Re: dd and mbr

On Wednesday, 12 January 2022 at  9:34:31 +0000, Roderick wrote:
>
> On Wed, 12 Jan 2022, Greg 'groggy' Lehey wrote:
>> As others have said, at the very
>> least you should have limited the length, otherwise you would
>> overwrite the entire disk, one sector at a time.
>
> That is what I wanted. I was deleting some old disks. I filled it
> with zeroes and not random in order not to make the process
> slower.

Ah, I guessed wrong.  Yes, in that case your sysctl would allow you to
overwrite the MBR as well.  Even without it, you *would* overwrite the
(rest of) the entire disk.

> Perhaps there is a faster tool than dd.

As others have suggested, use bs=64k.  Otherwise dd does an IO for
every single sector.  The speedup is really in the order of 100x.

Greg
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