[ #GUIDE ] How to make an Odin ROM #android

This needs a UNIX compatible OS - like Linux or Mac OS X. On Windows, you can use "Cygwin".

Use the dd (datadump) command to make the .rfs files 
Of course you need to connect your phone via USB and have ADB prepared on your computer.

# Get Root access first

su

# Do this first to mount the /system R/W

mount -o remount,rw /dev/block/stl9 /system

# Dump the needed data / partitions to your /sdcard

dd if=/dev/block/stl9 of=/sdcard/factoryfs.rfs bs=4096
dd if=/dev/block/stl11 of=/sdcard/cache.rfs bs=4096
dd if=/dev/block/bml7 of=/sdcard/zImage bs=4096
dd if=/dev/block/bml12 of=/sdcard/modem.bin bs=4096

# Make the tar ball 

tar -H ustar -c factoryfs.rfs cache.rfs modem.bin zImage > darky.tar

# MD5 it for a security check

md5sum –t darky.tar >> darky.tar

# Rename the tar file

mv darky.tar darky.tar.md5

Optional:
Make your own pit file 
The pit file is used to set the partition layout (Partition Information Table).

# Dump the pit

Code:

dd if=/dev/block/bml2 of=/sdcard/darky.pit bs=4096

This tut was copy from XDA site.