As I said in the previous section, I've chosen to mostly use CentOS for the recipes in this book. Hopefully, this gives you a good baseline for learning about Linux Administration, but also gives you a bit of a head start if you plan on going for any of the Red Hat exams.

Instead of requiring you to have a spare laptop handy, or renting a server somewhere, I'm going to advocate using VMs for testing and running through the examples given.

VMs are exactly as they sound – a way of virtualizing computer hardware on one or a cluster of physical machines, thus allowing you to test, break, and play to your heart's content, without risking rendering your own computer unbootable.

There are many ways of creating a VM: macOS has xhyve, Windows has Hyper-V, and Linux has a native implementation called Kernel Virtual Machine (KVM).

Another way of creating and managing VMs is a program called VirtualBox, which is now developed by Oracle. The nice thing about this software, and the reason I shall be using it here, is that it's cross-platform, being produced for macOS, Windows, and Linux.

I'm using Ubuntu to write this book, so I'll run through the basic way of installing VirtualBox on an Ubuntu desktop.

This will be slightly different to installing it on other distributions, but a good number of them package it for installation, and should provide a guide for installing it.

Open your Terminal and run the following:

$ sudo apt install virtualbox

You will likely be prompted to confirm installation of VirtualBox and its dependencies (there may be a lot—it's a complex program and if you haven't updated in a while, you may get a few dependency updates too).

Hit Y and Enter to continue. The following screenshot shows an example of the installation if started from the command line:

Once done, you should have a working VirtualBox installation.

If you'd like, you can also install VirtualBox through Ubuntu software.

Simply search for the software you desire, in this case, VirtualBox, and click through to its store page.

Once there, click Install and the package will be installed, no Terminal required!

After installation, your screen will change to show Launch and Remove options.

Although I'm using Ubuntu, it's not the end of the world if you're not. macOS is a fine OS too, and handily it supports VirtualBox.

In this recipe, we'll run through a couple of ways of installing VirtualBox in macOS. You'll find that the layout is extremely similar, regardless of the OS you use.

If you already have the command-line program brew installed, then getting VirtualBox is as easy as running the following command:

$ brew cask install virtualbox

You may be prompted for a superuser password to complete the installation.

Oracle also provides an installation image for macOS, if you'd like to install it in the more traditional way.

Simply navigate to https://www.virtualbox.org/wiki/Downloads and select the OS X hosts option.

This will prompt you to download the installer to your local system, which you can unpack and install.

Running through the installation, you may be prompted for your superuser password.

If you're not using a Linux flavor on your computer, and you're not using macOS, it's a good bet that you're running Windows (unless you've delved into FreeBSD on the desktop or similar, in which case I can't help you here—we'd need an entire afternoon).

If using Windows, I can suggest VirtualBox again, due to its cross-OS nature, and it can again be installed from Oracle's site.

Like the macOS installation, navigate to https://www.virtualbox.org/wiki/Downloads and select the Windows hosts option:

This will download an executable that can be run.