Identify Features of Linux

Question 1

Answer 1

Ubuntu 20 running the GNOME desktop with a virtual terminal window open to run commands
in the Bash command environment.

Question 2

Answer 2

Viewing the root directory and file system hierarchy standard (FHS) subdirectories in Ubuntu Linux.

Question 3

Answer 3

Listing package manager sources in Ubuntu Linux.

Question 4

Answer 4

Listing all processes on the system. Note that a question mark indicates that a process has no controlling terminal.

Question 5

Answer 5

Listing the state of running processes.

Question 6

kernal

Answer 6

the core of the operating system, acting as the bridge between hardware and software applications.

Question 7

distribution (distro)

Answer 7

a complete, packaged operating system built upon the Linux kernel.

Question 8

shell

Answer 8

a command-line interpreter that acts as an interface between the user and the operating system’s kernel.

Question 9

bash

Answer 9

is a powerful command-line interpreter and scripting language.

Question 10

shell

Answer 10

Linux provides various shell environments, such as Bash, zsh, and ksh, enabling users to interact with the OS and applications. These shells differ in functionality, including tab completion, command history, and syntax highlighting.

Question 11

distros

Answer 11

Many Linux distros operate without a graphical interface, relying on a terminal connected to the shell via a teletype (tty) device. Input and output are managed through three primary streams:
- stdin (0): User keyboard input
- stdout (1): Displays shell-generated output
- stderr (2): Handles error messages

Question 12

For systems with a graphical desktop environment, Linux uses Xorg as the display system.

Answer 12

Popular desktop environments include Gnome, KDE, Cinnamon, and Xfce. Within these, a terminal emulator allows users to access the command shell.

Question 13

Console switching lets users toggle between multiple tty consoles using:

Answer 13

CTRL+ALT+Fx, where each console can support distinct login prompts and shells.

Question 14

Linux commands

Answer 14

consist of a command name, optional switches for modifying behavior, and arguments that specify data; execution can be streamlined using pipes (|) for redirection or semicolons (;) to run multiple commands sequentially.

Question 15

executable

Answer 15

is a file that the operating system can directly run to execute a program or script.

Question 16

PATH

Answer 16

is an environment variable that lists the directories where the shell searches for executable files when a command is entered.

Question 17

switches or options

Answer 17

They are used to customize a command’s actions, for example, enabling or disabling features, or providing additional instructions.

Question 18

Arguments

Answer 18

are values supplied to the command for it to operate on, such as file names. Arguments must be supplied in the correct order for the command’s
syntax.

Question 19

semicolon

Answer 19

You can issue more than one command on a single line by placing a semicolon ( ; ) between the commands.

Question 20

Command –help

Answer 20

The help is often several pages long so it common to pipe the output to the** more **command. more shows the results a page at a time. For example: ls
–help | more
Alternatively, you can use **man **to view the help pages for a particular command.

Question 21

Linux file editors like Nano

Answer 21

provide a simple interface with keyboard shortcuts, while vi/vim offer advanced functionality using insert and command modes, requiring specific keystrokes for editing (i for insert, :w to save, :q! to quit without saving). esc key to escape mode.

Question 22

Linux organizes everything as files within a unified file system:

Answer 22

starting at /, distinguishing devices like /dev/sda for storage, avoiding Windows-style drive letters, and following the File System Hierarchy Standard (FHS) for directories like /home for user data and /etc for configurations, navigation using commands like pwd, cd, ls, and cat.

Question 23

Navigation Commands

pwd command

Answer 23

The **pwd** command displays the current working directory, because any commands you use which don’t specify a path as an argument will
default to the working directory; some Linux prompts show this location directly or represent the home directory with a tilde (~).

Question 24

Navigation Commands

cd command

Answer 24

changes the current working directory, allowing navigation between directories using absolute paths (e.g., cd /etc from root), relative paths (e.g., cd documents within the current directory), or moving up one level (cd ..).

Question 25

# Navigation Commands The **`ls`** command

Answer 25

lists directory contents, similar to `dir` in Windows, with options like `-l` for a detailed view and `-a` for showing hidden files, as seen in `ls -la /etc`, which provides a full, formatted listing of the `/etc` directory.

Question 26

# Navigation Commands The `cat` command

Answer 26

displays file contents, with options like `-n` to add line numbers; output can be **paged** (`cat | more` or `cat | less`), **overwritten** (`cat > file`), or **appended** (`cat >> file`), and redirection operators apply to other commands as well.

Question 27

# Navigation Commands cat command

Answer 27

is a versatile utility used for displaying, creating, and manipulating text files.

Question 28

# Search Commands The `find` command

Answer 28

searches for files using a **path** and **expression**, with options like `-name` (file name), `-size` (file size), `-user` (owner), and `-perm` (permissions); unlike Windows, where file types are defined by extensions, Linux's `-type` distinguishes files, directories, block devices, sockets, symbolic links, and pipes.

