RED HAT ENTERPRISE LINUX

Getting Started with the Shell

Logging In and Running Simple Commands

CIS126RH | RHEL System Administration 1
Mesa Community College

Welcome to your first hands-on module in Red Hat Enterprise Linux system administration. This module covers the foundational skills you'll use every day as a Linux administrator: logging into a system and running commands in the shell. The shell is your primary interface to Linux. While graphical interfaces exist, real system administration happens at the command line. The shell gives you power, flexibility, and the ability to automate tasks that would take hours through a GUI. We'll start with the basics: how to log in, what a shell is, how to read the command prompt, and how to run simple commands. You'll learn essential navigation and information commands that you'll use constantly. We'll also cover command syntax, getting help, and keyboard shortcuts that make you more efficient. These skills are the foundation for everything else in this course. Master them well - you'll use them in every module that follows.

Learning Objectives

Log in to a Linux system

Access local consoles, graphical environments, and remote systems via SSH

Understand the shell environment

Know what a shell is, identify Bash, and interpret the command prompt

Run basic commands

Execute commands for navigation, file listing, and system information

Use command syntax and shortcuts

Understand options, arguments, and keyboard shortcuts for efficiency

We have four main learning objectives for this introductory module. First, we'll learn how to log in to a Linux system. This includes local console access - both text and graphical - as well as remote access via SSH. You need to be able to access a system before you can administer it, so this is our starting point. Second, we'll understand the shell environment. You'll learn what a shell actually is, why Bash is the default shell in RHEL, and how to read the information that the command prompt provides. This context helps you understand what's happening when you type commands. Third, we'll run basic commands. We'll cover essential commands for navigating the filesystem, listing files, and getting system information. These are commands you'll use dozens of times every day. Fourth, we'll learn command syntax and shortcuts. Understanding how commands are structured - with options and arguments - helps you use any command correctly. Keyboard shortcuts make you faster and more efficient. These fundamentals prepare you for everything else in this course.

What is a Shell?

A shell is a command-line interpreter that provides an interface between the user and the operating system kernel. It reads commands you type, interprets them, and executes them.

→

Shell (Bash)

→

Kernel

→

Hardware

Bash

Bourne Again Shell - the default shell in RHEL and most Linux distributions

sh, zsh, fish

Other shells with different features - Bash is most common for administration

Let's start with a fundamental concept: what exactly is a shell? Think of the shell as a translator between you and the computer. When you type a command, the shell interprets what you want, translates it into something the operating system kernel understands, and executes it. The results come back through the shell to your screen. The kernel is the core of Linux - it directly controls hardware, manages memory, handles processes, and provides core services. But you don't interact with the kernel directly. The shell provides a human-friendly interface. Bash (Bourne Again Shell) is the default shell on RHEL and most Linux distributions. It's an enhanced version of the original Unix Bourne shell, with features like command history, tab completion, and scripting capabilities. Other shells exist - sh (the original Bourne shell), zsh (popular with developers for its customization), fish (user-friendly features) - but Bash is the standard for system administration. Scripts are typically written for Bash, and it's what you'll find on virtually every Linux system. When we talk about "the command line" or "the terminal," we're really talking about interacting with a shell - usually Bash.

Ways to Access the Shell

Terminal Emulator

Graphical application like GNOME Terminal that provides shell access

SSH (Remote)

Secure Shell protocol for remote command-line access over the network

# Connect to a remote server via SSH
[student@workstation ~]$ ssh student@server.example.com
student@server.example.com's password:
[student@server ~]$

# SSH with specific options
[student@workstation ~]$ ssh -l student 192.168.1.100
[student@workstation ~]$ ssh student@192.168.1.100 -p 22

Most Common: As a system administrator, you'll primarily access servers remotely via SSH. Physical console access is for emergencies or initial setup.

There are several ways to access a shell on a Linux system, depending on your situation. Local console access means you're physically at the machine (or connected via a remote console like IPMI or a VM console). You can use text-mode virtual consoles or open a terminal application in a graphical environment. Terminal emulators are graphical applications that provide shell access. GNOME Terminal is the default on RHEL with a graphical desktop. You open it like any application and get a shell prompt. This is convenient for desktop use. SSH (Secure Shell) is the most common method for server administration. Servers typically don't have monitors and keyboards attached - they sit in data centers. SSH provides encrypted remote access over the network. You connect from your workstation to the server. The ssh command connects to remote systems. The basic syntax is "ssh username@hostname" - you specify who you want to log in as and which system. You'll be prompted for a password (or use SSH keys, which we cover in another module). Once connected, you have a shell on the remote system. Everything you type is sent over the encrypted connection, executed on the server, and results sent back. For servers, SSH is your daily driver. Physical console is for emergencies when SSH isn't working or for initial setup of new systems.

