Mastering Linux Commands: Interactive Learning Platform

Chapter 1: Navigating the Filesystem

Learn the basics of moving around and understanding your Linux environment.

Linux Terminal

user@linux:~$ Type 'pwd' to see current directory

pwd — Print Working Directory

Show the absolute path of the current directory.

pwd
# Output: /home/user

Displays the full path from the root to your current location.

💡 Practice: What command would you use to display your current directory?

cd [directory] — Change Directory

cd /home/user/Documents
cd ..    # Go up one level
cd ~     # Go to home directory
cd -     # Go to previous directory

Use cd .. to go up one level, cd ~ for home directory.

ls — List Directory Contents

ls
ls -la   # Long format with hidden files
ls -lh   # Human readable file sizes
ls -t    # Sort by modification time

Which ls option shows hidden files?

A. ls -a

B. ls -l

C. ls -h

Chapter 2: File Operations

Learn how to create, copy, move, and delete files and directories.

mkdir [directory] — Create Directory

mkdir new_folder
mkdir -p parent/child/grandchild   # Create nested directories
mkdir dir1 dir2 dir3   # Create multiple directories

rm [file] — Remove Files/Directories

rm file.txt
rm -r directory/      # Remove directory recursively
rm -f file.txt        # Force remove without confirmation
rm -i file.txt        # Interactive mode (ask before removing)

⚠️ Be careful with rm -rf! It can delete your entire system if used incorrectly.

cp [src] [dest] — Copy Files

cp file.txt backup/
cp -r source/ destination/   # Copy directories recursively
cp -i file.txt backup/       # Interactive (ask before overwrite)
cp -v file.txt backup/       # Verbose (show what's being copied)

Challenge Create a backup of a directory with all its contents

Chapter 3: Text Processing

Powerful commands for working with text files.

cat [file] — Concatenate and Display

cat file.txt
cat file1.txt file2.txt > combined.txt   # Combine files
cat > newfile.txt   # Create new file (Ctrl+D to save)

grep [pattern] [file] — Search Text

grep "error" logfile.txt
grep -r "TODO" ./src/   # Recursive search
grep -i "warning" log.txt   # Case-insensitive
grep -v "success" log.txt   # Invert match (show non-matching lines)

Search Practice

user@linux:~$ Let's search for errors in a log file

Chapter 4: Permissions and Ownership

Understand Linux file permissions and security.

Permission

Description

r (4)

Read permission

w (2)

Write permission

x (1)

Execute permission

chmod [permissions] [file] — Change Permissions

chmod 755 script.sh
chmod u+x file.txt    # Add execute for user
chmod go-w file.txt   # Remove write for group and others
chmod -R 644 dir/     # Recursive change

chown [user]:[group] [file] — Change Ownership

chown user:group file.txt
chown user file.txt    # Change user only
chown :group file.txt  # Change group only
chown -R user:group dir/  # Recursive change

Chapter 5: Process Management

Control and monitor running processes.

ps — Process Status

ps aux          # Show all processes
ps -ef          # Full format listing
ps aux | grep nginx  # Find specific process

kill [signal] [pid] — Terminate Processes

kill 1234        # Send TERM signal (default)
kill -9 1234    # Force kill (SIGKILL)
killall nginx   # Kill all processes named nginx

⚠️ SIGKILL (-9) cannot be caught or ignored by the process. Use as last resort.

Comprehensive Quiz

Test your knowledge of Linux commands with this interactive quiz.

1. Which command would you use to find files modified in the last 24 hours?

A. find . -mtime -1

B. ls -l

C. grep "24 hours"

2. How would you make a script executable for all users?

A. chmod u+x script.sh

B. chmod a+x script.sh

C. chown user script.sh