Why virtual hosting serves multiple domains in Nginx - Why It Works

Introduction

When you want to run several websites on one server, virtual hosting lets you do that by directing visitors to the right site based on the website address they use. This saves money and resources by sharing one server for many domains.

When you want to host multiple websites on a single server without buying separate servers for each.

When you want to save costs by sharing server resources among different websites.

When you want to manage different websites with different domain names on the same IP address.

When you want to test multiple websites locally on one machine before going live.

When you want to organize websites for different clients on one server but keep them separate.

Config File - nginx.conf

nginx.conf

events {}
http {
    server {
        listen 80;
        server_name example.com;
        root /var/www/example.com;
        index index.html;
    }

    server {
        listen 80;
        server_name testsite.com;
        root /var/www/testsite.com;
        index index.html;
    }
}

This configuration file tells Nginx to listen on port 80 for two different domain names: example.com and testsite.com.

Each server block defines settings for one domain, including where its website files live (root) and the default page (index).

Nginx uses the server_name to decide which website to show when a visitor comes in.

Commands

This command checks if the Nginx configuration file is correct before restarting the server to avoid errors.

Terminal

sudo nginx -t

Expected Output

nginx: the configuration file /etc/nginx/nginx.conf syntax is ok

nginx: configuration file /etc/nginx/nginx.conf test is successful

This command reloads Nginx to apply the new configuration without stopping the server, so websites stay online.

Terminal

sudo systemctl reload nginx

Expected Output

No output (command runs silently)

This command simulates a visitor requesting example.com to verify Nginx serves the correct website based on the domain name.

Terminal

curl -H "Host: example.com" http://localhost

Expected Output

<html>...content of example.com homepage...</html>

This command simulates a visitor requesting testsite.com to verify Nginx serves the correct website for that domain.

Terminal

curl -H "Host: testsite.com" http://localhost

Expected Output

<html>...content of testsite.com homepage...</html>

Key Concept

Virtual hosting lets one server use the website address visitors type to decide which site to show, so multiple domains share one server smoothly.

Common Mistakes

Forgetting to set the correct server_name for each server block.

Nginx won't know which website to serve, so visitors may see the wrong site or an error.

Always specify the exact domain name in the server_name directive for each website.

Not testing the configuration with 'nginx -t' before reloading.

Errors in the config can cause Nginx to fail to reload, making websites unavailable.

Run 'sudo nginx -t' to check for syntax errors before reloading.

Using the same root directory for multiple domains.

Different websites will show the same content, losing separation between sites.

Use separate root directories for each domain to keep their files separate.

Summary

Virtual hosting uses the server_name to serve different websites from one server.

Each website has its own server block with its own root folder and domain name.

Always test Nginx configuration before reloading to avoid downtime.

Practice

1. What is the main purpose of virtual hosting in nginx?

easy

A. To create backups of website data automatically

B. To increase the server's CPU speed

C. To block unwanted visitors from accessing the server

D. To serve multiple websites from a single server using different domain names

Solution

1. Step 1: Understand virtual hosting concept

   Virtual hosting allows one server to handle many websites by using domain names to select content.

2. Step 2: Identify the main purpose

   This means the server can serve different websites without needing separate servers for each domain.

3. Final Answer:

   To serve multiple websites from a single server using different domain names -> Option D

4. Quick Check:

   Virtual hosting = multiple domains on one server [OK]

Hint: Virtual hosting means many sites, one server [OK]

Common Mistakes:

• Thinking virtual hosting speeds up CPU
• Confusing virtual hosting with backups
• Believing it blocks visitors

2. Which nginx directive is used to specify the domain names for virtual hosting?

easy

A. server_name

B. location

C. listen

D. root

Solution

1. Step 1: Recall nginx configuration directives

   The server_name directive tells nginx which domain names a server block should respond to.

2. Step 2: Match directive to purpose

   Other directives like root set content folder, listen sets port, location defines URL paths.

3. Final Answer:

   server_name -> Option A

4. Quick Check:

   Domain names use server_name [OK]

Hint: Domain names go in server_name directive [OK]

Common Mistakes:

• Using root for domain names
• Confusing listen with domain matching
• Thinking location sets domain

3. Given this nginx server block snippet, what domain will it serve?

server {
  listen 80;
  server_name example.com www.example.com;
  root /var/www/example;
}

medium

A. Only example.com

B. Only www.example.com

C. Both example.com and www.example.com

D. Any domain on port 80

Solution

1. Step 1: Read server_name directive

   The server_name lists both example.com and www.example.com, so nginx matches requests for either domain.

2. Step 2: Understand nginx matching

   Requests to either domain on port 80 will serve content from /var/www/example.

3. Final Answer:

   Both example.com and www.example.com -> Option C

4. Quick Check:

   server_name lists multiple domains = serve all listed [OK]

Hint: server_name can list many domains separated by spaces [OK]

Common Mistakes:

• Assuming only first domain is served
• Thinking root defines domain
• Believing nginx serves all domains by default

4. You configured two server blocks with the same server_name but different root paths. What will happen when a request comes for that domain?

medium

A. nginx will merge both roots and serve combined content

B. nginx will serve content from the first server block it finds

C. nginx will return an error about duplicate server_name

D. nginx will randomly choose one root each time

Solution

1. Step 1: Understand nginx server block matching

   When multiple server blocks have the same server_name, nginx uses the first matching block it finds in the config.

2. Step 2: Result of duplicate server_name

   It does not merge roots or error out; it simply picks the first block, so only one root is used.

3. Final Answer:

   nginx will serve content from the first server block it finds -> Option B

4. Quick Check:

   Duplicate server_name = first block wins [OK]

Hint: Duplicate server_name uses first matching block [OK]

Common Mistakes:

• Expecting nginx to merge content folders
• Thinking nginx throws error on duplicates
• Assuming random selection

5. You want to serve two domains, site1.com and site2.com, on the same nginx server. Which configuration correctly uses virtual hosting to serve different content for each domain?

hard

A. server { listen 80; server_name site1.com; root /var/www/site1; } server { listen 80; server_name site2.com; root /var/www/site2; }

B. server { listen 80; server_name site1.com site2.com; root /var/www/site1; }

C. server { listen 80; server_name site1.com; root /var/www/site1; } server { listen 80; server_name site1.com; root /var/www/site2; }

D. server { listen 80; root /var/www/site1; } server { listen 80; root /var/www/site2; }

Solution

1. Step 1: Check domain to root mapping

   server { listen 80; server_name site1.com; root /var/www/site1; } server { listen 80; server_name site2.com; root /var/www/site2; } uses two server blocks, each with a unique server_name and root folder, correctly separating content by domain.

2. Step 2: Analyze other options

   server { listen 80; server_name site1.com site2.com; root /var/www/site1; } serves both domains from one root, so content is not separated. server { listen 80; server_name site1.com; root /var/www/site1; } server { listen 80; server_name site1.com; root /var/www/site2; } duplicates server_name causing conflict. server { listen 80; root /var/www/site1; } server { listen 80; root /var/www/site2; } lacks server_name, so domains won't be matched properly.

3. Final Answer:

   Two server blocks with distinct server_name and root for each domain -> Option A

4. Quick Check:

   Separate server blocks = separate domains and content [OK]

Hint: Use separate server blocks for each domain with server_name [OK]

Common Mistakes:

• Putting multiple domains in one block with one root
• Duplicating server_name in multiple blocks
• Omitting server_name directive