5 ms·

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

shykes 11y ago
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.
- BrainInAJar 11y ago
  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.
  - shykes 11y ago
    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.
    - kazinator 11y ago
      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!
      - shykes 11y ago
        > 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.
        BrainInAJar 11y ago
        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
  - nostrademons 11y ago
    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?
    - igravious 11y ago
      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.
      - geon 11y ago
        > hypervisor has become the OS A hypervisor is an OS. A rose by any other name.
      - lmm 11y ago
        > 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.
      - lilred 11y ago
        >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 :)
nulltype 11y ago
Well hopefully your VMs are at least as well isolated as a linux process is.

shykes 11y ago

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.

BrainInAJar 11y ago
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.
- shykes 11y ago
  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.
  - kazinator 11y ago
    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!
    - shykes 11y ago
      > 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.
      - BrainInAJar 11y ago
        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
- nostrademons 11y ago
  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?
  - igravious 11y ago
    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.
    - geon 11y ago
      > hypervisor has become the OS A hypervisor is an OS. A rose by any other name.
    - lmm 11y ago
      > 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.
    - lilred 11y ago
      >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 :)

nulltype 11y ago

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