Running a script immediately (but not a cron job)

I'm not sure that can be done through cpanel itself, although if you were careful of security you could write a PHP script to implement that.

If you want something that can be run from root, try installing Configserver Explorer from www.configserver.com. It appears down the bottom of WHM and allows you to manipulate files and run stuff from anywhere. It does run as root though so can't be given out to users; use the PHP solution for them.

 

Or just a terminal / shell

 

You could just do a cron job and set the time as a specific date & time.....Would cause it to only be ran once.