This modification eleminates the case described below:
If PostgreSQL (probaly with Linux) was shut down wrong way (power off, any other damage, kill, etc... ) it left opened the file(socket) /tmp/.s.PGSQL.5432 . It is found by Postmaster's next start with message:
===
Starting postgresql service: FATAL: StreamServerPort: bind() failed: errno=98
        Is another postmaster already running on that port?
        If not, remove socket node (/tmp/.s.PGSQL.<portnr>)and retry.
/usr/bin/postmaster: cannot create UNIX stream port
===
so, You are in situation that Linux was completely started, all services are running ok except the postgres - and if You miss it, Your server can be running hours without poperly serving the database. 

= = = = = 

If You find it usefull, make following modification to the file:

	/etc/rc.d/init.d/postgresql

on Your RedHat Linux (other Linux or Unix versions will probably need some changes in locations, filenames etc...)
Begin of the changed lines is marked
         # [B] added by daniel.peder@infoset.cz
End is marked
         # [E] added by daniel.peder@infoset.cz

other text stuff was left for Your better orientation where put the changes...

so here we are:
======================================================
#!/bin/sh
...
...
[ -f /usr/bin/postmaster ] || exit 0

# See how we were called.
case "$1" in
  start)
        # [B] added by daniel.peder@infoset.cz
        echo -n "Checking status of last postgresql service shutdown: "
        psql_socket="/tmp/.s.PGSQL.5432"
        if [ -e $psql_socket -a "`pidof postmaster`" = "" ]; then
            rm -f $psql_socket
            echo "incorrect"
        else
            echo "correct"
        fi
        # [E] added by daniel.peder@infoset.cz

        echo -n "Starting postgresql service: "
        su postgres -c '/usr/bin/postmaster -S -D/var/lib/pgsql'
        sleep 1
        pid=`pidof postmaster`
        echo -n "postmaster [$pid]"
        touch /var/lock/subsys/postmaster
        echo
        ;;
  stop)
        echo -n "Stopping postgresql service: "
        killproc postmaster
        sleep 2
        rm -f /var/lock/subsys/postmaster
        echo
        ;;...
...
======================================================


--

dpeder@infoset.cz
Daniel Peder
http://shop.culture.cz

Fri, 24 Sep 1999 17:26:02 +0200
=?iso-8859-2?Q?Daniel_P=E9der?= <dpeder@infoset.cz>
postgres startup script modification (Linux RedHat)