Comment by iheartmemcache | Hacker News Reader

Comment by iheartmemcache | Hacker News Reader

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I have no dog in this fight. That is, I'm neither financially nor emotionally invested in Docker or any sort of container technology, nor their Solaris OS thing, nor CoreOS, nor any unikernel. I read this blog not knowing who he is and very little about Joyent so I held no previous malcontent against the man (edit: nor do I now, in case that clause implied otherwise). That being said - you weren't even remotely harsh.

He made a bunch of wild claims without backing it up even with simple links to buqtraq/securityfocus/whatever providing evidence that hypervisors are inherently additive to your 'surface area' by which you can be attacked. He also, as you mentioned, failed to provide even cursory benchmarks, much less cite any 3rd party, academic, peer reviewed analyses. Thirdly, he asserted a false choice between unikernels and on-the-metal. There's nothing stopping you from firing up a heterogeneous environment, using unikernels when they perform well, and containers when the situation dictates them. So yeah, you weren't too harsh - IMO, your post was more well-balanced and thought out than his entire blog post. But hey, who knows, maybe he intentionally wanted to be incendiary so we'd all be talking about his company's product (in some capacity at least) on a slow Friday afternoon.

Unikernels, to me, are basically a resurrection of the type of operating system exemplified by Mac OS 9, 8, 7... No memory protection; programs just duking it out against each other with pointers in the same arena, like gladiators. But to invoke an image of disciplined violence in the Roman Empire is too kind; really, this is more like a regression to the Stone Age.

Right there aren't supposed to be multiple applications in there? But eventually there will. Things only start small, as a rule.

Look, we have had pages and memory management units since the 1960's already. Protection was considered performant enough to be wortwhile on mainframes built from discrete integrated circuits on numerous circuit boards, topping out at clock speeds of some 30 mHz. Fast forwarding 30 years, people were happily running servers using 80386 and 80486 boxes with MMU-based operating systems.

Why would I want to give up the user/kernel separation and protection on hardware that blows away the protected-memory machine I had 20 years ago.

That would be true if applications ran on only one computer at a time. But nowadays applications run across many computers - sometimes tens of thousands of them. These applications don't need the operating system to protect processes from each other, because they are not running on the same computer.

Now that hypervisors are a mature commodity, this model is practical at smaller scale too: instead of running in separate physical computers, process run in separate virtual computers.

In short: unikernels make way more sense if you zoom out and think of your entire swarm of computers as a single computer.

That would be true if computers ran only one unikernel at a time, but you need to protect each unikernel from each other

Computers do run only one unikernel at a time. It's just that sometimes they are virtual computers. Remember that virtualization is increasingly hardware-assisted, and the software parts are mature. So for many use cases it's reasonable to separate concerns and just assume that VMs are just a special type of computer.

For the remaining use cases where hypervisors are not secure enough, use physical computers instead.

For the remaining use cases where the overhead of 1 hypervisor per physical computer is not acceptable, build unikernels against a bare metal target instead. (the tooling for this still has ways to go).

If for your use cass hypervisors are not secure enough, 1 hypervisor per physical machine is too much overhead, and the tooling for bare metal targets is not adequate, then unikernels are not a good solution for your use case.

Yes, and processes in a traditional OS have hardware support too through the MMU and things. At the end of the day something needs to schedule processes/vms, and something needs to coordinate disk writes and what I'm driving at here is that whether you call them processes and a kernel or vms and a hypervisor, you arrive at the same thing, except operating systems are mature at that task, and hypervisors are not.

I think we could spend a long time discussing the relative strengths and weaknesses of hypervisors and traditional operating systems. It's definitely not a one-size-fits-all situation (which is kind of what you're implying).

In any case, I was not arguing that hypervisors are superior to traditional operating systems. I was simply pointing out why the comparison of unikernels to macos8 and calling it a "regression to the stone age" was missing the point entirely, because of the distributed nature of modern applications.

The distributed nature just means that if attackers find one exploit, they can apply it repeatedly to the distributed application, to give themselves an entire botnet.

All code is privileged, so any remote execution exploit in any piece of code makes you own the whole machine (physical or virtual, as the case may be). A buffer overflow in some HTML-template-stuffing code is as good as one in an ethernet interrupt routine. Wee!

