title: Why does disabling --hwvirtex in Vagrant solves problems running a 64-bit OS?
body: <p>I have set up a Vagrant VM using VirtualBox and the default Ubuntu 12.04 64-bit image from the Vagrant team (see <a href="http://files.vagrantup.com/precise64.box" rel="nofollow noreferrer">http://files.vagrantup.com/precise64.box</a>).</p>
  
  <p>When I <code>vagrant up</code> on my MacBook Pro using OS X 10.8.5, in 90% of the times I get an error that the VM entered an invalid state (<code>aborted</code>). Running the VM with a UI didn't help any further.</p>
  
  <p>Now, while playing around, I found out by random that if I change</p>
  
  <pre><code>config.vm.provider :virtualbox do |vb|
    vb.customize [ "modifyvm", :id, "--memory", 1024, "--cpus", 2 ]
  end
  </code></pre>
  
  <p>to</p>
  
  <pre><code>config.vm.provider :virtualbox do |vb|
    vb.customize [ "modifyvm", :id, "--hwvirtex", "off", "--memory", 1024, "--cpus", 2 ]
  end
  </code></pre>
  
  <p>everything is fine. Can anybody explain what setting <code>--hwvirtex</code> to <code>off</code> does and why this solves my issue?</p>
  
  <p>I'm very confused about this problem as I used a default image from the Vagrant team, and I guess that there are plenty of people who run this image on OS X. So I would have expected to find answers on this when googling, but I didn't.</p>
  
  <p>Any advice?</p>
  
  <p>Using the hint by <a href="https://stackoverflow.com/users/1286453/che">che---</a> and the documentation on <a href="http://www.virtualbox.org/manual/ch10.html#hwvirt" rel="nofollow noreferrer">Hardware vs software virtualization</a>, things get worse: I understand what this setting is good for, but not, why it works if I <em>disable</em> hardware virtualization.</p>
  
  <p>The documentation states:</p>
  
  <blockquote>
    <p>Even though VirtualBox does not always require hardware virtualization, enabling it is <em>required</em> in the following scenarios: […] VirtualBox's 64-bit guest support (added with version 2.0) and multiprocessing (SMP, added with version 3.0) both require hardware virtualization to be enabled.</p>
  </blockquote>
  
  <p>As OS X is 64-bit, and the guest is as well - why does it work at all if I disable hardware virtualization?</p>
  
  <p><em>This question is not programming-related, but it is related to a tool which is commonly used by programmers. The FAQ states clearly that questions like these are welcome, hence I posted it here.</em></p>