Cloudmon UI Shows “Welcome to nginx” – Troubleshooting Guide

Cloudmon UI Shows “Welcome to nginx” – Troubleshooting Guide

Overview

After installing Cloudmon, accessing the application URL may display the default “Welcome to nginx” page instead of the Cloudmon UI.
You may also encounter the error below while reloading NGINX:

nginx: [emerg] duplicate default server for 0.0.0.0:80

This article explains why this happens and how to resolve it.

Symptoms

  • Cloudmon installation is completed

  • NGINX service is running

  • Accessing the server IP/URL shows “Welcome to nginx”

  • NGINX reload fails with a duplicate default server error

Root Cause

  • NGINX is serving its default site instead of Cloudmon

  • Multiple NGINX server blocks are configured with:

    listen 80 default_server;

  • NGINX allows only one default server per IP and port

Step 1: Verify NGINX Is Listening on Port 80

ss -tulnp | grep :80

Expected:

  • NGINX listening on 0.0.0.0:80 and [::]:80

  • Multiple PIDs indicate worker processes, not multiple NGINX instances

Step 2: Check Enabled NGINX Sites

ls /etc/nginx/sites-enabled/

If the default site is enabled, NGINX will show the welcome page.

  • Removing the default site prevents conflicts and ensures Cloudmon loads correctly.

Step 3: Fix the Duplicate Default Server Error

The error occurs because more than one configuration file is marked as the default server.

First: Identify All Files Using default_server

Run:

grep -R "default_server" /etc/nginx/

This will show which configuration files contain:

listen 80 default_server;

You should ensure only one file (or none) contains this directive.

If the file below exists:

/etc/nginx/sites-enabled/default

Remove it:

sudo rm /etc/nginx/sites-enabled/default

Why this works:

  • The default file serves the NGINX welcome page.

  • Cloudmon has its own configuration.

  • Removing the default site prevents conflicts and ensures Cloudmon loads correctly.

Option B: Remove default_server from the Conflicting File

If you need to keep both configuration files:

  1. Open the file that should NOT be the default:

    sudo nano /etc/nginx/sites-enabled/default

  2. Change:

    listen 80 default_server;

    To:

    listen 80;

  3. Save and exit.

Important:
Only one configuration file should contain default_server, or none at all.

Step 4: Test and Reload NGINX

sudo nginx -t
sudo systemctl reload nginx

Expected output:

syntax is ok
test is successful

Verification

The NGINX welcome page should no longer appear, and Cloudmon should load once correctly mapped.

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