Useful command reference's

Question 1

man <tool></tool>

Answer 1

Opens man pages for the specified tool.

Question 2

<tool> -h
</tool>

Answer 2

Prints the help page of the tool.

Question 3

apropos <keyword></keyword>

Answer 3

Searches through man pages’ descriptions for instances of a given keyword.

Question 4

cat

Answer 4

Concatenate and print files.

Question 5

whoami

Answer 5

Displays current username.

Question 6

id

Answer 6

Returns users identity.

Question 7

hostname

Answer 7

Sets or prints the name of the current host system.

Question 8

uname

Answer 8

Prints operating system name.

Question 9

pwd

Answer 9

Returns working directory name.

Question 10

ifconfig

Answer 10

The ifconfig utility is used to assign or view an address to a network interface and/or configure network interface parameters.

Question 11

ip

Answer 11

Ip is a utility to show or manipulate routing, network devices, interfaces, and tunnels.

Question 12

netstat

Answer 12

Shows network status.

Question 13

ss

Answer 13

Another utility to investigate sockets.

Question 14

ps

Answer 14

Shows process status.

Question 15

who

Answer 15

Displays who is logged in.

Question 16

env

Answer 16

Prints environment or sets and executes a command.

Question 17

lsblk

Answer 17

Lists block devices.

Question 18

lsusb

Answer 18

Lists USB devices.

Question 19

lsof

Answer 19

Lists opened files.

Question 20

lspci

Answer 20

Lists PCI devices.

Question 21

sudo

Answer 21

Execute command as a different user.

Question 22

su

Answer 22

The su utility requests appropriate user credentials via PAM and switches to that user ID (the default user is the superuser). A shell is then executed.

Question 23

useradd

Answer 23

Creates a new user or update default new user information.

Question 24

userdel

Answer 24

Deletes a user account and related files.

Question 25

usermod

Answer 25

Modifies a user account.

Question 26

addgroup

Answer 26

Adds a group to the system.

Question 27

delgroup

Answer 27

Removes a group from the system.

Question 28

passwd

Answer 28

Changes user password.

Question 29

dpkg

Answer 29

Install, remove and configure Debian-based packages.

Question 30

apt

Answer 30

High-level package management command-line utility.

Question 31

aptitude

Answer 31

Alternative to apt.

Question 32

snap

Answer 32

Install, remove and configure snap packages.

Question 33

gem

Answer 33

Standard package manager for Ruby.

Question 34

pip

Answer 34

Standard package manager for Python.

Question 35

git

Answer 35

Revision control system command-line utility.

Question 36

systemctl

Answer 36

Command-line based service and systemd control manager.

Question 37

ps

Answer 37

Prints a snapshot of the current processes.

Question 38

journalctl

Answer 38

Query the systemd journal.

Question 39

kill

Answer 39

Sends a signal to a process.

Question 40

bg

Answer 40

Puts a process into background.

Question 41

jobs

Answer 41

Lists all processes that are running in the background.

Question 42

fg

Answer 42

Puts a process into the foreground.

Question 43

curl

Answer 43

Command-line utility to transfer data from or to a server.

Question 44

wget

Answer 44

An alternative to curl that downloads files from FTP or HTTP(s) server.

Question 45

python3 -m http.server

Answer 45

Starts a Python3 web server on TCP port 8000.

Question 46

ls

Answer 46

Lists directory contents.

Question 47

cd

Answer 47

Changes the directory.

Question 48

clear

Answer 48

Clears the terminal.

Question 49

touch

Answer 49

Creates an empty file.

Question 50

mkdir

Answer 50

Creates a directory.

Question 51

tree

Answer 51

Lists the contents of a directory recursively.

Question 52

mv

Answer 52

Move or rename files or directories.

Question 53

cp

Answer 53

Copy files or directories.

Question 54

nano

Answer 54

Terminal based text editor.

Question 55

which

Answer 55

Returns the path to a file or link.

Question 56

find

Answer 56

Searches for files in a directory hierarchy.

Question 57

updatedb

Answer 57

Updates the locale database for existing contents on the system.

Question 58

locate

Answer 58

Uses the locale database to find contents on the system.

Question 59

more

Answer 59

Pager that is used to read STDOUT or files.

Question 60

less

Answer 60

An alternative to more with more features.

Question 61

head

Answer 61

Prints the first ten lines of STDOUT or a file.

Question 62

tail

Answer 62

Prints the last ten lines of STDOUT or a file.

Question 63

sort

Answer 63

Sorts the contents of STDOUT or a file.

Question 64

grep

Answer 64

Searches for specific results that contain given patterns.

Question 65

cut

Answer 65

Removes sections from each line of files.

Question 66

tr

Answer 66

Replaces certain characters.

Question 67

column

Answer 67

Command-line based utility that formats its input into multiple columns.

Question 68

awk

Answer 68

Pattern scanning and processing language.

Question 69

sed

Answer 69

A stream editor for filtering and transforming text.

Question 70

wc

Answer 70

Prints newline, word, and byte counts for a given input.

Question 71

chmod

Answer 71

Changes permission of a file or directory.

Question 72

chown

Answer 72

Changes the owner and group of a file or directory.