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Beginner · Linux and the shell · topic 1 of 57 · 30 min

What Linux and Red Hat Enterprise Linux are

Explanation

Linux is a free operating system kernel; a distribution adds tools, a package manager and support around it. Red Hat Enterprise Linux (RHEL) is the paid, supported distribution that banks, telecoms and governments run. You can practise on a free RHEL developer subscription, or on Rocky Linux or AlmaLinux, which are built to behave like RHEL.

Why learn Linux at all?

Most servers on the internet run Linux. When you open a banking app, book a train ticket or watch a video, a Linux server answers you somewhere. Cloud platforms such as AWS, Azure and Google Cloud run huge numbers of Linux virtual machines, and almost every container image is a small Linux system. So anyone who keeps servers running, deploys apps or works in cloud and DevOps needs Linux every day.

Kernel, operating system and distribution

An operating system (OS) is the base software that runs a computer and shares its CPU, memory and disks between programs. The kernel is the core of the OS: it talks to the hardware, starts programs (processes), and decides which one runs when. Linux, strictly, is only a kernel. It was started by Linus Torvalds in 1991 and is free and open source, which means anyone can read, change and share the code.

A kernel alone is not useful. You also need a shell to type commands, basic tools like ls and cp, a way to install software, and a way to start services at boot. A distribution (a "distro") is a complete package: the Linux kernel plus all these tools, tested to work together.

Think of it like this: The kernel is like the engine of a car. A distribution is the full car: engine, seats, dashboard, service book and warranty. Maruti, Tata and Hyundai can all use similar engines, but each sells a different car with its own service network.

The Red Hat family

NameWhat it isCost
FedoraFast-moving community distro; new ideas appear here firstFree
CentOS StreamThe development branch just ahead of the next RHEL minor releaseFree
RHELRed Hat Enterprise Linux: stable, certified, supported for about 10 years per major versionPaid subscription (free developer option)
Rocky Linux, AlmaLinuxCommunity rebuilds made to be compatible with RHELFree

RHEL 9 came out in 2022 and RHEL 10 in 2025. Each major version gets many years of updates, so companies run RHEL 8, 9 and 10 side by side for a long time. This course uses RHEL 9 commands; almost all of them work the same on RHEL 10, and we point out the few differences.

Why companies pay for RHEL

  • Support: a phone number and engineers to call when production breaks at 2 am.
  • Long life: security fixes for a major version for about ten years, so a bank does not have to rebuild every server every year.
  • Certification: hardware vendors and software like SAP and Oracle Database are tested and certified on RHEL.
  • Security and compliance tools that auditors in banking and government ask for.

Building a free practice lab

You learn Linux by typing, not by reading. You need a machine you are allowed to break. Install a virtual machine (VM): a computer simulated by software such as VirtualBox, VMware, KVM/virt-manager on Linux, or Hyper-V on Windows. Then install one of these inside it:

  1. RHEL itself, through the free Red Hat Developer Subscription for Individuals (sign up at developers.redhat.com). It covers a small number of personal systems; check the current terms.
  2. Rocky Linux 9 or AlmaLinux 9: free, and the commands in this course behave the same.

Give the VM 2 CPUs, 2 to 4 GB of RAM and a 20 GB disk. Add one or two extra small disks (5 GB each) now; you will need them for the storage module. Take a snapshot after installing, so you can roll back when you break something.

bash
$ cat /etc/redhat-release
Red Hat Enterprise Linux release 9.4 (Plow)
$ uname -r
5.14.0-427.13.1.el9_4.x86_64
cat /etc/redhat-release shows the RHEL release; uname -r shows the running kernel version.
Careful: Common mistake: practising on your only laptop as root and deleting something important. Always practise inside a VM with a snapshot. Second mistake: learning on Ubuntu and expecting the exam to match. Ubuntu uses apt and different config paths; for RHCSA, practise on RHEL, Rocky or Alma.
Tip: Install the "Server" or "Minimal" option, not the desktop, at least once. Real servers have no screen; you will work only through the terminal and SSH.

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What Linux and Red Hat Enterprise Linux are · 1/7

Linux and RHEL

Welcome to Linux and Red Hat. In this first lesson you will learn what Linux and RHEL actually are.

Prefer a video by a teacher? Find free videos on “what is red hat enterprise linux rhel explained beginners” on YouTube ↗

In real life: A Bengaluru fintech picks RHEL

A payments start-up in Bengaluru runs its card-processing servers on RHEL because its bank partners and the payment card security auditors ask for a supported, regularly patched OS. Its developers practise on free AlmaLinux VMs on their laptops, and the same Ansible playbooks then run on the paid RHEL servers in production. The commands they learnt on Alma work unchanged.

bash
$ cat /etc/os-release | head -3
NAME="Red Hat Enterprise Linux"
VERSION="9.4 (Plow)"
ID="rhel"
On AlmaLinux the same file says NAME="AlmaLinux" but the tools are the same.

Practice (0/2 done)

Task 1 · Question

Which statement is correct?

Task 2 · Practice

Build your practice lab: a VM with RHEL 9 (developer subscription), Rocky Linux 9 or AlmaLinux 9.

Quick quiz

Question 1

1.What does the Linux kernel do?

Question 2

2.Which of these is a free rebuild designed to be compatible with RHEL?

Question 3

3.Which command shows the RHEL release?

Question 4

4.Why do banks usually pay for RHEL?

Read more (free)

Open a question to see the answer and why. The first ones are this topic's own quiz, so try the quiz above before you peek.

What does the Linux kernel do?

Answer: Talks to the hardware and runs processes

The kernel is the core of the OS: hardware, memory, processes.

Which of these is a free rebuild designed to be compatible with RHEL?

Answer: Rocky Linux

Rocky Linux and AlmaLinux aim to match RHEL behaviour.

Which command shows the RHEL release?

Answer: cat /etc/redhat-release

/etc/redhat-release holds the release line. uname -r shows the kernel version instead.

Why do banks usually pay for RHEL?

Answer: Support, long update life and certification

They pay for support, long-term fixes and certified hardware and software.

Which package manager do you use on Rocky Linux?Related

Answer: dnf

Rocky Linux and other RHEL-family systems use dnf. apt is for Debian and Ubuntu, apk for Alpine.

From The Linux filesystem and everyday commands

Which package provides RHEL System Roles?Related

Answer: rhel-system-roles

rhel-system-roles.

From RHEL System Roles and Ansible Vault

An alternative security-focused Linux similar to Kali is…Related

Answer: Parrot Security OS

Parrot Security OS is a comparable distribution.

From Kali Linux: the attacker machine

Which skill most often moves a Linux admin towards DevOps roles?Related

Answer: Automation (Ansible, scripting) plus cloud and containers

Automation and cloud are the bridge.

From Careers, salaries in India and your next steps

Pass the quiz (60% or more) or mark this topic as done when you are ready.

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Next: The filesystem hierarchy and paths →

Next steps

  1. 5 more topics in “Linux and the shell” before its exam: The filesystem hierarchy and paths, Shell basics and getting help, Working with files: ls, cp, mv, rm, links and find, Reading text: grep, less, pipes and redirection, Editing files with vim.
  2. Module 1 exam: Linux and the shell · 13 questions · 20 min, without help. 6 topics of this module still to finish first.
  3. Then the next module, Permissions, users and sudo. 57 topics left in the course before the final exam.