As declared on the first day of the year, from the end of last year 2010, started testing Natty (Ubuntu 11.04) alpha 1. To use English environment with full ja_JP, wanna set en_US as default language. but...
$ locale locale: Cannot set LC_MESSAGES 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.UTF-8:en LC_CTYPE="en_US.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_AG.utf8 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=
In detail, lc_messages is wrong:
$ locale [...] LC_MESSAGES=en_AG.utf8 [...]
and lc_all is empty:
$ locale [...] LC_ALL=
soon after the installing Ubuntu 11.04 alpha 1 on VirtualBox.