Question 29

# Search Commands The `grep` command

Answer 29

searches and filters file contents, matching either **literal text** or **regular expressions (regex)**; useful for scanning large files like system logs (`grep -i "uid=1003" /var/log/messages`), it can also filter directory listings (`ls -l | grep audit`).

Question 30

# search command Metacharacters and Escaping

Answer 30

in Linux have special meanings and require **escaping** to be treated as literals, using `\` for single-character escaping (`\*` for `*`), **single quotes (`'`)** for strong escaping (preserving everything as literal), and **double quotes (`"`)** for weak escaping, which allows variable expansion and command substitution.

Question 31

File Management Commands

Answer 31

File management commands are used to move, copy, and delete data.

Question 32

# File Management Commands The `cp` command **cp file1.txt file1.old**

Answer 32

Copy file1.txt in the current working directory to a new file called file1. old in the same directory

Question 33

# File Management Commands cp command cp /etc/hosts /tmp

Answer 33

Copy the file hosts from the directory /etc into the directory /tmp, keeping the file name the same

Question 34

# File Management Commands cp command cp -v /var/log/message* /home/david

Answer 34

Copy all files beginning with the name message from the /var/log directory into /home/david. The -v option displays the files copied

Question 35

# File Management Commands The `mv` command

Answer 35

moves files between directories or renames them, such as keeping the same name when relocating (`mv /home/david/data.txt /tmp`), renaming while moving (`mv alarm.dat /tmp/alarm.bak`), or renaming within the same directory (`mv /var/log/app1.dat /var/log/app1.old`).

Question 36

# File Management Commands The `rm` command

Answer 36

deletes files and directories, with simple file removal (`rm data.old`), wildcard-based deletion (`rm /var/log/*.bak`), and recursive directory removal (`rm -r /home/david/data`).

Question 37

# File Management Commands The `df` command (“disk free”)

Answer 37

shows available disk space, including file system details and usage percentages, while the `du` (“disk usage”) command reports storage consumption, displaying sizes of directories and files.

Question 38

# User Account Management The **root user**

Answer 38

in Linux has full administrative privileges and should only be used when necessary; instead, regular user accounts are created for daily tasks, with privilege elevation managed through special commands rather than remaining logged in as root.

Question 39

# User account management The `su` command (switch user)

Answer 39

switches to another user account, prompting for the target user's password; omitting the username switches to **root**, while `su -` launches a new shell under **root's** full environment, making it the preferred method.

Question 40

# User Account Management The `sudo` command (superuser do)

Answer 40

grants temporary superuser privileges to users listed in the `/etc/sudoers` file, allowing them to execute specific commands with administrative rights, often requiring password confirmation if not recently cached.

Question 41

# User Account Management user management commands

Answer 41

User settings are stored in `/etc/passwd`, group settings in `/etc/group`, and encrypted password hashes in `/etc/shadow`; user accounts can be managed with `useradd` (add), `usermod` (modify), and `userdel` (delete), while passwords can be updated using the `passwd` command.

Question 42

# User Account Management Group Management Commands

Answer 42

Users in Linux are assigned to groups for managing file permissions, with **groupadd**, **groupmod**, and **groupdel** handling group membership, while **newgrp** allows users to switch their **effective group ID**, as listed in `/etc/passwd`.

Question 43

File Permissions Commands

Answer 43

control access using three rights: **read (`r`)** for viewing, **write (`w`)** for modifying or deleting, and **execute (`x`)** for running files or accessing directories; permissions are assigned to the **owner, group, and others**, represented in **symbolic notation** (`rwx`, `r-x`, `r--`) or **numeric notation** (`7` for full rights, `5` for read/execute, `4` for read-only).

Question 44

# File permssion values File permissions commands use **octal values (0–7)**

Answer 44

to represent access levels: **read (4)**, **write (2)**, and **execute (1)**. Adding these defines specific permissions—for instance, `0754` translates to **owner (`7 = rwx`), group (`5 = r-x`), and others (`4 = r--`)**. A common alternative is `6`, granting **read and write** access.

Question 45

Linux file permissions use symbolic notation

Answer 45

(r, w, x, or -) to define access levels for the owner, group, and others. For example: - drwxr-xr-x indicates a directory (d), where the owner has full access (rwx), the group and others have read/execute (r-x).

Question 46

# file permissions The `chmod` command

Answer 46

modifies file and directory permissions using **symbolic notation** (`rwx`, `r-x`, etc.) or **octal values** (`755`, `644`, etc.), ensuring security control; only the **owner** can alter permissions.

Question 47

# file permssions The `chown` command

Answer 47

lets the **superuser** change a file or directory's **owner**, but regular users **cannot** modify ownership, even for their own files; however, they **can** change the file's **group** using the `chgrp` command.

Question 48

Package Management Commands

Answer 48

Linux software can be installed as **source code** (requiring compilation) or **pre-compiled packages** managed by **package managers**, which vary by distribution: - **APT (Advanced Packaging Tool)**: Used in **Debian-based** systems, handles `.deb` packages. - **YUM (Yellowdog Updater, Modified)**: Used in **Red Hat-based** systems, manages `.rpm` packages. These tools simplify software installation and updates across different Linux distributions.

