What is the environment all about?

This page explains the process to create the classes environment on your computer. Everything we do in this course is on a virtual machine. So you need to install support for virtual machines, then create one and configure it.

Why do we need a virtual machine?

Why can't I run everything directly on my real (non-virtual) machine?

The answer is because we want to avoid "but it works on my machine" at any cost. Take a look:

http://www.cafepress.com/+but-it-works-on-my-machine+hats-caps

This is so recurring in the IT field that it even became an inside joke. When you write your programs you will have the environment influencing the way your programs work. Perhaps your machine has just the right version of Java. Perhaps your machine has just the right amount of memory. etc etc. So when you share your program with other programmers you start to see that things do not run exactly the same way on other platforms.

We cannot waste precious time trying to check every single thing that can influence program execution. If we all run our programs on the same virtual machine we can almost eliminate such effect. So a solution for an exercise will run precisely the same way on everyone's computer no matter the actual operating system that this computer has.

What do I need to run a virtual machine on my computer?

In order to run a virtual machine you need what is called a hypervisor. In a virtualization, you have one computer running inside of another computer. The hypervisor is what makes such a thing possible.

The hypervisor we will use is called VirtualBox, which works pretty well for our needs on this course. The problem about VirtualBox is that it takes time to get started with it. All the boring details about VirtualBox are made much more simple by Vagrant.

Vagrant is then a set of procedures to make it easy to use VirtualBox, among other hypervisors. With Vagrant you can type a command like "create a virtual machine with Linux flavor X" and after a couple of minutes you magically have a virtual machine for you to use. It is that simple.

Virtualization hosts versus virtualization guests

On this guide you will need to use both the guest and the host machines, which are roles in a virtualization. Let us define them:

• host - The real machine. This is the operating system that runs the virtualization program, aka. hypervisor.
• guest - The virtual machine. This is the virtual operating system that runs on top of the hypervisor.

There are two sorts of command lines you will need to use: one on the host machine and another on the virtual machine.

What we will run on the host are just the commands we need to create and connect to the virtual machine. Your command line will most likely be different from this one, especially if you use Windows, but I hope you got the gist.

user@host:~$

Here is how the command line will look like on the virtual machine:

vagrant@vagrant-ubuntu-trusty-32:~$

Once we have set the virtual machine, we will only use the guest terminal.