====== [hemmerling] LPI Essentials ( LPI Linux Essentials, LPI Security Essentials, LPI Web Development Essentials, LPI Open Source Essentials ) ====== Related pages: *[[booting.html|Booting from Devices]]. *[[android.html|Google Android]]. *[[linux.html|Linux 1/8]]. *[[linux02.html|Linux 2/8 - Linux Distributions]]. *[[linux03.html|Linux 3/8 - Linux Boot Loaders, Linux Build Systems, Linux Installers and Linux Implementors]]. *[[linux04.html|Linux 4/8 - Linux Applications, Linux Tools and Linux Drivers]]. *[[linux05.html|Linux 5/8 - SUSE 7.1 Linux on Clevo 2700c Notebooks with SIS630S Chipset]]. *[[linux07.html|Linux 6/8 - Linux with X-Terminals and Terminals]]. *[[linux06.html|Linux 7/8 - Linux on X86, X64 and ARM Computers]]. *[[linux08.html|Linux 8/8 - Useful Linux Commands & Linux Tricks]]. *[[lpicone.html|Linux LPIC-1]]. *[[lpictwo.html|Linux LPIC-2]]. *[[linuxskills.html|Linux Skills & Skill Certification]]. ===== The Linux Professional Institute Inc. "Linux Essentials" ===== ==== Course & Objectives ==== *[[http://www.lpi.org/our-certifications/linux-essentials-overview/|The Linux Professional Institute Inc. "Linux Professional Institute Linux Essentials"]]. *[[http://www.lpi.org/our-certifications/exam-010-objectives/|The Linux Professional Institute Inc. "Linux Essentials Exam 010 Objectives"]]. ==== Literature ==== *[[http://learning.lpi.org/en/learning-materials/010-160/|The Linux Professional Institute Inc. "Linux Essentials"]] - Free PDF book. *[[http://www.amazon.de/exec/obidos/ASIN/078975455X/hemmerling-21|Christine Bresnahan, Richard Blum "LPI Linux Essentials Study Guide: Exam 010 v1.6"]], 2020. *[[http://www.amazon.de/exec/obidos/ASIN/B0F44Z9BCV/hemmerling-21|Anand Vemila "Study Guide for the 010-160: Linux Essentials Certificate Exam, version 1.6 by LPI (Linux Professional Institute)"]], 2025. ==== Topic 1: The Linux Community and a Career in Open Source ==== === 1.1 Linux Evolution and Popular Operating Systems === == Range of distributions of Amazon Cloud Services and Google Cloud == *Q: What range of distributions does Amazon Cloud Services and Google Cloud offer? Name at least three common ones and two different ones. *A:The common distributions between Amazon and Google Cloud Services are Ubuntu, CentOS and Red Hat Enterprise Linux. Each cloud provider also offers specific distributions that the other one doesn’t. Amazon has Amazon Linux and Kali Linux, while Google offers the use of FreeBSD and Windows Servers. *Popular: *[[http://www.debian.org/|Debian]]. *[[http://aws.amazon.com/marketplace/seller-profile?id=4d4d4e5f-c474-49f2-8b18-94de9d43e2c0|AWS Marketplace "Debian"]]. *[[http://console.cloud.google.com/marketplace/browse?q=debian|Google Cloud - Search for "debian"]], [[http://console.cloud.google.com/marketplace/product/google/debian12|Google Cloud "Debian 12 'Bookworm'"]]. *[[http://www.ubuntu.com/|Ubuntu]]. *[[http://aws.amazon.com/marketplace/seller-profile?id=565feec9-3d43-413e-9760-c651546613f2|AWS Marketplace "Canonical Group Limited"]], [[http://www.canonical.com/|Canonical Group Limited]] - "Ubuntu". *[[http://console.cloud.google.com/marketplace/browse?q=ubuntu|Google Cloud - Search for "ubuntu"]], [[http://console.cloud.google.com/marketplace/product/google/ubuntu2404|Google Cloud "Ubuntu 24.04"]]. *[[http://www.centos.org/|The CentOS Project]]. *[[http://aws.amazon.com/marketplace/seller-profile?id=e6a5002c-6dd0-4d1e-8196-0a1d1857229b|AWS Marketplace "Amazon Web