bedazzled@desktop ~ $ cat /etc/locale.gen 
# /etc/locale.gen: list all of the locales you want to have on your system
#
# The format of each line:
# <locale> <charmap>
#
# Where <locale> is a locale located in /usr/share/i18n/locales/ and
# where <charmap> is a charmap located in /usr/share/i18n/charmaps/.
#
# All blank lines and lines starting with # are ignored.
#
# For the default list of supported combinations, see the file:
# /usr/share/i18n/SUPPORTED
#
# Whenever glibc is emerged, the locales listed here will be automatically
# rebuilt for you.  After updating this file, you can simply run `locale-gen`
# yourself instead of re-emerging glibc.

el_GR UTF-8
el_GR ISO-8859-7
bedazzled@desktop ~ $ sudo locale-gen
 * Generating 2 locales (this might take a while) with 1 jobs
 *  (1/2) Generating el_GR.UTF-8 ...                                                                                                                                                             [ ok ]
 *  (2/2) Generating el_GR.ISO-8859-7 ...                                                                                                                                                        [ ok ]
 * Generation complete
bedazzled@desktop ~ $ locale -a
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_COLLATE to default locale: No such file or directory
C
POSIX
el_GR
bedazzled@desktop ~ $ locale   
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory
LANG=
LC_CTYPE=el_GR.utf8
LC_NUMERIC="POSIX"
LC_TIME="POSIX"
LC_COLLATE=el_GR.utf8
LC_MONETARY="POSIX"
LC_MESSAGES="POSIX"
LC_PAPER="POSIX"
LC_NAME="POSIX"
LC_ADDRESS="POSIX"
LC_TELEPHONE="POSIX"
LC_MEASUREMENT="POSIX"
LC_IDENTIFICATION="POSIX"
LC_ALL=