Red Hat Enterprise Linux 9 Administration: A comprehensive Linux system administration guide for RHCSA certification exam candidates

BIRMINGHAM—MUMBAI

Red Hat Enterprise Linux 9 Administration

Copyright © 2022 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the authors, nor Packt Publishing or its dealers and distributors, will be held liable for any damages caused or alleged to have been caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

Group Product Manager: Mohd Riyan Khan

Publishing Product Manager: Shrilekha Malpani

Senior Editor: Romy Dias

Technical Editor: Arjun Varma

Copy Editor: Safis Editing

Project Coordinator: Ashwin Kharwa

Proofreader: Safis Editing

Indexer: Manju Arasan

Production Designer: Aparna Bhagat

Marketing Coordinator: Nimisha Dua

First published: November 2021

Second edition: October 2022

Production reference: 1211022

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham

B3 2PB, UK.

ISBN 978-1-80324-880-6

www.packt.com

To all the people contributing to and being part of open source, building it one piece at a time, and pushing its boundaries to make huge things possible.

– Pablo Iranzo Gómez

To the ones that once crossed my path and made a difference.

– Pedro Ibáñez Requena

Contributors

About the authors

Pablo Iranzo Gómez is a software engineer who started his Linux exposure while studying physics. He was also involved in LUGs and some projects related to HPC clusters and system administration and consultancy.

Currently, he is a principal software engineer at Red Hat’s TelCo 5G OpenShift management integration department, leveraging his experience in consulting, cloud technical account management, and OpenStack software maintenance in industries such as hotel, retail, airlines, government, Telco, 5G, Partner, and IT – covering system administration and automation, virtualization, PaaS, support, the cloud, and so on. He has a broad understanding of different views, needs, and risks across the industry.

Pablo was born in and lives in Valencia, Spain, with his family.

I want to thank my wife, Eva and my sons, Pau and Roi, for the support provided while working on this project, Javier for the moral support provided during this writing, and Miquel for always being there. Not forgetting about Miguel, who gave me this opportunity and helped get the prior version ready, and, of course, the whole Packt team that has been helping, guiding, and advising during the whole process.

Pedro Ibáñez Requena is a software engineer who started his Linux adventure playing with Linux distributions provided on CDs by magazines. He was also involved in LUGs while studying software engineering at Universitat de València.

Currently, he is a principal systems engineer in Red Hat’s Telco 5G field engineering team, focusing on OpenShift, with experience in automation, security, high availability, and databases. His experience was built in industries such as retail, finance, insurance, and Telco. He has been involved in the design, configuration, and deployment of complex IT systems including data storage, networking, monitoring, and PaaS and SaaS systems where he has a broad understanding of different views, needs, and risks across the industry.

Pedro was born in Alcoy and lives in Valencia, Spain, with his family.

I want to thank my girls, Katja and Maya, for the endless days at home, playing, chatting, swimming, traveling, or discussing because, without them, I wouldn’t be who I am today. To my parents, for supporting me to study what I wanted and for providing when I needed it. To Carles and Alex, because their help in this race was life-changing. To Pablo, who thought about me helping him with this book, and lastly, to all the people that make my day, the Telco 5G field engineering team, and the Packt team that made this possible.

Miguel Pérez Colino is an experienced technology enthusiast with a clear orientation toward IT, free/open source software, and open standards. His career has grown in the IT field with connections in every direction. From user support and teaching; through systems and network administration; to systems engineering, systems architecture, IT strategy definition, and now, as a senior manager for the Tanzu portfolio to bring Kubernetes closer to customers. He loves designing solutions and tools, making them useful and easy to use.

Scott McCarty is a principal product manager at Red Hat for the container subsystem team, which enables key product capabilities in OpenShift Container Platform and Red Hat Enterprise Linux. His focus areas include container runtimes, tools, and images. Scott is a social media start-up veteran, an e-commerce old-timer, and a weathered government research technologist, with experience across a variety of companies and organizations, from 7-person start-ups to 15,000-employee technology companies. This has culminated in a unique perspective on open source software development, delivery, and maintenance.

