The PGDATA environment variable used to be used for this (but I never did get it satisfactorily working).
PGDATA should work fine if you always start the server directly. But if you sudo or su to another user, they likely won't inherit your environment variables. And if you use some kind of start-up script, they will likely override it. How do you start and stop PostgreSQL?
I'm sure it's in the manual yet I'm unsure just where to start reading.
If you are using start-up scripts that come with some installation package, then the details are up to the packager. The PostgreSQL manual is of little use in knowing what the packager decided to do. It will describe what the pieces are, but not how they got assembled together.
