LANG of the environment variable property of FESS's system information becomes US.UTF-8 instead of ja-JP.UTF-8

In the property of the environment variable of system information, “LANG = en_US.UTF - 8” is displayed, but what is the cause of this?

FESS is running as a Docker container on CentOS 7.5. (Image source is FROM openjdk: 8-jre)
At build time, locale is set in Dockerfile as follows.

RUN echo “ja_JP.UTF - 8 UTF - 8” >> /etc/locale.gen &&
locale-gen &&
update-locale LANG = ja_JP.UTF-8 &&
echo “export LANG = ja _ JP.UTF - 8” >> /etc/profile.d/

When entering the container with docker exec -it fess / bin / bash, LANG = ja-JP.UTF-8 is set.

Fess and Elasticsearch run on en_US.UTF-8.
It should not be changed.

THX for your answer.
Because Japanese path and filename can not be crawled, I thought that the system environment variable LANG = en_US.UTF-8 is caused, but it is another cause.
It is confirmed that the file name is UTF - 8.