Fdisk /mbr ?

[admiral_victory]

What exactly does the command "fdisk /mbr " accomplish when typed at a
command prompt ?



B.N.

 

[Sylvan Butler]

What exactly does the command "fdisk /mbr " accomplish when typed at a
command prompt ?

Executive summary: Puts a proper master boot record (mbr) in place
on the primary hard disk.

Details:

Reads the first logical sector of the first logical hard drive
(bios drive number 0x80).

Creates a new sector by replacing the first part of the original
sector (all but the partition table) with a valid boot program while
keeping the existing partition table data.

Writes the new sector (with valid boot program and old partition
table) to the first logical sector of the first logical hard drive.

This action can be thwarted by virus protection software or
firmware, or by malware resident in memory.

sdb

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[admiral_victory]

On Thu, 17 Jul 2003 13:22:53 -0600, Sylvan Butler

Thank you for that detailed reply.

If I may trouble you with further questions on this subject. This is
related to another post in this NG but another opinion would be
interesting :-

I have two hard drives - a Master and a Slave - and one of them
is causing a problem due to software installed in the mbr of one of
them which I need to remove . Moreover I'm not sure which mbr it is
which is the problem one. I have been advised that the solution to the
removal of this mbr impediment is to boot from a suitable floppy and
type " fdisk /mbr ".

My question is :-

Will this command replace the mbr's in both Hard Drives or only in
that of the Master Drive ?

The next question would be :-

If it would only replace the Master mbr - how would I replace the mbr
of the Slave drive ?

B.N.

 

[Joep]

fdisk /cmbr n [enter] is another way of using this command where n is
replaced by the number of the harddisk.

example: fdisk /cmbr [enter] 1 to write a standard MBR code to the first
physical disk.

 

[admiral_victory]

Careful with the FDISK /MBR command! If your hard drive uses a boot overlay,
like EZ-bios, then running FDISK /MBR of a floppy will kill access to the
drives.

I've taken note of your caution here .

One final question , ( if there is ever such a thing as a final
question <g ) , if access to a drive was killed by the use of FDISK
/MBR in the circumstances you warn against here , could access be
regained by a full hard disk FORMAT?

The reason I ask this is that I suspect the need to use FDISK /MBR
only applies to the Slave Drive and a FORMAT in this case would not be
the drastic step it usually is as this drive contains very little data
at the moment and is fully backed-up.


B.N.