About the reviewers

Derek Thurston is a senior solutions architect at Red Hat and has been working with open source software since the mid-1990s. After graduating from a small merchant marine college in coastal Maine, Derek landed a job in the IT department at a naval architecture firm in Arlington, VA, where he started using Linux. Derek has worked with SGI and HP/UX systems and did his part to help save the world by converting COBOL programs to four-digit years in the late 1990s. Having worked with a variety of public and private sector entities, he has spent over 25 years helping customers find the right open source tools and technologies.

I would like to thank my wife, who inspires me every day, my son, who is always down for a cool adventure, and my two dogs, who are my steadfast officemates.

Luis Sampaio is a system engineer. He has managed servers since 2010. He has experience with Red Hat, Ubuntu, and Debian. He has some certifications such as RHCE and RHCSA.

Luis has diverse experiences in different private, hybrid cloud architectures with Amazon Web Services and Azure, as well as experience with DevOps tools such as Ansible and containers.

He likes to share his tech views and experiments with a community. Luis loves playing poker with friends and visiting new cities.

I would like to thank my family (my mother, Silvia, for all the support, my wonderful wife, Yolanda, and my terrific and smart son, Bruno Miguel) for unlimited patience and tolerance.

My wife is my best friend, and I love her dearly. Without her love and the support from her, I would never have been able to finish the book.

Table of Contents

Preface

Part 1 – Systems Administration – Software, User, Network, and Services Management

1

Getting RHEL Up and Running

Technical requirements

Obtaining RHEL and a subscription

Installing RHEL 9

Preparation for a physical server installation

Preparation for a virtual server installation

Running an RHEL installation

Summary

2

RHEL 9 Advanced Installation Options

Technical requirements

Automating RHEL deployments with Anaconda

Deploying RHEL on the cloud

Installation best practices

Summary

3

Basic Commands and Simple Shell Scripts

Logging in as a user and managing multi-user environments

Using the root account

Using and understanding the command prompt

Changing users with the su command

Understanding users, groups, and basic permissions

Users

Groups

File permissions

Using the command line, environment variables, and navigating through the filesystem

Command line and environment variables

Navigating the filesystem

Bash auto-complete

The filesystem hierarchy

Understanding I/O redirection on the command line

Filtering output with grep and sed

Listing, creating, copying, and moving files, directories, links, and hard links

Directories

Copying and moving

Symbolic and hard links

Using tar and gzip

Creating basic shell scripts

for loops

if conditionals

Exit codes

Using system documentation resources

man pages

info pages

Other documentation resources

Summary

4

Tools for Regular Operations

Technical requirements

Managing system services with systemd

systemd unit file structure

Managing services to be started and stopped at boot

Managing boot targets

Scheduling tasks with cron and systemd

System-wide crontab

User crontab

systemd timers

Learning about time synchronization with chrony and NTP

NTP client

NTP server

Checking for free resources – memory and disk (free and df)

Memory

Disk space

CPU

Load average

Other monitoring tools

Finding logs, using journald, and reading log files, including log preservation and rotation

Log rotation

Summary

5

Securing Systems with Users, Groups, and Permissions

Creating, modifying, and deleting local user accounts and groups

Managing groups and reviewing assignments

Adjusting password policies

Configuring sudo access for administrative tasks

Understanding sudo configuration

Using sudo to run admin commands

Configuring sudoers

Checking, reviewing, and modifying file permissions

Using special permissions

Understanding and applying SUID

Understanding and applying SGID

Using the sticky bit

Summary

6

Enabling Network Connectivity

Technical requirements

Exploring network configuration in RHEL

Getting to know the configuration files and NetworkManager

Configuring network interfaces with IPv4 and IPv6

IPv4 and IPv6 – what do they mean?

Configuring interfaces with nmtui

Configuring interfaces with nm-connection-editor

Configuring interfaces with nmcli

Where does NetworkManager store configuration?

