30.3. Running Additional Programs at Boot Time
The /etc/rc.d/rc.local script is executed by the init command at boot time or when changing runlevels. Adding commands to the bottom of this script is an easy way to perform necessary tasks like starting special services or initialize devices without writing complex initialization scripts in the /etc/rc.d/init.d/ directory and creating symbolic links.
The /etc/rc.serial script is used if serial ports must be setup at boot time. This script runs setserial commands to configure the system's serial ports. Refer to the setserial man page for more information.