Web Server (Apache): HTTP Protocol, Installation, Control & Configuration

---

1. Understanding the HTTP Protocol (Quick Recap)

HTTP (HyperText Transfer Protocol) is used for communication between client (browser) and web server.

Working Flow

Browser (Client)
     ↓ HTTP Request
------------------------
   Apache Web Server
------------------------
     ↑ HTTP Response
Browser displays webpage

Key Points

• Stateless protocol
• Uses port 80 (HTTP) and 443 (HTTPS)
• Works on request–response model

---

2. Installing Apache HTTP Server

Apache is one of the most popular web servers.

---

2.1 On Ubuntu / Debian

sudo apt update
sudo apt install apache2

---

2.2 On RHEL / CentOS

sudo yum install httpd

---

2.3 Verify Installation

Open browser:

http://localhost

👉 Default Apache page should appear.

---

3. Starting, Stopping & Managing Apache

---

3.1 Start Apache

sudo systemctl start apache2      # Ubuntu
sudo systemctl start httpd        # RHEL

---

3.2 Stop Apache

sudo systemctl stop apache2

---

3.3 Restart Apache

sudo systemctl restart apache2

---

3.4 Check Status

sudo systemctl status apache2

---

3.5 Enable at Boot

sudo systemctl enable apache2

---

4. Apache Directory Structure

---

Ubuntu

• /etc/apache2/ → Configuration files
• /var/www/html/ → Web files
• /etc/apache2/sites-available/ → Virtual hosts
• /etc/apache2/sites-enabled/ → Active sites

---

RHEL

• /etc/httpd/ → Config files
• /var/www/html/ → Web root

---

5. Configuring Apache

---

5.1 Main Configuration File

Ubuntu:

/etc/apache2/apache2.conf

RHEL:

/etc/httpd/conf/httpd.conf

---

5.2 Basic Configuration Example

ServerName localhost
DocumentRoot /var/www/html

---

5.3 Creating a Simple Web Page

sudo vi /var/www/html/index.html

Example:

<h1>Welcome to My Apache Server</h1>

---

5.4 Virtual Host Configuration

Create file:

sudo vi /etc/apache2/sites-available/example.conf

Example:

<VirtualHost *:80>
    ServerName example.com
    DocumentRoot /var/www/example
</VirtualHost>

Enable site:

sudo a2ensite example.conf
sudo systemctl reload apache2

---

5.5 Directory Permissions

chmod -R 755 /var/www
chown -R www-data:www-data /var/www

---

5.6 Listening Port Configuration

sudo vi /etc/apache2/ports.conf

Example:

Listen 80

---

6. Testing Apache Server

---

Using Browser

http://localhost

---

Using Command Line

curl http://localhost

---

7. Firewall Configuration

sudo ufw allow 80
sudo ufw allow 443

---

8. Logs in Apache

Log File	Purpose
access.log	Client requests
error.log	Errors

Location:

/var/log/apache2/

---

9. Real-World Example

• Hosting website:
  • Files in /var/www/html
  • Apache serves pages via HTTP
• Used in:
  • Company websites
  • E-commerce platforms
  • APIs

---

10. Advantages of Apache

• Open source
• Highly configurable
• Supports modules
• Cross-platform
• Secure and stable

---

11. Conclusion

Apache HTTP Server is a powerful and widely used web server in Linux. Understanding HTTP, installation, service management, and configuration enables efficient web hosting and server administration, making it essential for developers and system administrators.

---