Compressing a VirtualBox VDI file for a Linux guest

In a previous posting, I have talked about compressing a virtual hard disk for a Windows guest system running in VirtualBox on a Linux system. Since then, I have needed to do the same for a Linux guest following some housekeeping. The Linux distribution used is Debian so the instructions are relevant to that and maybe its derivatives such as Ubuntu, Linux Mint and their kind.

While there are other alternatives like dd, I am going to stick with a utility named zerofree to overwrite the newly freed up disk space with zeroes to aid compression later on in the process for this and the first step is to install it using the following command:

apt-get install zerofree

Once that has completed, the next step is unmount the relevant disk partition. Luckily for me, what I needed to compress was an area that I reserved for synchronisation with Dropbox. If it was the root area where the operating system files are kept, a live distro would be needed instead. In any event, the required command takes the following form with the mount point being whatever it is on your system (/home, for instance):

sudo umount [mount point]

With the disk partition unmounted, zerofree can be run by issuing a command that looks like this:

zerofree -v /dev/sdxN

Above, the -v switch tells zerofree to display its progress and a continually updating percentage count tells you how it is going. The /dev/sdxN piece is generic with the x corresponding to the letter assigned to the disk on which the partition resides (a, b, c or whatever) and the N being the partition number (1, 2, 3 or whatever; before GPT, the maximum was 4). Putting all this together, we get an example like /dev/sdb2.

Once, that had completed, the next step is to shut down the VM and execute a command like the following on the host Linux system ([file location/file name] needs to be replaced with whatever applies on your system):

vboxmanage modifyhd [file location/file name].vdi --compact

With the zero filling in place, there was a lot of space released when I tried this. While it would be nice for dynamic virtual disks to reduce in size automatically, I accept that there may be data integrity risks with those so the manual process will suffice for now. It has not been needed that often anyway.

Installing FreeBSD in a VirtualBox Virtual Machine

With UNIX being the basis of Linux, I have a soft spot for trying out any UNIX that can be installed on a PC. For a while, I had OpenSolaris on the go and even vaguely recall having a look at one of the BSD’s. However, any recent attempt to install one of the latter, and there are quite a few around now, got stymied by some sort of kernel panic caused by using AMD CPU’s. With the return to the Intel fold arising from the upgrade of my main home PC last year, it perhaps was time to try again.

The recent release of FreeBSD 10.0 was the cue and I downloaded a DVD image for a test installation in a VirtualBox virtual machine with 4 GB of memory and a 32 GB virtual hard drive attached (expanding storage was chosen so not all the allocated space has been taken so far). The variant of FreeBSD chosen was the 64-bit x86 one and I set to installing it in there. Though not as pretty in appearance as those in various Linux distros, the installer was not that user unfriendly to me. Mind you, I have experience of installing Arch Linux so that might have acclimatised me somewhat.

Those installation screens ask about the keyboard mapping that you want and I successfully chose one of the UK options. There was limited opportunity for adding extras though there was a short list of few from which I made some selections. User account set up also was on offer and I would have been better off knowing what groups to assign for my personal user account so as to have to avoid needing to log in as root so often following system start up later. Otherwise, all the default options were sufficient.

When the installation process was complete, it was time to boot into the new system and all that was on offer was a command line log in session. After logging in as root, it was time to press pkg into service in order to get a desktop environment in place. The first step was to install X:

pkg install xorg

Then, it was time to install a desktop environment. While using XFCE or KDE were alternatives, I chose GNOME 2 due to familiarity and more extensive instructions on the corresponding FreeBSD handbook page. Issuing the following command added GNOME and all its helper applications:

pkg install gnome2

So that GNOME starts up at the next reboot, some extra steps are needed. The first of these is to add the following line into /etc/fstab:

proc /proc procfs rw 0 0

Then, two lines were needed in /etc/rc.conf:


The first enables the GNOME display manager and the second activates other GNOME programs that are needed for a desktop session to start. With each of these in place, I got a graphical login screen at the next boot time.

With FreeDSB being a VirtualBox Guest, it was time to consult the relevant FreeBSD manual page. Here, there are sections for a number of virtual machine tools so a search was needed to find the one for VirtualBox. VirtualBox support for FreeBSD is incomplete in that there is no installation media for BSD systems though Linux and Solaris are supported along with Windows. Therefore, it is over to the FreeBSD repositories for the required software:

pkg install virtualbox-ose-additions

Aside from the virtual machine session not capturing and releasing the mouse pointer automatically, that did everything that was needed even if it was the open source edition of the drivers and their proprietary equivalents. To resolve the mouse pointer issue, I needed to temporarily disable the GNOME desktop session in /etc/rc.conf to drop down to a console only session where xorg. conf could be generated using the following commands:

Xorg -configure
cp /etc/xorg.conf

In the new xorg.conf file, the mouse section needs to be as follows:

Section “InputDevice”
Identifier  “Mouse0”
Driver      “vboxmouse”

If it doesn’t look like the above and it wasn’t the case for me then it needs changing. Also, any extra lines from the default set up also need removing or the mouse will not function as it should. The ALT+F1 (for accessing GNOME menus) and ALT+F2 (for running commands) keyboard shortcuts then become crucial when your mouse is not working as it should and could avert a panic too; knowing that adjusting a single configuration file will fix a problem when doing so is less accessible is not a good feeling as I discovered to my own cost. The graphics settings were fine by default but here’s what you should have in case it isn’t for you:

