Gómez P.I. and other / Гомес П.И. и другие - Red Hat Enterprise Linux 9 Administration: A comprehensive Linux system administration guide for RHCSA certification exam candidates, 2nd Edition / Администрирование Red Hat Enterprise Linux 9 [2022,

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Preface xvii
Part 1 – Systems Administration – Software, User, Network, and Services Management
1
Getting RHEL Up and Running 3
Technical requirements 3
Obtaining RHEL and a subscription 4
Installing RHEL 9 7
Preparation for a physical server installation 7
Preparation for a virtual server installation 10
Running an RHEL installation 14
Summary 39
2
RHEL 9 Advanced Installation Options 41
Technical requirements 41
Automating RHEL deployments with Anaconda 42
Deploying RHEL on the cloud 47
Installation best practices 56
Summary 58
3
Basic Commands and Simple Shell Scripts 59
Logging in as a user and managing multi-user environments 60
Using the root account 61
Using and understanding the command prompt 62
Changing users with the su command 62
Table of Contents
Understanding users, groups, and
basic permissions 64
Users 65
Groups 66
File permissions 67
Using the command line,
environment variables, and
navigating through the filesystem 69
Command line and environment variables 69
Navigating the filesystem 71
Bash auto-complete 72
The filesystem hierarchy 74
Understanding I/O redirection on
the command line 77
Filtering output with grep and sed 80
Listing, creating, copying, and
moving files, directories, links,
and hard links 83
Directories 84
Copying and moving 85
Symbolic and hard links 88
Using tar and gzip 90
Creating basic shell scripts 92
for loops 94
if conditionals 95
Exit codes 97
Using system documentation
resources 97
man pages 98
info pages 100
Other documentation resources 100
Summary 101
4
Tools for Regular Operations 103
Technical requirements 103
Managing system services with
systemd 104
systemd unit file structure 106
Managing services to be started and stopped
at boot 108
Managing boot targets 110
Scheduling tasks with cron and
systemd 113
System-wide crontab 113
User crontab 115
systemd timers 116
Learning about time synchronization
with chrony and NTP 117
NTP client 118
NTP server 121
Checking for free resources –
memory and disk (free and df) 121
Memory 122
Disk space 123
CPU 124
Load average 125
Other monitoring tools 126
Finding logs, using journald, and
reading log files, including log
preservation and rotation 131
Log rotation 133
Summary 135
5
Securing Systems with Users, Groups, and Permissions 137
Creating, modifying, and deleting
local user accounts and groups 138
Managing groups and reviewing
assignments 142
Adjusting password policies 142
Configuring sudo access for
administrative tasks 148
Understanding sudo configuration 148
Using sudo to run admin commands 150
Configuring sudoers 151
Checking, reviewing, and modifying
file permissions 152
Using special permissions 159
Understanding and applying SUID 159
Understanding and applying SGID 160
Using the sticky bit 161
Summary 162
6
Enabling Network Connectivity 165
Technical requirements 166
Exploring network configuration in
RHEL 166
Getting to know the configuration
files and NetworkManager 168
Configuring network interfaces with
IPv4 and IPv6 170
IPv4 and IPv6 – what do they mean? 171
Configuring interfaces with nmtui 172
Configuring interfaces with nm-connectioneditor
174
Configuring interfaces with nmcli 178
Where does NetworkManager store
configuration? 181
Configuring hostname and hostname
resolutions (DNS) 181
An overview of firewall configuration 184
Configuring the firewall 187
Testing network connectivity 188
Summary 189
7
Adding, Patching, and Managing Software 191
RHEL subscription registration
and management 192
Managing repositories and signatures
with yum/dnf 198
Doing software installations, updates,
and rollbacks with YUM/DNF 207
Creating and syncing repositories
with createrepo and reposync 217
Understanding RPM internals 223
Summary 224
Part 2 – Security with SSH, SELinux, a Firewall,
and System Permissions
8
Administering Systems Remotely 227
Technical requirements 228
SSH and OpenSSH overview and
base configuration 228
OpenSSH server 229
OpenSSH client 230
Enabling root access via SSH
(and when not to do it) 231
Accessing remote systems with SSH 232
Key-based authentication with SSH 234
