Appendix A. Rare Nginx Error Messages

We conclude our book with a reference of interesting and not very common error messages that you might encounter in your log files. The table in this appendix may be an emergency reference or another peek into what could go wrong in your setup. In general, Nginx is pretty good at reporting its own problems. The messages usually have a standard format with common items, such as severity, function name, and pointers to external data that caused the problem.

We would recommend against leaving this table unread until a problem occurs because the notes column may contain interesting insights into how Nginx works and help you understand it better. Some of these messages you might not see in your real working experience, which is okay, as the error conditions are exceptions by definition.

could not open error log file: open() "/var/log/nginx/error.log" failed

This is a very common error, which usually indicates problems with permissions...