school-of-sre/courses/linux_basics/intro.md

Introduction

Prerequisites

• Experience of working on any operating systems like Windows, Linux or Mac
• Basics of operating system

What to expect from this course

This course is divided into three parts. In the first part, we will cover the fundamentals of linux operating systems. We will talk about linux architecture, linux distributions and uses of linux operating systems. We will also talk about difference between GUI and CLI.

In the second part, we will study about some of the basic commands that are used in linux. We will focus on commands used for navigating file system, commands used for manipulating files, commands used for viewing files, I/O redirection etc.

In the third part, we will study about linux system administration. In this part, we will focus on day to day tasks performed by linux admins like managing users/groups, managing file permissions, monitoring system performance, log files etc.

In the second and third part, we will be taking examples to understand the concepts.

What is not covered under this course

We are not covering advanced linux commands and bash scripting in this course. We will also not be covering linux internals.

Course Content

The following topics has been covered in this course:

• Introduction to Linux
  • What are Linux Operating Systems
  • What are popular Linux distributions
  • Uses of Linux Operating Systems
  • Linux Architecture
  • Graphical user interface (GUI) vs Command line interface (CLI)
• Command Line Basics
  • Lab Environment Setup
  • What is a Command
  • File System Organization
  • Navigating File System
  • Manipulating Files
  • Viewing Files
  • Echo Command
  • Text Processing Commands
  • I/O Redirection
• Linux system administration
  • Lab Environment Setup
  • User/Groups management
  • Becoming a Superuser
  • File Permissions
  • SSH Command
  • Package Management
  • Process Management
  • Memory Management
  • Daemons and Systemd
  • Logs
• Conclusion
  • Applications in SRE Role
  • Useful Courses and tutorials

What are Linux operating systems

Most of us will be familiar with the windows operating system which is used in more than 75% of the personal computers. The windows operating systems are based on windows NT kernel. A kernel is the most important part of an operating system which performs important functions like process management, memory management, filesystem management etc.

Linux operating systems are based on the Linux kernel. A linux based operating system will consist of linux kernel, GUI/CLI, system libraries and system utilities. The Linux kernel was independently developed and released by Linus Torvalds. The linux kernel is free and open-source - https://github.com/torvalds/linux

History of Linux - https://en.wikipedia.org/wiki/History_of_Linux

What are popular Linux distributions

A linux distribution(distro) is an operating system that is based on the linux kernel and a package management system. A package management system consists of tools that helps in installing, upgrading, configuring and removing softwares on the operating system.

Softwares are usually adopted to a distribution and are packaged in a distro specific format. These packages are available through a distro specific repository. Packages are installed and managed in the operating system by a package manager.

List of popular Linux distributions:

• Fedora

• Ubuntu

• Debian

• Centos

• Red Hat Enterprise Linux

• Suse

• Arch Linux

Packaging systems	Distributions	Package manager
Debian style (.deb)	Debian, Ubuntu	APT
Red Hat style (.rpm)	Fedora, CentOS, Red Hat Enterprise Linux	YUM

Linux Architecture

• The Linux kernel is monolithic in nature.

• System calls are used to interact with the linux kernel space.

• Kernel code can only be executed in the kernel mode. Non-kernel code is executed in the user mode.

• Device drivers are used to communicate with the hardware devices.

Uses of Linux Operating Systems

Operating system based on linux kernel are widely used in:

• Personal computers

• Servers

• Mobile phones - Android is based on linux operating system

• Embedded devices - watches, televisions, traffic lights etc

• Satelites

• Network devices - routers, switches etc.

Graphical user interface (GUI) vs Command line interface (CLI)

A user interacts with a computer with the help of user interfaces. The user interface can be either GUI or CLI.

Graphical user interface allows a user to interact with the computer using graphics such as icons and images. When a user clicks on an icon to open an application on a computer, he or she is actually using the GUI. It's easy to perform tasks using GUI.

Command line interface allows a user to interact with the computer using commands. A user types the command in a terminal and the system helps in executing these commands. A new user with experience on GUI may find it difficult to interact with CLI as he/she needs to be aware of the commands to perform a particular operation.

Shell vs Terminal

Shell is a program that takes command or a group of commands from the users and gives them to the operating system for processing. Shell is an example of command line interface. Bash is one of the most popular shell programs available on linux servers. Other popular shell programs are zsh, ksh and tcsh.

Terminal is a program that opens a window and lets you interact with the shell. Some popular examples of terminals are gnome-terminal, xterm, konsole etc.

Linux users do use the terms shell, terminal, prompt, console etc. interchangeably. In simple terms, these all refer to a way of taking commands from the user.