Week 6: Linux File Management & Permissions

Welcome to Week 6! 🎉

What You'll Learn Today

✅ Edit files using GUI and Terminal
✅ Move and copy files efficiently
✅ Understand Linux users and groups
✅ Master file permissions for security
✅ Practice on Ubuntu and Kali Linux

💡 Pro Tip: Linux has two ways to do everything - GUI (clicking) and CLI (typing commands). Both are equally important!

Quick Setup Check

# Run these commands to check your setup
whoami
pwd
uname -a
ls ~

🖥️ GUI

Graphical User Interface

Point, click, drag & drop

Easy for beginners

⌨️ CLI

Command Line Interface

Type commands in Terminal

Fast & powerful

🐧 Linux

Open-source OS

Ubuntu & Kali Linux

Used by professionals

📝 Editing Files in Linux

Simple Explanation

Editing files is like writing in a notebook. Linux gives you two ways to do it:

GUI Way: Use a text editor (like Notepad on Windows)
Terminal Way: Use commands like nano or vim

Method 1: Using GUI (Ubuntu)

🎯 Exercise: Create Your First File

Click "Show Applications" (bottom left)
Search for "Text Editor"
Type: Hello, this is my first Linux file!
Click "Save As"
Name it: myfile.txt
Save to Documents folder

Method 2: Using Terminal (Ubuntu & Kali)

# Step 1: Go to Documents folder
cd ~/Documents

# Step 2: Create and open file with nano editor
nano myfile.txt

# Step 3: Type your text in nano
# "Hello from Terminal!"

# Step 4: Save and exit
# Press Ctrl + O (save)
# Press Enter (confirm)
# Press Ctrl + X (exit)

# Step 5: Read your file
cat myfile.txt

💡 Nano Editor Shortcuts:
• Ctrl + O → Save file
• Ctrl + X → Exit nano
• Ctrl + K → Cut line
• Ctrl + U → Paste line

Practice Exercise

✏️ Task: Create week6notes.txt

Create a file with your name and today's date using Terminal:

cd ~/Desktop
nano week6notes.txt

# Type this:
# Name: [Your Name]
# Date: November 17, 2025
# Topic: Linux File Management

cat week6notes.txt

🚚 Moving and Copying Files

What's the Difference?

Action	What Happens	Like Windows
Move	File goes from A to B (original disappears)	Cut & Paste
Copy	File appears in B, stays in A (2 copies)	Copy & Paste

Moving Files

# Check where you are
pwd

# Move file from Documents to Downloads
mv ~/Documents/myfile.txt ~/Downloads/

# Verify the move
ls ~/Downloads/
ls ~/Documents/

💡 Understanding Paths:
• ~ = Your home folder
• ~/Documents = /home/yourname/Documents
• . = Current directory
• .. = Parent directory

Copying Files

# Copy file from Downloads to Documents with new name
cp ~/Downloads/myfile.txt ~/Documents/myfile_backup.txt

# Verify both files exist
ls ~/Downloads/
ls ~/Documents/

🎯 Challenge: Create, Move, and Backup

# Step 1: Create file on Desktop
cd ~/Desktop
echo "This is my test file" > testfile.txt

# Step 2: Move to Downloads
mv testfile.txt ~/Downloads/

# Step 3: Copy to Documents as backup
cp ~/Downloads/testfile.txt ~/Documents/testfile_backup.txt

# Step 4: Verify all locations
ls ~/Desktop/        # Should NOT have testfile.txt
ls ~/Downloads/      # Should have testfile.txt
ls ~/Documents/      # Should have testfile_backup.txt

👥 Users and Groups

Think of Linux Like a School

Users = Students (each person has their own account)
Groups = Classes (students can be in multiple classes)
Permissions = Rules about who can access what

Key Concepts

Term	What It Means	Example
UID	User ID (unique number)	User "john" = UID 1001
GID	Group ID (unique number)	Group "students" = GID 2001
Primary Group	Your default group	Created with your account
Secondary Group	Extra groups you join	Join "developers" for project

Check Your User Info

# Who am I?
whoami

# Show my user ID and groups
id

# Show all my groups
groups

# Show my user account information
cat /etc/passwd | grep $(whoami)

Creating and Managing Groups

🎯 Exercise: Create a Project Team

# Step 1: Create a group called "projectteam"
sudo groupadd projectteam

# Step 2: Verify it was created
cat /etc/group | grep projectteam

# Step 3: Add yourself to the group
sudo usermod -aG projectteam $USER

# Step 4: Check your groups
groups $USER

⚠️ Important: You need sudo (admin privileges) to create groups and add users!