Services"]] - "CentOS Stream". *[[http://aws.amazon.com/marketplace/seller-profile?id=79e4b2cd-a4a8-47b7-a0f2-db8b7a69f8fb|AWS Marketplace "Supported Images"]], [[http://www.supportedimages.com/|Supported Images]] - "CentOS", "Ubuntu"... *[[http://console.cloud.google.com/marketplace/browse?q=centos|Google Cloud - Search for "centos"]], [[http://console.cloud.google.com/marketplace/product/centos-cloud/centos-stream-9|Google Cloud "CentOS Stream 9"]]. *[[http://www.redhat.com/|Red Hat]]. *[[http://aws.amazon.com/marketplace/seller-profile?id=8bb46e3b-6208-4ac2-bdbd-339bb37b0e64|AWS Marketplace "Red Hat"]]. *[[http://console.cloud.google.com/marketplace/browse?q=redhat|Google Cloud - Search for "redhat"]], [[http://console.cloud.google.com/marketplace/product/redhat-marketplace/redhat-proserv|Google Cloud "Red Hat Professional Services"]]. *Also available: *"Microsoft Windows Server". *[[http://aws.amazon.com/marketplace/seller-profile?id=e6a5002c-6dd0-4d1e-8196-0a1d1857229b|AWS Marketplace "Amazon Web Services"]] - "Microsoft Windows Server". *[[http://console.cloud.google.com/marketplace/browse?q=windows|Google Cloud - Search for "windows"]], [[http://console.cloud.google.com/marketplace/product/cloud-infrastructure-services/windows-server-2022-datacenter|Google Cloud "Windows Server 2022 Datacenter"]]. *[[http://www.freebsd.org/|The FreeBSD Project]]. *[[http://aws.amazon.com/marketplace/seller-profile?id=92bb514d-02bc-49fd-9727-c474863f63da|AWS Marketplace "FreeBSD"]]. *[[http://console.cloud.google.com/marketplace/browse?filter=partner:FreeBSD|Google Cloud "FreeBSD"]]. *[[http://www.kali.org/|Kali Linux]]. *[[http://aws.amazon.com/marketplace/pp/prodview-fznsw3f7mq7to|AWS Marketplace "Kali Linux"]]. *[[http://console.cloud.google.com/search?q=kali|Google Cloud - Search for "kali"]], [[http://console.cloud.google.com/marketplace/product/cloud-infrastructure-services/kali-linux|Google Cloud "Kali Linux with XFCE4 Desktop GUI"]]. *AWS only: *"Amazon Linux" ( [[http://aws.amazon.com/de/linux/amazon-linux-2023/|Amazon AWS "Amazon Linux 2023"]], [[http://aws.amazon.com/amazon-linux-2/|Amazon AWS "Amazon Linux 2"]], [[http://aws.amazon.com/marketplace/seller-profile?id=e6a5002c-6dd0-4d1e-8196-0a1d1857229b|AWS Marketplace "Amazon Web Services"]] ). == The most popular Linux Applications == *[[http://www.linuxquestions.org/questions/2021-linuxquestions-org-members-choice-awards-133/|LinuxQuestions.org]]. *[[http://www.linuxquestions.org/questions/2018-linuxquestions-org-members-choice-awards-128/|LinuxQuestions.org "2018 LinuxQuestions.org Members Choice Awards"]] ( mentioned in "Linux Essentials Version 1.6" ), [[http://www.linuxquestions.org/questions/2021-linuxquestions-org-members-choice-awards-133/|LinuxQuestions.org "2021 LinuxQuestions.org Members Choice Awards"]] ( the latested award ). === 1.2 Major Open Source Applications === == Commands == *.deb: apt-cache search figlet sudo apt-get install figlet figlet Awesome! sudo apt-get remove figlet apt-get purge figlet *.rpm: yum search speaking cow sudo yum install cowsay cowsay "Brought to you by yum" sudo yum remove cowsay == Developer Resources == *[[http://developer.mozilla.org/|Mozilla Developers]]. == Desktop Applications == *Blender. *GIMP. *[[http://www.audacityteam.org/|Audacity]]. *[[http://en.wikipedia.org/wiki/Audacity_(audio_editor)|EN.Wikipedia "Audacity (audio editor)"]], [[http://de.wikipedia.org/wiki/Audacity|DE.Wikipedia "Audacity"]]. *[[http://www.imagemagick.org/|ImageMagick]]. *[[http://en.wikipedia.org/wiki/ImageMagick|EN.Wikipedia "ImageMagick"]], [[http://de.wikipedia.org/wiki/ImageMagick|DE.Wikipedia "ImageMagick"]]. *[[http://www.inkscape.org/|Inkscape]]. *[[http://en.wikipedia.org/wiki/Inkscape|EN.Wikipedia "Inkscape"]], [[http://de.wikipedia.org/wiki/Inkscape|DE.Wikipedia "Inkscape"]]. *Video players: *VLC. *[[http://www.smplayer.info/en/|SMPlayer]]. *[[http://en.wikipedia.org/wiki/SMPlayer|EN.Wikipedia "SMPlayer"]]. *Audio players: *Audacious, Banshee, Amarok. == Network File Systems, Domain Controllers & Authentication Subsystems == *[[http://en.wikipedia.org/wiki/Network_File_System|EN.Wikipedia "Network File System"]], [[http://de.wikipedia.org/wiki/Network_File_System|DE.Wikipedia "Network File System"]]. *[[http://en.wikipedia.org/wiki/Samba_(software)|EN.Wikipedia "Samba (software)"]], [[http://de.wikipedia.org/wiki/Samba_(Software)|DE.Wikipedia "Samba (Software)"]]. *[[http://en.wikipedia.org/wiki/System_Security_Services_Daemon|EN.Wikipedia "System Security Services Daemon"]] ( SSSD ) - Authentication subsystem. == Server Applications == *[[http://en.wikipedia.org/wiki/Apache_HTTP_Server|EN.Wikipedia "Apache HTTP Server"]], [[http://de.wikipedia.org/wiki/Apache_HTTP_Server|DE.Wikipedia "Apache HTTP Server"]]. *[[http://en.wikipedia.org/wiki/Nginx|EN.Wikipedia "Nginx"]], [[http://de.wikipedia.org/wiki/Lighttpd|DE.Wikipedia "nginx"]]. *[[http://en.wikipedia.org/wiki/Lighttpd|EN.Wikipedia "lighttpd"]], [[http://de.wikipedia.org/wiki/Lighttpd|DE.Wikipedia "Lighttpd"]]. == Data Sharing == *[[http://www.nextcloud.com/|Nextcloud]]. *[[http://en.wikipedia.org/wiki/Nextcloud|EN.Wikipedia "Nextcloud"]], [[http://de.wikipedia.org/wiki/Nextcloud|DE.Wikipedia "Nextcloud"]]. *[[http://www.owncloud.com/|ownCloud]]. *[[http://en.wikipedia.org/wiki/OwnCloud|EN.Wikipedia "ownCloud"]], [[http://de.wikipedia.org/wiki/OwnCloud|DE.Wikipedia "ownCloud"]]. == Guided Exercises == apt-get install blender apt-get purge cups === 1.3 Open Source Software and Licensing === *Copyleft licenses. *Permissive licenses. === 1.4 ICT Skills and Working in Linux === == Resources == *[[http://www.allaboutdnt.com/|allaboutdnt.com]], [[http://fpf.org/thank-you-for-visiting-allaboutdnt-com/|Future of Privacy Forum "allaboutdnt.com"]]. *[[http://wiki.mozilla.org/Security/Server_Side_TLS|Mozilla Wiki "Security/Server Side TLS"]]. *[[http://en.wikipedia.org/wiki/Transport_Layer_Security|EN.Wikipedia "Transport_Layer_Security"]], [[http://de.wikipedia.org/wiki/Transport_Layer_Security|DE.Wikipedia "Transport_Layer_Security"]] ( TLS ). *[[http://www.gnupg.org/|The GNU Privacy Guard ( GnuPG )]]. *[[http://wiki.archlinux.org/title/GnuPG|Archlinux Wiki "GnuPG"]]. *[[http://en.wikipedia.org/GNU_Privacy_Guard|EN.Wikipedia "GNU Privacy Guard"]], [[http://de.wikipedia.org/wiki/GNU_Privacy_Guard|DE.Wikipedia "GNU Privacy Guard"]]. == Explorational Exercises == *[[http://addons.mozilla.org/en-GB/firefox/addon/lightbeam-chikl/|Mozilla Firefox Addons "Lightbeam"]]. *[[http://www.haveibeenpwned.com/|Have I Been Pwned: Check if your email address has been exposed in a data breach]]. ==== Topic 2: Finding Your Way on a Linux System ==== === 2.1 Command Line Basics === == 2.1.1 Command Line Basics, Lession #1 == $ ls -al $ ls -a -l $ ls --all --format=long $ type echo echo is a shell builtin $ type man man is /usr/bin/man $ TWOWORDS="two words" $ touch $TWOWORDS $ ls -l -rw-r--r-- 1 carol