Red Hat System Administration I · RH124

Chapter 1

Introduction to Red Hat Enterprise Linux

What Linux is · What RHEL is · How this course is organized

CIS126RH — Mesa Community College

Chapter Objective

Describe what Linux and Red Hat Enterprise Linux are, how RHEL fits into the broader open-source ecosystem, and how this course is structured.

No Commands This Chapter

Chapter 1 is conceptual groundwork for everything that follows.

What Is Linux?

Linux is an open-source operating system kernel, originally created by Linus Torvalds in 1991. On its own, the kernel just manages hardware, memory, and running processes — what most people call "Linux" is really a full operating system built by combining the kernel with a large collection of supporting software: shells, utilities, libraries, and system services, much of it from the GNU Project.

A complete, installable combination of the kernel plus this supporting software is called a distribution (or "distro"). Hundreds exist, each making different choices about package management, defaults, and target use case — Red Hat Enterprise Linux, Fedora, Ubuntu, and Debian are all examples.

Why It Matters — Nearly all of the internet's server infrastructure, most cloud platforms, the majority of the world's supercomputers, and the Android operating system all run on Linux. Whatever career path a system administrator takes, Linux skills are difficult to avoid needing.

What Is Red Hat Enterprise Linux?

Red Hat Enterprise Linux (RHEL) is a Linux distribution built and supported by Red Hat, an IBM company, specifically for enterprise and production use. It prioritizes stability, long-term support, security certification, and predictable, well-tested updates over always shipping the newest version of every package.

Characteristic	What It Means
Long release lifecycle	Each major version is supported for roughly a decade
Certified hardware and software	Vendors test and certify their products specifically against RHEL
Subscription model	Access to updates, patches, and support is tied to a Red Hat subscription (see Chapter 4)
Enterprise support	Red Hat provides direct support contracts, SLAs, and a knowledgebase

Tip — RHEL Isn't the Only Red Hat-Related Distro — Fedora is Red Hat's fast-moving, community-driven upstream project, where new features are tried out well before they're stable enough for RHEL. CentOS Stream sits in between, as a rolling preview of what's headed into the next RHEL minor release.

Open Source and the Enterprise

RHEL's source code is open — anyone can inspect, modify, and rebuild it. What businesses pay for isn't the software's existence but Red Hat's subscription: tested builds, security patches, certified compatibility, and support when something breaks.

Note — This distinction — open source code, paid support and lifecycle around it — is common across enterprise Linux and is worth understanding early, since it explains why registration (Chapter 4) matters even though the underlying software is freely licensed.

RHEL Editions and the Release Lifecycle

RHEL releases follow a numbered major.minor scheme (for example, RHEL 9.4, RHEL 10.1). Major versions are supported for years, with minor versions delivering incremental updates along the way.

Phase	What Happens
Full support	New features, bug fixes, and security patches
Maintenance support	Critical bug fixes and security patches only
Extended life / ELS	Optional extended coverage for systems that can't upgrade yet

Warning — Know Your Support Window — Running a RHEL version past the end of its support lifecycle means no more security patches — a serious risk for any system connected to a network. Part of an administrator's job is tracking where each managed system sits in its lifecycle.

Ways to Access RHEL

You'll interact with RHEL in this course — and in the field — through more than one interface, covered in depth in later chapters.

Method	Typical Use
GNOME graphical desktop	Local workstation use, when a GUI is installed
Terminal / virtual console	Direct command-line access, with or without a GUI
SSH	Remote command-line access over the network
Text-mode server install	The default for most production RHEL servers — no GUI at all

Tip — This Course Is Command-Line First — RH124 emphasizes the command line specifically because most RHEL systems in production run headless, with no graphical desktop installed. Comfort at the shell prompt isn't optional for a working system administrator.

How This Course Is Organized

RH124 builds skills roughly in the order you'll need them, moving from the shell itself outward to the systems it manages.

Getting oriented — the command line, local documentation, registration, and AI-assisted help (Chapters 2–5)
Working with files — the filesystem hierarchy, file management, text editing, and I/O redirection (Chapters 6–9)
Users and access — accounts, groups, permissions, and secure remote access (Chapters 10–11, 19)
Software and media — package management with RPM and Flatpak, and removable storage (Chapters 12–14)
Processes and services — monitoring workloads and controlling systemd (Chapters 15–16)
Networking — connecting systems and managing their configuration (Chapters 17–18)

Note — Later Red Hat System Administration courses (RH134 and beyond) build on this foundation with storage management, SELinux, containers, and automation — RH124 is deliberately scoped to the fundamentals every administrator needs first.

Key Terms for Chapter 1

kernel: The core of the operating system, managing hardware, memory, and processes
distribution (distro): A complete, installable operating system built from the Linux kernel plus supporting software
RHEL: Red Hat Enterprise Linux; a stability- and support-focused Linux distribution for enterprise use
Fedora: Red Hat's fast-moving, community-driven upstream project, previewing future RHEL features
CentOS Stream: A rolling preview distribution positioned between Fedora and the next RHEL release
subscription: Red Hat's support offering: tested builds, patches, certified compatibility, and assistance
release lifecycle: The defined support timeline a RHEL version moves through, from full support to end of life

Review Questions

What is the difference between "the Linux kernel" and "a Linux distribution"?
What does RHEL prioritize that distinguishes it from a fast-moving distribution like Fedora?
If RHEL's source code is open, what exactly is a customer paying for with a Red Hat subscription?
What is the relationship between Fedora, CentOS Stream, and RHEL?
Why does running a RHEL system past the end of its support lifecycle matter?
Why does this course emphasize the command line so heavily, rather than the graphical desktop?
Broadly, in what order does this course move through its topics, from Chapter 2 through Chapter 19?

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