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🐧 Linux Essential Commands: Beginner to Intermediate Guide

A clean, structured reference handbook for learning Linux commands step by step.

Table of Contents

  1. File & Directory Management
  2. File Viewing & Editing
  3. File Searching
  4. Permissions & Ownership
  5. Process Management
  6. Networking
  7. Package Management
  8. Disk Management
  9. User Management
  10. Archiving & Compression
  11. System Information & Control
  12. Redirects, Pipes & Useful Tricks

1. File & Directory Management

pwd — Print Working Directory

pwd

Displays the full path of the current directory you are in.

$ pwd
/home/username/Documents

ls — List Directory Contents

ls [options] [directory]

Lists files and folders in the current (or specified) directory.

ls              # basic listing
ls -la          # detailed list including hidden files

cd — Change Directory

cd [directory]

Navigates to a specified directory.

cd /home/username/Documents   # go to a specific path
cd ..                         # go one level up
cd ~                          # go to home directory

mkdir — Make Directory

mkdir [options] directory_name

Creates a new directory.

mkdir projects                    # create a single folder
mkdir -p projects/web/css         # create nested folders at once

rmdir — Remove Empty Directory

rmdir directory_name

Deletes an empty directory.

rmdir old_folder

touch — Create an Empty File

touch filename

Creates a new empty file, or updates the timestamp of an existing one.

touch notes.txt
touch file1.txt file2.txt   # create multiple files at once

cp — Copy Files or Directories

cp [options] source destination

Copies a file or directory from one location to another.

cp report.txt backup/report.txt       # copy a file
cp -r projects/ projects_backup/      # copy a directory recursively

mv — Move or Rename Files

mv [options] source destination

Moves a file/directory to a new location, or renames it.

mv old_name.txt new_name.txt          # rename a file
mv report.txt /home/username/docs/    # move a file to another directory

rm — Remove Files or Directories

rm [options] file

Deletes files or directories. Use with caution — this is irreversible.

rm unwanted.txt               # delete a file
rm -rf old_project/           # forcefully delete a directory and its contents

ln — Create Links

ln -s target link_name

Creates a symbolic (soft) link to a file or directory.

ln -s /usr/local/bin/python3 ~/mypy    # create a shortcut to python3

2. File Viewing & Editing

cat — Concatenate and Display File Contents

cat [options] filename

Prints the entire content of a file to the terminal.

cat notes.txt
cat file1.txt file2.txt     # display multiple files in sequence

less — View File Content Page by Page

less filename

Opens a file for scrollable reading. Press q to quit, arrow keys to navigate.

less /var/log/syslog

head — Show First Lines of a File

head [options] filename

Displays the first 10 lines of a file by default.

head access.log               # first 10 lines
head -n 20 access.log         # first 20 lines

tail — Show Last Lines of a File

tail [options] filename

Displays the last 10 lines of a file. Useful for monitoring logs.

tail error.log                # last 10 lines
tail -f /var/log/syslog       # follow live log updates in real time

nano — Simple Terminal Text Editor

nano filename

Opens a beginner-friendly terminal editor. Use Ctrl+O to save, Ctrl+X to exit.

nano config.txt

vim — Advanced Terminal Text Editor

vim filename

A powerful editor. Press i to enter insert mode, Esc then :wq to save and quit.

vim script.sh

wc — Word Count

wc [options] filename

Counts lines, words, and characters in a file.

wc -l report.txt      # count lines only
wc -w essay.txt       # count words only

3. File Searching

find — Search for Files and Directories

find [path] [options] [expression]

Searches for files and directories based on name, type, size, and more.

find /home -name "*.txt"              # find all .txt files in /home
find . -type d -name "config"         # find directories named "config"

grep — Search Text Inside Files

grep [options] pattern [file]

Searches for a specific pattern (text or regex) within files.

grep "error" server.log               # find lines containing "error"
grep -ri "todo" ~/projects/           # case-insensitive recursive search

locate — Quickly Find Files by Name

locate filename

Searches a pre-built database for files (much faster than find). Run sudo updatedb to refresh the database.

