Editing Troubleshooting of nginx errors (section)

== Troubleshooting of Nginx Errors ==
=== Nginx and Apache Server Conflict Troubleshooting Guide ===
'''Problem Overview'''

When trying to access files through Nginx (such as {{kbd | key=<nowiki>http://example.com/example_folder/example.png</nowiki>}}), you encounter a 404 error, even though the file definitely exists on the server.

'''Environment Overview'''

* Operating System: Debian
* Web Server: Nginx and Apache installed simultaneously
* File Path: <code>/usr/share/nginx/html/example_folder/example.png</code>

'''Investigation of Issue'''

1. Verify File Existence

<pre lang="bash">
= Confirm the file exists in the correct location on the server =
ls -lht /usr/share/nginx/html/example_folder/
</pre>

Output shows the file exists:
<pre>
total 628K
* rw-r--r-- 1 username username 501K Apr 18 12:14 example.png
</pre>

2. Check And Fix Nginx Configuration

Check the Nginx configuration file syntax for any errors
<pre lang="bash">
sudo nginx -t
</pre>

3. Try Restarting Nginx

<pre lang="bash">
sudo systemctl restart nginx
</pre>

Encountered error:
<pre>
Job for nginx.service failed because the control process exited with error code.
</pre>

4. Diagnose Startup Failure Reason

Check service status:
<pre lang="bash">
systemctl status nginx.service
</pre>

Error message:
<pre>
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
</pre>

5. Check Port Usage

<pre lang="bash">
sudo lsof -i :80
</pre>

Output shows Apache is using port 80:
<pre>
COMMAND    PID     USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
apache2   1447     root    4u  IPv6  25157      0t0  TCP *:http (LISTEN)
apache2  72832 www-data    4u  IPv6  25157      0t0  TCP *:http (LISTEN)
...
</pre>

'''Solutions'''

Disable Apache, Enable Nginx

<pre lang="bash">
# Stop and disable Apache
sudo systemctl stop apache2
sudo systemctl disable apache2

# Start and enable Nginx
sudo systemctl start nginx
sudo systemctl enable nginx
</pre>


Verify Configuration

After restarting Nginx, try accessing your file:
<pre>
http://example.com/example_folder/example.png
</pre>

=== Common Permission Issues ===

If you still have access problems, check file permissions: Ensure Nginx user can access the directory

<pre lang="bash">
sudo chown -R www-data:www-data /usr/share/nginx/html/example_folder
sudo chmod -R 755 /usr/share/nginx/html/example_folder
</pre>