Introduction to Red Hat Enterprise Linux

CIS126RH · Red Hat System Administration I

Conceptual groundwork for everything that follows

No commands in this chapter — the goal is to understand the environment first.

• Describe what Linux is.
• Describe what Red Hat Enterprise Linux (RHEL) is.
• Explain how RHEL fits into the broader open-source ecosystem.
• Understand the organization of RH124.

• Linux is an open-source operating system kernel.
• Originally created by Linus Torvalds in 1991.
• The kernel manages hardware, memory, and processes.
• A complete operating system combines the kernel with shells, utilities, libraries, and services.

Examples of distributions: RHEL, Fedora, Ubuntu, Debian.

• Linux is widely used in server infrastructure.
• It underlies many cloud platforms.
• Most of the world's supercomputers run Linux.
• Android is also built on the Linux kernel.

For system administrators, Linux skills are difficult to avoid needing.

Red Hat Enterprise Linux (RHEL) is a Linux distribution built and supported by Red Hat, an IBM company, for enterprise and production use.

• Stability
• Long-term support
• Security certification
• Predictable, well-tested updates

Think of this as a progression from experimentation toward enterprise stability.

RHEL's source code is open: it can be inspected, modified, and rebuilt.

Businesses pay for Red Hat's subscription, including:

• Tested builds
• Security patches
• Certified compatibility
• Enterprise support

Open source does not necessarily mean free enterprise support.

RHEL uses a major.minor version scheme, such as RHEL 9.4 or RHEL 10.1.

Running a RHEL version past the end of its support lifecycle means no more security patches.

• This creates a serious risk for network-connected systems.
• Administrators must track where managed systems are in their lifecycle.

• Many production RHEL systems run headless.
• Headless means there is no graphical desktop.
• Administrators therefore need to be comfortable at the shell prompt.

Command-line skills are a core system-administration skill, not an optional extra.

• Ch. 2–5: Command line, documentation, registration, AI-assisted help
• Ch. 6–9: Filesystem, file management, editing, I/O redirection
• Ch. 10–11, 19: Users, groups, permissions, secure remote access
• Ch. 12–14: Packages, RPM/Flatpak, removable storage
• Ch. 15–16: Processes and systemd services
• Ch. 17–18: Networking

RH124 moves from the shell itself outward to the systems it manages.

Later Red Hat administration courses build on this foundation with:

• Storage management
• SELinux
• Containers
• Automation

RH124 deliberately focuses on the fundamentals every administrator needs first.

kernel

Core of the operating system; manages hardware, memory, and processes.

distribution

Complete operating system built from the Linux kernel plus supporting software.

RHEL

Enterprise Linux distribution focused on stability and support.

subscription

Red Hat's support offering: builds, patches, compatibility, and assistance.

release lifecycle

Defined support timeline from full support through end of life.

1. What is the difference between the Linux kernel and a Linux distribution?
2. What does RHEL prioritize that distinguishes it from Fedora?
3. If RHEL is open source, what does a customer pay for?
4. What is the relationship among Fedora, CentOS Stream, and RHEL?
5. Why does the support lifecycle matter?

• Linux is the kernel; a distribution combines it with supporting software.
• RHEL is designed for stable, supported enterprise use.
• Red Hat's subscription provides tested updates, support, and certified compatibility.
• Administrators must understand release lifecycles.
• RH124 emphasizes the command line because it is central to production administration.

Next: begin working at the RHEL shell.