Configuring hostname and hostname resolutions (DNS)

An overview of firewall configuration

Configuring the firewall

Testing network connectivity

Summary

7

Adding, Patching, and Managing Software

RHEL subscription registration and management

Managing repositories and signatures with yum/dnf

Doing software installations, updates, and rollbacks with YUM/DNF

Creating and syncing repositories with createrepo and reposync

Understanding RPM internals

Summary

Part 2 – Security with SSH, SELinux, a Firewall, and System Permissions

8

Administering Systems Remotely

Technical requirements

SSH and OpenSSH overview and base configuration

OpenSSH server

OpenSSH client

Enabling root access via SSH (and when not to do it)

Accessing remote systems with SSH

Key-based authentication with SSH

SSH agent

Remote file management with SCP/rsync

Transferring files with an OpenSSH secure file copy

Transferring files with sftp

Transferring files with rsync

Advanced remote management – SSH tunnels and SSH redirections

Remote terminals with tmux

Introduction to Ansible automation

Inventory

Playbook

Summary

9

Securing Network Connectivity with firewalld

Introduction to the RHEL firewall – firewalld

Enabling firewalld in the system and reviewing the default zones

Reviewing the different configuration items under firewalld

Enabling and managing services and ports

Creating and using service definitions for firewalld

Configuring firewalld with the web interface

Summary

10

Keeping Your System Hardened with SELinux

Technical requirements

SELinux usage in enforcing and permissive modes

Reviewing the SELinux context for files and processes

Tweaking the policy with semanage

Restoring changed file contexts to the default policy

Using SELinux Boolean settings to enable services

SELinux troubleshooting and common fixes

Integrity Measurement Architecture, digital hashes, and signatures for enhancing security

EVM and trusted keys

Enabling IMA and EVM in the system kernel

Summary

11

System Security Profiles with OpenSCAP

Getting started with OpenSCAP and discovering system vulnerabilities

Using OpenSCAP with security profiles for OSPP and PCI DSS

Scanning for OSPP compliance

Scanning for PCI DSS compliance

Summary

Part 3 – Resource Administration – Storage, Boot Process, Tuning, and Containers

12

Managing Local Storage and Filesystems

Technical requirements

Let’s start with a definition

A bit of history

Partitioning disks (MBR and GPT disks)

