Linux Essentials Study Notes Flashcards

A comprehensive set of practice flashcards covering Linux Essentials exam topics, including commands, filesystem hierarchy, scripting, and networking.

What are the five domains covered in the Linux Essentials exam?

1. The Linux Community and a Career in Open Source, 2. Finding Your Way on a Linux System, 3. The Power of the Command Line, 4. The Linux Operating System, 5. Security and File Permissions

What is the minimum score required to pass the Linux Essentials exam?

$500$ points

Approximately what percentage of web servers run on Linux?

Over $96\%$

What is the 'Kernel' in a Linux distribution?

A low-level computer program which functions as the bridge between the user and the computer’s resources

In the software development life cycle, what are the characteristics of the 'Alpha' version?

It is very new and contains a lot of bugs

What is the purpose of the Hardware Compatibility List (HCL)?

It lists tested, compatible, and sometimes incompatible hardware devices for a particular distribution

What are the three main types of software licenses mentioned for open source?

GNU General Public License, Apache License, and MIT License

Which package format is used by Debian-based distributions like Ubuntu?

.deb

What is a Linux Shell?

A program that takes commands from the keyboard and gives them to the kernel to execute

What does the command 'ls -a' do?

Displays all the files in the directory, including hidden files

What is the function of the 'man' command?

Shows all information about a command being used (Manual Pages)

What characterizes a 'Rolling Release' schedule?

Ongoing updates rather than specific version releases

What is the 'Root User' in Linux?

The administrator account with access to all parts of the system

What is the general structure of a Linux command?

Command (What to do?) > Options (How to do it?) > Arguments (What to do with it?)

What is the naming rule for variables in Linux?

Variables must start with a letter and must not contain embedded spaces; punctuation marks are not allowed

Which command is used to display all environmental variables?

printenv

What is 'Quoting' in the context of the Linux shell?

The act of protecting shell meta-characters from being treated specially or expanded by the shell

What does the 'Filesystem Hierarchy Standard (FHS)' distinguish between?

Shareable and unshareable files, and static and variable files

What character is used to represent the 'Root' of the filesystem?

A single forward slash ($/$)

How do you hide a file in Linux?

By adding a dot ($.$) at the beginning of the filename

In a relative file path, what does '..' refer to?

The parent directory

What is a 'Hard Link' in Linux?

A duplicate directory entry where both entries point to the same file

What wildcard character stands for exactly one single character?

The question mark ($?$)

What does the command line pipe symbol ($|$) do?

It takes the standard output from one program and uses it as input for a second program

What is the function of the 'grep' command?

Searches for keywords in the output or within files

What is the difference between the '>' and '>>' redirector operations?

'>' creates a new file containing standard output, while '>>' appends the output to an existing file

Which text editor is described as very small and usually installed by default but difficult to use?

vi

In a shell script, how are arguments (parameters) represented?

By a dollar sign ($) followed by a number, such as$0, $1, or$2

What is the 'Init Process'?

The process responsible for starting up all basic programs Linux needs to run; it is the parent of other processes

What command is used to see how much memory is being used by the system?

free

Where are most log files stored in Linux?

/var/log

What is the purpose of the 'dmesg' command?

To display the kernel ring buffer messages, which are useful for diagnosing hardware and driver problems

In networking, what does DNS stand for?

Domain Name System

Which command is used to configure a network adapter's IP address and netmask?

ifconfig

What configuration file contains the IP addresses of DNS servers?

/etc/resolv.conf

Which file defines most account features like Username, UID, and GID?

/etc/passwd

What is a 'Salted Hash'?

A non-readable password produced by a one-way mathematical process with additional random input

What is the difference between 'su' and 'sudo'?

'su' switches the user (often to root), while 'sudo' only works for one command at a time with administrative privileges

What command is used to change a file's owner?

chown

What does the numeric permission code '777' represent?

Read, write, and execute permissions for all users

What is the 'Sticky Bit'?

A special filesystem flag that limits a user to only deleting their own files within a directory

What does the octal code '4' signify when setting special execute permissions?

It sets the Set User ID (SUID) bit

What is a Linux Distribution?

A version of the Linux operating system packaged with additional software and usually a package management system.

What is the purpose of a Package Manager?

To automate the process of installing, upgrading, configuring, and removing software packages.

What does the acronym 'GNU' stand for?

GNU's Not Unix, a Unix-like operating system that is free software.

What is a Virtual Machine?

A software simulation of hardware that allows running multiple operating systems on one physical machine.

What is an open source software?

Software with source code that anyone can inspect, modify, and enhance.

What does CLI stand for?

Command Line Interface, a means of interacting with the computer using text commands.

What is the command to change the permissions of a file?

chmod.

What does the command 'pwd' do?

Prints the current working directory.

What is the purpose of the 'echo' command?

To display a line of text or a variable value in the command line.

What is the role of a 'Daemon'?

A background process that runs continuously to handle requests for services.

What file manages user authentication?

/etc/shadow.

What is a symbolic link?

A type of file that is a reference to another file or directory.

What does 'sudo' allow a user to do?

Execute commands with the privileges of another user, typically the superuser or root.

What is the use of 'top' command?

Displays the tasks currently being managed by the Linux kernel.

What are environment variables?

Dynamic values that can affect the way running processes will behave on a computer.

What does the 'kill' command do?

Terminates processes based on their process ID.

What is a 'Shell Script'?

A file containing a series of commands that the shell can execute.

What is the significance of the '/etc/fstab' file?

It contains information about filesystems and their mount points.

What command is used to view running processes?

ps.

What does the command 'man' do?

Displays the manual for a command.

What is the purpose of the 'chmod' command?

To change the file/directory permissions.

What does 'ifconfig' command do?

Displays or configures network interfaces.

What command is used to display disk usage?

df.

What does the 'ping' command do?

Checks connectivity to another network host.

What is the primary purpose of the shell?

To interpret and execute user commands.

What are 'cron jobs'?

Scheduled tasks that run at specified intervals.

What is the purpose of the '/var' directory?

Contains variable data files like logs.

What does the command 'htop' do?

An interactive process viewer.

What is the function of the 'shutdown' command?

To halt, power off, or reboot the system as specified.

What does 'df -h' command do?

Displays disk usage in a human-readable format.

What is a 'pipe' in Linux?

A mechanism to send the output of one command as input to another command.

What command is used to count lines, words, and characters in a file?

wc (word count).

What is a 'repository' in the context of Linux software?

A storage location for software packages that can be retrieved and installed.

What does the 'echo $HOME' command display?

The path to the current user's home directory.

What is the purpose of the 'tar' command?

To create, view, and extract tar archives (compressed files).

What command can be used to search for a specific package in a repository?

apt search or yum search, depending on the package manager used.

What does the 'chmod 755' command set?

Sets the permissions to read, write, and execute for the owner, and read and execute for group and others.

What is the purpose of the 'rsync' command?

To synchronize files and directories between two locations over a network or locally.