Book Image

Learn Linux Quickly

By : Ahmed AlKabary
Book Image

Learn Linux Quickly

By: Ahmed AlKabary

Overview of this book

Linux is one of the most sought-after skills in the IT industry, with jobs involving Linux being increasingly in demand. Linux is by far the most popular operating system deployed in both public and private clouds; it is the processing power behind the majority of IoT and embedded devices. Do you use a mobile device that runs on Android? Even Android is a Linux distribution. This Linux book is a practical guide that lets you explore the power of the Linux command-line interface. Starting with the history of Linux, you'll quickly progress to the Linux filesystem hierarchy and learn a variety of basic Linux commands. You'll then understand how to make use of the extensive Linux documentation and help tools. The book shows you how to manage users and groups and takes you through the process of installing and managing software on Linux systems. As you advance, you'll discover how you can interact with Linux processes and troubleshoot network problems before learning the art of writing bash scripts and automating administrative tasks with Cron jobs. In addition to this, you'll get to create your own Linux commands and analyze various disk management techniques. By the end of this book, you'll have gained the Linux skills required to become an efficient Linux system administrator and be able to manage and work productively on Linux systems.
Table of Contents (24 chapters)

The /etc/passwd file

In Linux, user information is stored in the /etc/passwd file. Every line in /etc/passwd corresponds to exactly one user. When you first open /etc/passwd, you will see a lot of users, and you will wonder, where are all these users coming from? The answer is simple: most of these users are service users, and they are used by your system to start up various applications and services. However, our main focus of this chapter will be system users; those are real people like you and me!

Every line in /etc/passwd consists of 7 fields, each separated by a colon, and each field represents a user attribute. For example, the entry for user elliot will look something like this:

Figure 1: The 7 fields in /etc/passwd

The following table breaks down those seven fields in /etc/passwd and explains each one of them:


Field

What does it store?

1

This field stores the username.

2

This field usually has an X in it, which means the user's password is encrypted and...