When starting postgres, it hangs like it is still connected to stdout

[Susan Cassidy <susan.cassidy@xxxxxxxxxxxxxxxxxxxxxxxx>]

When I start postgres using postgres -D $PGDATA, it hangs, and I see that postgres and all the other attendant processes are running, but I never get my prompt back.

If I hit ctl/C, postgres ends running.

I can't seem to figure out why.

This is postgres 9.2.

What am I doing wrong?

Thanks,
Susan