locate nginx.conf

which — Find Command Location

which command_name

Shows the full path of a command's executable.

which python3
which git

4. Permissions & Ownership

chmod — Change File Permissions

chmod [options] mode file

Changes read/write/execute permissions for a file or directory.

chmod 755 script.sh           # rwx for owner, rx for group & others
chmod +x deploy.sh            # add execute permission for everyone

Permission reference:

Number Permission
4 Read (r)
2 Write (w)
1 Execute (x)

chown — Change File Owner

chown [options] owner[:group] file

Changes the owner (and optionally the group) of a file or directory.

chown alice report.txt                # change owner to alice
chown alice:developers project/       # change owner and group

chgrp — Change Group Ownership

chgrp group_name file

Changes only the group ownership of a file.

chgrp developers app.py

umask — Set Default Permission Mask

umask [mask]

Displays or sets the default permission mask applied when new files are created.

umask          # show current mask
umask 022      # set default: files get 644, dirs get 755

5. Process Management

ps — Display Running Processes

ps [options]

Shows a snapshot of currently running processes.

ps aux                        # show all running processes with details
ps aux | grep nginx           # find a specific process

top — Real-Time Process Viewer

top

Displays a live, updating view of running processes and system resource usage. Press q to quit.

top

htop — Enhanced Interactive Process Viewer

htop

A more user-friendly, colorful alternative to top (may need to be installed).

htop

kill — Terminate a Process by PID

kill [signal] PID

Sends a signal to a process, usually to terminate it.

kill 1234           # gracefully stop process with PID 1234
kill -9 1234        # forcefully kill the process

killall — Kill Processes by Name

killall process_name

Kills all running processes with the specified name.

killall firefox
killall -9 nginx

bg / fg — Background and Foreground Jobs

bg [job_id]
fg [job_id]

bg resumes a suspended process in the background; fg brings it to the foreground.

bg %1       # resume job 1 in the background
fg %1       # bring job 1 to the foreground

jobs — List Background Jobs

jobs

Lists all jobs running in the background of the current shell session.

jobs

nohup — Run a Command That Survives Logout

nohup command &

Runs a command immune to hangups, keeping it running even after you log out.

nohup python3 server.py &

6. Networking

ping — Test Network Connectivity

ping [options] host

Sends ICMP packets to a host to check if it's reachable.

ping google.com
ping -c 4 192.168.1.1     # send exactly 4 packets

curl — Transfer Data from URLs

curl [options] URL

Fetches content from a URL. Useful for testing APIs and downloading files.

curl https://example.com
curl -O https://example.com/file.zip     # download a file

wget — Download Files from the Web

wget [options] URL

Downloads files from the internet directly to your machine.

wget https://example.com/archive.tar.gz
wget -c https://example.com/bigfile.zip   # resume a partial download

ifconfig / ip — Network Interface Configuration

ifconfig
ip addr show

Displays or configures network interface settings (IP addresses, etc.).

ifconfig                  # show all network interfaces (older systems)
ip addr show              # modern equivalent

netstat — Network Statistics

netstat [options]

Displays active network connections, ports, and routing tables.

netstat -tuln             # show listening TCP/UDP ports
netstat -an | grep :80    # check if port 80 is in use

ssh — Secure Shell Remote Login

ssh [options] user@host

Connects to a remote machine securely over the network.

ssh alice@192.168.1.10
ssh -p 2222 alice@server.example.com    # connect on a custom port

scp — Secure Copy Over SSH

scp source user@host:destination

Copies files between local and remote machines securely.

scp report.txt alice@192.168.1.10:/home/alice/
scp alice@192.168.1.10:/var/log/app.log ./local/   # download from remote

nslookup / dig — DNS Lookup

nslookup domain
dig domain

Queries DNS to resolve a domain name to an IP address.

nslookup google.com
dig openai.com

7. Package Management

Debian / Ubuntu — apt

sudo apt update              # refresh package list
sudo apt upgrade             # upgrade all installed packages
sudo apt install package     # install a package
sudo apt remove package      # uninstall a package
sudo apt search keyword      # search for a package

