where does the -i go?

I've seen there are multiple ways of doing the -i for postmaster.
Someone said something like:  Uncomment #PGOPTS= -i  Iv'e also seen it
in the postmaster call  e.g.  postmaster -i  foo

Do I need to add it to /rc.d/init.d/postgresql in the line below?
 Where?

su -l postgres -c "/usr/bin/pg_ctl -D $PGDATA -p /usr/bin/postmaster
start  >/dev/null 2>&1"