Problems setting up DB at a different location

Hi,
I'm trying to place a database on a different harddisk than the default one
PostgreSQL uses. I've read and followed the instructions of the User
Documentation Sections 6.1.1 and 10.2.

export PGDATA2="/data/db"
initlocation PGDATA2

so far, so good, everything worked.
But now, when I createdb mydb -D PGDATA2 from the commandline or
CREATE DATABASE mydb WITH LOCATION = 'PGDATA2';
from psql, I get the message

ERROR:  Postmaster environment variable 'PGDATA2' not set

despite it being set, obviously. Trying to SET it again from within psql
resulted in being told that 'pgdata2' was not a valid option name.

This is PostgreSQL 7.1.2 from the Debian Linux distribution.
Can anyone point me to what I'm doing wrong?

Regs,
Sven

--
Sven Riedel                      sr@gimp.org
Osteroeder Str. 6 / App. 13      sven.riedel@tu-clausthal.de
38678 Clausthal                  "Call me bored, but don't call me boring."
                                 - Larry Wall