How to add an image to the hard-disk of an android phone Dont mention about custom Roms, I want to load an image into the hard-disk and be able to access it from a computer can I do so?

I want to know how to write to memory, and that includes wipping off the / directory.

May be want to load linux into it(Assume)
DriveDroid can help

DriveDroid allows you to boot your PC from ISO/IMG files stored on your phone. This is ideal for trying Linux distributions or always having a rescue-system on the go... without the need to burn different CDs or USB pendrives.
DriveDroid also includes a convenient download menu where you can download USB-images of a number of operating systems from your phone (like Mint, Ubuntu, Fedora, OpenSUSE and Arch Linux). Around 35 different systems are available at this moment.

Needs root
Related Creating a bootable USB through android