Operating Systems and Linux Kernel

Fundamental Components of Computers

• Hardware: is the physical components inside a computer
• Software: allows hardware components to manipulate data via a set of instructions or programs

Hardware Components

• Hardware components include the Processor (CPU)
• Physical memory (RAM)
• Hard disk and solid state drives
• CD and DVD drives
• Flash memory card readers (SD cards)
• Sound and video cards
• Network adapter cards
• Ports
• Mainboards (motherboards)

Types of Programs on Computers

• Applications (apps): programs designed for a specific use with which a user interacts
• Operating System (OS) software: software components which control the hardware of the computer

Device Drivers and User Interfaces

• Device driver: software containing instructions which the OS uses to control and interact with a specific device
• User interface: an application program which accepts user input, forwards the input to the OS, and gives results back to the user
• User interfaces can be a command line prompt or a graphical user interface (GUI)

Linux

• Linux: An OS used to run a variety of applications on different hardware components
• It is a multiuser and multitasking OS and has the ability to manage thousands of tasks at the same time
• It allows multiple users to access the system simultaneously

Linux Kernel

• Linux kernel: the core component of the Linux OS
• It is written almost entirely in the C programming language
• Software modifies Linux's appearance, but the the kernel is universal
• It's important to choose the correct kernel version
• Deciding on a kernel version requires a good understanding of system hardware

Linux Kernel Version Components

• Major Kernel Number: indicates major revision to Linux kernel
• Minor Kernel Number: indicates minor revision and stability of the Linux kernel
• Production kernel: the kernel has been thoroughly tested and is stable
• Developmental kernel: the kernel is not fully tested and has implied instability
• Revision number: represents current changes to the version

Open Source Software

• Open Source Software (OSS) is freely developed and continuously improved by a large community of software developer
• Source code: a list of instructions a software developer writes to compose a program
• The format and structure of source code follows rules defined by the programming language

Implications of OSS development

• Software develops rapidly through widespread collaboration
• Bugs (errors) are marked quickly and promptly fixed
• Software features evolve quickly based on users' needs
• Perceived value increases because it is based on usefulness, not on price

Linux Advantages: Risk Reduction

• OSS products allows the user to maintain and change the source code.
• Changes in the market or customer needs cause companies to frequently change software which can be costly and time-consuming.
• Support for closed source software may end if the vendor goes goes out of business or their software version is retired

Linux Advantages: Meeting Business Needs

• Common software is available for Linux
• This includes scientific and engineering software, software emulators, Web servers, Web browsers, e-commerce suites, desktop productivity software, graphics manipulation software, database software, and security software

Linux Advantages: Stability

• The collaborative open source approach to testing and fixing bugs increases the stability of Linux, and bugs and security loopholes can be identified and fixed quickly
• Code is freely available and scrutinized by many developers
• With closed source OS, consumers must rely on the vendor to fix any bugs, and waiting for a hot fix may take weeks or months

Linux Advantages: Flexibility and Customization

• Linux has flexibility for different hardware platforms
• Partial list of hardware platforms on which Linux can run include: Intel x86/x64 and Itanium, PA-RISC and Mainframe (S/390, z/Architecture), ARM and MIPS, SPARC/Ultra-SPARC, and PowerPC/POWER
• Linux also has an ease of customization because of the ability to control OS inner workings
• The user can chose to only install only software packages needed
• Different programming languages such as shell and PERL scripts can be used to customize or automate tasks

Linux Advantages: Support and Cost

• Linux also has ease of obtaining support because of Linux documentation found on the Internet
• This documentation include Linux User Groups (LUGs), FAQs, HOWTO documents, and Internet newsgroups
• Linux is also less expensive that other OSs and wealth of OSS can run on a variety of different hardware platforms running Linux
• Largest costs associated with Linux concern costs associated with hiring people to maintain the system
• Total cost of ownership (TCO) is the the overall cost of using a particular OS

UNIX

• UNIX was evolved from Multiplexed Information and Computing Service (MULTICS)
• AT&T sold UNIX source code to several companies that then Each developed its own variety while adhering to standards agreed upon by all
• Berkeley Software Distribution (BSD) is a Version of the original UNIX source code
• Common flavors of UNIX today: BSD, Hewlett-Packard's HP-UX, IBM's AIX and Apple's macOS and iOS operating systems

Hacker Culture

• Hacker culture is a person who attempts to expand knowledge of computing through experimentation
• Cracker: someone who illegally uses computers for personal benefit or to cause damage
• Richard Stallman, a hacker who worked at MIT, formed the Free Software Foundation (FSF) and Encouraged free software development
• The GNU project by Richard Stallman promoted free development for a free OS that was not UNIX and led to publication of GNU Public License (GPL)

Linux

• First developed by Linus Torvalds in 1991 under the GNU license
• The linux kernel was developed collaboratively and centrally managed, and hackers developed Linux add-on packages and distributions
• Distribution: collection of software containing Linux kernel and libraries, combined with add-on software
• Some distributions incude: Red Hat, OpenSUSE, Debian and Ubuntu, Gentoo, Linux Mint, and Arch

Linux Distributions

• Varied Linux distributions have important differences but are essentially the same under the surface
• Some distributions include a large number of server-related tools such as Web and Database servers
• Most distributions include a GUI that can be further customized; a core component of this GUI is X Windows
• The two competing GUI environments in Linux are GNU Object Model Environment(GNOME) and K Desktop Environment(KDE)
• Package managers install and maintains software
• The Red Hat Package Manager is the most widely supported package manager
• A tarball is a compressed archive of files containing scripts that install software to the correct location on the system but is difficult to manage, upgrade, or remove from system

Common Uses of Linux

• Linux may be customized to provide a variety of services in different situations
• It has both workstation and server configurations
• These configurations can be Internet, file and print, and application servers, cloud systems and supercomputers, scientific and office/personal workstations, and cybersecurity workstations
• Following Apple iPhone introduction in 2007 several Linux-based smartphone and tablets appeared
• By 2017, Android (started in 2008) was installed on most smartphones, with Google Play Store hosting millions of apps that has been downloaded billions of times
• AsteroidOS, postmarketOS, and Sailfish OS, SHR and Tizen, and Ubuntu Touch are other Linux distributions on mobile devices

Explore the functions of operating systems and computer hardware. Includes details on RAM, software types, and the development and licensing of the Linux kernel. Also defines open-source software and its importance.