Nginx Commands

Nginx is the web server that handles all HTTP requests for Zal Ultra. These commands help you manage, troubleshoot, and maintain the Nginx service.

🟠 MEDIUM RISK

Restarting or stopping Nginx will temporarily disconnect all web users. Schedule maintenance during low-traffic periods.

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Table of Contents

1. Service Management
2. Configuration Testing
3. Log Management
4. Performance Monitoring
5. Troubleshooting

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Service Management

Check Nginx Status

sudo systemctl status nginx

Purpose: Shows if Nginx is running, uptime, and recent log entries.

Output Indicators:

• active (running) - Service is healthy
• inactive (dead) - Service is stopped
• failed - Service crashed

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Start Nginx

sudo systemctl start nginx

Purpose: Starts the Nginx service if it's stopped.

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Stop Nginx

🔴 SERVICE OUTAGE

Stopping Nginx will make Zal Ultra completely inaccessible via web browser.

sudo systemctl stop nginx

Purpose: Completely stops the Nginx service.

When to use:

• Major configuration changes
• Server maintenance
• Troubleshooting conflicts

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Restart Nginx

🟠 BRIEF DOWNTIME

Restart causes a brief interruption (1-2 seconds) for all connected users.

sudo systemctl restart nginx

Purpose: Stops and starts Nginx. Use when configuration changes require a full restart.

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Reload Nginx (Graceful)

sudo systemctl reload nginx

Purpose: Reloads configuration without dropping connections. Preferred method for config changes.

Benefits:

• No downtime
• Existing connections continue
• New connections use new config

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Enable Nginx on Boot

sudo systemctl enable nginx

Purpose: Ensures Nginx starts automatically when server reboots.

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Disable Nginx on Boot

sudo systemctl disable nginx

Purpose: Prevents Nginx from starting on boot. Rarely needed.

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Configuration Testing

Test Configuration Syntax

sudo nginx -t

Purpose: Validates Nginx configuration files for syntax errors.

Always run this before reloading/restarting!

Example Output (Success):

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

Example Output (Error):

nginx: [emerg] unknown directive "servre" in /etc/nginx/sites-enabled/default:10
nginx: configuration file /etc/nginx/nginx.conf test failed

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Show Nginx Version

nginx -v

Purpose: Shows installed Nginx version.

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Show Nginx Compile Options

nginx -V

Purpose: Shows version and all compile-time options/modules.

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Show Current Configuration

sudo nginx -T

Purpose: Dumps the full processed configuration (all includes resolved).

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Log Management

View Access Logs (Real-time)

sudo tail -f /var/log/nginx/access.log

Purpose: Watch incoming requests in real-time.

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View Error Logs (Real-time)

sudo tail -f /var/log/nginx/error.log

Purpose: Watch errors in real-time. Essential for troubleshooting.

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View Last 100 Error Lines

sudo tail -n 100 /var/log/nginx/error.log

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Search for Specific Errors

sudo grep "error" /var/log/nginx/error.log | tail -50

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Clear Nginx Logs

🟠 CAUTION

This deletes log history. Consider backing up logs first.

# Truncate logs (keeps file, clears content)
sudo truncate -s 0 /var/log/nginx/access.log
sudo truncate -s 0 /var/log/nginx/error.log

# Or rotate logs properly
sudo logrotate -f /etc/logrotate.d/nginx

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Check Log File Sizes

sudo du -sh /var/log/nginx/*

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Performance Monitoring

Check Active Connections

# If stub_status module is enabled
curl http://localhost/nginx_status

# Or check with netstat
sudo netstat -an | grep :80 | wc -l
sudo netstat -an | grep :443 | wc -l

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Check Nginx Process Memory Usage

ps aux | grep nginx

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Check Worker Processes

ps -ef | grep nginx

Expected output: One master process and multiple worker processes.

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Troubleshooting

Common Issues and Solutions

Port Already in Use

# Find what's using port 80
sudo lsof -i :80
sudo netstat -tlnp | grep :80

# Kill the process if needed
sudo kill -9 <PID>

Permission Denied Errors

# Fix ownership
sudo chown -R www-data:www-data /var/www/html

# Fix permissions
sudo chmod -R 755 /var/www/html
sudo chmod -R 775 /var/www/html/storage

502 Bad Gateway

# Usually means PHP-FPM is down
sudo systemctl status php8.3-fpm
sudo systemctl restart php8.3-fpm

504 Gateway Timeout

# Check PHP-FPM and increase timeouts if needed
sudo nano /etc/nginx/sites-available/default
# Increase: fastcgi_read_timeout 300;
sudo nginx -t && sudo systemctl reload nginx

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Check Nginx Configuration Files

# Main config
sudo nano /etc/nginx/nginx.conf

# Site configs
ls -la /etc/nginx/sites-available/
ls -la /etc/nginx/sites-enabled/

# View default site config
sudo nano /etc/nginx/sites-available/default

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Quick Reference Card

Action	Command
Check status	sudo systemctl status nginx
Start	sudo systemctl start nginx
Stop	sudo systemctl stop nginx
Restart	sudo systemctl restart nginx
Reload (graceful)	sudo systemctl reload nginx
Test config	sudo nginx -t
View errors	sudo tail -f /var/log/nginx/error.log
View access	sudo tail -f /var/log/nginx/access.log