[CentOS] How to move my MBR

Tue May 27 22:14:43 UTC 2008
Mike McCarty <Mike.McCarty at sbcglobal.net>

Scott Moseman wrote:
>> The BIOS determines which disk (the first) will be chosen to boot from.
> I have no problems configuring the boot order in the BIOS.
> I must have the MBR on /dev/hdc (which is being removed).
> The /boot partition is on /dev/sda (where I want to move MBR).
>> To make a plain bootsector copy:
>> dd if=/dev/sda of=/dev/sdb bs=512 count=1
> sda = old MBR source and sdb = new MBR source, I assume?
> So, in my instance, I'm going to want to run it in this syntax:
> dd if=/dev/hdc of=/dev/sda bs=512 count=1
> I'm assuming the first 512 bytes are allocated purely for MBR and
> won't hold any data that could be overwritten?  Would that be true?

It is not guaranteed to be true. Every disc has an MBR. The MBR
has three fields (depending on how one counts, some say two).
One field is the code area, another is the Partition Table (PT)
and the third is the Boot Marker (some include this in the PT).
You don't want to copy the PT from one disc to another. Copying
all 512 bytes will overwrite the PT.

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