Question 49

Distributions and Repositories

Answer 49

Linux **distributions** package precompiled software, hosted in **repositories** containing supported, beta, and experimental versions. **Package managers** configure repository URLs for installing, updating, or removing software. Security is ensured through **cryptographic hashes** (MD5, SHA-256) or **GNU Privacy Guard (GPG) signing**, verifying package integrity before installation.

Question 50

# package management tool The `apt-get` command

Answer 50

for **APT** in Debian-based systems, used for updating and installing software: - `apt-get update` refreshes the local package database. - `apt-get upgrade` installs updates for all packages. - `apt-get install PackageName` installs a specified application. This streamlines software maintenance in Linux environments.

Question 51

# package management tooll The `yum` command

Answer 51

for **YUM** in Red Hat-based systems, used for installing and updating software: - `yum check-update` refreshes the local package database. - `yum update` upgrades all installed packages to the latest versions. - `yum install PackageName` installs a specified application. This simplifies software maintenance across Red Hat distributions.

Question 52

anti-virus

Answer 52

Linux is **resistant to widespread malware** but still faces **targeted attacks and repository vulnerabilities**, making tools like **ClamAV** and **Snort IPS** essential for securing web servers and preventing malware transmission to Windows systems.

Question 53

# Process Monitoring Commands The `ps` command

Answer 53

retrieves the **process table**, showing currently running processes. Without options, it lists processes from the **current shell**, including **PID**, associated terminal, CPU time, and initiating command. Additional options refine the display to filter specific fields or processes.

Question 54

Process Monitoring Commands

Answer 54

Each Linux process has a unique **process ID (PID)**, a **non-negative integer** that increments for every new process; **PID 1** is assigned to the `init` daemon, the first process that starts and the **parent of all others**, while subsequent processes receive increasing PID values.

Question 55

# Process Monitoring Commands The `top` command

Answer 55

dynamically monitors **running processes** in real-time, allowing **sorting, prioritization, and termination**. Common keystrokes include: - **ENTER**: Refresh process statuses. - **SHIFT+N**: Sort by descending **PID**. - **M**: Sort by **memory usage**. - **P**: Sort by **CPU usage**. - **u**: Filter by **specific user**. - **q**: Exit process monitoring. This makes `top` an essential tool for system performance management.

Question 56

Network Management Commands

Answer 56

interfaces using names like `eth0`, `eth1`, etc., though modern distributions may use **`en` prefixes**. **Running configurations** apply in real-time, while **persistent configurations** remain after reboot. Traditional setups modified `/etc/network/interfaces` and used `ifup`/`ifdown` scripts, but many distributions now rely on **NetworkManager** (`nmcli` tools) or **systemd-networkd** for streamlined network configuration management.

Question 57

# Network Management Commands The `ip` command

Answer 57

part of **iproute2**, replaces legacy **net-tools** commands like `ifconfig`, providing modern network management for **interfaces, addresses, and routes**; changes made with `ip addr` and `ip link` affect the **running configuration** but aren't persistent unless included in a **startup script**.

Question 58

# Network Management Commands The `dig` command

Answer 58

Is a powerful **DNS lookup tool**, commonly available on Linux distributions, used to **test name resolution** and gather domain-related information. Its output includes: - The **IP address** mapped to a domain. - The **DNS server** that responded. - The **query response time**. Basic usage: - `dig domainname` queries the default DNS. - `dig @server domainname` resolves the domain using a **specific DNS server**. This command is essential for troubleshooting domain resolution issues.

Question 59

# Network Management Commands **Samba

Answer 59

is an **SMB-compatible file sharing protocol** for Linux, allowing seamless **integration** with Windows systems. A Linux workstation with Samba can **access shared Windows resources**, while a Linux server running Samba can **share directories to Windows clients** using the **SMB protocol**. **

Question 60

Backup and Scheduling Commands

Answer 60

Linux lacks an **official backup tool**, but users can create custom solutions using **cron** for scheduling and **tar/gzip** for compression. Open-source tools like **Amanda, Bacula, Fwbackups, and Rsync** provide structured backup options. The **cron task scheduler** allows users to manage **automated jobs** via **crontab**, where commands like `crontab -l`, `crontab -r`, and `crontab -e` help list, remove, and edit scheduled tasks. Jobs are scheduled using a **time-based syntax** (minute, hour, day, month, weekday, command), with wildcard options (`*`, `,`, `-`, `/2`) enabling flexible scheduling. A typical crontab entry might run an **Rsync backup** at a specific time (e.g., `15 02 * * 5` for **Friday at 2:15 a.m.**).

Question 61

For example, consider the following crontab entry: **§ 15 02 * * 5 /usr/bin/rsync –av --delete /home/ sam/mount/rsync**

Answer 61

This would cause the system to run the rsync backup program at 2:15 a.m. on a Friday (day 5), synchronizing the** /home/sam** directory with the **/mount/sync** folder (which could be a mount point to an external backup device).