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🐧 Day 2: Linux & Terminal Basics on Raspberry Pi

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🎯 Learning Objectives

By the end of today, learners will:

• Navigate the Linux filesystem using the terminal.

• Use essential Linux commands for managing files and directories.

• Install and remove software using apt.

• Understand file permissions and user roles.

• Enable and use SSH & VNC to remotely access the Raspberry Pi.

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ssh pi1@raspberry1.local

🧠 Topics & Content

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🗂️ 1. Linux Filesystem Structure

Explain the hierarchy using a tree:

/
├── bin        # Essential binary programs
├── boot       # Boot loader files
├── dev        # Device files
├── etc        # System configuration files
├── home       # User home directories
│   └── pi     # Home directory for user 'pi'
├── lib        # System libraries
├── media      # Mounted drives (USB, SD)
├── opt        # Optional application software
├── tmp        # Temporary files
├── usr        # User programs and data
└── var        # Variable data (e.g., logs)

✅ Tip: Your working directory is usually /home/pi
Use pwd to check where you are.

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💻 2. Basic Linux Commands

Practice the following:

Practice Task:

cd ~
mkdir day2
cd day2
nano hello.txt

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📦 3. Package Management with APT

APT (Advanced Package Tool) is used for installing and managing software.

• Update package list:

    sudo apt update
  

• Upgrade installed packages:

    dsudo apt upgrade -y
  

• Install a package:

    sudo apt install cowsay
    cowsay "Linux is fun!"
  

• Remove a package:

    sudo apt remove cowsay
  

🔍 Explore: Try installing neofetch, htop, or python3-pip

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🔐 4. File Permissions and Users

Use ls -l to check permissions:

-rw-r--r-- 1 pi pi  1234 Jun 14  hello.txt

Breakdown:

• rw- → owner can read/write

• r-- → group can read

• r-- → others can read

Change permissions:

chmod 755 myscript.sh

Change ownership:

sudo chown pi:pi myfile

User management:

whoami
sudo adduser student

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🔗 5. Remote Access: SSH and VNC

• SSH (for terminal access over network)

• VNC (for GUI desktop access)

✅ Enable SSH & VNC:

sudo raspi-config
# Go to "Interface Options" > Enable SSH and VNC

Alternatively:

sudo systemctl enable ssh
sudo systemctl start ssh

🖥️ Install VNC Viewer on PC/Mac:

• Download: https://www.realvnc.com/en/connect/download/viewer

• Enter Raspberry Pi’s IP (e.g., 192.168.1.42) and login

To check IP:

hostname -I

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🛠️ Activities

1. Create and Navigate Folders

mkdir ~/projects/day2
cd ~/projects/day2

2. Edit and View Files

nano notes.txt
cat notes.txt

3. Install Software

sudo apt install figlet
figlet "Hello Pi"

4. Enable SSH & VNC and connect from another device

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📋 Homework

• Try installing any fun terminal program (cmatrix, sl, etc.)

• Create a bash script named myinfo.sh that displays:

  • Current user (whoami)

  • Date/time (date)

  • IP address (hostname -I)

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✅ Summary

• Terminal is your gateway to full control in Linux.

• You can move, create, and edit files efficiently.

• With apt, you can install nearly anything.

• SSH and VNC let you work remotely from any device.

LED Blinking with Raspberry Pi

To make an LED blink on a Raspberry Pi, you'll need:

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🧰 Hardware Requirements

• Raspberry Pi (any model with GPIO)

• 1x LED

• 1x 330Ω resistor

• Breadboard and jumper wires

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⚙️ Wiring

Connect like this:

📌 Example:

• GPIO 17 → Resistor → LED anode

• LED cathode → GND

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💻 Python Code to Blink LED

You can use the gpiozero or RPi.GPIO library.

✅ Using gpiozero (simpler):

from gpiozero import LED
from time import sleep

led = LED(17)  # GPIO pin 17

while True:
    led.on()
    sleep(1)
    led.off()
    sleep(1)

✅ Using RPi.GPIO:

import RPi.GPIO as GPIO
import time

LED_PIN = 17

GPIO.setmode(GPIO.BCM)
GPIO.setup(LED_PIN, GPIO.OUT)

try:
    while True:
        GPIO.output(LED_PIN, GPIO.HIGH)
        time.sleep(1)
        GPIO.output(LED_PIN, GPIO.LOW)
        time.sleep(1)
except KeyboardInterrupt:
    GPIO.cleanup()

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▶️ To Run the Script

1. Save it as blink.py

2. Open terminal and run:

python3 blink.py

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Let me know if you want to:

• Control the LED via a web interface

• Blink with different patterns

• Use a button to control it

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LED.html

<!DOCTYPE html>
<html>
<head>
    <title>LED Control</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            text-align: center;
            padding-top: 50px;
        }
        button {
            padding: 15px 30px;
            font-size: 18px;
            margin: 10px;
            cursor: pointer;
            border: none;
            border-radius: 8px;
        }
        .on {
            background-color: #4CAF50;
            color: white;
        }
        .off {
            background-color: #f44336;
            color: white;
        }
    </style>
</head>
<body >
    <h1>LED Control</h1>
    <p>Current LED status: <strong>{{ 'ON' if status else 'OFF' }}</strong></p>
    <a href="/on"><button class="on">Turn ON</button></a>
    <a href="/off"><button class="off">Turn OFF</button></a>
</body>
</html>

flask_led.py

from flask import Flask, render_template
import RPi.GPIO as GPIO

app = Flask(__name__)

# GPIO setup
LED_PIN = 17
GPIO.setmode(GPIO.BCM)
GPIO.setup(LED_PIN, GPIO.OUT)
GPIO.output(LED_PIN, GPIO.LOW)

def is_led_on():
    return GPIO.input(LED_PIN) == GPIO.HIGH

@app.route('/')
def index():
    return render_template('led.html', status=is_led_on())

@app.route('/on')
def turn_on():
    GPIO.output(LED_PIN, GPIO.HIGH)
    return render_template('led.html', status=is_led_on())

@app.route('/off')
def turn_off():
    GPIO.output(LED_PIN, GPIO.LOW)
    return render_template('led.html', status=is_led_on())

@app.route('/cleanup')
def cleanup():
    GPIO.cleanup()
    return "GPIO Cleaned up!"

if __name__ == "__main__":
    try:
        app.run(host="0.0.0.0", port=5000, debug=True)
    finally:
        GPIO.cleanup()