PostgreSQL init script

Hi,

Our OS is CentOS5.2.  We're upgrading our PostgreSQL database from v8.2.3 to
v9.0.3.  Is there any default init script available in v9.0.3 for starting
up the PostgreSQL server so that it can be added to "/etc/init.d/"?  I
couldn't find any service file in the installation source directory.  I'm
installing PostgreSQL from source code.  I wonder why postgresql service
file is not available as part of the installation source?

Regards,
Gnanam