After creating an image file with :

dd
disk/mbr
disk/fdisk
disk/prep

the resulting partition table in the mbr  is buggy :

the chs values in the mbr are incompatible with bios.

bios uses the formula (c*H+h)*S+s-1 to calculate the lba values with H=256, S=63 while c (cylinder), h(head), s(sector) are the values from chs entries in the mbr partition table.

disk/fdisk uses the same formula while setting H=64, S=32.

If you write this image to real Hardware (HDD, USB-Sticks) some bios won't boot from such media especially if your boot drive has a size less than 8GB cause for media with sizes less than this size some bios'es use CHS addressing and some verify that sector id's from chs and lba are equal.


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