Formatting and mounting filesystems

Setting default mounts and options in fstab

Using network filesystems with NFS

Summary

13

Flexible Storage Management with LVM

Technical requirements

Understanding LVM

Creating, moving, and removing physical volumes

Combining physical volumes into volume groups

Creating and extending logical volumes

Adding new disks to a volume group and extending an logical volume

Removing logical volumes, volume groups, and physical volumes

Reviewing LVM commands

Summary

14

Advanced Storage Management with Stratis and VDO

Technical requirements

Understanding Stratis

Installing and enabling Stratis

Managing storage pools and filesystems with Stratis

Preparing systems to use VDO

Creating and using a VDO volume

Testing a VDO volume and reviewing the stats

Summary

15

Understanding the Boot Process

Understanding the boot process – BIOS and UEFI booting

Working with GRUB, the bootloader, and the initrd system images

Managing the boot sequence with systemd

Intervening in the boot process to gain access to a system

Summary

16

Kernel Tuning and Managing Performance Profiles with tuned

Technical requirements

Identifying processes, checking memory usage, and killing processes

Adjusting kernel scheduling parameters to better manage processes

Installing tuned and managing tuning profiles

Creating a custom tuned profile

Using the web console for observing performance metrics

Summary

17

Managing Containers with Podman, Buildah, and Skopeo

Technical requirements

Introduction to containers

Installing container tools

Running a container using Podman and UBI

Basic container management – pull, run, stop, and remove

Attaching persistent storage to a container

Deploying a container on a production system with systemd

Building a container image using a Dockerfile or Containerfile

Configuring Podman to search registry servers

Summary of Podman options

When to use Buildah and Skopeo

Building container images with Buildah

Inspecting a remote container with Skopeo

Summary

Part 4 – Practical Exercises

18

Practice Exercises – 1

Technical requirements

Tips for the exercise

Practice exercise 1

Exercise 1 solution

19

Practice Exercise – 2

Technical requirements

Tips for the exercise

Practice exercise 2

Exercise 2 resolution

Index

Other Books You May Enjoy

Preface

Linux is everywhere, from personal devices to the largest supercomputers, from the computer labs at universities to Wall Street or the International Space Station, and even Mars! Red Hat Enterprise Linux (RHEL) is the most used Linux distribution in enterprise environments and knowing how to use it is a key skill for anyone in technology. No matter whether you are completely into managing infrastructure or you are a developer interested in knowing more about the platform you want to deploy on, learning about Linux – and, more precisely, about RHEL – will help you be more effective and could even boost your career.

In this book, we cover the basic RHEL administration skills from a very practical perspective, providing examples and tips that we have learned from our experience in the trenches. You will be able to follow it from beginning to end, being able to practice with each step while learning about how things are built and why they behave as they do.

We hope you enjoy this book, that you make the most of it, and that you end up, after reading it, with a strong foundation of RHEL administration skills. That’s what we wrote it for.

Enjoy reading...and practicing!

Who this book is for

Anyone that aspires to build and work on IT infrastructures using Linux will benefit from this book as a reference for different useful tasks, tips, and best practices. It will help anyone seeking to pass the Red Hat Certified Systems Administrator (RHCSA) exam, although it will be no substitute for the official training, in which labs and specially crafted tests will be run during the whole process. The scope of the book is adjusted to the RHCSA, extending it with advice from real-world experience and many practical examples.

What this book covers

Chapter 1, Getting RHEL Up and Running, covers the installation of RHEL, from obtaining the software and the subscriptions to the installation of the system itself.

Chapter 2, RHEL 9 Advanced Installation Options, introduces advanced use cases for the installer, including deploying instances in the cloud and automating the installation.

Chapter 3, Basic Commands and Simple Shell Scripts, explains the daily commands that will be used during system administration, and how can they be automated via shell scripting.

Chapter 4, Tools for Regular Operations, shows the simple tools that are available in our system that can be used for regular daily operations, such as starting or enabling a system service or reviewing what is going on in the system through logs.

Chapter 5, Securing Systems with Users, Groups, and Permissions, covers how to manage users, groups, and permissions in any Linux system, with some specifics on RHEL.

Chapter 6, Enabling Network Connectivity, goes through the steps to connect a system to the network and the possible ways it can be configured.

Chapter 7, Adding, Patching, and Managing Software, reviews how the steps to add, remove, and update can be managed in our system, including examples for upgrades and rollbacks.

Chapter 8, Administering Systems Remotely, covers how to remotely connect to your system in order to be more effective. It includes using ssh connections to create keys and using a terminal multiplexer (tmux).

Chapter 9, Securing Network Connectivity with firewalld, instructs you on how the network firewall configuration works in RHEL and how to properly manage it, including managing zones, services, and ports.

Chapter 10, Keeping Your System Hardened with SELinux, covers usage and basic troubleshooting of SELinux.

Chapter 11, System Security Profiles with OpenSCAP, explains how to run security profiles with OpenSCAP and check compliance in RHEL with typical regulations.

Chapter 12, Managing Local Storage and Filesystems, covers filesystem creation, mount points, and general storage management.

Chapter 13, Flexible Storage Management with LVM, explains how Logical Volume Manager (LVM) empowers more flexible storage management by being able to add disks and extend logical volumes.

Chapter 14, Advanced Storage Management with Stratis and VDO, introduces Virtual Data Optimizer (VDO) and how it can be used in our system to deduplicate storage, as well as using Stratis to manage storage more easily.

Chapter 15, Understanding the Boot Process, explains how the system boots and the details that make it important.

Chapter 16, Kernel Tuning and Managing Performance Profiles with tuned, explains how kernel tunning works and how to use tuned for predefined profile usage.

