diff --git a/README.md b/README.md
index 8ec1170..0a77311 100644
--- a/README.md
+++ b/README.md
@@ -16,12 +16,12 @@ Requirements:
 * [Packer](https://www.packer.io/intro/getting-started/install.html)
 * [Vagrant](https://www.vagrantup.com/docs/installation/)
 * [Vagrant Reload Plugin](https://github.com/aidanns/vagrant-reload#installation)
-* [VirtualBox](https://www.virtualbox.org/wiki/Downloads)
+* [VirtualBox](https://www.virtualbox.org/wiki/Downloads) or libvirt/qemu-kvm
 * Internet connection
 
 To build automatically:
 
-1. On Linux/OSX run `./build.sh windows2008` to build the Windows box or `./build.sh ubuntu1404` to build the Linux box. On Windows, run `build_win2008.ps1` in a powershell terminal to build the Windows box.
+1. On Linux/OSX run `./build.sh windows2008` to build the Windows box or `./build.sh ubuntu1404` to build the Linux box. If /tmp is small, use `TMPDIR=/var/tmp ./build.sh ...` to store temporary packer disk images under /var/tmp. On Windows, run `build_win2008.ps1` in a powershell terminal to build the Windows box.
 2. If the command completes successfully, run `vagrant up`.
 3. When this process completes, you should be able to open the VM within VirtualBox and login. The default credentials are U: `vagrant` and P: `vagrant`.