Running 2 postmaster Instances on different ports

Environement: debian, postgresql 7.4.5

This is my problem:
"/etc/init.d/postgresql2 restart
Stopping PostgreSQL database server: postmasterpg_ctl: could not find
/var/lib/postgres/data2/postmaster.pid
Is postmaster running?
.
Starting PostgreSQL database server: postmaster(FAILED)
ERROR: pg_ctl: Another postmaster may be running.  Trying to start
postmaster anyway.
pg_ctl: cannot start postmaster
Examine the log output."

The problem seems to be the "/etc/postmaster.conf",
this file seems to be used by both postmaster instances,
but since both postmaster instances have different data-dirs (two
different clusters), this is a problem. I would like the two clusters to
be started at boottime automatically.

I changed all the references in the "/etc/init.d/postgresql2" script to
the files in data-dir of second instance (with an adapted copy
postmaster.conf), but still this doesnt do the trick.

How do i solve this problem?