carol 0 Mar 10 14:56 two -rw-r--r-- 1 carol carol 0 Mar 10 14:56 words $ touch "$TWOWORDS" $ ls -l -rw-r--r-- 1 carol carol 0 Mar 10 14:56 two -rw-r--r-- 1 carol carol 0 Mar 10 14:58 'two words' -rw-r--r-- 1 carol carol 0 Mar 10 14:56 words $ touch '$TWOWORDS' $ ls -l -rw-r--r-- 1 carol carol 0 Mar 10 15:00 '$TWOWORDS' -rw-r--r-- 1 carol carol 0 Mar 10 14:56 two -rw-r--r-- 1 carol carol 0 Mar 10 14:58 'two words' -rw-r--r-- 1 carol carol 0 Mar 10 14:56 words $ echo I am $USER I am tom $ echo "I am $USER" I am tom $ touch new file $ ls -l -rw-rw-r-- 1 tom students 0 Oct 8 15:18 file -rw-rw-r-- 1 tom students 0 Oct 8 15:18 new $ touch "new file" $ ls -l -rw-rw-r-- 1 tom students 0 Oct 8 15:19 new file $ echo I am $USER I am tom $ echo 'I am $USER' I am $USER $ echo $USER carol $ echo \$USER $USER == 2.1.1 Command Line Basics, Explorational Exercises #1 == $ touch game{1..5} $ ls game1 game2 game3 game4 game5 $ rm game? == 2.1.2 Command Line Basics, Lession #2 == $ greeting=hello $ echo greeting greeting $ echo $greeting hello # in another shell: $ echo $greeting $ echo $greeting world hello world $ bash -c 'echo $greeting world' world $ echo $greeting hey $ unset greeting $ echo $greeting $ greeting=hello $ export greeting $ export greeting=hey $ echo $greeting world hey world $ bash -c 'echo $greeting world' hey world $ TZ=EST date Thu 31 Jan 10:07:35 EST 2019 $ TZ=GMT date Thu 31 Jan 15:07:35 GMT 2019 $ echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin $ PATH=$PATH:/home/user/bin $ echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/home/user/bin *Example: Adding "/opt/bin" to the path: $ mybin=/opt/bin $ PATH=$PATH:$mybin $ echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/home/user/bin:/opt/bin *Example: Deleting "/usr/sbin" directory ( where editor "nano" is stored ) from the path $ echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin $ which nano /usr/bin/nano $ PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/sbin:/bin:/usr/games $ echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/sbin:/bin:/usr/games $ which nano which: no nano in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/sbin:/bin:/usr/games) $ PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin $ which nano /usr/bin/nano == Guided Exercises == $ number=5 export ORDER=desc $ echo number number $ echo ORDER ORDER $ echo $number 5 $ echo $ORDER desc == Explorational Exercises == $ nr_files=`wc -l /etc/passwd` $ export ME=$USER $ ME=$ME:$HOME $ echo $ME user:/home/user $ today=$(TZ=GMT date) $ echo $today Thu 31 Jan 15:07:35 GMT 2019 $ today=$(TZ=EST date) $ echo $today Thu 31 Jan 10:07:35 EST 2019 $ today1=$(date) $ echo $today1 Thu 31 Jan 10:07:35 EST 2019 === 2.2 Using the Command Line to Get Help === *[[http://www.man7.org/linux/man-pages/man7/man-pages.7.html|Michael Kerrisk "man-pages(7) — Linux manual page"]]. $ man mkdir $ info mkdir === 2.3.1 Using Directories and Listing Files, Lession #1 === === 2.3.2 Using Directories and Listing Files, Lession #2 === === 2.4 Creating, Moving and Deleting Files === ==== Topic 3: The Power of the Command Line ==== === 3.1 Archiving Files on the Command Line === === 3.2.1 Searching and Extracting Data from Files, Lession #1 === === 3.2.2 Searching and Extracting Data from Files, Lession #2 === === 3.3.1 Turning Commands into a Script, Lession #1 === === 3.3.2 Turning Commands into a Script, Lession #2 === ==== Topic 4: The Linux Operating System ==== === 