Linux Essentials Study Guide

Linux Essentials (Study Notes) Introduction ● Welcome o Five Domains ▪ The Linux Community and a Career in Open Source ▪ Finding Your Way on a Linux System ▪ The Power of the Command Line ▪ The Linux Operating System ▪ Security and File Permissions ● About the Exam o Closed book o Up to 60 minutes o 40 multiple-choice items o Minimum score of 500 points to pass o No prerequisites o Lifetime certification 1 Linux Essentials (Study Notes) Evolution of Linux • An Introduction to Linux o Linux ▪ A family of open source Unix-like operating system, typically packaged into a distribution o Examples ▪ Ubuntu, Debian, Fedora o Command Line Interface (CLI) or the terminal o Why study Linux? ▪ Over 96% of web servers are run on Linux ▪ Low cost ▪ Open source ▪ Ease of scalability • Open Source Philosophy o Open Source ▪ Concept of making source codes available for public use or modification from its original design o Examples ▪ Apache, WordPress o Software License Types ▪ GNU General Public License ▪ Apache License ▪ Unlicense • Linux Distributions o Distribution or Distro ▪ Linux kernel ▪ Supporting software and libraries ▪ Configuration files o Kernel ▪ A low-level computer program which functions as the bridge between the user and the computer’s resources o Different distributions have different scripts and utilities to launch programs o Installation ▪ Image file on a CD ▪ USB flash drive ▪ Virtual server or cloud service 2 Linux Essentials (Study Notes) • Distribution Life Cycle o Release Schedule ▪ Distribution life cycle that specifies when are new versions released to the public o Pre-Release Versions ▪ Recommended to be used only for testing and debugging ▪ Categories • Alpha – very new and contains a lot of bugs • Beta – where most testing are done o Examples ▪ Disco Dingo (19.04), Cosmic Cuttlefish (18.10) o Support Versions ▪ Short-term ▪ Long-term o Rolling Release Schedule – ongoing updates • Embedded Systems o Embedded System ▪ A controller with a dedicated function within a larger mechanical or electrical system o Example Applications ▪ Industrial automation ▪ Navigation equipment ▪ Medical devices ▪ Wearable technology ▪ Home appliances o Examples ▪ Arduino ▪ Raspberry Pi ▪ Android • Highly-scalable • User-friendly • Open source • Free to use • Hardware Requirements o System requirements ▪ Prerequisites that are often used as a guide and not an absolute rule 3 Linux Essentials (Study Notes) o Hardware Compatibility List (HCL) ▪ Lists tested, compatible, and sometimes incompatible hardware devices for a particular distribution o Minimum Requirements ▪ The lowest possible hardware specification that your computer should have to boot successfully and use with basic functionality o Recommended Requirements ▪ Hardware that one should have in order to fully maximize a system’s potential • Operating System Differences o Windows ▪ 90% of home users ▪ Widely-available and widely-supported ▪ Most prone to malware ▪ Requires a license ▪ GUI-based o Mac OSX ▪ 7% of home users ▪ Free but only works on Apple systems ▪ GUI-based o Linux ▪ Less than 2% of home users ▪ More than 75% of enterprise server environments ▪ Known as the OS for computer experts and hackers ▪ Source code is available for modification ▪ Open source ▪ Can run from the command line only 4 Linux Essentials (Study Notes) Open Source Applications • What is Open Source? o Open-source Software ▪ Software released under a license in which the copyright holder grants users the rights to study, change, and distribute it to anyone and for any purpose o Advantages ▪ Security ▪ Affordability ▪ Transparency ▪ Interoperability ▪ Scalability ▪ Localization o Open-source Initiative ▪ Public benefit corporation that promotes the use of open-source software o Open Source Definition (OSD) ▪ A document which determines whether a software license can be labeled with the open-source certification mark • Cost of Open Source o Technical support, training, administration, and maintenance o Public Domain ▪ No ownership, copyright, trademark, or patent o Hacking Culture o Free License ▪ Private funding ▪ Crowdfunding ▪ Donations ▪ Commercialization • Package Installs and Repositories o Linux applications generally don’t run on every distribution o Linux users don’t normally download and install applications from the applications’ websites o Archives contain a list of files o Package Formats ▪ .deb 5 Linux Essentials (Study Notes) • ▪ ▪ .rtm • Gets its name from Debian; also used by Debian-based distros such as Ubuntu Originally stood for Red Hat Package Manager; used by Fedora and openSUSE .tar Considered