When dealing with multiple Nginx installations, you can use these commands to identify which binary is actually running:

# Method 1: Using ps command
ps aux | grep nginx

# Method 2: Using which/whereis
which nginx
whereis nginx

# Method 3: Checking running process path
sudo ls -l /proc/$(pidof nginx)/exe

The active configuration file path can be found through several approaches:

# Method 1: Using the -V flag (capital V)
nginx -V 2>&1 | grep -i 'conf-path'

# Method 2: Checking running process arguments
ps aux | grep nginx | grep -v grep | awk -F'-c' '{print $2}' | cut -d' ' -f1

# Method 3: Standard locations to check
/etc/nginx/nginx.conf
/usr/local/nginx/conf/nginx.conf
/opt/nginx/conf/nginx.conf

For your specific Passenger installation case, you should verify:

# Check if Passenger module is loaded
nginx -V 2>&1 | grep passenger

# Validate the running binary
sudo /usr/sbin/nginx -V
sudo /opt/nginx/sbin/nginx -V

# Compare output to see which one matches your running instance

# Create symlinks for easier management
sudo ln -sf /opt/nginx/sbin/nginx /usr/local/bin/nginx-custom

# Use absolute paths in service files
# Example systemd unit file modification:
[Service]
ExecStart=/opt/nginx/sbin/nginx -c /opt/nginx/conf/nginx.conf

If you encounter problems after replacing the binary:

# Check for library dependencies
ldd $(which nginx)

# Verify config syntax
nginx -t -c /path/to/your/nginx.conf

# Check error logs
tail -f /var/log/nginx/error.log
/opt/nginx/logs/error.log

Remember that when using Passenger with Nginx, you'll need to ensure the Passenger root path in your configuration matches what was compiled into the binary.

When dealing with multiple Nginx installations, the first step is identifying which binary is actually being executed. The most reliable command is:

which nginx
ps aux | grep nginx

For more detailed information about the running Nginx instance including compile-time options and version:

nginx -V

The master Nginx process reveals its configuration file path through these methods:

# Method 1: Using process information
cat /proc/$(cat /var/run/nginx.pid)/cmdline | tr '\\0' ' '

# Method 2: Testing configuration (shows path)
nginx -T 2>&1 | head -n 1

# Method 3: Checking common include paths
grep -r "include" /etc/nginx/nginx.conf

In your specific case with Passenger, here's how to verify the setup:

# Check which binary is found first in PATH
which nginx

# Verify the running process path
sudo ls -l /proc/$(pgrep -o nginx)/exe

# Cross-check with installed Passenger module
/opt/nginx/sbin/nginx -V | grep passenger

Modern Nginx setups often use include directives. To see the complete expanded configuration:

sudo nginx -T

Common configuration file locations include:

• /etc/nginx/nginx.conf
• /usr/local/nginx/conf/nginx.conf
• /opt/nginx/conf/nginx.conf

# Create symbolic links for consistent access
sudo ln -sf /opt/nginx/sbin/nginx /usr/local/bin/nginx_custom

# Set up environment variables
export NGINX_CONF_PATH=/opt/nginx/conf/nginx.conf

Remember to always test configuration changes before applying them:

sudo nginx -t
sudo systemctl reload nginx