Introduction to Linux and Operating Systems

Introduction to Linux

• Linux is an operating system (OS) used to run various applications on diverse hardware.
• It supports multitasking, enabling the simultaneous management of numerous tasks.
• Linux also supports multiple users accessing the system concurrently.
• The core component of Linux is the kernel.
• The kernel is mostly written in the C programming language.
• It's important to understand Linux kernel version numbers to select suitable versions for users.

Operating Systems

• A computer has two fundamental components: hardware and software.
• Hardware includes physical components like the processor (CPU), RAM, hard drives, CD/DVD drives, flash memory card readers (SD cards), sound cards, video cards, and circuit boards.
• Software is a set of instructions or programs used to control the hardware.
• Applications are programs designed for specific user interactions.
• Operating system (OS) software controls computer hardware.
• Device drivers are software instructions that control specific devices.
• User interfaces (UI) receive and process user input, forwarding it to the OS to execute tasks and relay results to the user.
• This can be a command line prompt or a graphical user interface (GUI).
• A graphical user interface (GUI) allows users to interact with the computer using the keyboard and mouse.
• System services are applications that handle tasks, such as printing, scheduling programs, and network access.

The Linux Operating System

• Linux is an OS used for a range of applications across various hardware types.
• It supports multitasking, handling thousands of simultaneous tasks.
• It supports multiple users accessing the system concurrently.

Versions of the Linux Operating System

• The core component of Linux is the kernel.
• Software can be used to alter Linux's appearance, but the kernel is universal.
• Understanding kernel version numbers is crucial for selecting appropriate versions for users.

Identifying Kernel Versions

• Linux kernel versions consist of major, minor, and revision numbers.
• Major numbers signify substantial revisions.
• Minor numbers indicate revisions and stability.
• Odd minor numbers indicate developmental kernels, often not thoroughly tested.
• Even minor numbers represent production kernels, thoroughly tested for stability.
• Revision numbers are additional, specific to particular kernels. Examples of kernel versions are provided in the document's appendices.

Licensing Linux

• Open Source Software (OSS) refers to programs with freely available source code, allowing users to examine, modify, and improve the code.
• Source code lists the instructions used to create a program.
• The source code's format and structure comply with the programming language's rules.

Implications of OSS

• Software development rapidly accelerates through collaborative efforts.
• Software bugs are identified and fixed promptly.
• Software features adapt quickly to user needs.
• The value of the software is determined more by its effectiveness than its cost.

Software Types

• Open source software has readily available source code for modification.
• Closed source software does not provide source code; it is often costly.
• Freeware is closed-source software given out free of charge.
• Shareware is initially free but may require payment after a specified period or for specific features.

Types of Open Source Licenses

• GNU Public License (GPL) is developed by the Free Software Foundation (FSF).
• GPL requires that all software based on their license provides free access to its source code.
• Users modifying the source code are also obligated to distribute their modified code for free.
• Artistic license is an open-source license where the original author retains the right to reject modifications.

Types of Closed Source Licenses

• Most closed source software is sold commercially.
• Software usually carries the manufacturer's label.
• Freeware is closed-source software distributed for free; source code is not accessible.
• Shareware is initially offered for free but requires payment later to use its full functionality or after a certain timeframe.

Linux Advantages: Risk Reduction

• Changes in market demands or customer needs might force companies to continuously update and adapt their software.
• This can become costly and time-consuming.
• Supporting closed-source software can end.
• Software vendors may cease operations.
• Software versions may be deprecated. OSS products offer a means of maintaining and continuing the evolution of the source code.

Linux Advantages: Meeting Business Needs

• Common software applications available for use with Linux include:
  • scientific and engineering software
  • emulators
  • web servers, browsers, and e-commerce suites
  • desktop productivity software
  • graphics manipulation software
  • database software
  • security software The list demonstrates the broad applicability of Linux.

Linux Advantages: Stability and Security

• Users of closed-source OSs are reliant on the vendor to fix bugs.
• This process may take weeks or even months.
• The collaborative nature of open-source development improves Linux's stability and security.
• Bugs and vulnerabilities are identified and corrected quickly due to open source code scrutiny. Bugs can be quickly identified and fixed by a larger community of developers.

Linux Advantages: Ease of Customization

• Linux gives users control over its inner workings.
• Users can recompile the kernel to tailor features like internet server support.
• This results in smaller and faster kernels.
• Only the necessary software packages are installed.
• Programming languages like shell and PERL scripts enhance customization and automation of processes.

Linux Advantages: Cost Reduction

• Linux is less expensive than other operating systems.
• Acquiring Linux software is typically free.
• Many OSS programs run on diverse hardware platforms.
• The biggest cost associated with Linux comes from hiring personnel to maintain the system.
• Total cost of ownership (TCO) is the overall cost of using a specific OS. The document's text supports the notion of lower acquisition and maintenance costs.

UNIX

• UNIX evolved from the MULTICS system, providing the foundation for multitasking, and multiuser systems.
• The core of UNIX was rewritten in the C programming language, creating portability and execution on various hardware platforms.
• AT&T licensed UNIX source code to several companies, who then developed their own "flavors" of UNIX.
• Various companies built their own variations (flavor) of the UNIX operating system that adhere to the unified standards The presence of different flavors of UNIX and their adherence to agreed standards is highlighted.

Linux

• Linus Torvalds developed Linux in 1991.
• Linux is published under the GNU license.
• A distribution is a package collection combining the kernel with supplemental software for specialized uses.
• Examples include Red Hat and SuSE.
• Linux is a by-product of OSS development activities.
• The rise of embedded Linux solutions started around 2000 and still gains in popularity. The text emphasizes the wide-ranging applications of Linux systems.

Linux Distributions

• Debian Linux
• Ubuntu Linux
• Linux Mint
• TurboLinux
• Many distributions are available, all sharing a common kernel but with varied packaged applications. The text lists some of the many distributions.

Common Uses of Linux

• Linux is customizable to cater to diverse business needs and situations.
• Linux serves functions in both local (workstation) and network-based (server) settings.
• Current uses of Linux comprise:
  • Internet servers
  • File and print servers
  • Application servers
  • Cloud systems
  • Supercomputers
  • Scientific workstations
  • Office/personal workstations
  • Mobile devices The text provides a comprehensive list of common Linux applications.

Summary of Linux

• Linux is an open-source OS.
• It has a large developer community that freely develops and improves the kernel and supporting software.
• It is freely distributed under the GNU license.
• Companies value Linux for its stability, low risk, and flexibility.
• Available in numerous distributions, each featuring a common kernel accompanied by customized applications. The text summarizes Linux's key characteristics.