Fix Error "WARNING! Your environment specifies an invalid locale. on Ubuntu 16.04"

locale.md

Edit file /etc/default/locale

nano /etc/default/locale

paste this

LC_CTYPE=en_US.UTF-8
LC_ALL=en_US.UTF-8
LANG=en_US.UTF-8

and then, running command dpkg-reconfigure locales, choose en_US.UTF-8. last step, reboot server

Referensi: https://askubuntu.com/questions/1077398/fresh-installation-of-ubuntu-16-04-gives-me-warning-about-locale-unable-to-fix