[error_log_off] error_log set to off

What this check looks for

This plugin flags error_log off;.

Why this is a problem

Unlike access_log, the error_log directive does not support an off parameter. When you write error_log off;, NGINX interprets off as a path and creates a log file named off in the default config directory (often /etc/nginx).

That is confusing at best, and at worst it can fill a filesystem you did not expect to be writing to.

Bad configuration

error_log off;

This does not turn logging off; it just changes the log destination to a file named off.

Better configuration

In general, keep error logging enabled. If you have a very specific reason to suppress it, redirect to /dev/null and set a strict level:

# Disable error logging as much as possible
error_log /dev/null emerg;

Additional notes

NGINX still needs to validate the config during startup/reload. Errors during that phase can be written to the default error log path until the config is fully read. If you need to change the startup log path, use the -e / --error-log-path option when launching NGINX.