running a bash script upon boot

You can run the script via /etc/rc.d/rc.local file
eg: inserver the following line to the file:
/path-to/myscript

please read:
http://www.linuxtopia.org/online_books/centos_linux_guides/centos_linux_reference_guide/s1-boot-init-shutdown-process.html

or put the escript in /etc/rc2.d  or /etc/rc3.d depends at which run level you want to start the script.
You need to name the script looks like
S99myscript

must starting with a up case S follow by a number then whatever name.