- Added entry on installgin the VirtualBox extension pack.

content/vbox_extenstions.rst

+VirtualBox extensions
+#####################
+
+:date: 2017-01-17
+:summary: Installing the VirtualBox extension pack
+
+I happened to run into a Vagrant image today that required the USB2 controller
+extension to VirtualBox. The procedure to install the extension pack was not
+immediately clear to me.
+
+Installing through the VirtualBox GUI
+-------------------------------------
+
+When trying to go through the VirtualBox GUI, the
+application would close when I clicked on 'add new package' in the preferences
+window. Guessing it had something to do with root privileges I tried to run the
+GUI with :code:`sudo` but that failed because I'm using Wayland and it could
+not find display :0. Using Gnome3, :code:`gksudo` is no longer available and
+the replacement is :code:`pkexec` which uses PolicyKit. running :code:`pkexec
+VirtualBox` opened the nice Gnome3 authentication prompt but resulted in the
+same error. Giving up on starting the VirtualBox GUI as root, I moved my
+efforts to the :code:`VBoxManage` CLI.
+
+Installing with the VBoxManage CLI
+----------------------------------
+
+Here are the steps I took to successfully install the extension pack:
+
+#. Find the version of VirtualBox you have installed by running
+   :code:`VBoxManage --version`.
+
+#. Download the matching version of the extension pack from
+   https://www.virtualbox.org/wiki/Downloads if you're using the latest version
+   or from https://www.virtualbox.org/wiki/Download_Old_Builds if you're using
+   an older version.
+
+#. Assuming you're using version 5.1.10, install the extension pack by running
+   :code:`VBoxManage extpack install
+   Oracle_VM_VirtualBox_Extension_Pack-5.1.10-112026.vbox-extpack`. For me,
+   this opened the same nice Gnome3 authentication prompt.