4.1 Choosing an Operating System === === 4.2 Understanding Computer Hardware === === 4.3.1 Where Data is Stored, Lession #1 === === 4.3.2 Where Data is Stored, Lession #2 === === 4.4 Your Computer on the Network === ==== Topic 5: Security and File Permissions ==== === 5.1 Basic Security and Identifying User Types === === 5.2 Creating Users and Groups === === 5.3 Managing File Permissions and Ownership === === 5.4 Special Directories and Files === ===== The Linux Professional Institute Inc. "Security Essentials" ===== ==== Course & Objectives ==== *[[http://www.lpi.org/our-certifications/security-essentials-overview/|The Linux Professional Institute Inc. "Linux Professional Institute Security Essentials"]]. *[[http://www.lpi.org/our-certifications/exam-030-objectives/|The Linux Professional Institute Inc. "Security Essentials Exam 020 Objectives"]]. ==== Literature ==== *[[http://learning.lpi.org/en/learning-materials/020-100/|The Linux Professional Institute Inc. "Security Essentials"]] - Free PDF book :-). Not yet available in German language :-(. *[[http://www.amazon.de/exec/obidos/ASIN/1394196539/hemmerling-21|David Clinton "LPI Security Essentials Study Guide: Exam 020-100 (Sybex Study Guide) 1st Edition"]], 2023. ==== Topic 021: Security Concepts ==== === 021.1 Goals, Roles and Actors === === 021.2 Risk Assessment and Management === === 021.3 Ethical Behavior=== ==== Topic 022: Encryption ==== === 022.1.1 Cryptography and Public Key Infrastructure, Lession #1 === === 022.1.2 Cryptography and Public Key Infrastructure, Lession #2 === === 022.2 Web Encryption === === 022.3 Email Encryption === === 022.4 Data Storage Encryption === ==== Topic 023: Device and Storage Security ==== === 023.1 Hardware Security === === 023.2 Application Security === === 023.3 Malware === === 023.4 Data Availability === ==== Topic 024: Network and Service Security ==== === 024.1.1 Networks, Network Services and the Internet, Lession #1 === === 024.1.2 Networks, Network Services and the Internet, Lession #2 === === 024.2 Network and Internet Security === === 024.3.1 Network Encryption and Anonymity, Lession #1 === === 024.3.2 Network Encryption and Anonymity, Lession #2 === ==== Topic 025: Identity and Privacy ==== === 025.1 Identity and Authentication === === 025.2 Information Confidentiality and Secure Communication === === 025.3 Privacy Protection === ===== The Linux Professional Institute Inc. "Web Development Essentials" ===== ==== Course & Objectives ==== *[[http://www.lpi.org/our-certifications/web-development-essentials-overview/|The Linux Professional Institute Inc. "Web Development Essentials"]]. *[[http://www.lpi.org/our-certifications/exam-030-objectives/|The Linux Professional Institute Inc. "Web Development Essentials Exam 030 Objectives"]]. ==== Literature ==== *[[http://learning.lpi.org/en/learning-materials/030-100/|The Linux Professional Institute Inc. "Web Development Essentials"]] - Free PDF book. *[[http://www.amazon.de/exec/obidos/ASIN/1739002318/hemmerling-21|David Clinton "The Complete LPI Web Development Essentials Exam Study Guide: Learn the basics of HTML, CSS, JavaScript, Express.js, and Node.js and launch your career in full stack web development"]], 2023. *[[http://www.amazon.de/exec/obidos/ASIN/B0D3RLBXH7/hemmerling-21|Marco Colombo "FULL STACK WEB DEVELOPMENT FOR THE LPI WEB DEVELOPMENT ESSENTIALS CERTIFICATION: The Simplified Study Guide for Beginners to Learn HTML, CSS, ... Complete and Functional