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Lemp troubleshoot

Troubleshooting a LEMP stack (Linux, NGINX, MySQL/MariaDB, PHP) means checking each layer methodically. Here's a practical guide to help you isolate and resolve issues:

🔍 1. Check NGINX (Web Server)

  • Is it running? bash sudo systemctl status nginx
  • Test config syntax: bash sudo nginx -t
  • Check logs: bash sudo tail -f /var/log/nginx/error.log
  • ** Check port**
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Common issues: - “Welcome to NGINX” page → default config still active. - 404 errors → wrong root path or missing files. - 502 Bad Gateway → PHP-FPM not responding.

Here’s how to fix it:

✅ Check if PHP-FPM is Running

sudo systemctl status php74-php-fpm

If it’s not running, start it:

sudo systemctl start php74-php-fpm

🔍 Confirm the Actual Socket Path

Check the listen directive in the PHP-FPM pool config:

grep ^listen /etc/opt/remi/php74/php-fpm.d/www.conf

You might see something like:

listen = /var/opt/remi/php74/run/php-fpm/www.sock

Make sure this matches what NGINX is using.

🛠️ Update NGINX Config (if needed)

In your NGINX config, ensure the fastcgi_pass line matches the actual socket:

fastcgi_pass unix:/var/opt/remi/php74/run/php-fpm/www.sock;

🔄 Restart Services

After syncing the paths:

sudo systemctl restart php74-php-fpm
sudo systemctl reload nginx

Common issues: - Blank pages → PHP errors or misconfigured fastcgi_pass. - 502 errors → PHP-FPM socket mismatch or service down.

🗄️ 3. Check MySQL/MariaDB (Database)

  • Is it running? bash sudo systemctl status mysqld
  • Can you connect? bash mysql -u root -p

Common issues: - “Connection refused” → service down or firewall blocking. - “Access denied” → wrong credentials or host permissions.

🧰 4. Use journalctl for Unified Logs

This is a powerful way to view logs across services:

sudo journalctl -u nginx -u php-fpm -u mysqld --since today

It helps correlate issues across the stack in one view.

🧪 5. Test the Stack

  • Create a test.php file in your web root: ```php

- Access it via browser or curl:bash curl http://localhost/test.php ```

If it doesn’t render, PHP isn’t being processed correctly.

Want to automate these checks or build a health dashboard? I can help you script it out or integrate with monitoring tools like Prometheus or Netdata. Just say the word. 🚦📊