Chapter 17, Managing Containers with Podman, Buildah, and Skopeo, covers containers and tools for managing and building them.

Chapter 18, Practice Exercises – 1, allows you to test your acquired knowledge.

Chapter 19, Practice Exercises – 2, gives more complex testing of your acquired knowledge.

To get the most out of this book

All software requirements will be indicated in the chapters. Note that this book assumes that you have access to a physical or virtual machine, or have access to the internet to create a cloud account in order to perform the operations that the book will guide you through.

If you are using the digital version of this book, we advise you to type the code yourself or access the code from the book’s GitHub repository (a link is available in the next section). Doing so will help you avoid any potential errors related to the copying and pasting of code.

Download the example code files

You can download the example code files for this book from GitHub at https://github.com/PacktPublishing/Red-Hat-Enterprise-Linux-RHEL-9-Administration. If there’s an update to the code, it will be updated in the GitHub repository.

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out!

Download the color images

We also provide a PDF file that has color images of the screenshots and diagrams used in this book. You can download it here: https://packt.link/NcDqa.

Conventions used

There are a number of text conventions used throughout this book.

Code in text: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: Mount the downloaded RHEL9.iso disk image file as another disk in your system.

A block of code is set as follows:

#!/bin/bash

echo Hello world

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

[default]

branch = main

repo = myrepo

username = bender

protocol = https

Any command-line input or output is written as follows:

$ mkdir scripts

$ cd scripts

Bold: Indicates a new term, an important word, or words that you see on screen. For instance, words in menus or dialog boxes appear in bold. Here is an example: Select System info from the Administration panel.

Tips or Important Notes

Appear like this.

Get in touch

Feedback from our readers is always welcome.

General feedback: If you have questions about any aspect of this book, email us at [email protected] and mention the book title in the subject of your message.

Errata: Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you have found a mistake in this book, we would be grateful if you would report this to us. Please visit www.packtpub.com/support/errata and fill in the form.

Piracy: If you come across any illegal copies of our works in any form on the internet, we would be grateful if you would provide us with the location address or website name. Please contact us at [email protected] with a link to the material.

If you are interested in becoming an author: If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, please visit authors.packtpub.com.

Share your thoughts

Once you’ve read Red Hat Enterprise Linux 9 Administration, we’d love to hear your thoughts! Please click here to go straight to the Amazon review page for this book and share your feedback.

Your review is important to us and the tech community and will help us make sure we’re delivering excellent quality content.

Download a free PDF copy of this book

Thanks for purchasing this book!

Do you like to read on the go but are unable to carry your print books everywhere? Is your eBook purchase not compatible with the device of your choice?

Don’t worry, now with every Packt book you get a DRM-free PDF version of that book at no cost.

Read anywhere, any place, on any device. Search, copy, and paste code from your favorite technical books directly into your application. 

The perks don’t stop there, you can get exclusive access to discounts, newsletters, and great free content in your inbox daily

Follow these simple steps to get the benefits:

Scan the QR code or visit the link below

https://packt.link/free-ebook/9781803248806

Submit your proof of purchase

That’s it! We’ll send your free PDF and other benefits to your email directly

Part 1 – Systems Administration – Software, User, Network, and Services Management

Deploying and configuring systems and keeping them up to date is the base task that every system administrator performs in their day-to-day work. In this part, the core parts of doing so are explored in a restructured way so that you can follow the tasks one by one and learn, practice, and understand them properly.

The following chapters are included in this part:

Chapter 1, Getting RHEL Up and Running

Chapter 2, RHEL 9 Advanced Installation Options

Chapter 3, Basic Commands and Simple Shell Scripts

Chapter 4, Tools for Regular Operations

Chapter 5, Securing Systems with Users, Groups, and Permissions

Chapter 6, Enabling Network Connectivity

Chapter 7, Adding, Patching, and Managing Software

1

Getting RHEL Up and Running

The first step to start working with Red Hat Enterprise Linux (RHEL) is to have it running. Whether on your own laptop as the main system, on a virtual machine, or on a physical server, its installation is necessary in order to get your hands on the system you want to learn to use. It is highly encouraged that you get yourself a physical or virtual machine to use the system while reading this book.

