Nginx Cheatsheet

Basics for Projects

Use this Nginx reference while you build software engineering projects, review code for technical interview prep, or polish examples for a software engineer resume.

Install

# Debian/Ubuntu
sudo apt update && sudo apt install nginx

# RHEL/CentOS/Fedora
sudo dnf install nginx

# macOS (Homebrew)
brew install nginx

# Check installed version
nginx -v
nginx -V   # includes compiled-in modules and configure flags

Service Control

Command	What it does
`sudo systemctl start nginx`	Start the service
`sudo systemctl stop nginx`	Stop the service
`sudo systemctl restart nginx`	Full stop + start (drops connections)
`sudo systemctl reload nginx`	Graceful reload — zero downtime config swap
`sudo systemctl enable nginx`	Enable auto-start on boot
`sudo systemctl status nginx`	Show running state and recent logs
`sudo nginx -s reload`	Reload without systemctl (sends HUP signal)
`sudo nginx -s stop`	Fast shutdown
`sudo nginx -s quit`	Graceful shutdown (finish in-flight requests)

Config Testing

sudo nginx -t           # Test config, print errors
sudo nginx -T           # Test + dump full merged config to stdout
sudo nginx -t -c /path/to/nginx.conf   # Test a non-default config file

Always run nginx -t before reloading. A bad config aborts the reload — the running process keeps serving.

Key File Paths

Path	Purpose
`/etc/nginx/nginx.conf`	Main config (Debian/Ubuntu/RHEL)
`/usr/local/etc/nginx/nginx.conf`	Main config (Homebrew macOS)
`/etc/nginx/sites-available/`	Vhost definitions (Debian convention)
`/etc/nginx/sites-enabled/`	Symlinks to active vhosts
`/etc/nginx/conf.d/`	Drop-in config snippets (RHEL convention)
`/var/log/nginx/access.log`	Default access log
`/var/log/nginx/error.log`	Default error log
`/var/run/nginx.pid`	PID file for the master process
`/usr/share/nginx/html/`	Default document root

Process Model

Master process   — reads config, binds privileged ports, spawns workers
  └── Worker 1   — handles connections (non-privileged)
  └── Worker 2
  └── ...

worker_processes auto; — one worker per CPU core (recommended)
Each worker can handle thousands of concurrent connections via async I/O
Master never handles client traffic — only workers do

Enable a Site (Debian/Ubuntu)

# Create symlink from sites-available to sites-enabled
sudo ln -s /etc/nginx/sites-available/mysite.conf /etc/nginx/sites-enabled/

# Disable a site
sudo rm /etc/nginx/sites-enabled/mysite.conf

sudo nginx -t && sudo systemctl reload nginx

Useful One-liners

# Watch error log live
sudo tail -f /var/log/nginx/error.log

# Watch access log live
sudo tail -f /var/log/nginx/access.log

# Count active connections by state
ss -s

# Show which process owns port 80
sudo ss -tlnp | grep ':80'

# Send USR1 to rotate logs without downtime
sudo kill -USR1 $(cat /var/run/nginx.pid)