CentOS Quick Start Guide

Get up and running with CentOS server administration

Shiwang Kalkhanda

• Publisher: Packt Publishing
• Year: 2018
• ISBN:
  9781789341461
• Edition: 1
• Topic: Computer Science
• Subtopic: Cyber Security
• Index: Computer Science

A concise walk-through of CentOS 7, starting from installation to securing it's environment.

Key Features

• No previous Linux environment experience needed for reading this book
• Get comfortable with a popular and stable Red Hat Enterprise Linux distribution
• Most of the command line based concepts are explained with graphics

Book Description

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.

What you will learn

• Understand file system hierarchy and essential command-line skills
• Use Vi editor, I/O redirections and how to work with common text manipulating tools
• Create, delete, modify user accounts and manage passwords and their aging policy
• Manage file ownership, permissions, and ACL
• Execute process management and monitoring on the command line
• Validate and manage network configuration using nmcli
• Manage remote logins using SSH and file transfer using SCP and Rsync
• Understand system logging, how to control system services with systemd and systemctl, and manage firewalId

Who this book is for

Any individual who wants to learn how to use Linux as server or desktop in his environment. Whether you are a developer, budding system administrator, or tech lover with no previous Linux administration background, you will be able to start your journey in Linux using CentOS 7 with this book.

Overview of Essential Advance Utilities

In this chapter, we will learn some advanced and essential concepts related to the system, such as logging, controlling system services, firewalls, and Security Enhanced Linux (SELinux). Logging plays a key role in debugging and troubleshooting system applications. A solid understanding of logging will make your daily operations easier to handle and will also give you a deep insight into the application's functioning.

In this final chapter, we will learn the different logging mechanisms available in CentOS 7, such as journald and rsyslog. By now, you have seen how to install, update, and remove applications. Now, we will see how to control these applications and system services using the systemd and systemctl utilities. Finally, we will understand the basic usage of firewalld and SELinux to secure running services and harden the security of the system.

We will cover the following:

• Understanding system logging
• Working with rsyslogd and journald
• Understanding control of systems and services
• Working with systemd and systemctl
• Understanding SELinux concepts
• Working with SELinux
• Understanding firewall concepts in CentOS 7
• Working with firewalld

Understanding system logging

Most application programs and the kernel write their event information in log files maintained at different locations. It helps in keeping track of activities that are taking place on the system and also forms an essential part of system auditing. Monitoring of log files helps in spotting any unusual activity in the system. Logging also helps in troubleshooting any application problems. By convention, Linux uses the /var/log/ directory for storing logs in the system.

Starting with CentOS 7, we have two logging services that exist in the system:

• Rsyslog service
• Systemd-journald service

System time service should be properly configured before configuring log services, as time is an important component of log files.

Working with rsyslog

The rsyslog service centrally collects the log messages from different applications running in the Linux system. It collects the logs based on their type and their priorities, and stores them persistently in the /var/logfollows:/ directory.

The following table lists some important log files maintained by rsyslog, along with their description:

Log file path	Description
/var/log/messages	Most standard log messages are stored here, except authentication logs, email logs, and some application debugging logs.
/var/log/secure	Authentication logs containing errors and other messages are stored here.
/var/log/maillog	Mail server logs are stored here.
/var/log/boot.log	Boot/system startup messages are logged here.
/var/log/cron	It stores cron job (scheduler) logs.
/var/log/wtmp	Login activity logs are kept here.
/var/log/dmesg	Kernel messages are stored here.
/var/log/cups	Printing service logs are stored here.
/var/log/samba	Samba service logs are kept here, not managed by rsyslog. The Samba service directly writes logs here.
/var/log/httpd	This directory contains Apache web server logs, not managed by rsyslog. Apache directly writes logs in these files.
/var/log/audit/	Contains the auditd service logs and SELinux log files.

Rsyslogd is an application in Linux syst...

Table of contents

• Title Page
• Copyright and Credits
• Dedication
• About Packt
• Contributors
• Preface
• Getting Started with CentOS 7
• Command-Line and Filesystem Navigation
• Managing Text Files
• User and Group Management
• Managing File Permissions
• Process Management
• Managing Networking in CentOS
• Software Package Management
• Overview of Essential Advance Utilities
• Other Books You May Enjoy