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

Scheduling tasks with cron and systemd

The skills you will learn in this section will be concerned with scheduling periodic tasks in the system for business services and maintenance.

For regular system usage, there are tasks that need to be executed periodically, ranging from temporary folder cleanup, updating the cache’s refresh rate, and performing check-in with inventory systems, among other things.

The traditional way to set them up is via cron, which is provided in RHEL 9 via the cronie package.

cronie implements a daemon that’s compatible with the traditional Vixie cron and allows us to define both user and system crontabs.

A crontab defines several parameters for a task that must be executed. Let’s see how it works.

System-wide crontab

A system-wide crontab can be defined in /etc/crontab or in individual files at /etc/cron.d. Other additional folders exist, such as /etc/cron.hourly, /etc/cron.daily, /etc/cron.weekly, and /etc/cron.monthly...