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Nginx Commands

Introduction​

Nginx (pronounced "engine-x") is a powerful, high-performance web server and reverse proxy that has gained immense popularity due to its efficiency and scalability. Whether you're deploying a simple website or managing complex microservices, understanding Nginx commands is essential for effective server management.

This guide covers the most important Nginx commands you'll need to know for day-to-day operations, configuration management, and troubleshooting. By the end, you'll be comfortable controlling Nginx from the command line and have a solid foundation for advanced server management.

Basic Nginx Commands​

Starting and Stopping Nginx​

The most fundamental commands allow you to control the Nginx service:

bash
# Start Nginx
sudo nginx

# Stop Nginx immediately
sudo nginx -s stop

# Stop Nginx gracefully (wait for workers to finish processing)
sudo nginx -s quit

# Reload configuration without stopping service
sudo nginx -s reload

# Reopen log files
sudo nginx -s reopen

The -s flag stands for "signal" and allows you to send various control commands to the Nginx master process.

Checking Nginx Status​

Before making changes, it's often useful to check the current status of your Nginx installation:

bash
# Check if Nginx is running
sudo systemctl status nginx

# Alternative method on non-systemd systems
ps aux | grep nginx

Output example:

● nginx.service - A high performance web server and a reverse proxy server
   Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)
   Active: active (running) since Tue 2025-03-11 07:15:22 UTC; 3 days ago
     Docs: man:nginx(8)
  Process: 1234 ExecReload=/usr/sbin/nginx -g daemon on; master_process on; -s reload (code=exited, status=0/SUCCESS)
 Main PID: 5678 (nginx)
    Tasks: 3 (limit: 4915)
   Memory: 3.5M
   CGroup: /system.slice/nginx.service
           ├─5678 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
           ├─5679 nginx: worker process
           └─5680 nginx: worker process

Configuration Commands​

Testing Configuration Files​

Before applying configuration changes, you should test them to prevent errors that might take down your server:

bash
# Test the syntax of your configuration files
sudo nginx -t

# Test with a specific configuration file
sudo nginx -t -c /path/to/nginx.conf

A successful test outputs:

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

Showing Configuration Details​

To see what configuration Nginx is currently using:

bash
# Show compilation-time options
nginx -V

# Get all running configuration
sudo nginx -T

The -V flag output shows build information:

nginx version: nginx/1.24.0
built by gcc 9.4.0 (Ubuntu 9.4.0-1ubuntu1~20.04.1)
built with OpenSSL 1.1.1f  31 Mar 2020
TLS SNI support enabled
configure arguments: --prefix=/etc/nginx ...

Debugging and Troubleshooting Commands​

Checking for Running Nginx Processes​

If you're unsure whether Nginx is running or need to see its processes:

bash
# Find all Nginx processes
ps aux | grep nginx

# Check which ports Nginx is listening on
sudo netstat -tulpn | grep nginx

Example output:

tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      5678/nginx: master
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN      5678/nginx: master

Viewing Logs​

Logs are crucial for troubleshooting Nginx issues:

bash
# View access logs
sudo tail -f /var/log/nginx/access.log

# View error logs
sudo tail -f /var/log/nginx/error.log

Process Control Commands​

Handling Nginx Processes​

For more fine-grained control over Nginx processes:

bash
# Get the master process ID
cat /var/run/nginx.pid

# Send custom signals to Nginx
sudo kill -s SIGNAL $(cat /var/run/nginx.pid)

Common signals include:

  • HUP: Reload configuration, start new worker processes
  • TERM: Shut down gracefully
  • USR1: Reopen log files
  • USR2: Upgrade executable on the fly
  • WINCH: Gracefully shut down worker processes

Practical Examples​

Example 1: Safe Configuration Updates​

When updating your Nginx configuration, follow this safe procedure:

bash
# Edit the configuration file
sudo nano /etc/nginx/nginx.conf

# Test the new configuration
sudo nginx -t

# If test is successful, reload Nginx
sudo nginx -s reload

Example 2: Upgrading Nginx Without Downtime​

This process allows you to upgrade Nginx while keeping your site online:

bash
# Install the new version but don't restart
sudo apt-get install nginx-core

# Get the current Nginx PID
old_pid=$(cat /var/run/nginx.pid)

# Upgrade the binary on the fly
sudo kill -USR2 $old_pid

# Gracefully shut down old worker processes
sudo kill -WINCH $old_pid

Example 3: Debugging a Failed Start​

If Nginx fails to start, use these commands to troubleshoot:

bash
# Check for syntax errors
sudo nginx -t

# Look for specific errors in logs
sudo tail -n 50 /var/log/nginx/error.log

# Check if something else is using Nginx's ports
sudo netstat -tulpn | grep ':80'

The Nginx Command Structure​

Let's visualize the basic command structure:

This diagram shows how Nginx commands branch into three main categories: basic actions, signals, and configuration options.

Summary​

Understanding Nginx commands is essential for effective web server management. We've covered:

  • Basic service control (start, stop, reload)
  • Configuration testing and validation
  • Troubleshooting techniques
  • Process management
  • Practical examples for common scenarios

With these commands in your toolkit, you'll be able to manage Nginx servers with confidence, whether for development or production environments.

Additional Resources​

To deepen your Nginx knowledge:

Exercises​

  1. Basic Control: Install Nginx, then practice starting, stopping, and reloading it.
  2. Configuration Test: Intentionally make a syntax error in your configuration file, then use the test command to find it.
  3. Log Analysis: Create a simple website, generate some traffic, and analyze the resulting access logs.
  4. Custom Configuration: Create a new server block for a test domain and reload Nginx to apply it.
  5. Zero-Downtime Practice: Set up a test environment and practice upgrading Nginx without service interruption.

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