Virtual Consoles

tty1

Ctrl+Alt+F1

GUI or Text

tty2

Ctrl+Alt+F2

Text

tty3

Ctrl+Alt+F3

Text

tty4

Ctrl+Alt+F4

Text

tty5

Ctrl+Alt+F5

Text

tty6

Ctrl+Alt+F6

Text

# See which terminal you're on
[student@server ~]$ tty
/dev/tty2

# See who is logged into which terminals
[student@server ~]$ w
USER     TTY      FROM             LOGIN@   WHAT
student  tty2     -                09:15    -bash
student  pts/0    192.168.1.50     09:20    w

Virtual consoles give you multiple independent terminal sessions on a single Linux system. This is useful for running multiple tasks, troubleshooting when the graphical interface freezes, or when you need direct console access. On most RHEL systems, you have six virtual consoles accessible with Ctrl+Alt+F1 through F6. The graphical environment typically runs on tty1 (sometimes tty2). The others provide text-mode logins. To switch between consoles, press Ctrl+Alt and the function key. If you're already at a text console (not in a graphical environment), just Alt+F# works. Each virtual console is independent - you can log in as different users, run different tasks, and switch between them freely. The tty command shows which terminal device you're using. /dev/tty2 means you're on virtual console 2. If you see /dev/pts/0, you're in a pseudo-terminal - usually an SSH connection or terminal emulator window. The w command shows who's logged in and what they're doing. You can see users on different terminals, where they connected from (IP address for SSH, hyphen for local), and what command they're currently running. Virtual consoles are especially useful when the graphical interface crashes. Ctrl+Alt+F2 gets you to a text console where you can troubleshoot and restart the graphics service without rebooting.

The Login Process

Red Hat Enterprise Linux 9 - Console Login

Red Hat Enterprise Linux 9.0 (Plow)
Kernel 5.14.0-70.el9.x86_64 on an x86_64

server login: student
Password: ••••••••

Last login: Mon Jan 15 09:15:22 2024 from 192.168.1.50
[student@server ~]$

Username: Your account name (case-sensitive)

Password: Characters not displayed as you type

Last login: Shows when and from where

Prompt: Ready for commands

⚠ Note: Linux usernames and passwords are case-sensitive. "Student" and "student" are different users!

Let's walk through what happens when you log in to a Linux console. The login prompt shows the system name and waits for you to enter a username. In RHEL, you'll see the distribution name, version, kernel version, and architecture before the prompt. Enter your username and press Enter. Usernames in Linux are case-sensitive - "student" and "Student" are different accounts. Next, you're prompted for your password. For security, nothing appears as you type - no asterisks, no dots, nothing. This prevents shoulder surfing (someone seeing how many characters your password has). Just type your password and press Enter. If authentication succeeds, you'll see information about your last login - when it was and where it came from. This is a security feature - if you see a login you don't recognize, someone else might have accessed your account. Finally, you get the shell prompt, indicating the system is ready for your commands. If login fails, you'll see "Login incorrect" and can try again. After several failed attempts (typically 3-5), the system may impose a delay or lock the account temporarily. Once you're logged in, you have access according to your account's permissions. Regular users can access their files and run programs. Administrative tasks require additional privileges (we'll cover sudo later).

Understanding the Prompt

student

server

● student — Current username (who you're logged in as)

● server — Hostname (which system you're on)

● ~ — Current directory (~ means home directory)

● $ — Prompt symbol ($ for regular user, # for root)

# Regular user prompt
[student@server ~]$

# Root user prompt - note the # symbol
[root@server ~]#

# In a different directory
[student@server Documents]$

# Full path shown
[student@server /var/log]$

The command prompt isn't just decoration - it conveys important information. Let's decode each part. The username shows who you're logged in as. This matters because different users have different permissions. You might be logged into the same server as different users in different windows. The hostname shows which system you're on. When you're administering multiple servers via SSH, this prevents you from running commands on the wrong machine - a common and potentially disastrous mistake. The current directory shows where you are in the filesystem. The tilde (~) is shorthand for your home directory. As you navigate around, this changes to show your current location. If you're in /var/log, the prompt shows that. The prompt symbol is critical: $ means you're a regular user, # means you're root (the superuser). This visual cue helps prevent accidents - you should be extra careful when you see #. The prompt is customizable through environment variables (PS1), but the default in RHEL provides this useful information. Some administrators customize it further, adding things like the current time or exit status of the last command.

Command Syntax

comman

Getting Started with the Shell

Logging In and Running Simple Commands

Learning Objectives

What is a Shell?

Bash

sh, zsh, fish

Ways to Access the Shell

Local Console

Terminal Emulator

SSH (Remote)

Virtual Consoles

The Login Process

Understanding the Prompt

Command Syntax