nixpkgs/nixos/doc/manual/installation/installing-virtualbox-guest.xml

<section xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         version="5.0"
         xml:id="sec-instaling-virtualbox-guest">
 <title>Installing in a VirtualBox guest</title>

 <para>
  Installing NixOS into a VirtualBox guest is convenient for users who want to
  try NixOS without installing it on bare metal. If you want to use a pre-made
  VirtualBox appliance, it is available at
  <link
  xlink:href="https://nixos.org/nixos/download.html">the downloads
  page</link>. If you want to set up a VirtualBox guest manually, follow these
  instructions:
 </para>

 <orderedlist>
  <listitem>
   <para>
    Add a New Machine in VirtualBox with OS Type "Linux / Other Linux"
   </para>
  </listitem>
  <listitem>
   <para>
    Base Memory Size: 768 MB or higher.
   </para>
  </listitem>
  <listitem>
   <para>
    New Hard Disk of 8 GB or higher.
   </para>
  </listitem>
  <listitem>
   <para>
    Mount the CD-ROM with the NixOS ISO (by clicking on CD/DVD-ROM)
   </para>
  </listitem>
  <listitem>
   <para>
    Click on Settings / System / Processor and enable PAE/NX
   </para>
  </listitem>
  <listitem>
   <para>
    Click on Settings / System / Acceleration and enable "VT-x/AMD-V"
    acceleration
   </para>
  </listitem>
  <listitem>
   <para>
    Save the settings, start the virtual machine, and continue installation
    like normal
   </para>
  </listitem>
 </orderedlist>

 <para>
  There are a few modifications you should make in configuration.nix. Enable
  booting:
 </para>

<programlisting>
<xref linkend="opt-boot.loader.grub.device"/> = "/dev/sda";
</programlisting>

 <para>
  Also remove the fsck that runs at startup. It will always fail to run,
  stopping your boot until you press <literal>*</literal>.
 </para>

<programlisting>
<xref linkend="opt-boot.initrd.checkJournalingFS"/> = false;
</programlisting>

 <para>
  Shared folders can be given a name and a path in the host system in the
  VirtualBox settings (Machine / Settings / Shared Folders, then click on the
  "Add" icon). Add the following to the
  <literal>/etc/nixos/configuration.nix</literal> to auto-mount them. If you do
  not add <literal>"nofail"</literal>, the system will no boot properly. The
  same goes for disabling <literal>rngd</literal> which is normally used to get
  randomness but this does not work in virtual machines.
 </para>

<programlisting>
{ config, pkgs, ...} :
{
  security.rngd.enable = false; // otherwise vm will not boot
  ...

  fileSystems."/virtualboxshare" = {
    fsType = "vboxsf";
    device = "nameofthesharedfolder";
    options = [ "rw" "nofail" ];
  };
}
</programlisting>

 <para>
  The folder will be available directly under the root directory.
 </para>
</section>