Computer Systems Basics

• Chapter 1 introduces Linux
• This chapter will cover: Purposes of Operating systems, features of the Linux operating system, origins of Linux, Linux distributions, Common uses of Linux in industry

Computer Fundamentals

• Computers contain hardware and software
• Hardware constitutes physical components inside a computer like the CPU, RAM, drives, cards, ports and mainboards
• Software comprises instructions that enable hardware to manipulate data
• Two types of software are application software, and operating systems
• Applications are designed to provide specific functionality that users interact with directly
• The operating system controls hardware components
• Device drivers enable the OS to interact with specific devices
• User interfaces allow users to input actions, send to the Operating system, which is returned for completion
• User interfaces can be command line prompts, or graphical user interfaces (GUI)
• A graphical user interface (GUI) enables user interaction via keyboard or mouse through menus, dialog boxes, and icons
• System services are components of an OS that handle tasks like printing, scheduling, and network access

The Linux OS

• Linux refers to an OS used for different hardware
• Linux is a multiuser, multitasking OS
• This means it can manage many tasks simultaneously
• Linux has the capacity for simultaneous user system access

Linux Versions

• The core component of Linux is the kernel
• Linux is written almost entirely in the C language
• Software is used to modify the appearance, while the kernel remains universal
• The Major number indicates major revision to Linux kernel
• The Minor number indicates revision and stability of Linux kernel, thoroughly tested and declared stable for "Production" kernel
• Revision number refers to the current change to the version
• Developmental kernel refers to code that has not been fully tested and may exhibit instability

Linux Licenses

• Open Source Software (OSS) is developed and improved by a large community freely
• Source code lists instructions for software development
• The format and structure of source code follows defined rules
• OSS development sees rapid software development through collaboration
• Bugs are quickly noted and fixed
• Software features evolve based directly on user need, increasing perceived value based on usefulness
• GNU Public License (GPL) was developed by the Free Software Foundation (FSF)
• This dictates source code of software under license must be available, and modifications redistributed freely
• An Artistic license ensure source code is freely available, but original authors have more control over changes
• Open source software can be obtained free for optional modification
• Closed source software typically is not free
• Freeware is closed source that is given free of charge
• Shareware is initially given out free, but payment is expected after some time

Linux Advantages

• OSS offers opportunities to maintain and change source code
• Common Software includes Scientific, Engineering software, software emulators, ecommerce suites, security software
• Bugs and Security loopholes are fixed faster because of the collaborative open source approach
• Linux can run on hardware platforms like Intel x86/x64, Itanium, PA-RISC, Mainframe, ARM, MIPS, SPARC, PowerPC etc
• Programming language support includes shell and PERL
• Support is available in Linux documentation websites, HOWTO documents, FAQs Internet newsgroups, Linux User Groups (LUGs)
• Often, there is no cost associated with acquiring software
• Cost savings comes from a wealth of OSS
• Cost of system admins may be less than the cost of software

History of Linux

• 1965- MULTICS Project started
• 1969 - Creation of UNIX
• 1973 - MIT changes file technology
• 1983 - Rapid UNIX development
• 1984 - Development of Hacker culture and GPL
• 1991 - Rapid Linux development
• 1998 - Approximately 7.5 million Linux users.
• 1999 - The Cathedral & the Bazaar
• 2018 - Worldwide adoption of Linux technology
• 2018 - Approximately 1.5 billion Linux users (including Android users)

UNIX

• UNIX evolved from Multiplexed Information and Computing Service (MULTICS) after the project was abandoned
• UNIX was Rewritten in the C language so that it could be run on different hardware platforms
• AT&T sold UNIX source code to several companies, each developed its own variety, or flavor, of UNIX yet adhered 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, Apple's macOS and iOS operating systems
• Hackers attempt to expand knowledge of computing through experimentation
• Crackers illegally use computers for personal benefit or to cause damage
• Richard Stallman: a hacker who worked at MIT, formed the Free Software Foundation (FSF), encouraged free software development
• GNU Project by Richard Stallman, promoted free OS development that was not UNIX>
• GNU Public License (GPL) legalized free distribution of source code and encouraged collaborative development
• The Hacker culture of collaborative development set the stage for Linux

Linux (cont.)

• Linus Torvalds first developed in 1991, Published under GNU License
• Linux kernel was collaboratively developed and centrally managed
• Hackers developed Linux add-on packages and distributions
• A distribution is a collection of software containing the Linux kernel and libraries
• Red Hat, OpenSUSE, Debian, Ubuntu, Gentoo, Linux Mint, and Arch are distributions
• Since 2000, there has been interest in embedded Linux, OS on smaller hardware like mobile devices
• Development can be expected from the OSS community in the next decade

Linux Distributions

• Distributions of Linux are the same, however are packaged differently
• Some distributions have server toolss such as web servers, and Databases
• most distributions include a core component of X Windows, the GUI, or a window manager and desktop
• Two GUI are GNU Object Model Environment (GNOME) and K Desktop Environment (KDE)
• Package managers are software systems for installing and maintaining software, like Red Hat Package Manager
• Tarball archives are compressed files containing software installation scripts

Linux Uses

• Linux may be customized to provide services for a variety of companies
• Workstation service are services used on a local computer, and server services are made available for other computers across a network
• Internet servers, File/Print, application, and scientific systems all commonly use linux

Servers

• Most Common Internet services include: web, DNS, DHCP, time, mail, FTP, authentication, certificate, routing, firewall/proxy, advanced security services
• Linux is well suited for centrally sharing resources, Inherently fast and light OS
• A distribution specific to a certain task can be installed on the central server to share resources with computers running other OS, using Samba Application server: intermediary between a client computer and a database with management functionality
• Database: organized collection of data that is arranged into tables of related information
• Database Management Systems (DBMSs): programs designed to allow for creation, modification, manipulation, maintenance, and access of information from databases
• Cloud is another word for internet, in which organizations are moving to data-centers and offer advantages of data access from multiple devices

Supercomputers

• Clustering: combining several computers act as one supercomputer using Beowulf clustering
• Message Passing Interface (MPI) passes information to separate computers
• Scalability: the ability of a computer to increase work load by adding more processors
• Computer clusters improve scalability

Workstations

• Scientific and engineering communities have customized programs, and many OSS programs are readily available
• Workstation software is designed for end users in office and home environments to create, organize, and manipulate documents and graphic art
• Several OSS packages Available: Graphics editing software, desktop publishing, media software, financial software, Office productivity suite, Bittorrent clients Cybersecurity Workstations
• Technologies and processes used to analyze existing security and provide data protections
• These include vulnerability assessments, penetration tests, and security monitoring Most tools for performing assessments, penetration, detecting and investigating security breaches are exclusively for Linux systems

Mobile Devices

• The Apple iPhone in 2007 gave rise to Linux-based smartphone and tablets.
• Google Android became notable in 2008
• By 2017, Android was installed on over 85 percent of smartphones worldwide.
• The Google Play Store hosted more than 3.5 million apps and over 85 billion downloads by 2017
• Distributions of Linux are AsteroidOS, postmarketOS, and Sailfish OS, SHR, Tizen, Ubuntu Touch

Summary

• Linux is an Open Source operating system (OSS) maintained, freely developed and used by a large community.
• Companies find Linux a stable, low-risk, and flexible alternative operating system
• Linux is available in different distributions, all having a common kernel, but packaged with different OSS applications
• A wide variety of documentation, communities, and resources are readily available
• Linux is an extremely versatile OS that provides a wide range of workstation and server services