How to solve the issue of nginx configuration changes not taking effect.

If you have made changes to the nginx configuration but they are not taking effect, you can try the following solutions:

1. Check the syntax of the configuration file: Make sure your configuration file doesn’t have any syntax errors. You can use the nginx -t command to check if the syntax of the configuration file is correct.
2. Restarting the nginx service: After making changes to the configuration file, it is necessary to restart the nginx service in order for the new configurations to take effect. You can use sudo service nginx restart to restart the nginx service.
3. Force reload configuration: If restarting the nginx service does not work, you can try to force reload the configuration. Use the command sudo service nginx reload to reload the configuration file.
4. Check file permissions: Make sure you have sufficient permissions for the configuration file. You can use the ls -l command to view the permissions of the configuration file and use the chmod command to change file permissions.
5. Check if other processes are using the port: If nginx cannot start, it may be because another process is using the same port. You can use the command `sudo netstat -tlnp` to view the ports that are currently listening and identify if any other processes are using the port that nginx needs to use.

If none of the above solutions work, you can try examining the error log file of Nginx, which is usually located at /var/log/nginx/error.log, to obtain more error information for further debugging and problem-solving.