🔒 File Permissions

Understanding Permissions

Every file in Linux has three levels of access:

Owner (you) - The person who created the file
Group (your team) - People in the same group
Others (everyone else) - All other users

For each level, there are three types of permissions:

r = Read (can view the file)
w = Write (can edit/delete the file)
x = Execute (can run the file as a program)

🎨 Interactive Permission Calculator

Select permissions to see the numeric value:

Owner

Read (4)

Write (2)

Execute (1)

Group

Read (4)

Write (2)

Execute (1)

Others

Read (4)

Write (2)

Execute (1)

chmod 000 filename

Common Permission Patterns

Permission	Notation	Use Case
644	rw-r--r--	Regular files (documents)
755	rwxr-xr-x	Executable files (scripts)
700	rwx------	Private files (only you)
600	rw-------	Secret files (passwords)
777	rwxrwxrwx	⚠️ DANGEROUS - Never use!

Viewing Permissions

# Create a test file
cd ~/Documents
echo "Test content" > permtest.txt

# View permissions
ls -l permtest.txt

# Example output:
-rw-rw-r-- 1 student student 13 Nov 17 10:30 permtest.txt
# │││││││││  │ │       │       │  └── filename
# │││││││││  │ │       │       └───── file size
# │││││││││  │ │       └───────────── group owner
# │││││││││  │ └─────────────────── user owner
# │││└└└└└└  └─────────────────────── number of links
# │││
# ││└─ Others: r-- (read only)
# │└── Group: rw- (read, write)
# └─── Owner: rw- (read, write)

Changing Permissions

Method 1: Using Numbers

# Give owner full access, group read/write, others read only
chmod 664 permtest.txt

# Check the change
ls -l permtest.txt

Method 2: Using Letters

# Add execute permission for owner
chmod u+x permtest.txt

# Remove write permission for group
chmod g-w permtest.txt

# Set others to read only
chmod o=r permtest.txt

# Check changes
ls -l permtest.txt

🛡️ Security Best Practices:
✅ Use 644 for regular files
✅ Use 755 for scripts
✅ Use 700 for private files
❌ NEVER use 777 (everyone can do everything - insecure!)

🎮 Complete Practice Scenario

Team Project Setup

Imagine you're working on a group project. Let's set everything up properly!

🎯 Final Challenge Exercise

Create a secure project environment following these requirements:

Create directory ~/secure_project
Create group 'developers'
Create three files with different security levels
Create executable script
Set appropriate permissions for each

# Step 1: Create directory and navigate
mkdir ~/secure_project
cd ~/secure_project

# Step 2: Create group and add yourself
sudo groupadd developers
sudo usermod -aG developers $USER

# Step 3: Create files
echo "# Public Project Information" > public_readme.txt
echo "Team collaboration notes" > team_notes.txt
echo "My personal passwords" > my_secrets.txt
echo '#!/bin/bash
echo "Project initialized!"' > initialize.sh

# Step 4: Set permissions
chmod 644 public_readme.txt      # Everyone can read
chmod 660 team_notes.txt         # Group can read/write
chmod 600 my_secrets.txt         # Only owner can access
chmod 700 initialize.sh          # Only owner can execute

# Step 5: Set group ownership
sudo chgrp developers team_notes.txt

# Step 6: Verify everything
echo "=== Verification ==="
ls -l

# Step 7: Test the script
./initialize.sh

echo "=== Challenge Complete! ==="

Quick Reference Card

File Operations

nano file.txt - Edit file

cat file.txt - View file

mv file dest/ - Move file

cp file copy - Copy file

User & Groups

whoami - Show username

id - Show user info

groups - Show groups

sudo groupadd - Create group

Permissions

ls -l - View permissions

chmod 755 - Change permissions

chown user - Change owner

chgrp group - Change group

🐧 Week 6: Linux File Management & Permissions

Welcome to Week 6! 🎉

What You'll Learn Today

Quick Setup Check

🖥️ GUI

⌨️ CLI

🐧 Linux

📝 Editing Files in Linux

Simple Explanation

Method 1: Using GUI (Ubuntu)

🎯 Exercise: Create Your First File

Method 2: Using Terminal (Ubuntu & Kali)

Practice Exercise

✏️ Task: Create week6notes.txt

🚚 Moving and Copying Files

What's the Difference?

Moving Files

Copying Files

🎯 Challenge: Create, Move, and Backup

👥 Users and Groups

Think of Linux Like a School

Key Concepts

Check Your User Info

Creating and Managing Groups

🎯 Exercise: Create a Project Team

🔒 File Permissions

Understanding Permissions

🎨 Interactive Permission Calculator

Owner

Group

Others

Common Permission Patterns

Viewing Permissions

Changing Permissions

Method 1: Using Numbers

Method 2: Using Letters

🎮 Complete Practice Scenario

Team Project Setup

🎯 Final Challenge Exercise

✅ Learning Checklist

Quick Reference Card

File Operations

User & Groups

Permissions