Introduction to Linux Operating System

Introduction to Linux

• Linux is an operating system (OS) used with a variety of applications and hardware.
• A computer has two fundamental components: hardware and software.
• Hardware includes the physical components inside a computer, such as the processor (CPU), physical memory (RAM), hard disk drives, CD and DVD drives, flash memory card readers (SD cards), sound cards, video cards, and circuit boards.
• Software is a set of instructions or programs that allow hardware components to manipulate data.
• Two types of programs are executed on a computer: applications and the operating system (OS).
• Applications are programs designed for a specific use and with which a user interacts.
• OS software contains components used to control the computer's hardware.
• Device drivers are software containing instructions the OS uses to control and interact with a specific device.
• The user interface (UI) is an application program that accepts user input, sends input to the OS for completion and returns results to the user.
• The UI can be a command line prompt or graphical user interface (GUI).
• A GUI is a component of an OS that allows the user to interact with the computer using the keyboard or mouse.
• System services are applications that handle system-related tasks, such as printing, scheduling programs, and gaining network access.
• Linux is used to run a variety of applications on a variety of hardware.
• Linux has multitasking capabilities, meaning it can manage thousands of tasks at once.
• Linux supports multi-user environments, allowing multiple users to access the system simultaneously.
• The core component of Linux is the kernel, which is written almost entirely in the C programming language.
• Software can be used to modify the appearance of Linux, but the kernel remains common to all versions.
• Understanding Linux kernel version numbers is important for selecting the appropriate version for user needs.
• Linux may be customized to provide services for a variety of companies in a variety of situations.
• Workstation services are services used on a local computer.
• Server services are services made available for other computers across a network.

Kernel Versions

• Linux kernel versions comprise of major, minor, and revision numbers.
• The major number indicates a major revision to the Linux kernel.
• The minor number indicates minor revisions and stability.
• Odd minor numbers denote developmental kernels, implying instability due to incomplete testing.
• Even minor numbers denote production kernels, indicating complete testing and stability.
• Kernel versions are often referred to as developmental or production, based on stability.

Licensing

• Linux is an Open Source Software (OSS). This means the software is distributed and licensed in a way that the source code is freely available.
• Source code refers to the list of instructions that programmers use to create programs, following rules set by programming languages.
• OSS encourages collaboration, leading to rapid development and quick bug fixes.
• Increased user needs dictate software feature evolution in OSS.
• OSS' perceived value increases because its worth is based on usefulness, rather than price.

Types of Open Source Licenses

• GNU Public License (GPL): This license was developed by the Free Software Foundation (FSF), stipulating that any software published under this license must be freely available.
• Users who modify the source code must also redistribute the modified code freely.
• Artistic license: Allows source code to be freely distributed, but changes must be at the discretion of the original author. The original author can reject changes.

Types of Closed Source Licenses

• Most closed source software is sold commercially.
• Software often bears the label of the manufacturer.
• Freeware is a type of closed source software that is given out free of charge.
• Source code isn't available.
• Shareware is a type of closed source software, initially free but paying after a certain time-period or to use certain features.

Linux Advantages

• Linux's open source nature allows for rapid adaptation to market changes. It reduces costs and time when changing software.
• Closed source software may experience support issues, vendor closures, or version retirements.
• The community-based development of OSS products allows the opportunity to maintain and change source code.
• A wealth of common software includes scientific and engineering software, emulators, web servers, web browsers, e-commerce suites, desktop productivity software, graphics manipulation software, database software, and security software.
• OSS products increase stability because the community collaborates on testing and fixing bugs.
• The open nature of the code leads to quick bug and security loophole identification and resolution.
• Linux OSs can be adapted and customized.
• A user can recompile the kernel for use on a specific task or situation.
• The ability to install only the required software packages, reduces the size and increases efficiency of the OS.
• Linux supports several programming languages, for creating customized and automated tasks, such as use of shell and PERL scripts.
• Linux is less expensive than other OSS offerings.
• There's no cost associated with acquiring software.
• A range of hardware platforms can run Linux.
• The largest cost of Linux is associated with hiring personnel to maintain the system.

UNIX

• UNIX evolved from a project called MULTICS.
• UNIX was the first true multitasking and multiuser OS.
• It was rewritten in the C programming language, making it portable to many different hardware platforms.
• AT&T sold UNIX source code.
• Various companies developed their versions (flavors) of UNIX, adhering to agreed-upon standards.

Common UNIX flavors

• Examples of popular UNIX today, include Oracle's Solaris, Hewlett-Packard's HP-UX, IBM's AIX UNIX, Apple's Macintosh OS X and iOS.

Common Linux Distributions

• Debian Linux

• Ubuntu Linux

• Linux Mint

• TurboLinux

• Red Hat (includes Fedora)

• SuSE

• These distributions are collections of software containing the Linux kernel and libraries, combined with add-on software specific to a given use.

Summary of Linux Distribution

• Linux is a by-product of Open Source Software (OSS) development.
• Interest in embedded Linux OSs for smaller devices, like mobile devices, has increased since 2000.
• Based on its significant development, more application development from the OSS community is expected over the next decade.
• Linux is available in various distributions.
• All distributions share a common kernel but come with different OSS applications.
• Common uses of Linux include: Internet servers, file and print servers, application servers, cloud systems, supercomputers, scientific workstations, office/personal workstations, and mobile devices.