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I am trying to create a new 64-bit Windows 7 virtual machine inside a 64-bit Debian 7.3.0 instance running in VirtualBox. I am allowed to run 32-bit machines, but I can not create 64-bit machines, as shown in the picture. Why is this? I have hardware virtualization enabled on the host.enter image description here

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  • Maybe because it's not turtles all the way down.
    – Daniel R Hicks
    Sep 23, 2014 at 23:03
  • The linked-as-duplicate question is not a duplicate, since that one was about Bochs (pure software) over any VM, and this question is specifically about VirtualBox on VirtualBox. Fortunately there are some useful answers there. Summary: it just has not been implemented (yet?): see virtualbox.org/ticket/4032. FWIW, VMWare does support nested VMs.
    – hmijail
    Nov 4, 2016 at 11:26

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I read this... "You must enable hardware virtualization for the particular VM for which you want 64-bit support; software virtualization is not supported for 64-bit VMs"

I am guessing since virtualbox is software, it will not support a 64-bit OS running from a 64-bit OS VM. That is my theory, maybe post system specs and what exactly is happening when you go to create another VM inside your VM.

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    Bingo. A VM cannot provide hardware virtualization support since it isn't hardware.
    – David Schwartz
    Feb 7, 2014 at 17:34
  • But there's no reason why hardware virtualization can't be simulated (other that, of course, performance, code size, memory, et al).
    – Daniel R Hicks
    Sep 23, 2014 at 23:05
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Let me get this straight. You have a host PC running VB. You then run 64bit Debian as a virtual machine. You then try to run a Windows VM inside the Debian VM?

Odd.

Well, @Snickerz is right, you need VM processor and BIOS support to run a 64bit VM, the Debian VM doesn't give you that. I suspect that the VB developers never thought it would be needed :)

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  • It's true that it is a bit of an odd setup. :) But I need to run some Linux software that again needs a virtual machine to work with, hence the machines inside the machines.
    – user1049697
    Feb 7, 2014 at 16:31
  • Fair enough - thought it might be something like that. You will have to live with 32bit and rubbish performance though I'm afraid.
    – Julian Knight
    Feb 7, 2014 at 16:41
  • @user1049697 "run some Linux software that again needs a virtual machine to work with" You realize VB can have more than 1 virtual machine on the host, even at the same time.
    – Robin Hood
    Sep 23, 2014 at 22:34
  • as Robin mentioned i would also use to vm's in the same host rather than a vm inside a vm. - the performance of the vm inside the vm earlier or later will drive you crazy
    – konqui
    Sep 24, 2014 at 5:59
  • Not such an odd set-up, we are using VMs to get around not having super user privileges on University machines.
    – Matt Stevens
    Apr 19, 2017 at 2:51

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