Локаль английская, менять ее не надо. Нужно только нормальное отображение кириллицы.
Вывод команды locale сейчас такой:
userXX@debian:~$ 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=en_US.UTF-8
LANGUAGE=en_US:en
LC_CTYPE=UTF-8
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=
userXX@debian:~$ locale -a
locale: Cannot set LC_CTYPE to default locale: No such file or directory
C
C.utf8
en_US.utf8
POSIX
ru_RU.utf8
userXX@debian:~$ sudo locale-gen
Generating locales (this might take a while)...
en_US.UTF-8... done
ru_RU.UTF-8... done
Generation complete.
userXX@debian:~$ sudo update-locale
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = "en_US:en",
LC_ALL = (unset),
LC_CTYPE = "UTF-8",
LANG = "en_US.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_US.UTF-8").
userXX@debian:~$