Multiple Postgres Instances

Hello,

I'm trying to run postgres on two different post 5432 and port 5433 with
different data directories for each instance:

[ -x /usr/local/pgsql/bin/postmaster ] && {
su -l postgres -c '/usr/local/pgsql/bin/postmaster -S -i'
echo -n ' pgsql'
}

[ -x /usr/local/pgsql/bin/postmaster ] && {
su -l postgres -c '/usr/local/pgsql/bin/postmaster
-D/usr/local/pgsql/data_5433 -p5433 -S -i'
echo -n ' pgsql'
}

But when I do a psql -p 5433 and drop a table it seems to drop in both
instances. If anyone has attempted this before I like to hear how it
worked.

David