Book Image

Red Hat Enterprise Linux 9 Administration - Second Edition

By : Pablo Iranzo Gómez, Pedro Ibáñez Requena, Miguel Pérez Colino, Scott McCarty
2 (2)
Book Image

Red Hat Enterprise Linux 9 Administration - Second Edition

2 (2)
By: Pablo Iranzo Gómez, Pedro Ibáñez Requena, Miguel Pérez Colino, Scott McCarty

Overview of this book

With Red Hat Enterprise Linux 9 becoming the standard for enterprise Linux used from data centers to the cloud, Linux administration skills are in high demand. With this book, you’ll learn how to deploy, access, tweak, and improve enterprise services on any system on any cloud running Red Hat Enterprise Linux 9. Throughout the book, you’ll get to grips with essential tasks such as configuring and maintaining systems, including software installation, updates, and core services. You’ll also understand how to configure the local storage using partitions and logical volumes, as well as assign and deduplicate storage. You’ll learn how to deploy systems while also making them secure and reliable. This book provides a base for users who plan to become full-time Linux system administrators by presenting key command-line concepts and enterprise-level tools, along with essential tools for handling files, directories, command-line environments, and documentation for creating simple shell scripts or running commands. With the help of command line examples and practical tips, you’ll learn by doing and save yourself a lot of time. By the end of the book, you’ll have gained the confidence to manage the filesystem, users, storage, network connectivity, security, and software in RHEL 9 systems on any footprint.
Table of Contents (26 chapters)
1
Part 1 – Systems Administration – Software, User, Network, and Services Management
9
Part 2 – Security with SSH, SELinux, a Firewall, and System Permissions
14
Part 3 – Resource Administration – Storage, Boot Process, Tuning, and Containers
21
Part 4 – Practical Exercises

Managing the boot sequence with systemd

We have already learned how the firmware of the system will take care of pointing at a disk to run the operating system loader, which, in RHEL, is GRUB.

GRUB will load the kernel and initrd to prepare the system to start. Then, it’s time to start the first process of the system, also referred to as process 1 or PID 1 (PID stands for process identifier). This process has to take care of loading all the required services in the system efficiently. In RHEL 9, the PID 1 is run by systemd.

In Chapter 4, Tools for Regular Operations, we described service and target management with systemd. In this chapter, let’s review these interactions with the boot sequence.

The first two things related to the boot sequence that we can do with systemd are to reboot the system and to power it off. We will do this with the systemctl tool:

[root@rhel-instance ~]# systemctl reboot

We can see that the system will reboot. We can check how...