You have single or multiple drives using your motherboard IDE, SATA or internal software RAID and want to add a RAID controller to your system.
Your drives are connected to a RAID controller. You are either trying to use a different card or give it up for an onboard controller.
but you rather keep your current OS installation, applications and files. You require no new OS installtion. All you have to do is to connect the RAID controller to your motherboard and power up the system, install the drivers and introduce it to your OS and restart. Once the card is visible to the OS simply image your current operating system, create your RAID arrays and restore the image to the active partition of your array. You can now boot from the new controller without having to do anything else.
I tested this once with Ubuntu and it didn’t work. Not sure about different distributions, though.