Book Image

CentOS Quick Start Guide

By : Shiwang Kalkhanda
Book Image

CentOS Quick Start Guide

By: Shiwang Kalkhanda

Overview of this book

Linux kernel development has been the worlds largest collaborative project to date. With this practical guide, you will learn Linux through one of its most popular and stable distributions. This book will introduce you to essential Linux skills using CentOS 7. It describes how a Linux system is organized, and will introduce you to key command-line concepts you can practice on your own. It will guide you in performing basic system administration tasks and day-to-day operations in a Linux environment. You will learn core system administration skills for managing a system running CentOS 7 or a similar operating system, such as RHEL 7, Scientific Linux, and Oracle Linux. You will be able to perform installation, establish network connectivity and user and process management, modify file permissions, manage text files using the command line, and implement basic security administration after covering this book. By the end of this book, you will have a solid understanding of working with Linux using the command line.
Table of Contents (11 chapters)

Understanding Linux filesystem permissions

On Linux/Unix-based operating systems, every file belongs to a user and to a group. By default, the user who creates the file is the owner of that file and the file belongs to that user's primary group. Access to the file via the Linux filesystem is controlled by permissions applied to that file. These permissions are classified for the owner (also known as the user) of the file, group (also known as the group owner) of that file, and for everybody else (also known as others) in the Linux system.

There are three types of standard permissions that are applied to files:

  • Read, represented by the letter r
  • Write, represented by the letter w
  • Execute, represented by the letter x

These are generally grouped in triplets (such as rwx or r-w) to represent a class of permissions. Each file has three classes of permissions; that is, these permissions...