Linux with Operating System Concepts

Type
Number of 
CPUs/Cores
DRAM
Storage Devices
Typical Cost
Operations 
Per Second
a
Super 
computer
Thousands to 
hundreds of 
thousands
100s–1000s 
GBytes
Storage area networks
$ Tens of 
millions
TFLOP to 
PFLOP range
Mainframe
Hundreds to 
thousands (or 
more)
Dozens to 
100s of 
GBytes
Server storage or 
storage area network
$100,000–$1 
million
GFLOP to 
TFLOP range
Server
1–8 multicore 
(up to 8 
cores)
Up to 
32 GBytes
Many hard disk drives 
(up to dozens)
$5,000–
$15,000
GFLOP range
Desktop
1–2 multicore 
(up to 8 
cores)
4–16 GBytes
1–2 Hard disk drives, 
optical disk drive, 
numerous USB ports
Under 
$2,400, often 
around 
$1,200
GFLOP range
Laptop
1 multicore 
(up to 8 
cores)
4–16 GBytes
1 Hard disk drive, 
optical disk drive, 
a few USB ports
Under 
$1,200, often 
around $900
GFLOP range
Tablet
1
4–8 GBytes
USB port, small 
capacity hard disk 
drive
$300–$700
Up to GFLOP 
range
Smart 
phone
1
Up to 2 
GBytes
USB port, internal 
storage (flash or disk) 
up to 64 GBytes
Under $500, 
often under 
$200
Hundreds of 
MFLOPs up 
to 1 GFLOP
a 
The word FLOP means “floating point operations per second” and is a common way of gaging processor 
speed. The letter preceding FLOP indicates the magnitude. P for peta, or quadrillion, T for tera, or trillion, G 
for giga, or billion, M for mega, or million.

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32
◾
Linux with Operating System Concepts
again differs because it offers both perspectives. Roughly the first half of the textbook covers 
the “user” perspective while the second half covers the “administration” perspective.
What you will see from here on out are topics on the following from the user perspective.
• 
CLI
: How to issue commands and the many shortcuts available.
• 
The Linux file system
: How to navigate and use it.
• 
Process management
: How to issue, monitor, and terminate your processes.
• 
Regular expressions
: What they are, how to use them, and why you might use them.
• 
Scripting
: How to write basic Bash and Csh scripts.
From the system administrator perspective, we view these topics.
• 
Installation
: How to install CentOS Linux.
• 
Account creation
: How to create user and group accounts and provide them with 
privileges.
• 
The Linux file system
: How to administer the Linux file system.
• 
The boot process
: Understanding and managing the Linux boot and initialization 
process.
• 
Services
: Understanding the role of the operating system service, how to start and 
stop them, and how to configure them.
• 
The network
: Configuring and understanding the Linux services and software related 
to network communication.
• 
Software installation
: Installing and configuring open source software.
• 
Troubleshooting
: Dealing with services, log files, and other areas of Linux.
• 
Servers
: Understanding how to install and configure some of the more commonly 
used servers in Linux.
Throughout the textbook, operating system concepts are introduced in an attempt to 
provide the reader with an understanding of what is going on beneath the command line. 
This book should not be confused with concepts of operating systems textbook which 
would be far less detailed in any specific operating system.
1.10 CHAPTER REVIEW
Concepts introduced in this chapter:
• Command line interface (CLI)—an interface used in Linux in which the user enters 
commands by typing instructions and parameters from a prompt. The command line 

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Introduction to Linux
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33
requires the use of an interpreter which will determine how to carry out the com-
mand entered. Linux interpreters permit the user to enter complex commands.
• Computer system—the collection of computer hardware, software, and users. 
The hardware would do nothing without software. Software are the programs that 
we run on the computer. The user is required to tell the computer what to do 
and when.
• Gnome—one of two common GUIs that are used in Linux, Gnome is the default GUI 
for Red Hat Linux.
• Graphical user interface (GUI)—allows the user to interact with the computer 
through pointing, dragging, and clicking motions of the mouse. The GUI is the more 
common approach used today whereas the CLI is the older of the approaches.
• Interpreter—a program which takes instructions, converts them into executable 
code, and executes them. Linux shells have built-in interpreters to execute command 
line instructions and run shell scripts.
• KDE—an alternate GUI from Gnome available in most Linux platforms.
• Kernel—the core component of the operating system responsible for most of the 
OS duties. Once the computer is booted, the kernel is loaded into memory where it 
remains until the computer is shut down or rebooted.
• Linux—an operating system developed starting in the early 1990s, based on the Unix 
operating system in part. Linux has become a popular operating system for servers 
and supercomputers and computer hobbyists although it only has a small presence in 
the overall marketplace.
• Linux market share—in spite of Linux’ popularity on the Internet as the principle 
operating system used for servers and supercomputers, the Linux market share trails 
behind Windows dramatically and is also behind Mac OS. Including mobile device 
forms of Linux and Unix, the market share is under 15%.
• Linux standard base—a standard for Linux developers to implement commonali-
ties in the underlying mechanisms of Linux so that all Linux dialects retain similar 
features.
• Open source—software that is developed by programmers in the open source 
community. The software is made available for free in either executable form or 
source code. The idea is that other programmers can freely obtain the software and 
modify it as desired, contributing back to the community with new or improved 
software.
• Operating system—a suite of programs that manage our computer system for us 
so that we as users do not have to worry about the details. The operating system is 
broken into several components, the most important of which is the kernel. Other 

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34
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Linux with Operating System Concepts
components include device drivers so that the operating system can communicate 
with specific hardware devices, shells which offer the user an interface that they can 
personalize services which handle communication and requests coming from dif-
ferent agents, and utilities which are add-on programs to further help manage and 
manipulate the computer system.
• Operating system platforms—the different types of operating systems used on differ-
ent devices. Aside from Linux, other popular operating systems are Windows (which 
has the biggest marketshare), Unix, iOS (the operating system found on Apple hand-
held devices), and Mac OS X.
• POSIX—Portable Operating System Interface which describes an application pro-
grammer interface that most Unix and Linux versions attempt to implement (at least