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Questions and Answers
What was a significant contribution of the students and faculty at Berkeley University to UNIX?
What was a significant contribution of the students and faculty at Berkeley University to UNIX?
Which company created the AIX version of UNIX?
Which company created the AIX version of UNIX?
What is the official name given to the combination of the Linux kernel with GNU tools?
What is the official name given to the combination of the Linux kernel with GNU tools?
Who initiated the GNU project aimed at creating a free UNIX-like operating system?
Who initiated the GNU project aimed at creating a free UNIX-like operating system?
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In what year did Linus Torvalds release the Linux kernel?
In what year did Linus Torvalds release the Linux kernel?
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What command is used to change the IP address of the Ethernet 0 interface to execute with root privileges?
What command is used to change the IP address of the Ethernet 0 interface to execute with root privileges?
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Which command would you use to halt a Linux system if you have root privileges?
Which command would you use to halt a Linux system if you have root privileges?
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What must precede commands for a normal user to execute shutdown or reboot?
What must precede commands for a normal user to execute shutdown or reboot?
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Which of the following commands is associated with restarting the system using systemd?
Which of the following commands is associated with restarting the system using systemd?
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What does 'sudo' stand for in Linux commands?
What does 'sudo' stand for in Linux commands?
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What is the main source of revenue for Canonical?
What is the main source of revenue for Canonical?
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Which Linux distribution is specifically known for its security tools?
Which Linux distribution is specifically known for its security tools?
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What differentiates Freeware from Free and Open Source Software (FOSS)?
What differentiates Freeware from Free and Open Source Software (FOSS)?
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What is implied by Public Domain Software?
What is implied by Public Domain Software?
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Which statement accurately describes the concept of FOSS?
Which statement accurately describes the concept of FOSS?
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What is the primary role of the kernel in an operating system?
What is the primary role of the kernel in an operating system?
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Which of the following statements about system libraries is true?
Which of the following statements about system libraries is true?
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What distinguishes a shell from a graphical user interface?
What distinguishes a shell from a graphical user interface?
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Which of the following shells is the most popular in Linux environments?
Which of the following shells is the most popular in Linux environments?
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How do most administrative tasks in Linux environments typically get performed?
How do most administrative tasks in Linux environments typically get performed?
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What is the default administrative account on a Linux system?
What is the default administrative account on a Linux system?
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Why do most Ubuntu distributions prevent the root account from being used for logging in?
Why do most Ubuntu distributions prevent the root account from being used for logging in?
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Which of the following statements about command line tools in Linux is accurate?
Which of the following statements about command line tools in Linux is accurate?
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What aspect of the Linux kernel code execution is essential for its functionality?
What aspect of the Linux kernel code execution is essential for its functionality?
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What is a key feature of a permissive free software license?
What is a key feature of a permissive free software license?
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What is NOT one of the criteria for the distribution terms of open-source software?
What is NOT one of the criteria for the distribution terms of open-source software?
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Which freedom is specifically related to accessing and modifying the source code?
Which freedom is specifically related to accessing and modifying the source code?
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What does CopyLeft allow users to do?
What does CopyLeft allow users to do?
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How does the GPL license differ from shareware licenses?
How does the GPL license differ from shareware licenses?
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Which condition is NOT mentioned as part of the essential freedoms of open-source software?
Which condition is NOT mentioned as part of the essential freedoms of open-source software?
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What is a requirement for derived works under open-source software?
What is a requirement for derived works under open-source software?
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Which condition must an open-source license meet to be considered technology neutral?
Which condition must an open-source license meet to be considered technology neutral?
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What is the primary philosophy behind open-source software?
What is the primary philosophy behind open-source software?
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Study Notes
Introduction to Linux
- UNIX was developed in 1969 at AT&T Bell Labs by Dennis Ritchie and Ken Thompson.
- UNIX was written in the C programming language and placed in the public domain.
- Berkley University developed tools, services and revisions to UNIX in 1975.
- In 1975, AT&T sold a commercial version of UNIX.
- An open source version of UNIX was named BSD UNIX, developed by Berkley Science Department.
- Many companies created their own versions of UNIX, including IBM with AIX, Sun Microsystems with Solstice, Hewlett Packard with HP-UX and Santa Clara Organization with SCO UNIX.
- Each version of UNIX had varying commands and syntax.
GNU Project and Linux Kernel
- The GNU project was started by Richard Stallman, aiming to standardize a UNIX-like operating system that was not proprietary and was freely available.
- “GNU is a recursive acronym for "GNU's Not Unix!", chosen because GNU's design is Unix-like, but differs from Unix by being free software and containing no UNIX code. The GNU project includes an operating system kernel”.
- The GNU kernel was named HURD but Linux kernel was released before HURD was completed.
- GNU/LINUX became the official name for the combination of the Linux kernel with GNU tools.
