changes the conversation. What looks like an eccentric home project can also be an inexpensive way to practice with virtualization platforms without dedicating a room full of physical servers. Students can encounter the structure of a multihost environment while working with machines already available in a classroom. The comment did not claim that every feature behaves exactly as it would on dedicated hardware, and it offered no measurements. Its point was more modest and more useful: this approach had been part of hands on training, not merely a stunt.

Those two replies make a surprisingly good pair. In one, a teacher supposedly laughs at a student for asking. In the other, classrooms already use the technique. There is no reason to assume the teachers, dates, hardware, or assignments were comparable. Still, the tension is real. The important question for a learner is less whether an idea sounds respectable and more whether it can be explored safely and understood afterward. An experiment that teaches someone how virtual machines interact may have value long before it becomes useful in production.

Can nested virtualization disrupt everyday VMs?

Yes, a crowded or poorly isolated nested lab can consume host resources and interfere with other guests.

Then came the comment that should make every enthusiastic homelabber hesitate for a moment. One person said they had done something similar and that it had wreaked havoc on their daily driver VM. They did not explain exactly what failed, what hardware was involved, or how the system was recovered. That is too little information to diagnose a cause. It is enough, however, to establish a very recognizable risk: the machine used for experimentation may also be the machine used for normal life. An interesting nested setup feels harmless until its problems interfere with the environment that handles everyday tasks.

That distinction between a lab and a daily driver is where the joke meets reality. Someone experimenting on an isolated system can often afford to break things. Someone experimenting on a VM they rely on has a different tolerance for surprise. The discussion did not establish that nested virtualization is inherently destructive, and one unhappy experience cannot prove it. What the warning does show is that successful experimentation involves choosing where failures are allowed to happen. A curious setup can be worth trying while still being a poor candidate for the environment holding your work, classes, files, or routine services. A funny idea does not become less funny because it deserves boundaries.

Another commenter called nesting Proxmox in a VM an interesting exercise of little practical use. That is a different objection. It is not a complaint about damage; it is a question of payoff. Why spend time building an extra virtualization layer when the immediate result might simply be more virtualization? The classroom reply provides a partial answer: practice is a use. The excited student's reply provides another: proving a possibility can matter. A production administrator, a learner, and a weekend experimenter may evaluate the same project against completely different goals, and none needs to pretend the others are pursuing an identical outcome.

When is nested Proxmox worth the extra layer?

Use nested Proxmox as a disposable lab; use direct installation on a host when you need stable production performance or straightforward recovery.

A quieter reply suggested moving from Proxmox VE 8 to 9 and expressed a preference for the newer version. The comment is a reminder of how these discussions tend to branch. Somebody shares something funny, and another person immediately notices an adjacent maintenance question. The source exchange does not establish which version the setup actually ran or whether an upgrade would have changed the experiment. The suggestion should therefore be read as a separate preference, not as a confirmed fix for a problem. Even in a lighthearted thread, infrastructure habits show through: people look for versions, configurations, and changes they would make to somebody else's machine.

It would be tempting to turn this story into a step by step nested virtualization guide, complete with commands and promises about performance. The comments do not supply that information. They do supply a more interesting set of expectations. The student wants an idea taken seriously. The classroom veteran considers it familiar. The practical skeptic wants a reason to do it. The person with the damaged daily VM wants others to know that complications are possible. The person who posted the image simply enjoyed the result.

And perhaps consensus would spoil the point. Home infrastructure sits somewhere between professional practice and a hobby where curiosity is allowed to outrun necessity. People build labs to learn concepts, test boundaries, reuse equipment, and sometimes entertain themselves. Nested virtualization belongs comfortably in that world as a possibility worth understanding, even when there is no reason to leave it running forever. The cautionary reply still deserves a place at the table. It is possible to admire an absurd experiment and decide to conduct the next one on a disposable test system instead of a daily workhorse. Enjoyment and restraint can coexist without draining the joy from either.

The most memorable part of this little exchange is the distance between the first laugh and the last practical warning. A person finds the result childishly funny. Someone else recalls being laughed at for proposing it. Another explains that students have practiced the same idea in a classroom. One veteran remembers the trouble it caused. Nobody needs to win that argument. The experiment already did something useful: it made people compare what they know, what they assumed was impossible, and how much inconvenience they are willing to risk for the pleasure of finding out. That is a better outcome than a joke that merely gets a laugh and disappears.

I would use nesting for teaching and testing, with tight resource limits and snapshots of the lab guest. If the workload is important enough to justify uptime guarantees, I would give it a direct host or a simpler VM arrangement instead.