Course 1 – An introduction to Linux

Welcome to’s Free Linux Training.
This is the first course in the Beginner series designed to get you familiar with the Linux family of operation systems.

This course covers basic PC concepts, knowledge, and other prerequisites so you can get started using Linux smoothly. Partitioning, BIOS, LiveCDs, Virtual Machines and more!

What is Linux?

Linux is an operating system that is deployed on countless computers and similar devices around the world.  If you want to learn more about this topic, read the great article below!

PC Hardware Concepts

Linux is primarily run on x86 and x86_64 platforms.  These are a series of microprocessors in use in most desktop and server systems.  When a computer is turned on, the BIOS searches storage devices for an operating system.  Typically, the main operating system of a computer is stored on the system’s primary hard drive, and information about how to load this operating system is stored in the “Master Boot Record,” or MBR, of that hard drive.  The MBR contains 2 pieces of information:  how the disk is partitioned and a basic boot loader which contains instructions to load the operating system.

Partitions and MBR are concepts that are key to understanding how operation systems are installed and how they are loaded.  Older computers usually shipped with an operation system installed, such as Microsoft Windows, with only 1 partition.  In the Microsoft world, this is referred to as the “C:” drive.  The C: drive refers to the first partition on the primary disk for the operating system.  In Linux, the equivalent of the C: drive is generally /dev/sda1

In newer Windows Computers, especially laptops, it’s not uncommon to see a second partition labeled as the D: drive.  This partition generally contains system restore software.  While not entirely obvious from Windows, the D: drive is actually on the same physical hard disk as the C: drive.  In Linux, a similar partition would be called /dev/sda2

The MBR lets the computer know where C: or /dev/sda1 ends and D: or /dev/sda2 starts.

Some computers, especially servers, may have more than 1 physical drive.  Each physical drive is generally partitioned into one or more partitions each.  In a system with two drives and one partition each, Linux would refer to the partitions as /dev/sda1 on disk /dev/sda and /dev/sdb1 on disk /dev/sdb .  Notice the sd<letter><number> format.  sd stands for ‘serial device’ , the letter for which physical drive, and the number for the physical partition.  To refer to an entire physical drive, you refer to the disk without a partition number.

See this wikipedia article for more information on basic PC hardware:

BIOS Concepts

Now that you know a little bit about the important hardware information that is needed to understand how operating systems are physically installed, we can talk briefly about BIOS.

BIOS stands for “Basic Input/Output System” and is software that is embedded on your computer’s motherboard which controls the initial mode of the computer system.  BIOS’s main job is to hand off control of the system to an operating system found on a storage device as described above.  Each PC or server will have a slightly different version of BIOS from another.  It’s an important job of any IT administrator to familiarize themselves with their system’s BIOS.

The most important concept for the BIOS in these courses will be the boot order.  As previously described, the BIOS will generally default to booting an operating system off the primary hard drive.  To actually install a Linux system, please refer to your computer’s manufacturer instructions about how to boot from a CD or USB key, as applicable.  For those using VirtualBox in later courses, I will cover those steps directly in the courses.

In modern computers, a technology called UEFI is replacing BIOS.  This is due to many technological reasons that I won’t outline here.  You would do well to familiarize yourself with UEFI, especially if your computer uses it in place of a traditional BIOS.

Choosing a Linux Distribution

Linux refers to a family of operating systems, and in that family each different variant is called a distribution, or distro.  The various distros are maintained by various organizations or people.  A great resource for finding information about many of the distros available is

For the purpose of this training, we’re going to be using CentOS 6.  I’m not going to get into the details of what CentOS is or isn’t, but essentially it is used as a free replacement for Red Hat Enterprise Linux.


On Windows and Mac computers, the operating system is installed on your hard disk.  Options are set in the BIOS to look for an operating system on the hard disk, and to load that software.  A LiveCD is an entire operating system on a CD or DVD, many can also be made to run on USB thumb drives.  You can instruct your BIOS to first look at the CD/DVD drive for bootable software instead of the hard disk.

LiveCD’s are available for most popular Linux distros.  An advantage of trying a LiveCD is that you can test drive the operating system to see how it works on your particular platform without having to partition or format your hard disks.  It’s a nice and simple way to see if you like using Linux on your computer in place of any other currently installed operating systems, if any.  If your system seems to be a little sluggish while running a LiveCD, remember that all operating system data must be read from your disk drive, which is a lot slower than reading information off of a modern hard disk.  An installed operating system will generally run much faster for this reason, but if you have decent specs in your PC, you should be just fine for testing purposes.

Virtual Machines (VM’s)

Nowadays Virtual Machines are quite popular, and you have probably heard of them.  As recently as 4 or 5 years ago, they were relatively scarce and much fewer people outside of Enterprise IT fields had used them.  If you are unfamiliar with VM’s, they are essential ‘virtual’ computers that run as a software application on top of your current operating system.  Virtual machines are a great tool, especially for test driving new operating systems and Linux distros.  If you are a brand new Linux user with a decently modern PC (circa 2008 or newer), you should be able to run a VM just fine.  For this purpose, I recommend Oracle’s (formerly Sun’s) VirtualBox.  You can learn more about it at the hompage.


Review Questions

1) What is the term for the different versions of available Linux operating systems?

2) What information does that MBR contain, and what does MBR stand for?

3) What is the difference between /dev/sda, /dev/sda1, and /dev/sdb1 ?

4) What is a good source of information to find out about the many different versions of linux operating systems available?


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  • Bill Colgrove

    Excellent. How do I get to subsequent lessons? The only lesson that is a link appears to be the first one?