Access Systems and Get Support

🎯 Introduction

The ability to access and navigate Linux systems is fundamental to system administration. As a system administrator, you'll need to connect to servers both locally (physical access) and remotely (over a network using SSH). Understanding these access methods and knowing how to find help when needed are critical first steps in your RHCSA journey.

This chapter will equip you with the essential skills to:

• Log in to a Linux system using a virtual console
• Connect to remote systems securely using SSH
• Navigate the Bash shell environment
• Access built-in documentation and help resources
• Understand command syntax and options

🖥️ Access the Local System

Virtual Consoles

RHEL 9 provides multiple virtual consoles that allow you to have several independent login sessions on a single physical system. By default, six text-based virtual consoles are available.

Switching Between Virtual Consoles

Use the following keyboard shortcuts to switch between virtual consoles:

• Ctrl+Alt+F1 through Ctrl+Alt+F6 - Access text consoles 1-6
• Ctrl+Alt+F1 - Return to graphical desktop (if installed)

Login Process

When you access a virtual console, you'll see a login prompt:

Red Hat Enterprise Linux 9.3 (Plow)
Kernel 5.14.0-362.el9.x86_64 on an x86_64

localhost login: _

[student@localhost ~]$ _

🔐 Access Remote Systems with SSH

What is SSH?

Secure Shell (SSH) is a cryptographic network protocol that provides a secure channel over an unsecured network. SSH encrypts all traffic, including passwords, to protect against eavesdropping and connection hijacking.

Basic SSH Syntax

ssh username@hostname

Or using IP address:

ssh username@192.168.1.100

SSH Connection Example

[student@workstation ~]$ ssh user@servera.example.com
The authenticity of host 'servera.example.com (192.168.1.10)' can't be established.
ECDSA key fingerprint is SHA256:1A2B3C4D5E6F7G8H9I0J.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'servera.example.com' (ECDSA) to the list of known hosts.
user@servera.example.com's password: 
[user@servera ~]$ 

SSH Key-Based Authentication

For better security and convenience, you can use SSH keys instead of passwords. This involves creating a public/private key pair.

Useful SSH Options

Exit SSH Session

To disconnect from an SSH session, use one of these methods:

exit
# or
logout
# or press
Ctrl+D

⌨️ Bash Shell Basics

Understanding the Command Prompt

The default Bash prompt shows useful information:

[student@localhost ~]$

Breaking it down:

• student - Current username
• localhost - Hostname of the system
• ~ - Current directory (~ represents home directory)
• $ - Regular user prompt (# for root user)

Basic Command Structure

command [options] [arguments]

Example:

ls -l /etc

• ls - Command (list directory contents)
• -l - Option (long format)
• /etc - Argument (directory to list)

Essential Bash Shortcuts

📚 Access Documentation

Man Pages

Manual pages (man pages) are the primary source of documentation for Linux commands and system calls.

Basic Usage

man command_name

Example:

man ls

Navigating Man Pages

Man Page Sections

Man pages are organized into sections:

1. User commands
2. System calls
3. Library functions
4. Special files (devices)
5. File formats
6. Games
7. Miscellaneous
8. System administration commands

To access a specific section:

man 5 passwd    # View passwd file format
man 1 passwd    # View passwd command

Info Pages

Some commands have more detailed documentation in Info format:

info command_name

--help Option

Most commands support the --help option for quick reference:

ls --help
mkdir --help

Documentation in /usr/share/doc

Additional documentation is often available in:

ls /usr/share/doc/