finding error logs

You can use lsof (list of open files) in most cases to find open log files without knowing the configuration.

Example:

Find the PID of httpd (the same concept applies for nginx and other programs):

$ ps aux | grep httpd
...
root     17970  0.0  0.3 495964 64388 ?        Ssl  Oct29   3:45 /usr/sbin/httpd
...

Then search for open log files using lsof with the PID:

$ lsof -p 17970 | grep log
httpd   17970 root    2w   REG             253,15     2278      6723 /var/log/httpd/error_log
httpd   17970 root   12w   REG             253,15        0      1387 /var/log/httpd/access_log

If lsof prints nothing, even though you expected the log files to be found, issue the same command using sudo.

source: https://stackoverflow.com/questions/1706111/where-can-i-find-the-error-logs-of-nginx-using-fastcgi-and-django