Re: [Nottingham] Very slow dd if=/dev/random

From: Paul Sladen (notlug@paul.sladen.org)
Date: Tue 29 Jul 2003 - 10:23:51 BST


On Tue, 29 Jul 2003, Martin wrote:

Hello Martin,

> Meanwhile, I tried:
> dd if=/dev/random of=/dev/hdg bs=1M

`/dev/random' produces very good quality random numbers--and consequently
there aren't many of these. What will normally happen is that a stream of
random numbers will be stored up over many hours and these will be emptied
very quickly if you try and copy a whole megabyte of them. It's designed
for fetching the odd 4-bytes or so; not several GB's worth.

`/dev/urandom' produces ``good enough'' random numbers, in quantity--this
is probably the source that you want for overwriting a disk with.

Out-of-interest, what's wrong with using `/dev/zero', which produces a very
high quality stream of bits, generally uncontaminated by "ones"?

        -Paul

-- 
War is inconsistent with Truth.  Nottingham, GB

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