to /var/lib/locales/supported.d/local
en_US.UTF-8 UTF-8
el_GR ISO-8859-7
~                         

to /etc/environment
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games"
LANG="en_US.UTF-8"
LANGUAGE="en_US:en"
~