> The distributed nature just means that if attackers find one exploit, they can apply it repeatedly to the distributed application, to give themselves an entire botnet

That may or may not be true... In any case it's completely orthogonal to unikernels. Distributed applications, and any security advantages/disadvantages, are a fact of life.

> All code is privileged, so any remote execution exploit in any piece of code makes you own the whole machine (physical or virtual, as the case may be). A buffer overflow in some HTML-template-stuffing code is as good as one in an ethernet interrupt routine. Wee!

I'm afraid you're parroting what you learned about security without really understanding it. Yes, an exploit will give you access to the individual machine. But what does that mean if the machine is a single trust domain to begin with, with no privileged access to anything other than the application that is already compromised? In traditional shared systems, running code in ring0 is a big deal because the machine hosts multiple trust domains and privileged code can hop between them. That doesn't exist with unikernels.

Add to that the tactical advantages of unikernels: vastly reduced attack surface, a tendency to use unikernels for "immutable infrastructure" which means you're less likely to find an opportunity to plant a rootkit before the machine is wiped, and the fact that unikernels are vastly less homogeneous in their layout (because more happens at build time), making each attack more labor-intensive. The result is that the security story of unikernels, in practice and in theory, is very strong.

You're assuming here that there aren't and never will be exploits that break out of the hypervisor. This is not the world we live in. In literally exactly the same way that you can break out of an application in to kernel space, you can break out of a guest VM in to hypervisor space. VM guests are processes, and hypervisors are operating systems. We've switched the terminology around a bit, but in doing so we've given up decades of OS development

> You're assuming here that there aren't and never will be exploits that break out of the hypervisor. This is not the world we live in.

Really? Here's what I wrote in this very thread, just above your message: If for your use case hypervisors are not secure enough, 1 hypervisor per physical machine is too much overhead, and the tooling for bare metal targets is not adequate, then unikernels are not a good solution for your use case. [1]

At this point I believe we are talking past each other, you are not addressing (and apparently not reading) any of my points, so let's agree to disagree.

[1] https://news.ycombinator.com/item?id=10956899

Why do you need to have both a kernel and a hypervisor, though? You've got two levels of abstraction that do the same thing, and just like with M:N threading over processes, they often work at cross purposes.

For most cloud deployments nowadays, the hypervisor is a given. Given that, why not get rid of the kernel?

Except you don't get rid of the kernel, they're not called unikernels for nothing I presume.

Surely, you should be saying: why do you need all of a kernel and hypervisor and an app when you could subsume the app into the kernel and just run the hypervisor and the kernelized app (or single-appified kernel, call it what you want).

I'm having a hard time seeing the benefits given the obvious increase in complexity.

What features of a full-fat OS do unikernels retain? If the answer is very little because hypervisors provide all the hardware access then it would be fair to say that hypervisor has become the OS and the traditional kernel (a Linux one in this case I presume) has become virtually * ahem * redundant.

> hypervisor has become the OS

A hypervisor is an OS. A rose by any other name.

> I'm having a hard time seeing the benefits given the obvious increase in complexity.

What? It's simpler. You remove all the overhead of separating the kernel and app. And that of running a full-featured multiuser, multiprocess kernel for the sake of a single app.

> What features of a full-fat OS do unikernels retain? If the answer is very little because hypervisors provide all the hardware access then it would be fair to say that hypervisor has become the OS and the traditional kernel (a Linux one in this case I presume) has become virtually * ahem * redundant.

Yes, that's entirely fair.

>hypervisor has become the OS and the traditional kernel (a Linux one in this case I presume) has become virtually * ahem * redundant.

That's the point of unikernels right there :)

Well hopefully your VMs are at least as well isolated as a linux process is.

On the contrary, you could argue that there is _more_ isolation, insofar as the multiple applications will be separate unikernels on the same hypervisor, and that the hypervisor will enforce a stricter separation between VMs/unikernels than your OS will between processes.

YEs, sometimes I wonder why UniKnernel isn't called the resurrection of DOS.

Because we're not using DOS?

held no previous malcontent against the man

That does not sound practical at all.

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