pwd

Displays the current working directory.

cd

Changes the current working directory.

cd ..

Moves to the parent directory.

ls

Lists files and directories in the current location.

ls -la

Lists all files and directories, including hidden ones, in detailed format.

man <command>

Displays the manual page for a command.

<command> --help

Displays available options for a command.

mkdir

Creates a new directory.

touch

Creates a new empty file.

cp

Copies a file or directory without modifying the original.

cp -r

Copies a directory and its contents recursively.

mv

Moves or renames a file or directory.

rm

Deletes a file.

rm -r

Deletes a directory and its contents recursively.

rmdir

Removes an empty directory.

cat

Displays the contents of a file.

nano

Opens a file in a simple terminal-based text editor.

echo "text" > file

Creates a file containing the given text.

echo $PATH

Displays the system's executable search paths.

less

Views file contents one page at a time; press q to quit.

head

Displays the first lines of a file.

tail

Displays the last lines of a file.

tail -f

Continuously displays new lines appended to a file — commonly used to monitor logs in real time.

passwd

Changes the password of the current user.

sudo su

Switches to the root user; use exit to return to the normal user.

lsattr

Displays the attributes of a file, such as the immutable flag (i).

chattr -i

Removes the immutable attribute from a file, making it editable again.

useradd -m -s /bin/bash <username>

Creates a new user with a home directory and bash shell.

usermod -aG sudo <username>

Adds a user to the sudo group.

userdel -r <username>

Deletes a user along with their home directory.

groupadd <groupname>

Creates a new group.

groups <username>

Displays the groups a user belongs to.

id <username>

Displays UID, GID, and group membership of a user.

whoami

Displays the current logged-in username.

apt update

Refreshes the local list of available packages and their versions.

apt install

Installs a specified package.

apt upgrade

Upgrades all installed packages to their latest available versions.

apt search

Searches available repositories for a package.

ifconfig

Displays network interface configuration, including IP address. Still functional on most systems, but no longer actively maintained — ip addr is the modern, recommended alternative.

ip addr

Displays and manages network interface addresses; the modern replacement for ifconfig.

netstat / ss

Displays active network connections and listening ports.

ps aux

Displays currently running processes.

top

Shows a live view of system processes.

htop

Displays an enhanced, interactive process monitor.

kill <PID>

Terminates a process by its process ID.

pstree

Displays running processes in a tree structure.

uname -a

Displays kernel and system information.

lsb_release -a

Displays OS/distribution information.

uptime

Shows how long the system has been running.

free -m

Displays RAM usage in megabytes.

cal

Displays a calendar.

fdisk -l

Lists disks and partitions.

df -h

Displays disk space usage per partition in a human-readable format.

du -h

Displays the disk space used by a file or directory in a human-readable format.

clear

Clears the terminal screen.

Ctrl + L

Clears the terminal (same as clear).

!!

Re-runs the last executed command.

Ctrl + Z

Sends the current process to the background.

history

Displays a list of previously executed commands.

sudo thunar

Opens the Thunar file manager with root privileges.

git clone

Downloads a copy of a remote Git repository to the local machine.

chmod

Changes the read, write, and execute permissions of a file or directory.

chown

Changes the owner of a file or directory.

chgrp

Changes the group ownership of a file or directory.

find

Searches for files and directories matching given criteria.

grep

Searches for text patterns within files.

which <command>

Displays the full path of an installed command.

whereis <command>

Locates the binary, source, and manual page files for a command.

wc

Counts lines, words, and characters in a file.

diff

Compares two files and shows the differences between them.

tar

Archives or extracts files, often combined with compression.

wget

Downloads files from the web directly via the command line.

curl

Transfers data to or from a server; commonly used for testing APIs or downloading files.

zip

Compresses files into a .zip archive.

unzip

Extracts files from a .zip archive.

rsync

Synchronizes files and directories between locations, transferring only the differences.

ping

Tests reachability of a host over the network.

traceroute

Displays the network path (hops) taken to reach a host.

ssh user@host

Connects to a remote machine over SSH.

scp file user@host:/path

Securely copies a file to or from a remote machine over SSH.

/bin

Contains essential commands and programs run by regular users.

/sbin

Contains system commands and programs typically run by the root user.

/etc

Contains system-wide configuration files.

/home

Contains personal directories for regular users.

/root

The home directory of the root user (not to be confused with /, the root of the filesystem).

/var

Contains variable data that changes while the system runs, such as log files.

/tmp

Contains temporary files and directories.

/run

Contains runtime data since the last boot, such as process IDs.

/dev

Contains device files representing hardware components.

/proc

Stores information about currently running processes.

/sys

Provides an interface to kernel and hardware information (similar to /proc).

/mnt

Used for temporarily mounting filesystems.

/media

Contains mount points for removable storage devices.

/usr

The primary directory for user applications and their associated files.

/lib

Contains shared libraries and kernel modules.

/opt

Contains optional, third-party software packages.

/boot

Contains critical files required to boot the operating system; deleting this as root can render the system unbootable.

/srv

Contains data related to services provided by the system.