File Log is not written in kong pod

Installation/Setup
1

Hello.
I set the file log option in env. but not working.

env:
  database: "off"
  proxy_access_log: /dev/stdout
  portal_api_access_log: /dev/stdout
  proxy_error_log: /dev/stderr
  portal_api_error_log: /dev/stderr

There are log files in “/dev”
But contents are nothing.
lrwxrwxrwx 1 root root 15 Oct 19 05:24 stderr -> /proc/self/fd/2
lrwxrwxrwx 1 root root 15 Oct 19 05:24 stdin -> /proc/self/fd/0
lrwxrwxrwx 1 root root 15 Oct 19 05:24 stdout -> /proc/self/fd/1

How can I add file log in kong pod.

[ENV]
DBless , kubernetes
kong:2.1
kong-ingress-controller:0.9.1

I found kong file log plugin.
This plugin support file log withoput kong process error log.
I wnat to collect kong process error log

2

I changed the file location due to file permissions.
“/dev/stdout” can not access “kong” user