[CentOS] Run one-time startup script

I have to change IP numbers across a number of virtual and physical 
machines because of network center move. This has to be done before 
network startup, of course. I'm thinking about the best method to do this. 
Where should I include/init this script? Or would it rather make more 
sense to do this on the last shutdown?

Changes largely involve removing old files and putting new files in place 
(resolv.conf, hosts, sysconfig/network + network-scripts, firewall, 
postfix, httpd etc.). The only other change besides replacing files would 
be changing the IP address in a webcontrol interface in a MySQL table, so 
this part has to be done after MySQL startup.

Could be run-once or have to disable manually after successful startup.

Thanks,

Kai