Examples:

sudo apt update && sudo apt upgrade
sudo apt install git curl vim

Red Hat / CentOS / Fedora — dnf / yum

sudo dnf update              # update all packages
sudo dnf install package     # install a package
sudo dnf remove package      # remove a package
sudo dnf search keyword      # search packages

Examples:

sudo dnf install nginx
sudo dnf remove httpd

snap — Snap Package Manager

snap install package_name
snap remove package_name
snap list

Installs sandboxed, self-contained applications.

sudo snap install code --classic     # install VS Code
snap list                            # list installed snaps

8. Disk Management

df — Disk Free Space

df [options]

Shows disk space usage for all mounted filesystems.

df -h         # human-readable sizes (KB, MB, GB)
df -h /home   # check a specific partition

du — Disk Usage of Files/Directories

du [options] [path]

Shows how much disk space files or directories are using.

du -sh ~/Documents          # total size of Documents folder
du -sh * | sort -h          # list sizes sorted smallest to largest

lsblk — List Block Devices

lsblk

Displays a tree of all storage devices and their partitions.

lsblk
lsblk -f      # also show filesystem types and mount points

mount / umount — Mount and Unmount Filesystems

mount device mountpoint
umount mountpoint

Attaches or detaches a storage device to the filesystem tree.

sudo mount /dev/sdb1 /mnt/usb
sudo umount /mnt/usb

fdisk — Partition Manager

sudo fdisk -l

Lists all disk partitions. Use interactively to create/delete partitions.

sudo fdisk -l                  # list all partitions
sudo fdisk /dev/sdb            # open partition editor for /dev/sdb

9. User Management

whoami — Show Current User

whoami

Prints the username of the currently logged-in user.

$ whoami
alice

who — Show Logged-In Users

who

Lists all users currently logged into the system.

who

id — Show User and Group IDs

id [username]

Displays the UID, GID, and group memberships of a user.

id
id alice

useradd — Add a New User

sudo useradd [options] username

Creates a new user account.

sudo useradd -m bob           # create user with a home directory
sudo useradd -m -s /bin/bash carol

passwd — Change User Password

passwd [username]

Sets or changes a user's password.

passwd                  # change your own password
sudo passwd bob         # change another user's password (as root)

userdel — Delete a User

sudo userdel [options] username

Removes a user account from the system.

sudo userdel bob               # remove user only
sudo userdel -r bob            # remove user and their home directory

usermod — Modify a User Account

sudo usermod [options] username

Modifies an existing user's properties.

sudo usermod -aG sudo alice         # add alice to the sudo group
sudo usermod -l newname oldname     # rename a user

groups — Show Group Memberships

groups [username]

Lists all groups a user belongs to.

groups
groups alice

sudo — Execute Command as Superuser

sudo command

Runs a command with administrator (root) privileges.

sudo apt update
sudo nano /etc/hosts

10. Archiving & Compression

tar — Archive Files

tar [options] archive_name files

Creates or extracts .tar archives. Commonly combined with compression flags.

tar -czvf archive.tar.gz folder/    # create a compressed archive
tar -xzvf archive.tar.gz            # extract a compressed archive
tar -tzvf archive.tar.gz            # list contents without extracting

Flag reference:

Flag Meaning
-c Create archive
-x Extract archive
-z Use gzip compression
-j Use bzip2 compression
-v Verbose (show progress)
-f Specify filename

gzip / gunzip — Compress and Decompress Files

gzip filename
gunzip filename.gz

Compresses a file into .gz format, or decompresses it.

gzip report.txt             # creates report.txt.gz
gunzip report.txt.gz        # restores report.txt

zip / unzip — Zip Archive Management

zip archive.zip file1 file2
unzip archive.zip

Creates or extracts .zip archives.

zip -r project.zip project/         # zip a folder recursively
unzip project.zip -d /tmp/output/   # extract to a specific directory

11. System Information & Control

uname — System Information

uname [options]

Displays system and kernel information.

uname -a        # all system info (kernel, architecture, hostname)
uname -r        # kernel version only

uptime — System Uptime

uptime

Shows how long the system has been running, and the current load average.