Section “Device”
### Available Driver options are:-
### Values: <i>: integer, <f>: float, <bool>: “True”/”False”,
### <string>: “String”, <freq>: “<f> Hz/kHz/MHz”
### [arg]: arg optional
Identifier  “Card0”
Driver      “vboxvideo”
VendorName  “InnoTek Systemberatung GmbH”
BoardName   “VirtualBox Graphics Adapter”
BusID       “PCI:0:2:0”

The next step is to ensure that your HAL settings are as they should. I needed to create a file in /usr/local/etc/hal/fdi/policy called 90-vboxguest.fdi that contains the following:

<?xml version=”1.0″ encoding=”utf-8″?>
# Sun VirtualBox
# Hal driver description for the vboxmouse driver
# $Id: chapter.xml,v 1.33 2012-03-17 04:53:52 eadler Exp $
Copyright (C) 2008-2009 Sun Microsystems, Inc.
This file is part of VirtualBox Open Source Edition (OSE, as
available from This file is free software;
you can redistribute it and/or modify it under the terms of the GNU
General Public License (GPL) as published by the Free Software
Foundation, in version 2 as it comes in the “COPYING” file of the
VirtualBox OSE distribution. VirtualBox OSE is distributed in the
hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
Clara, CA 95054 USA or visit if you need
additional information or have any questions.
<deviceinfo version=”0.2″>
<match key=”info.subsystem” string=”pci”>
<match key=”info.product” string=”VirtualBox guest Service”>
<append key=”info.capabilities” type=”strlist”>input</append>
<append key=”info.capabilities” type=”strlist”>input.mouse</append>
<merge key=”input.x11_driver” type=”string”>vboxmouse</merge>
<merge key=”input.device” type=”string”>/dev/vboxguest</merge>

With all that set, it is time to ensure that the custom user account is added to the wheel and operator groups using this command:

pw user mod [user name] -G wheel operator

Executing the above as root means that the custom account can run the su command so that logging in as root at the start of a desktop session no longer is needed. That is what being in the wheel group allows and the anyone in the operator group can shut down or restart the system. Both are facilities readily available in Linux so I fancied having them in FreeBSD too.

Being able to switch to root in a terminal session meant that I could go on to add software like Firefox, Libreoffice, GIMP, EMACS, Geany, Netbeans, Banshee and so on. There may be a line of opinion that FreeBSD is a server operating system but all of these make it more than passable for serving as a desktop one too. There may be no package management GUI as such and the ones that come with GNOME do not work either but anyone familiar with command line working will get around that.

FreeBSD may be conservative but that has its place too and being able to build up a system one item at a time teaches far more than getting everything already sorted in one hit. So far, there is enough documentation to get me going and I hope to see where else things go too. So far, the OS hasn’t been that intimidating and that’s good to see.

Getting Gnome Shell going for Fedora 16 running in VirtualBox

There are a number of complaints out there about how hard it is to get GNOME Shell running for a Fedora 16 installation in a VirtualBox virtual machine. As with earlier versions of Fedora, preparation remains a matter of having make, gcc and kernel-devel (kernel headers, in other words). While I have got away with just those, adding dkms (dynamic kernel module support) to the list might be no bad idea either. To get all of those instated, it is a matter of running the following command as root or using sudo:

yum -y install make gcc kernel-devel dkms

The -y switch ensures that any Y/N prompts that usually appear are suppressed and that the installation is completed. Just leave it out if you are inclined to get second thoughts. Another item that has been needed with a previous release of Fedora is libgomp but I haven’t had to add this for Fedora 16 if I remember correctly.

Once those are in place, it is time to install the VirtualBox Guest Additions.  Going to Devices > Install Guest Additions… mounts a virtual CD that can be used for the installation of the various drivers that are needed. To do the installation, first go to where the installer is located using the following command:

cd /media/VBOXADDITIONS_4.1.6_74713/

Note that this location will change according to the release and build numbers of VirtualBox but the process essentially will be the same other than this. Once in there, issue the following command as root or using sudo:


Hopefully, this will complete without errors now with the precursor software that has been added beforehand. However, there is one more thing that needs doing or you will get the GNOME 3 fallback desktop instead. It pertains to SELinux, an old adversary of mine that got in the way when I was setting up a web server on a machine running Fedora. It doesn’t recognise the new VirtualBox drivers as it should so the following command needs executing as root or using sudo:

restorecon -R -v /opt

Doing this restores the SELinux contexts for the /opt directories within which the VirtualBox software directories are found. The -R switch tells it to act recursively and -v makes it verbose. When it has done its work, hopefully successfully, it is time to reboot the virtual machine and you should have a GNOME Shell desktop interface when you log in.

A spot of roughness with VirtualBox 3.02 on Ubuntu

Among the various things that I needed to do on Saturday, I got to looking at why VirtualBox Windows guests could not shut down and the processes killed. Though it wasn’t clear at the outset, my suspicions began to centre on the sound hardware emulation and how it interacted with the host’s sound capabilities. A look at the  VirtualBox log sent me that way after a spot of experimentation with reinstalling Windows 7 and adding the Guest Additions along with removal and reinstatement of the same for a Windows XP guest that makes my like easier. It also seems that the same problem blighted the start up of Linux guests too. Either removing virtual sound hardware or using the null sound driver seems to allow things to run smoothly. That may not sound ideal but it doesn’t bother me with the host providing all that I need. Also, it’s a moot point as to whether I have come across a bug in VirtualBox or whether using Ubuntu on a hardware configuration on which it wasn’t originally installed is the cause but I have found a way forward that suits me. Saying that, if I find that the issue disappears in a future, that would be even better.