In this chapter, you will deploy your own RHEL 9 system to be able to follow all the examples mentioned in this book, as well as discover more about Linux.

The topics to be covered in this chapter are as follows:

Obtaining RHEL software and a subscription

Installing RHEL 9

Technical requirements

The best way to get started is by having an RHEL 9 virtual machine to work with. You can do it on your main computer as a virtual machine or using a physical machine. In the following section, we will review both options and you will be able to run your own RHEL 9 system.

Tip

A virtual machine is a way to emulate a complete computer. To be able to create this emulated computer on your own laptop, if you are using macOS or Windows, you will need to install virtualization software such as VirtualBox, for example. If you are running Linux, it is already prepared for virtualization, and you will only need to add the virt-manager package.

Obtaining RHEL and a subscription

To be able to deploy RHEL, you will need a Red Hat subscription to obtain the images to be used, as well as access to repositories with software and updates. You can obtain, free of charge, a developer subscription from the developers’ portal site of Red Hat using the following link: https://developers.redhat.com/. You then need to follow these steps:

Log in or create an account at https://developers.redhat.com/.

Click on the Log in button:

Figure 1.1 – The developers.redhat.com home page, indicating where to click to log in

Once on the login page, use your account or, if you do not have one, create one by clicking on Register in the top-right corner or on the Register for a Red Hat account button directly in the registration box, as follows:

Figure 1.2 – Red Hat login page (common to all Red Hat resources)

You can choose to use your credentials in several services (in other words, Google, GitHub, or Twitter) if you prefer to do so.

Once you have logged in, go to the Products section in the top bar. You can find the Red Hat Enterprise Linux section in the navigation bar before the content:

Figure 1.3 – Accessing the Linux page at developers.redhat.com

Click on Download RHEL at no-cost, which appears as a red button on the next page:

Figure 1.4 – Accessing the RHEL download page at developers.redhat.com

Then, the ISO image for the x86_64 (8 GB) architecture will start downloading:

Figure 1.5 – Download dialog for RHEL 9

The ISO image is a file that contains an exact copy of the contents of a full DVD (even when we are not using a DVD). This file will later be used to install our machines, whether dumping it to a USB drive for bare metal installations, unpacking it for network installations, or attaching it for virtual machine installations (or using out-of-band capabilities in servers such as IPMI, iLO, or iDRAC)

Tip

To verify the ISO image, and ensure that the one we have obtained is not corrupted or altered, a mechanism called checksum can be used. Checksums are a way to review a file and provide a set of letters and numbers that can be used to verify that the file is precisely the same one as in the origin. Red Hat provides a list of sha256 checksums for doing so in the downloads section of the customer portal (access.redhat.com). An article describing the process is available here: https://access.redhat.com/solutions/8367.

We have the software, in this case, the ISO image, to install RHEL 9 on any computer. These are the same bits that are used in production machines worldwide, and that you can use yourself for learning purposes with your developer subscription. Now, it is time to give them a go in the next section.

Installing RHEL 9

In this section, we will follow the typical installation process to have RHEL installed on a machine. We will follow the default steps, reviewing the options available for each one.

Preparation for a physical server installation

A physical server requires some initial setup before beginning with installation. Common steps include configuring the disks in the internal array, connecting it to the networks, preparing the switches for any interface aggregation that is expected (teaming, bonding), preparing access to external disk arrays (in other words, fiber channel arrays), setting up out-of-band capabilities, and securing the BIOS configuration.

We will not get into the details of these preparations, except for the boot sequence. The server will require to boot (start loading the system) from an external device such as a USB thumb drive or optical disk (whether physical or emulated through the out-of-band capabilities).

