Book Image

Linux Utilities Cookbook

By : James Kent Lewis
Book Image

Linux Utilities Cookbook

By: James Kent Lewis

Overview of this book

<p>Linux is a stable, reliable and extremely powerful operating system. It has been around for many years, however, most people still don't know what it can do and the ways it is superior to other operating systems. Many people want to get started with Linux for greater control and security, but getting started can be time consuming and complicated. <br /><br />A practical, hands-on guide that provides you with a number of clear step-by-step examples to help you solve many of the questions that crop up when using an operating system you may not be familiar with.</p> <p>Presenting solutions to the most common Linux problems in a clear and concise way, this helpful guide starts with spicing up the terminal sessions by command retrieval and line editing, and shell prompt variables. We will then get to know the different desktops (GUIs) available for Linux systems and which is the best fit for you. We will then explore the world of managing files and directories, connectivity, and what to do when it goes wrong. We will also learn a range of skills, from creating and managing user accounts to securing your system, managing and limiting processes, and letting information flow from one process to another using pipes. Later, we will master disk management, working with scripts and automating tasks quickly, and finally, understand the need for a custom kernel and tips on how to build one.</p> <p><br />Based on the author's extensive experience, there is a section on best practices that every Linux user should be familiar with.</p>
Table of Contents (19 chapters)
Linux Utilities Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

What is using that port? The /etc/services file


From time to time you may need to know what service is running on a particular port. The /etc/services file contains that information and more.

How to do it...

Here we will take a look at some common services on a Linux system:

  1. View your /etc/services file: more /etc/services.

  2. Press the Space bar once to scroll the page down. See where it shows "ftp"?. The 21 in the next column indicates the port that FTP is using. The /tcp and /udp means that port is available for both protocols.

  3. You should also see telnet (if not, press Enter a few times). It should show port 23.

  4. Now let's search for a service. Press the Backspace key a few times to go back to the top, and enter /nameserver.

  5. We can see that nameserver is using port 42 and is available for both TCP and UDP.

  6. The file is quite long (over 11,000 lines on my system) as there are many, many standard ports.

There's more...

By convention, ports numbered 0 to 1023 are considered the "well-known ports". Ports...