Debug mode in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Enable debug logging in nginx configuration

You want to enable debug logging in nginx to troubleshoot request handling. Which directive correctly enables debug logging in the main nginx configuration file?

A error_log /var/log/nginx/error.log debug;

B access_log /var/log/nginx/access.log debug;

C log_level debug;

D debug_log /var/log/nginx/debug.log;

💡 Hint

Debug logging in nginx is controlled by the error_log directive with a specific log level.

The error_log directive controls error and debug logging in nginx. Setting its level to debug enables detailed debug logs. The access_log directive does not accept a debug level. There is no log_level or debug_log directive in nginx.

💻 Command Output

intermediate

Check if debug mode is active in nginx

After enabling debug logging, you want to verify if nginx is running with debug mode active. Which command output confirms debug mode is enabled?

Nginx

nginx -V

A debug=true

B error_log set to debug

C debug_mode=on

D built with --with-debug

💡 Hint

Check the nginx build options to see if debug support is compiled in.

The nginx -V command shows build options. The presence of --with-debug means nginx was compiled with debug support. The other options are not part of the nginx -V output.

❓ Configuration

advanced

Configure debug logging only for a specific location

You want to enable debug logging only for requests to the /api location in nginx, without affecting other locations. Which configuration snippet achieves this?

A

location /api {
    error_log /var/log/nginx/api_error.log debug;
}

B

error_log /var/log/nginx/api_error.log debug;
location /api {}

C

location /api {
    access_log /var/log/nginx/api_access.log debug;
}

D

location /api {
    debug_log /var/log/nginx/api_debug.log;
}

💡 Hint

The error_log directive can be set inside a location block to control logging for that location.

Setting error_log with debug level inside the location /api block enables debug logging only for that location. The access_log directive does not support debug level. The other options either set logging globally or use invalid directives.

❓ Troubleshoot

advanced

Debug logs not appearing after enabling debug mode

You enabled debug logging in nginx with error_log /var/log/nginx/error.log debug; but no debug messages appear in the log. What is the most likely cause?

A The log file path is incorrect and nginx cannot write logs

B The error_log directive must be in the http block, not main

C nginx was not compiled with --with-debug option

D Debug logging requires restarting the server with --debug flag

💡 Hint

Check if your nginx binary supports debug mode by build options.

If nginx was not compiled with --with-debug, debug logging directives are ignored. The error_log directive can be in main or http blocks. Incorrect log path causes errors but usually logs warnings. There is no --debug flag for nginx start.

✅ Best Practice

expert

Best practice for enabling debug mode in production nginx

You need to enable debug logging temporarily on a production nginx server to troubleshoot an issue. What is the best practice to minimize impact?

A Enable debug logging globally and restart nginx to apply changes

B Enable debug logging only for the affected location and reload nginx configuration

C Enable debug logging and leave it on permanently for continuous monitoring

D Stop nginx, enable debug logging, then start nginx to avoid partial logs

💡 Hint

Limit debug logging scope and avoid full restarts in production.

Enabling debug logging only for the affected location reduces performance impact. Reloading configuration applies changes without downtime. Global debug logging or permanent debug mode can degrade performance. Stopping nginx is unnecessary and causes downtime.