Web Applications"]], 2024. *[[http://www.amazon.de/exec/obidos/ASIN/B0BGNF1MFD/hemmerling-21|Marco Colombo "Web Development Essentials Practice Exams: A Collection of Questions and Answers to Pass the 030-100 Exam (LPI Web Development Essentials Certification)"]], 2022. ==== Topic 031: Software Development and Web Technologies ==== === 031.1 Software Development Basic === === 031.2 Web Application Architecture === === 031.3 HTTP Basics === ==== Topic 032: HTML Document Markup ==== === 032.1 HTML Document Anatomy === === 032.2 HTML Semantics and Document Hierarchy === === 032.3 HTML References and Embedded Resources === === 032.4 HTML Forms === ==== Topic 033: CSS Content Styling ==== === 033.1 CSS Basics === === 033.2 CSS Selectors and Style Application === === 033.3 CSS Styling === === 033.4 CSS Box Model and Layout === ==== Topic 034: JavaScript Programming ==== === 034.1 JavaScript Execution and Syntax === === 034.2 JavaScript Data Structures === === 034.3.1 JavaScript Control Structures and Functions, Lession #1 === === 034.3.2 JavaScript Control Structures and Functions, Lession #2 === === 034.4 JavaScript Manipulation of Website Content and Styling === ==== Topic 035: NodeJS Server Programming ==== === 035.1 NodeJS Basics=== === 035.2.1 NodeJS Express Basics, Lession #1 === === 035.2.2 NodeJS Express Basics, Lession #2 === === 035.3 SQL Basics === ===== The Linux Professional Institute Inc. "LPI Open Source Essentials" ===== ==== Course & Objectives ==== *[[http://www.lpi.org/our-certifications/open-source-essentials/|The Linux Professional Institute Inc. "Linux Professional Institute Open Source Essentials"]]. *[[http://www.lpi.org/our-certifications/exam-050-objectives/|The Linux Professional Institute Inc. "Open Source Essentials Exam 050 Objectives"]]. ==== Literature ==== *[[http://learning.lpi.org/en/learning-materials/050-100/|The Linux Professional Institute Inc. "Open Source Essentials"]] - Free PDF book. *[[http://www.amazon.de/exec/obidos/ASIN/B0CK3Q8DCF/hemmerling-21|David Clinton "The Complete LPI Open Source Essentials Exam Study Guide"]], 2023. ==== Topic 051: Software Fundamentals ==== === 051.1 Software Components === === 051.2 Software Architecture === === 051.3 On-Premises and Cloud Computing === ==== Topic 052: Open Source Software Licenses ==== === 052.1 Concepts of Open Source Software Licenses === === 052.2 Copyleft Software Licenses === === 052.3 Permissive Software Licenses === ==== Topic 053: Open Content Licenses ==== === 053.1 Concepts of Open Content Licenses === === 053.2 Creative Commons Licenses === === 053.3 Other Open Content Licenses === ==== Topic 054: Open Source Business Models ==== === 054.1 Software Development Business Models === === 054.2 Service Provider Business Models === === 054.3 Compliance and Risk Mitigation === ==== Topic 055: Project Management ==== === 055.1 Software Development Models === === 055.2 Product Management / Release Management === === 055.3 Community Management === ==== Topic 056: Collaboration and Communication ==== === 056.1 Development Tools === === 056.2 Source Code Management === === 056.3 Communication and Collaboration Tools === ===== Literature ===== *[[http://learning.lpi.org/en/learning-materials/all-materials/|The Linux Professional Institute Inc. "All Resources"]]. *[[http://learning.lpi.org/en/learning-materials/learning-materials/|The Linux Professional Institute Inc. "LPI Learning Materials"]] - Free PDFs. {{tag>Linux}}