Linux System Administration Overview

Linux System Administration

• Linux is a free and open-source operating system, known for its flexibility, security, and collaborative development.
• It powers many devices and systems worldwide.
• It can be configured as a full graphical desktop or a small appliance.
• Linux distributions are installable operating systems built from a Linux kernel and supporting user programs and libraries.

Why Learn Linux?

• Linux is widely used in internet infrastructure, cloud computing, and mobile apps.
• Learning Linux boosts career opportunities and technical skills.

What Makes Linux Great

• Open-source: Anyone can view, modify, and share the code, leading to rapid innovation and transparency.
• Powerful Command-Line Interface (CLI): Efficient automation and system administration. Easy access and powerful scripting are possible.
• Modular and Flexible: Easy customization and upgrades. Components can be upgraded and updated when needed, making Linux ideal for software development, testing, and general computing tasks or specialized applications.

Open Source Software

• Software with publicly accessible source code allows study, modification, and sharing.
• It promotes collaboration, transparency, and cost-effectiveness.
• Open Source has many benefits for the user, such as control over the code, training opportunities, enhanced security, and stability.

Types of Open Source Licenses

• Copyleft Licenses (GPL, LGPL): Derivative works must also be open-source.
• Permissive Licenses (MIT, BSD, Apache): Allow commercial use and modification without sharing changes.

Linux Distributions

• A complete operating system built on top of the Linux kernel, providing a user-friendly experience with pre-installed software and tools.
• Open-source construction.
• Pre-packaged convenience.
• Variety for choice.
• Essential characteristics: Typically include a Linux kernel, user programs, installation, and update tools, and support from vendors and communities.

Red Hat

• Leading provider of open-source solutions, including Red Hat Enterprise Linux, JBoss middleware, and cloud technologies.
• Red Hat's role is connecting customers with the open-source community.

Fedora

• Community-driven Linux distribution known for its fast-paced innovation and cutting-edge features.

RHEL

• Red Hat Enterprise Linux, a commercially supported Linux distribution.
• A leading platform for open-source computing.
• Major releases are derived from the CentOS Stream project.

RHEL for Edge

• An image-based variant of RHEL with a different deployment mechanism.
• Image-based deployment uses a tool called Image Builder to create operating system images.
• Efficient deployment, saving time in lifecycle and customization.

Red Hat CoreOS (RHCOS)

• Built from RHEL components & managed as part of Red Hat.
• OpenShift Container Platform (RHOCP) for cloud-native applications.
• Uses the Container Runtime Interface (CRI-O)-compliant engine.
• Red Hat Universal Base Image (UBI)
• Freely redistributable & serves as foundation for cloud-native applications.

Command Line Interface (CLI)

• A text-based interface for interacting with a computer system using commands.
• Shell: A program that provides the CLI, interpreting and executing commands.
• Prompt: Indicates the shell is ready for input.
• Regular user prompt: Ends with $
• Superuser prompt: Ends with #
• Terminal: An interface allowing interaction with the shell.

Command Structure

• Command: The action you want to perform
• Options: Adjusting behavior, start with - or -- to distinguish them from arguments
• Arguments: Targets of the command

Logging In

• Local: Physical console, Keyboard and display, Virtual Consoles
• Remote: Secure Shell (SSH)

Logging Out

• exit command
• Ctrl + D

File Systems

• Linux uses a single, inverted tree structure to control directories and files. The root directory (/) is the top of the tree and is denoted with a single slash (/). Subdirectories extend outward from the root.

• The '/' character acts as the directory separator

• Static content: Remains unchanged until explicitly edited.

• Dynamic content: Subject to modification or appending by active processes.

• Persistent content: Remains after a reboot (settings).

• Runtime content: Only needed while system is running

Viewing File Contents

• cat: Displays entire contents of a file simultaneously.

• less: Displays contents of a file one page at a time.

• head: Displays first 10 lines of a file (configurable).

• tail: Displays last 3 lines of a file (configurable).

• wc: counts lines, words and character numbers

Locating Files by Name

• Path: Unique location of a file or directory in the file system.

• Spaces should be avoided, surrounded by quotes if necessary, to avoid misinterpretation.

• Absolute Path: Specifies the complete location of a file, starting from the root directory (/). Always begins with a "/".

• Relative Path: Specifies the location of a file relative to the current working directory. It does not begin with a "/".

Commands

• pwd: Displays current working directory.

• Is: Lists directory contents

• cd: Changes current working directory

• touch: Creates empty files or updates timestamps.

Managing Files and Directories

• mkdir: Creates directories

• cp : Copies files or directories.

• rm: Removes files or directories

• rm -r: Removes directories, including subdirectories.

• mv : Moves or renames files or directories.

###Command History

• history: Displays previously executed commands
• !number: Re-executes a command by its number.

Editing the Command Line

• Shortcuts for navigation and editing using Ctrl + keys.

• Ctrl + A: Start of line

• Ctrl + E: End of the line

• Ctrl + U: Clear everything before the cursor

• Ctrl + K: Clear everything after the cursor

• Ctrl + Left Arrow: Previous word, Ctrl + Right Arrow: Next word

• Ctrl + R: Search command history

This quiz covers the fundamentals of Linux system administration, including its advantages, features, and applications in various environments. Discover why Linux is a vital skill for technical careers and how its open-source nature promotes innovation. Test your knowledge on the powerful command-line interface and modular design of Linux.