uptime

free — Memory Usage

free [options]

Displays total, used, and free RAM and swap memory.

free -h         # human-readable format

history — Command History

history [n]

Lists previously entered commands. Use !number to re-run a command.

history          # show full history
history 20       # show last 20 commands
!42              # re-run command number 42

date — Show or Set Date and Time

date [options]

Displays the current date and time, or sets it.

date
date "+%Y-%m-%d %H:%M:%S"    # custom format

reboot / shutdown — Restart or Power Off

sudo reboot
sudo shutdown [options] [time]

Reboots or shuts down the system.

sudo reboot
sudo shutdown -h now          # shut down immediately
sudo shutdown -r +5           # reboot in 5 minutes

systemctl — Manage System Services

systemctl [command] service_name

Controls systemd services (start, stop, restart, enable on boot, etc.).

sudo systemctl start nginx          # start the nginx service
sudo systemctl stop nginx           # stop it
sudo systemctl restart nginx        # restart it
sudo systemctl enable nginx         # start on boot
sudo systemctl status nginx         # check its status

journalctl — View System Logs

journalctl [options]

Queries and displays logs from the systemd journal.

journalctl -u nginx               # logs for the nginx service
journalctl -f                     # follow live log output
journalctl --since "1 hour ago"   # recent logs

alias — Create Command Shortcuts

alias name='command'

Creates a shortcut for a longer command. Add it to ~/.bashrc to make it permanent.

alias ll='ls -la'
alias update='sudo apt update && sudo apt upgrade'

12. Redirects, Pipes & Useful Tricks

| — Pipe Output to Another Command

Sends the output of one command as input to another.

ls -la | less                     # scroll through a long listing
ps aux | grep python              # filter process list
cat access.log | grep "404"       # find 404 errors in a log

> and >> — Redirect Output to a File

> overwrites a file; >> appends to it.

echo "Hello World" > hello.txt        # write (overwrite)
echo "Another line" >> hello.txt      # append
ls -la > file_list.txt                # save directory listing to file

< — Redirect Input from a File

Feeds a file's contents as input to a command.

sort < names.txt
wc -l < report.txt

2> — Redirect Error Output

Redirects standard error (stderr) to a file separately from normal output.

command 2> errors.log             # save errors only
command > output.log 2>&1         # save both output and errors to one file

&& and || — Chain Commands

&& runs the next command only if the previous one succeeded. || runs it only if the previous one failed.

sudo apt update && sudo apt upgrade       # upgrade only if update succeeds
mkdir newdir && cd newdir                 # create dir and enter it
ping -c1 google.com || echo "No internet"

xargs — Build Commands from Input

command | xargs another_command

Takes output from one command and passes it as arguments to another.

find . -name "*.log" | xargs rm         # delete all found .log files
cat urls.txt | xargs wget               # download all URLs in a file

tee — Read and Write Simultaneously

command | tee filename

Writes output to both the terminal and a file at the same time.

ls -la | tee directory_listing.txt
ping google.com | tee ping_results.txt

clear — Clear the Terminal Screen

clear

Clears all text from the terminal window. Shortcut: Ctrl + L.

man — Manual Pages

man command_name

Opens the official manual/documentation for any Linux command. Press q to quit.

man ls
man grep
man chmod

Quick Reference Cheat Sheet

Category Key Commands
Navigation pwd, ls, cd, tree
Files touch, cp, mv, rm, mkdir, rmdir
Viewing cat, less, head, tail, wc
Searching find, grep, locate, which
Permissions chmod, chown, chgrp, umask
Processes ps, top, kill, jobs, bg, fg
Networking ping, curl, wget, ssh, scp
Packages apt, dnf, snap
Disk df, du, lsblk, mount
Users whoami, useradd, passwd, sudo, usermod
Archiving tar, gzip, zip, unzip
System uname, uptime, free, systemctl, history
Shell Tricks |, >, >>, &&, man, alias

💡 Tip: When in doubt, use man <command> or command --help to explore options for any Linux command.

Guide level: Beginner → Intermediate | Best used as a study and daily reference.