SSH agent 240
Remote file management with
SCP/rsync 243
Transferring files with an OpenSSH secure
file copy 243
Transferring files with sftp 245
Transferring files with rsync 247
Advanced remote management –
SSH tunnels and SSH redirections 252
Remote terminals with tmux 254
Introduction to Ansible automation 257
Inventory 258
Playbook 258
Summary 262
9
Securing Network Connectivity with firewalld 263
Introduction to the RHEL firewall –
firewalld 264
Enabling firewalld in the system and
reviewing the default zones 265
Reviewing the different configuration items
under firewalld 268
Enabling and managing services and
ports 271
Creating and using service
definitions for firewalld 277
Configuring firewalld with the web
interface 279
Summary 285
10
Keeping Your System Hardened with SELinux 287
Technical requirements 288
SELinux usage in enforcing and
permissive modes 288
Reviewing the SELinux context for
files and processes 291
Tweaking the policy with semanage 296
Restoring changed file contexts to the
default policy 298
Using SELinux Boolean settings to
enable services 300
SELinux troubleshooting and
common fixes 302
Integrity Measurement Architecture,
digital hashes, and signatures for
enhancing security 306
EVM and trusted keys 307
Enabling IMA and EVM in the system kernel 307
Summary 311
11
System Security Profiles with OpenSCAP 313
Getting started with OpenSCAP and
discovering system vulnerabilities 313
Using OpenSCAP with security
profiles for OSPP and PCI DSS 324
Scanning for OSPP compliance 326
Scanning for PCI DSS compliance 330
Summary 331
Part 3 – Resource Administration – Storage, Boot
Process, Tuning, and Containers
12
Managing Local Storage and Filesystems 335
Technical requirements 335
Let’s start with a definition 336
A bit of history 336
Partitioning disks (MBR and
GPT disks) 337
Formatting and mounting filesystems 344
Setting default mounts and options
in fstab 347
Using network filesystems with NFS 349
Summary 350
13
Flexible Storage Management with LVM 351
Technical requirements 351
Understanding LVM 355
Creating, moving, and removing
physical volumes 357
Combining physical volumes into
volume groups 362
Creating and extending logical
volumes 364
Adding new disks to a volume group
and extending an logical volume 366
Removing logical volumes, volume
groups, and physical volumes 372
Reviewing LVM commands 377
Summary 378
14
Advanced Storage Management with Stratis and VDO 379
Technical requirements 380
Understanding Stratis 380
Installing and enabling Stratis 381
Managing storage pools and
filesystems with Stratis 382
Preparing systems to use VDO 387
Creating and using a VDO volume 388
Testing a VDO volume and reviewing
the stats 390
Summary 392
15
Understanding the Boot Process 393
Understanding the boot process –
BIOS and UEFI booting 394
Working with GRUB, the bootloader,
and the initrd system images 395
Managing the boot sequence with
systemd 401
Intervening in the boot process to
gain access to a system 404
Summary 407
16
Kernel Tuning and Managing Performance Profiles with tuned 409
Technical requirements 410
Identifying processes, checking
memory usage, and killing processes 410
Adjusting kernel scheduling
parameters to better manage
processes 415
Installing tuned and managing
tuning profiles 419
Creating a custom tuned profile 422
Using the web console for observing
performance metrics 426
Summary 430
17
Managing Containers with Podman, Buildah, and Skopeo 433
Technical requirements 433
Introduction to containers 434
Installing container tools 435
Running a container using Podman
and UBI 436
Basic container management – pull, run, stop,
and remove 437
Attaching persistent storage to a container 440
Deploying a container on a production
system with systemd 441
Building a container image using a Dockerfile
or Containerfile 442
Configuring Podman to search registry servers 443
Summary of Podman options 445
When to use Buildah and Skopeo 445
Building container images with Buildah 446
Inspecting a remote container with Skopeo 447
Summary 448
Part 4 – Practical Exercises
18
Practice Exercises – 1 451
Technical requirements 451
Tips for the exercise 451
Practice exercise 1 452
Exercise 1 solution 454
19
Practice Exercise – 2 471
Technical requirements 471
Tips for the exercise 471
Practice exercise 2 472
Exercise 2 resolution 473
Index 489
Other Books You May Enjoy 504