For over a decade, the CentOS project has provided the community with a free, enterprise-grade operating system through the rebranding and recompilation of the Red Hat Enterprise Linux source. Since CentOS users rely almost exclusively on the community for their support needs, I was keen to write this book when Packt approached me about the project's latest release, CentOS 7. The recipes we chose cover a wide range of topics, from getting started to managing many common web services, and hopefully administrators of any skill level will find something of interest.
However, writing a book is a huge undertaking. Because of this, I want to thank the staff at Packt, my family, and my friends, for their support. The dog needs to be taken for a walk, family engagements need attending, and emergencies arise at the workplace. Without the understanding and encouragement of those around me and the editorial staff, you wouldn't be reading this book.
The recipes presented in this book aim to make even the most difficult configuration tasks easy by providing step-by-step instructions and discussion. Here's a quick rundown of what you can expect from each of the 12 chapters.
Chapter 1, Getting Started with CentOS, contains recipes for installing CentOS using graphical, text-based, and kick-start approaches. How to set up a CentOS platform for projects running Docker and on Amazon Web Services is also discussed.
Chapter 2, Networking, contains recipes to help you complete common networking tasks, such as how to set up a static IP address, assign multiple addresses to a single network interface, bond multiple interfaces with the same address, and configure the system's firewall using FirewallD and iptables. It also presents recipes for configuring network services such as DHCP, NFS, and Samba.
Chapter 3, User and Permission Management, shows you how to increase the security of your system by enforcing password restrictions, adjusting the default permissions given to newly created files and directories, and the use of sudo to avoid circulating the root password. How to work with SELinux is also discussed.
Chapter 4, Software Installation Management, provides recipes focused on working with software repositories and installing software. You'll learn how to register the EPEL and Remi repositories, prioritize the repositories packages are installed from, and update your software automatically. You'll also learn how to compile and install software from source code.
Chapter 5, Managing Filesystems and Storage, presents recipes that show you how to set up and work with RAID and with LVM. These services leverage your system's storage to maintain availability, increase reliability, and to keep your data safe against inevitable disk failures.
Chapter 6, Allowing Remote Access, aims to help you provide remote access to your CentOS system in a secure manner. Its recipes cover using SSH, configuring a chroot jail, and tunneling VNC connections through an encrypted SSH tunnel.
Chapter 7, Working with Databases, collects recipes that provide you with the necessary steps to get started with various database services such as MySQL, MongoDB, and OpenLDAP. You'll also learn how to provide backup and redundancy for these services.
Chapter 8, Managing Domains and DNS, takes us into the world of DNS. The recipes show you how to set up a resolving DNS server to decrease latency caused by domain lookups and how to manage your own domain with an authoritative DNS server.
Chapter 9, Managing E-mails, will help you set up your own mail server. The recipes discuss configuring Postfix to provide SMTP services, configuring Dovecot to provide IMAP and POP3 services, and securing these services with TLS. You'll also find instructions on how to set up SpamAssassin to help reduce unsolicited bulk e-mails.
Chapter 10, Managing Web Servers, contains recipes about configuring Apache to server web content. You'll learn how to set up name-based virtual hosting, server pages over HTTPS, and perform URL rewriting. How to set up NGINX as a load balancer is also discussed.
Chapter 11, Safeguarding Against Threats, contains recipes to help protect the investment you've made in your CentOS server. They cover logging, threat monitoring, virus and rootkits, and network backups.
Chapter 12, Virtualization, shows you how CentOS can function as a host operating system to one or more virtualized guests. This allows you to take better advantage of your hardware resources by running multiple operating systems on the same physical system.
To follow the recipes in this book, first and foremost you'll need a system capable of running CentOS 7. The minimum requirements (and maximum capabilities) are documented in the Red Hat Enterprise Linux knowledge base available online at https://access.redhat.com/articles/rhel-limits. In brief, you'll need a system that has the following:
x86_64 processor (RHEL/CentOS 7 does not support x86)
1 GB RAM
8 GB Disk capacity
Apart from a system to install CentOS on, you'll also need a copy of the CentOS installation media and a working network connection. You can download a copy directly from https://www.centos.org/download/ or using BitTorrent.
This book is for Linux professionals with basic Unix/Linux functionality experience, perhaps even having set up a server before, who want to advance their knowledge in administering various services.
In this book, you will find several headings that appear frequently (Getting ready, How to do it..., How it works..., There's more..., and See also).
To give clear instructions on how to complete a recipe, we use these sections as follows.
This section tells you what to expect in the recipe, and describes how to set up any software or any preliminary settings required for the recipe.
This section usually consists of a detailed explanation of what happened in the previous section.
This section consists of additional information about the recipe in order to make the reader more knowledgeable about the recipe.
In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "The repositories' configuration files are found in the /etc/yum.repos.d directory."
A block of code is set as follows:
[sshd]
enabled=true
bantime=86400
maxretry=5Any command-line input or output is written as follows:
firewall-cmd --zone=public --permanent --add-service=dns
New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "Select your desired language and click on Continue."
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