Linux commands organized by category.

Basic Navigation

Command Description
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.

File & Directory Operations

Command Description
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.

User & Permissions

Command Description
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.

User & Group Management

Command Description
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.

Package Management

Command Description
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.

Networking

Command Description
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.

Process Management

Command Description
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.

System Information

Command Description
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.

Terminal Shortcuts

Command Description
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.

Misc / GUI & Version Control

Command Description
sudo thunar Opens the Thunar file manager with root privileges.
git clone Downloads a copy of a remote Git repository to the local machine.

File Permissions

Command Description
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.

Search & Find

Command Description
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.

Archive & Transfer

Command Description
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.

Network Diagnostics

Command Description
ping Tests reachability of a host over the network.
traceroute Displays the network path (hops) taken to reach a host.

Remote Access

Command Description
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.

File System Structure

Command Description
/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.