Chapter 9: Domain Names, DNS and Subdomains

9.8 Configure the web server for the domain

By Ravindra Bagale Last updated: 15 October 2026

DNS brings the visitor to your IP. The web server must now recognise the name. That's why you write the domain in server_name or ServerName.

DNS व्हिजिटरला तुमच्या IP वर आणतं. आता वेब सर्व्हरला ते नाव ओळखता यायला हवं. म्हणून server_name किंवा ServerName मध्ये डोमेन लिहावा लागतो.

DNS विज़िटर को आपके IP तक लाता है. अब वेब सर्वर को वो नाम पहचानना चाहिए. इसलिए server_name या ServerName में डोमेन लिखना पड़ता है.

# Nginx: /etc/nginx/conf.d/example.conf  (Ubuntu: sites-available/example + symlink)
server {
    listen 80;
    listen [::]:80;
    server_name example.com www.example.com;
    root /var/www/example;
    index index.html;
    location / { try_files $uri $uri/ =404; }
}

# Apache: /etc/httpd/conf.d/example.conf  (Ubuntu: sites-available/example.conf + a2ensite)
<VirtualHost *:80>
    ServerName  example.com
    ServerAlias www.example.com
    DocumentRoot /var/www/example
    <Directory /var/www/example>
        Require all granted
    </Directory>
</VirtualHost>

sudo mkdir -p /var/www/example && echo '<h1>example.com is live!</h1>' | sudo tee /var/www/example/index.html
sudo nginx -t && sudo service nginx reload                  # Nginx
sudo apachectl configtest && sudo service httpd reload      # Apache AL2023/CentOS
sudo apache2ctl configtest && sudo service apache2 reload   # Apache Ubuntu
curl -I http://example.com

If you had put the public IP in server_name in Chapter 7, replace it with the domain names now.

Ravindra Bagale's Tip

Many students write only example.com and forget www.example.com – then opening it with www shows the default welcome page. In Nginx put both names in server_name, and in Apache keep ServerAlias along with ServerName.

Ravindra Bagale's Tip – मराठी

खूप students फक्त example.com लिहितात आणि www.example.com विसरतात – मग www ने उघडल्यावर default welcome page दिसतो. Nginx मध्ये दोन्ही नावं server_name मध्ये, आणि Apache मध्ये ServerName सोबत ServerAlias ठेवा.

Ravindra Bagale's Tip – हिंदी

बहुत students सिर्फ़ example.com लिखते हैं और www.example.com भूल जाते हैं – फिर www से खोलने पर default welcome page दिखता है. Nginx में दोनों नाम server_name में, और Apache में ServerName के साथ ServerAlias रखो.

Lab

Chala, tumchya server var /etc/nginx/conf.d/example.conf madhe tumcha domain aani www taka, aani sudo nginx -t && sudo service nginx reload chalva. Mag curl -I http://example.com aani curl -I http://www.example.com donhi 200 detat ka te bagha.

Got it? DNS is the address, and server_name is the name on the door – only when both match does the visitor reach the right home. Now let's move on to verifying DNS.

समजलं का? DNS म्हणजे पत्ता, आणि server_name म्हणजे दारावरचं नाव – दोन्ही जुळतात तेव्हाच व्हिजिटर बरोबर घरी पोहोचतो. आता पुढे जाऊया DNS व्हेरिफाय करायला.

समझ आया? DNS मतलब पता, और server_name मतलब दरवाज़े पर लिखा नाम – दोनों मिलते हैं तभी विज़िटर सही घर पहुँचता है. अब आगे चलते हैं DNS वेरिफ़ाई करने.

Extended teaching notes

Why this lesson matters

Cloud security is mostly IAM, network exposure, logging and secure defaults. The shared responsibility model means the provider patches the metal; you patch what you configure.

No public databases or public admin panels.
Roles / OIDC instead of long-lived access keys.
CloudTrail / Activity Logs / Audit Logs on and retained.
S3/Blob/GCS: Block Public Access; encrypt; least privilege.

Mini case study

Suppose we are on a purple-team exercise for an Indian mid-size company (sample data). Red notes a technique from this lesson against a lab clone. Blue must show the control that stops it, the log that would have fired, and the ticket that hardens production. That is the standard this course trains you for.

Defender's worksheet (do this today)

Write the lesson title, date and the exact lab target you are allowed to use.
List three owned systems (VMs, apps, or cloud accounts) where this lesson applies.
Run one safe check from the lesson on a lab system only. Paste the command and output.
Write a two-sentence fix you would give a teammate.
Name one related public advisory (CERT-In, CISA, NVD, or a vendor bulletin) with its date.

Indian workplace (sample data)

Suppose we are a junior analyst at Infosys, TCS, Wipro or a fintech SOC in Bengaluru/Pune. Turn this lesson into one checklist item with an owner, a due date and a place to store evidence (ticket + screenshot).

Global practice

Compare your notes with OWASP, CIS Benchmarks, NIST CSF/IR guidance or a cloud Well-Architected security question. Write five lines on what overlaps.

Everyday analogy

Explain the risk and the fix to a family member without jargon. If they can repeat the warning, you understand it well enough to teach juniors.

Key terms

Control: a safeguard (patch, config, process, detection).
Finding: a weakness backed by evidence.
Remediation: the fix plus how you verified it.
Scope: systems you have written permission to touch.
Least privilege: only the access the task needs.
Defence in depth: several layers so one failure does not end the story.

Common mistakes

Skipping written permission "just for a quick scan".
Practising on hostel, office or public targets without authorisation.
Collecting tool output without writing the fix.
Copying attack steps onto production to "verify". Defenders verify with versions, configs and patches.
Publishing screenshots that contain secrets, cookies or internal hostnames.

Recap

Evidence, fix, owner, date.
Own lab only.
Fix > spectacle.