
Pre-requisites:
You need a running kernel which is one of the following:
- The default from the system installation
- A personal kernel compilation
References:
Guide: Build the Linux kernel
- A custom kernel which meets specific features:
References:
Guide: 
Optimization and performance, speed up computer, save battery power

Sometimes you require to add a driver module to specific image directory to make the driver work or work properly. This is the case of the SCSI hard drives of certain DELL computers.

If you have installed more than one kernel, remember that the current kernel  is the kernel you chose in the Grub2 menu, when the computer booted up.
To verify the current kernel version:
$ uname -r
(Pending)

References:
Web: http://www.thegeekstuff.com/2009/07/how-to-view-modify-and-recreate-initrd-img/
File: How to View, Modify and Recreate initrd.pdf

