Introduction to Linux

What is Linux?

• Linux is a Unix clone, written from scratch by Linus Torvalds with the assistance of hackers across the Internet.
• Unix is a multitasking, multi-user operating system originally developed in 1969 by AT&T employees at Bell Labs.
• Linux and Unix aim to be POSIX compliant.
• 64% of the world's servers run Unix or Linux.
• The Android phone and the Kindle run Linux.

Features of Operating Systems

• Task Scheduling
• Memory Management
• Network Communication Handling
• Data and User Security

History of Linux

• UNIX was created in 1969 by Thompson & Ritchie at AT&T Bell Labs.
• Sun, HP, IBM, SGI, and DEC are commercial vendors.
• In 1984, Richard Stallman created the GNU with FSF, using GPL for open source.

Components of Linux System

• Kernel: Linux's core, responsible for all major operating system activities.
• System Library: Special functions or programs that application programs or system utilities use to access the Kernel's features.
• System Utility: Programs that perform specialized tasks.

Basic Features of Linux

• Portable: Software operates similarly across different hardware types.
• Open Source: The Linux source code is freely available for community-based development.
• Multiprogramming: Linux can run multiple applications concurrently.
• Security: User security is provided through authentication features like password protection, controlled file access, and data encryption.

Linux Commands

• Network: ssh, scp, ping, telnet, nslookup, wget
• Shells: BASH, TCSH, alias, watch, clear, history, chsh, echo, set, setenv, xargs
• System Information: w, whoami, man, info, which, free, echo, date, cal, df, free, man, info
• Command Information: man, info
• Symbols: |, >, >>, <, &, &&, 2>&1, ;, ``, ~, …, $!, !:, !
• Filters: grep, egrep, more, less, head, tail
• Hotkeys: ,
• File System: ls, mkdir, cd, pwd, mv, ln, touch, cat, file, find, diff, cmp, /net//, mount, du, df, chmod, find
• Line Editors: awk, sed
• File Editors: vim, gvim, emacs -nw, emacs
• User manual: man command

Linux Command-Line Interface

• Linux shells are command interpreters that allow commands to be typed via a keyboard to interact with the operating system kernel.
• sh (Bourne Shell) was developed for UNIX back in the late 1970s
• bash (Bourne-Again Shell) is the default shell used by most Linux distributions and is an improved version of the sh shell.
• csh (C Shell) was developed for BSD UNIX and uses a syntax similar to C programming.
• tcsh shell is an improved version of the C Shell and is the default shell used on FreeBSD systems.
• zsh (Z Shell) is an improved version of the bash shell.

Linux Architecture Layers

• Hardware layer: Includes all peripheral devices like RAM, HDD, and CPU.
• Kernel: The core, interacts with hardware, and provides low-level services.
• Shell: Takes commands from the user and executes kernel functions.
• Utilities: Programs that provide the user with most operating system functionalities.

Kernel Information

• The kernel interacts with hardware in machine language.
• The kernel manages file system, memory, scheduling, data transfer, and interrupt issues.

Linux vs. Windows

• Linux is freely available for download, while Windows requires purchasing a license.
• Windows updates are slower than Linux.
• Linux supports backward compatibility, unlike Windows.
• Most software on Windows needs to be licensed, whereas in Linux, most software is freely available.

Reasons to Use Linux

• Costless
• Stable
• Reliable
• Powerful
• Highly Secure

Linux Merits and Demerits

• Linux can be accessible to older computers.
• Linux is not suitable for gaming.
• Linux is not easy to understand for those new to it.
• Programmers commonly use Linux.
• Linux is used for both commercial and personal purposes, however, Windows is mostly preferred for home use.