To complete the exercises in this chapter (and the following chapters), you will need either a PC or laptop with at least 2 GHz of CPU power, 10 GB of hard disk space, and about 1 GB of RAM to spare. Pretty much all hardware created in the last 5 years should suffice.

A virtual machine is an emulation of a physical machine. This means it runs inside a physical machine, as opposed to directly on the hardware. A physical machine has direct access to all hardware, such as the CPU, the RAM, and other devices such as the mouse, the keyboard, and the monitor. It is, however, impossible to share the CPU or the RAM between multiple physical machines. Virtual machines do not directly get access to hardware, but through an emulation layer, which means resources can be shared between multiple virtual machines.

Because we're discussing Bash shell scripting in general, in theory it does not matter what kind of an installation is performed. As long as that installation runs a compatible Linux operating system with Bash 4.4 or later, all exercises should work. There are, however, many advantages...

To use virtual machines, we need software called a hypervisor. A hypervisor manages resources between the host machine and the virtual machines, provides access to disks, and has an interface to manage it all. There are two different types of hypervisors: type-1 and type-2. Type-1 hypervisors are the so-called bare-metal hypervisors. These are installed instead of a regular operating system such as Linux, macOS, or Windows, directly on the hardware. These types of hypervisors are used for corporate servers, cloud services, and so on. For this book, we will use a type-2 hypervisor (also called hosted hypervisors): these are installed within another operating system, as a piece of software not much different than, for example, a browser.

There are many type-2 hypervisors. The most popular choices at the time of writing are VirtualBox, VMware workstation player...

In this book, we're scripting with Bash, which means we do not need a GUI for our Linux installation. We have chosen to use Ubuntu Server 18.04 LTS as the virtual machine operating system, for a number of reasons:

• Ubuntu is considered a beginner-friendly Linux distribution
• The 18.04 is a Long-Term Support (LTS) release, which means it will receive updates until April 2023
• Because an Ubuntu server offers a CLI-only installation, it is easy on system resources and representative of real-life servers

At the time of writing, Ubuntu is maintained by Canonical. You can download the ISO image from https://www.ubuntu.com/download/server. Download the file now, and remember where you save this file, since you'll need it soon.

In this chapter, we have started preparing our local machine for the rest of the book. We now know about the differences between virtual and physical machines, and why we prefer to use a virtual machine for the remainder of this book. We've learned about the two different types of hypervisors. We have installed and configured VirtualBox with a virtual machine, on which we have installed the Ubuntu 18.04 operating system. Finally, we have connected to our running virtual machine using SSH instead of the VirtualBox terminal, which affords better usability and options.

The following command was introduced in this chapter: ssh and exit.

In the next chapter, we will finish setting up our local machine by looking at some different tools we can use that will help us with bash scripting, both on the GUI and on the virtual machine CLI.

1. What are some of the reasons running a virtual machine would be preferable to a bare-metal installation?
2. What are some of the downsides of running a virtual machine as opposed to a bare-metal installation?
3. What is the difference between a type-1 and type-2 hypervisor?
4. In which two ways can we start a virtual machine on VirtualBox?
5. What makes an Ubuntu LTS version special?
6. What should we do if, after the Ubuntu installation, the virtual machine boots to the Ubuntu installation screens again?
7. What should we do if we accidentally reboot during installation, and we never end up at the Ubuntu installation (but instead see an error)?
8. Why did we set up NAT forwarding for the virtual machine?

The following resources might be interesting if you'd like to go deeper into the subjects of this chapter:

• Getting Started with Oracle VM VirtualBox by Pradyumna Dash, Packt: https://www.packtpub.com/virtualization-and-cloud/getting-started-oracle-vm-virtualbox
• Mastering Ubuntu Server – Second Edition by Jay LaCroix, Packt: https://www.packtpub.com/networking-and-servers/mastering-ubuntu-server-second-edition