Linux Commands

Question 1

ls

Answer 1

List the contents of a directory.

Question 2

cd

Answer 2

Change the current working directory.

Question 3

pwd

Answer 3

Print the current working directory.

Question 4

mkdir

Answer 4

Create a new directory.

Question 5

rmdir

Answer 5

Remove an empty directory.

Question 6

rm

Answer 6

Remove files or directories.

Question 7

cp

Answer 7

Copy files or directories.

Question 8

mv

Answer 8

Move or rename files or directories.

Question 9

touch

Answer 9

Create an empty file or update the access and modification times of an existing file.

Question 10

cat

Answer 10

Concatenate and display files.

Question 11

less

Answer 11

View the contents of a file one screen at a time.

Question 12

grep

Answer 12

search for a string in groups of files. When it finds a pattern that matches in more than one file, it prints the name of the file, followed by a colon, then the line matching the pattern.

Question 13

find

Answer 13

Search for files in a directory hierarchy based on criteria such as name, size, or modification time.

Question 14

chmod

Answer 14

Change the file permissions.

Question 15

whoami

Answer 15

Display the username of the current user.

Question 16

echo

Answer 16

Output text or variables to the terminal or a file.

Question 17

man / -h

Answer 17

Display the manual page for a specified command or keyword.

Question 18

su

Answer 18

Switch to another user account or temporarily elevate privileges.

Question 19

ps

Answer 19

Display information about running processes. single snapshot and does not continuously run.

Question 20

systemctl

Answer 20

manages both system and service configurations, enabling administrators to manage the OS and control the status of services

Question 21

sha256sum

Answer 21

Calculate and verify SHA256 checksums for files.

Question 22

&

Answer 22

Run a command in the background, allowing other tasks to be performed simultaneously.

Question 23

&&

Answer 23

Execute the next command only if the previous command has succeeded (returned a zero exit status).

Question 24

>

Answer 24

Redirect standard output from a command to a file, overwriting the file’s existing contents.

Question 25

>>

Answer 25

Redirect standard output from a command to a file, appending to the file's existing contents.

Question 26

top

Answer 26

Display information about running processes. continuous until stopped.

Question 27

kill

Answer 27

Terminate a process by sending a signal.

Question 28

tar

Answer 28

Create, extract, or list the contents of a tar archive.

Question 29

gzip

Answer 29

Compress or decompress files using the gzip format.

Question 30

ssh

Answer 30

Secure Shell client for remote logins and command execution.

Question 31

scp

Answer 31

Securely copy files between hosts using SSH.

Question 32

wget

Answer 32

Download files from the web.

Question 33

diff

Answer 33

Compare files line by line and display differences.

Question 34

curl

Answer 34

Transfer data from or to a server using various protocols, often used for API interactions.

Question 35

history

Answer 35

Display the command-line history.

Question 36

alias

Answer 36

Create a shorthand or alias for a longer command.

Question 37

yum

Answer 37

Package management system for Red Hat-based systems.

Question 38

apt

Answer 38

Package management system for Debian and Ubuntu-based systems.

Question 39

groupdel

Answer 39

Delete a group.

Question 40

groupadd

Answer 40

Create a new group.

Question 41

useradd

Answer 41

Create a new user account.

Question 42

crontab

Answer 42

Schedule tasks to run at specific times, manage the cron table for a user.

Question 43

traceroute

Answer 43

Display the route and transit delays of packets across an IP network.

Question 44

ping

Answer 44

Send network packets to test the reachability of a host on an IP network.

Question 45

ifconfig

Answer 45

Display and configure network interfaces.

Question 46

uname

Answer 46

Display system information, such as the operating system name, kernel version, and hardware platform.

Question 47

userdel

Answer 47

Delete a user account and related files.

Question 48

apropos

Answer 48

Search the manual page names and descriptions for a specified keyword, helping to find relevant commands or manual pages based on a particular topic or functionality. Equivalent to using man -k.

Question 49

tree

Answer 49

displays the directory structure of a given path in a tree-like format. It shows the nested arrangement of directories and files, making it easier to visualize the hierarchy of the filesystem.

Question 50

which

Answer 50

locates the executable file associated with a given command. It searches through the directories listed in the PATH environment variable and returns the path of the first match it finds.

Question 51

locate

Answer 51

searchs for files and directories by name. It uses a database created by the 'updatedb' command to perform a fast search. It is case-insensitive by default but can be made case-sensitive using the '-i' option.

Question 52

wc

Answer 52

counts the number of lines, words, and bytes in a file. It can also count characters if the '-m' option is used.

Question 53

What is tar used for in linux?

Answer 53

tar is used for archiving files (combining all files into one)

Question 54

What is gzip used for in linux?

Answer 54

gzip is used for compressing file (making the file size smaller)

Question 55

dpkg

Answer 55

used to manage Debian packages (.deb files) on Debian and Debian-based Linux distributions.

Question 56

pico

Answer 56

text editor that provides less features and less complexity

Question 57

usermod

Answer 57

used to modify the user's account

Question 58

passwd

Answer 58

used to change or reset the password of the user's account

Question 59

groupmod

Answer 59

used to modify a group

Question 60

dnf

Answer 60

updated version of yum command and used to install and remove software on Red Hat

Question 61

rpm

Answer 61

low-level too that is used to install and remove software on Red Hat

Question 62

ip

Answer 62

used for configuring network interfaces. updated version of 'ifconfig'

Question 63

dig

Answer 63

used to query the DNS to get information about the different DNS records

Question 64

what does the '$' do?

Answer 64

used to reference the value of a variable.

Question 65

chsh

Answer 65

change the shell you are using. -s to change default and put the path to the shell after.

Question 66

*

Answer 66

wildcard. b* for example, will show all files starting with letter 'b'

Question 67

?

Answer 67

wildcard for a single letter

Question 68

df

Answer 68

used to display the amount of available and used disk space. Also displays the file system type and its mount point.

Question 69

du

Answer 69

used to estimate the disk pace usage of a file or directory. It shows the size of the file or directory, as well as the size of its subdirectories, if any.

Question 70

What are the 3 file descriptors?

Answer 70

Data Stream for Input STDIN – 0 Data Stream for Output STDOUT – 1 Data Stream for Output that relates to an error occurring. STDERR – 2

Question 71

What does < do?

Answer 71

uses file or stream as input for a command instead of typing

Question 72

What does EOF function do?

Answer 72

ends user input

Question 73

What does '<<' do?

Answer 73

is used to pass multiple lines of input to a command. It allows you to define a block of input text within a script or command line, and that block will be passed as input to the command.

Question 74

How to redirect errors?

Answer 74

'command' '2> /dev/null'

Question 75

What does | do?

Answer 75

redirects STDOUT from one command to be processed by another