Book Image

Red Hat Enterprise Linux 8 Administration

By : Miguel Pérez Colino, Pablo Iranzo Gómez, Scott McCarty
Book Image

Red Hat Enterprise Linux 8 Administration

By: Miguel Pérez Colino, Pablo Iranzo Gómez, Scott McCarty

Overview of this book

Whether in infrastructure or development, as a DevOps or site reliability engineer, Linux skills are now more relevant than ever for any IT job, forming the foundation of understanding the most basic layer of your architecture. With Red Hat Enterprise Linux (RHEL) becoming the most popular choice for enterprises worldwide, achieving the Red Hat Certified System Administrator (RHCSA) certification will validate your Linux skills to install, configure, and troubleshoot applications and services on RHEL systems. Complete with easy-to-follow tutorial-style content, self-assessment questions, tips, best practices, and practical exercises with detailed solutions, this book covers essential RHEL commands, user and group management, software management, networking fundamentals, and much more. You'll start by learning how to create an RHEL 8 virtual machine and get to grips with essential Linux commands. You'll then understand how to manage users and groups on an RHEL 8 system, install software packages, and configure your network interfaces and firewall. As you advance, the book will help you explore disk partitioning, LVM configuration, Stratis volumes, disk compression with VDO, and container management with Podman, Buildah, and Skopeo. By the end of this book, you'll have covered everything included in the RHCSA EX200 certification and be able to use this book as a handy, on-the-job desktop reference guide. This book and its contents are solely the work of Miguel Pérez Colino, Pablo Iranzo Gómez, and Scott McCarty. The content does not reflect the views of their employer (Red Hat Inc.). This work has no connection to Red Hat, Inc. and is not endorsed or supported by Red Hat, Inc.

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Table of Contents (25 chapters)
Preface
Preface
Who this book is for
What this book covers
To get the most out of this book
Download the example code files
Download the color images
Conventions used
Get in touch
Share Your Thoughts
1
Section 1: Systems Administration – Software, User, Network, and Services Management
Section 1: Systems Administration – Software, User, Network, and Services Management
Free Chapter
2
Chapter 1: Installing RHEL8
Chapter 1: Installing RHEL8
Technical requirements
Obtaining RHEL software and a subscription
Installing RHEL8
Summary
3
Chapter 2: RHEL8 Advanced Installation Options
Chapter 2: RHEL8 Advanced Installation Options
Technical requirements
Automating RHEL deployments with Anaconda
Deploying RHEL on the cloud
Installation best practices
Summary
4
Chapter 3: Basic Commands and Simple Shell Scripts
Chapter 3: Basic Commands and Simple Shell Scripts
Logging in as a user and managing multi-user environments
Changing users with the su command
Understanding users, groups, and basic permissions
Using the command line, environment variables, and navigating through the filesystem
Understanding I/O redirection in the command line
Filtering output with grep and sed
Listing, creating, copying, and moving files and directories, links, and hard links
Using tar and gzip
Creating basic shell scripts
Using system documentation resources
Summary
5
Chapter 4: Tools for Regular Operations
Chapter 4: Tools for Regular Operations
Technical requirements
Managing system services with systemd
Scheduling tasks with cron and systemd
Learning about time synchronization with chrony and NTP
Checking for free resources – memory and disk (free and df)
Finding logs, using journald, and reading log files, including log preservation and rotation
Summary
6
Chapter 5: Securing Systems with Users, Groups, and Permissions
Chapter 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
Checking, reviewing, and modifying file permissions
Using special permissions
Summary
7
Chapter 6: Enabling Network Connectivity
Chapter 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
Configuring hostname and hostname resolutions (DNS)
Overview of firewall configuration
Testing network connectivity
Summary
8
Chapter 7: Adding, Patching, and Managing Software
Chapter 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
9
Section 2: Security with SSH, SELinux, a Firewall, and System Permissions
Section 2: Security with SSH, SELinux, a Firewall, and System Permissions
10
Chapter 8: Administering Systems Remotely
Chapter 8: Administering Systems Remotely
Technical requirements
SSH and OpenSSH overview and base configuration
Accessing remote systems with SSH
Key-based authentication with SSH
SCP/rsync – remote file management
Advanced remote management – SSH tunnels and SSH redirections
Remote terminals with tmux
Summary
11
Chapter 9: Securing Network Connectivity with firewalld
Chapter 9: Securing Network Connectivity with firewalld
Introduction to the RHEL firewall – firewalld
Enabling firewalld in the system and reviewing the default zones
Enabling and managing services and ports
Creating and using service definitions for firewalld
Configuring firewalld with the web interface
Summary
12
Chapter 10: Keeping Your System Hardened with SELinux
Chapter 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
Summary
13
Chapter 11:System Security Profiles with OpenSCAP
Chapter 11:System Security Profiles with OpenSCAP
Getting started with OpenSCAP and discovering system vulnerabilities
Using OpenSCAP with security profiles for OSPP and PCI DSS
Summary
14
Section 3: Resource Administration – Storage, Boot Process, Tuning, and Containers
Section 3: Resource Administration – Storage, Boot Process, Tuning, and Containers
15
Chapter 12: Managing Local Storage and Filesystems
Chapter 12: Managing Local Storage and Filesystems
Technical requirements
Partitioning disks (MBR and GPT disks)
Formatting and mounting filesystems
Setting default mounts and options in fstab
Using network filesystems with NFS
Summary
16
Chapter 13: Flexible Storage Management with LVM
Chapter 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 a logical volume
Removing logical volumes, volume groups, and physical volumes
Reviewing LVM commands
Summary
17
Chapter 14: Advanced Storage Management with Stratis and VDO
Chapter 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 a VDO volume
Assigning a VDO volume to an LVM volume
Testing a VDO volume and reviewing the stats
Summary
18
Chapter 15: Understanding the Boot Process
Chapter 15: Understanding the Boot Process
Understanding the boot process – BIOS and UEFI booting
Working with GRUB, the bootloader, and initrd system images
Managing the boot sequence with systemd
Intervening in the boot process to gain access to a system
Summary
19
Chapter 16: Kernel Tuning and Managing Performance Profiles with tuned
Chapter 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
Summary
20
Chapter 17: Managing Containers with Podman, Buildah, and Skopeo
Chapter 17: Managing Containers with Podman, Buildah, and Skopeo
Technical requirements
Introduction to containers
Running a container using Podman and UBI
When to use Buildah and Skopeo
Summary
21
Section 4: Practical Exercises
Section 4: Practical Exercises
22
Chapter 18: Practice Exercises – 1
Chapter 18: Practice Exercises – 1
Technical requirements
Tips for the exercise
Practice exercise 1
Exercise 1 resolution
23
Chapter 19: Practice Exercise – 2
Chapter 19: Practice Exercise – 2
Technical requirements
Tips for the exercise
Practice exercise – 2
Answers to practice exercise 2
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24
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Advanced remote management – SSH tunnels and SSH redirections

SSH has two really powerful features; that is, SSH tunnels and SSH redirections. When an SSH connection is established, it can not only be used to send commands to the remote host and let us work on them as if they were our local system, but we can also create tunnels that interconnect our systems.

Let's try to imagine a scenario that is common in many companies, where a VPN is used to reach the internal network with all the services and servers, but with SSH instead of a regular VPN.

So, let's put some context into this imaginary scenario.

We can use a host that gets external traffic for ssh redirected from our internet router to the ssh service in that system. So, in brief, our router gets connections on port 22 via TCP and the connection is forwarded to our server. We will be naming this server bastion in this exercise.

With this in place, our common sense tells us that we will be able to...

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