Creating a bootable USB thumb drive from a machine with Linux or macOS is as simple as doing a disk dump with the dd application. Perform the following steps:

Find your USB device in the system, usually /dev/sdb in Linux, or /dev/disk2 in macOS (in macOS, this command requires special privileges; please run it as sudo dmesg | grep removable):

$ dmesg | grep removable

[66931.429805] sd 0:0:0:0: [sdb] Attached SCSI removable disk

Important Note

Please verify the disk name very carefully, as the procedure for using disk dump will completely overwrite the disk target.

Check whether the USB is mounted and if so, dismount it (for macOS users, please use diskutil list to ascertain whether the device is mounted):

$ lsblk /dev/sdb

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT

sdb      8:0   1  3,8G  0 disk

├─sdb1   8:1    1  1,8G  0 part /run/media/miguel/USB

├─sdb2   8:2    1 10,9M  0 part

└─sdb3   8:3    1 22,9M  0 part

In this case, only partition one of the sdb disk, referred to as sdb1, is mounted. We will need to unmount all the partitions mounted. In this example, this is straightforward as there is only one. To do so, we can run the following command:

$ sudo umount /dev/sdb1

Important Note

By using super-user do (sudo) for administrative tasks such as unmounting devices, we can open an administrator shell (root in Linux and Unix-like systems) or run the command using sudo, which provides administrative privileges to the current user. When running commands with sudo, the user will be requested to enter their password (not the admin password, but the user’s own password) to proceed with the execution (this default behavior may be overridden in the sudoers configuration file).

Dump the image! (Warning, this will erase the selected disk!):

$ sudo dd if=rhel-baseos-9.0-beta-x86_64-dvd.iso of=/dev/sdb bs=512k

Tip

Alternative graphical tools are available for creating a boot device that can help select both the image and the target device. In Fedora Linux (the development branch used to create Red Hat Enterprise Linux, and a workstation for many engineers and developers), the Fedora Media Writer tool can be used. For other environments, the UNetbootin tool could also serve to create your boot media.

Now, with the USB thumb drive, we can install any physical machine, from a tiny laptop to a huge server. The next part involves making the physical machine boot from the USB thumb drive. The mechanism for doing that will depend on the server being used. However, it is becoming common to offer an option to select a boot device during bootup. The following is an example of how to select a temporary boot device for a laptop:

Interrupt the normal startup. In this case, the boot process shows that I can do that by pressing Enter:

Figure 1.6 – Example of a BIOS message to interrupt normal startup

Choose a temporary startup device, in this case, by pressing the F12 key:

Figure 1.7 – Example of a BIOS menu for interrupted startup

Select the device to boot from. We want to boot from our USB thumb drive, which, in this case, is USB HDD: ChipsBnk Flash Disk:

Figure 1.8 – Example of a BIOS menu to choose the USB HDD boot device

Let the system start the installer from the USB drive.

Once we know how to prepare a USB drive with an RHEL installer and how to make a physical machine boot from it, we can skip to the Running an RHEL installation section and proceed to install it. This can be pretty useful if we have a mini server (in other words, an Intel NUC), an old computer, or a laptop to be used as the machine for following along with this book.

Next, we will look at how to prepare a virtual machine in your installation, in case you are considering following this book with your current main laptop (or workstation) but you still want to keep a separate machine to work with.

Preparation for a virtual server installation

A virtual server works as if having some virtualization software that emulates a real machine in your current system. In a Linux workstation, installing virt-manager will add all the under-the-hood components required to run (for your information, these components are KVM, Libvirt, Qemu, and virsh, among others). Other no-cost virtualization software recommended for Windows or macOS systems includes Oracle VirtualBox and VMware Workstation Player.

The examples in this section will be executed using virt-manager, but are easily applicable to any other virtualization software, whether in a laptop or in the largest deployments.

The preliminary steps have been described previously and require obtaining the Red Hat Enterprise Linux ISO image, which, in this case, will be rhel-baseos-9.0-beta-0-x86_64-dvd.iso. Once downloaded and, if possible, having checked its integrity (as mentioned in the last tip