Postmaster error (newbie questian)

Hello
I installed the postgre 7.2.3 from rpm files of my distro. (Conectiva8)
I am trying to execute postmaster, but the console show this message.
postmaster does not know where to find the database system data.
You must specify the directory that contains the database system
either by specifying the -D invocation option or by setting the
PGDATA environment variable.
and I don't know what directory is this PGDATA.
Thanks for your time
Hugs
Dirceu Semighini Filho

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