In Debian, I am used to set the LANGUAGE environment variable in /etc/environment.  Now with Debian testing I found /etc/default/locale, which is updated by update-locale.  The update-locale man page states it performs some sanity checks but never details them, so: what are these checks?  are they important or even essential?  can I set /etc/default/locale as I did /etc/environment, or should I absolutely use update-locale?
Why should one use update-locale instead of directly setting LANGUAGE?
debian;environment variables;locale;etc
There are just two sanity checks:the requested locale must exist (otherwise update-locale exits and /etc/default/locale isn't modified)if a value is specified for LANGUAGE, it must be valid (otherwise it is ignored)So there's nothing which requires you to use update-locale instead of editing /etc/default/locale yourself, but it is a good idea to use it to avoid mistakes.