a universal package format and is used by distros such as ArchLinux and Slackware • Can be .tar, .tgz, or .tar.gz o Personal Package Archives (PPAs) ▪ Contains software compiled by individual users and teams that have newer features that are not in the official distributions • 6 Linux Essentials (Study Notes) The Linux Environment • Linux Desktop Environment o Kernel ▪ Translates software commands into hardware-specific requests o Command Syntax ▪ Rules in which commands need to be run o Desktop Environment ▪ Graphical user interface (GUI) ▪ Linux desktop environments are modular o Examples ▪ Ubuntu – Unity, Kubuntu, Xubuntu • Linux Shell and Commands o Linux Shell ▪ Program that takes commands from the keyboard and gives them to the kernel to execute o Examples ▪ Bourne Again Shell (Bash) • Acts as the shell program within the command line interface ▪ ksh (Korn shell) ▪ tcsh (Tee See shell) ▪ zsh (Zee shell) o Terminal (terminal emulator) ▪ Provides access to a shell session ▪ Examples • gnome-terminal • konsole • xterm • rxvt • kvt • nxterm • eterm o Common commands ▪ List (ls) • Shows the files, folders, and directories within the system ▪ Change directory (cd) • Switches between directories ▪ Move (mv) • Moves a file from one folder directory to another 7 Linux Essentials (Study Notes) ▪ ▪ ▪ ▪ ▪ ▪ ▪ • Manual (man) • Shows all information about a command being used Make directory (mkdir) • Makes a new empty folder or directory inside the filesystem Remove directory (rmdir) • Removes an empty, existing folder or directory Touch (touch) • Makes a file using the command line Remove (rm) • Removes files and directories Locate (locate) • Finds a file within the system Clear (clear) • Clears the screen or terminal environment Managing Software Packages o Package ▪ A compressed file archive containing all of the files that come with a particular application ▪ Package prerequisites = dependencies o Common types of packages ▪ .deb • Debian, Debian-derived distros • Package managers: DPKG, APT-GET, and APT ▪ .rpm • Red Hat, Fedora, openSUSE • Package managers: RPM, YUM, and DNF ▪ .tgz • the “universal” Linux format 8 Linux Essentials (Study Notes) The Command Line • Basic Shell o Users are allowed to install various GUI terminal programs o Root User ▪ Administrator account in Linux • Command Line Syntax o Computer operation steps ▪ Computer waits for user input ▪ User selects a command and enters it using a keyboard or a mouse ▪ Computer executes the command o In Linux, the shell displays a prompt o Command ▪ A sequence of characters in a line which ends by pressing the enter key and is subsequently evaluated by the shell o Syntax - rules o The first word is usually the command name, while the other words are the parameters ▪ Types of parameters • Options (switches) – start with a dash and allow certain commands to be switched on or off • Argument – no leading dashes; often the names of fi les that the command should process o General command structure ▪ Command (What to do?) > Options (How to do it?) > Arguments (What to do with it?) • Variables o Shell Script ▪ A file containing a series of commands o Variables ▪ Areas of memory that can be used to store information and are referred to by a name ▪ Act as a placeholder o Naming rules ▪ Variable names must start with a letter ▪ A name must not contain embedded spaces (Underscores are used instead) ▪ Punctuation marks are not allowed 9 Linux Essentials (Study Notes) o Print Environment (printenv) ▪ Displays all the environmental variables (variables in ALL CAPS) • Quoting o Shell meta-characters ▪ Treated in a special way in the command line o Examples of meta-characters ▪ Blank or space character ( “ “ ) • Tells a shell to use separate arguments between commands • Any number of blanks or spaces are treated as one ▪ Dollar sign ( $ ) ▪ Star ( * ) ▪ Semi-colon ( ; ) ▪ Rreater-than symbol ( > ) ▪ Question mark ( ? ) ▪ Ampersand ( & ) ▪ Pipe ( | ) o Quoting ▪ The act of protecting shell meta-characters from being treated specially by the shell ▪ Prevents the shell from acting on and expanding the meta-characters ▪ Done in double quotes ( “ “ ), single quotes ( ‘ ‘ ), or backslash ( \ ) ▪ Backlashes can be used to quote or turn off a special character’s ability • Man and Info Pages o Manual (Man) Pages ▪ A set of pages explaining every command available on the system ▪ man ▪ man -k ▪ / o Commands ▪ Long hand • More human-readable • Lets users remember what the command is doing • Example: --all ▪ Short hand • Quicker to type out • Allows for multiple options to be chained together and is quicker to type out • Example: -a 10