Ubuntu - Executing a script at startup and shutdown

[original site]http://ccm.net/faq/3348-ubuntu-executing-a-script-at-startup-and-shutdown
User-defined tasks can be done by executing a script at startup and shutdown for Linux. To execute script at startup of Ubuntu, the rc.local can be modified to include additional commands. To execute script when rebooting Ubuntu, the script has to be copied to the relevant directory. Once the permissions of the script have been changed to executable, it will run when rebooting the Linux operating system. Scripts are run in the alphabetical order in the directories and the scripts should be named following the nomenclature rules when executing a script at startup and shutdown with all distributions of Linux.

To execute a script at startup of Ubuntu

Edit /etc/rc.local and add your commandsThe script must always end with exit 0 

To execute a script upon rebooting Ubuntu

Put your script in /etc/rc0.dMake it executable (sudo chmod +x myscript)Note: The scripts in this directory are executed in alphabetical order 

The name of your script must begin with K99 to run at the right time.
To execute a script at shutdown

Put your script in /etc/rc6.dMake it executable (sudo chmod +x myscript)Note: The scripts in this directory are executed in alphabetical order 

The name of your script must begin with K99 to run at the right time.