I use VirtualBox [1] a lot as (local) virtualization software. It is a full-featured virtualization host, and supports multiple underlying disk image file types for guests.

One of those is VirtualBox' native Virtual Disk Image or VDI file type. An advantage of this type is that one can create a dynamically allocated image. This image will initially be very small and not occupy any space for unused virtual disk sectors, but will grow when a disk sector is written to for the first time. VirtualBox does this by checking for unused sectors.

However, this poses issues for disks with multiple partitions. If the last partition is say a (unused) swap partition, then VirtualBox does not automatically grow the underlying image. Even though the first partition is full, VirtualBox will not grow and therefore the host disk will be full without having reached its full potential.

To solve this issue, the machine needs to be partitioned using one big happy partition. Then VirtualBox will dynamically resize according to expectations.

I use packer [2] to prepare disk images for Debian, together with a preseed [3] file. Using preseeding to partition the disk is limited to what is supported by the partition tool …

I'm a big fan of the DevOps attitude of "cattle" versus "pets": machines should be built in a repeatable, automated and consistent way. If there's something wrong, don't be afraid to replace a sick "cow" instead of trying to revive your "pet".

This Zen mindset also helps when preparing for demos, trainings and workshops: Usually I need a number of machines, and what better way than create them by using automation ? For that I'm using the tools Ansible, Packer, Vagrant and VirtualBox - they are all Open Source and can be used on a number of platforms (e.g. Windows, Linux and Mac OS X).

Ansible is a tool for managing systems and deploying applications, licensed under the GNU General Public License version 3 (my personal favorite).

Vagrant is a tool for managing virtual machines and is licensed under the MIT license.

VirtualBox is a virtualization environment for local use, licensed under the GNU General Public License version 2.

Packer creates a machine image by installing an operating system to a multitude of local and cloud platforms, for example VMWare, VirtualBox as well as Docker, Amazon EC2 and DigitalOcean. Packer is licensed under the Mozilla Public License Version 2.0.

How …