Linux Distributions
- In 1991, Linus Torvalds wrote a POSIX compliant kernel for an x386 computer.
- POSIX is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems.
- Ubuntu is a popular Linux distribution named after "Ubuntu" which is a Southern African philosophy meaning "human-ness".
- SuSE was one of the first server distributions.
- Kali Linux includes security tools not found in other distributions.
- Linux Mint is based on Ubuntu/Debian and includes many multimedia tools.
Software Licensing
- Proprietary Software is owned by a specific vendor, users must purchase a license to use the software, for example Microsoft Windows operating system and Office suite of tools.
- Free and Open Source Software (FOSS) is free to use but under conditions set by the author or vendor, the author retains copyright and ownership.
- Public Domain Software is software where the author has given up all rights, allowing users to freely copy, distribute, and modify it.
Open Source Software Criteria
- Open source software must adhere to the following criteria, according to the Open Source Definition by the Open Source Initiative:
- Free Redistribution (no royalty or fee)
- Source Code (must be provided)
- Derived Works (allow modifications to be distributed)
- Integrity of the Author’s source code
- No Discrimination Against Person or Group
- No Discrimination Against Fields of Endeavour
- License Must not be Specific to a Product
- License Must not be Restrictive to Other Software
- License Must be Technology Neutral
Free Software Philosophy
- The philosophy of free software emphasizes freedom over cost.
- The four essential freedoms:
- The freedom to run the program as you wish, for any purpose.
- The freedom to study how the program works, and change it so it does your computing as you wish.
- The freedom to redistribute copies so you can help your neighbor.
- The freedom to distribute copies of your modified versions to others.
CopyLeft
- CopyLeft allows others to use software but under certain restrictions.
- If someone uses the software and makes any alterations or enhancements, they must make the changes available to others.
- They cannot make these changes proprietary.
GPL
- The GNU General Public License (GPL) is a copyleft license that allows others to use, modify, and distribute software as long as they adhere to the terms of the GPL license, including the need to make all modifications available to others.
Permissive Free Software Licenses
- Permissive licenses have minimal restrictions and prioritize freedom of use and modification.
- Examples include the BSD license and the MIT license.
Linux Architecture
- Linux is composed of three main bodies of code:
- User programs
- Shared libraries
- Linux kernel
Kernel
- The kernel is responsible for maintaining the important abstractions of the operating system.
- Abstractions provide a common interface (API) that programs use to interact with computer hardware, without having to know the exact code required by each piece of hardware.
- Kernel code executes in kernel mode with full access to all physical resources.
- All kernel code and data structures are kept in the same address space.
Libraries & Utilities
- System libraries define a standard set of functions applications use to interact with the kernel, implementing much of the OS functionality that doesn't need kernel privileges.
- System utilities perform individual specialized management tasks.
- User-mode programs include shells like bash (Bourne Again Shell).
Shells
- A shell is a command interpreter program (CLI).
- From a Graphical User Interface (GUI), opening a terminal window gives access to a shell.
- TTY refers to a terminal window.
Shell Types
- Linux offers various shells with different command syntax and built-in functions:
- bash - Bourne Again Shell
- sh - Bourne shell
- csh – C shell
- ksh – Korn Shell
- Tsh – compatible to Berkley UNIX shell
Command Line Interfaces
- Most Linux server installations do not have GUIs.
- Many Linux tools, especially administrative tools, are command line tools.
- Many GUI-based tools are less flexible than their command line equivalents.
- Remote admin access to Linux systems is almost always done using CLI:
- Telnet
- ssh
Root Account
- The administrative account on Linux is named root.
- For security, the root account on most Ubuntu distros does not have a password and cannot be used for logging onto a system.
- The system administrator has an unprivileged account that is used for initial login.
- The administrator's unprivileged account is made a member of a group that has permission to run the sudo command to temporarily gain administrative privileges.
SUDO Command
- SUDO stands for "Super User Do" and allows users to execute commands with root privileges.
- The ifconfig command, used to change the IP address on an interface, requires root privileges.
- To change the IP address of the Ethernet 0 interface, use the command:
sudo ifconfig eth0
. - A list of commands and associated users is maintained in the sudoers file.
System Shutdown & Restart
- A Linux system can only be shut down by root:
-
shutdown –h now
( -h for halt) -
systemctl poweroff
(systemd new in 2013) -
init 0
(older versions systemV, replaced by systemd)
-
- A Linux system can be restarted by the root user:
-
shutdown –r now
( -r for reload ) -
systemctl reboot
(systemd new in 2013) -
init 6
(older versions, replaced by systemd)
-
- If logged in with a normal user account, the above commands would need to be preceded with
sudo
.
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Description
Explore the origins of UNIX and the progression to Linux in this quiz. Learn about the key developments from AT&T Bell Labs to the GNU Project initiated by Richard Stallman. Understand the various versions of UNIX and their impact on modern operating systems.