linux-kernel - Re: dd if=/dev/random of=data.bin bs=512 count=1

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Message-ID: <4A184ABB.1070902@jguk.org>
Date:	Sat, 23 May 2009 20:12:59 +0100
From:	Jon <jg@...k.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: dd if=/dev/random of=data.bin bs=512 count=1

Hello KOSAKI,

Thank you for your reply.

KOSAKI Motohiro wrote:
>> Hello
>>
>> Issuing this command, I expected to get a file 4096 bytes in size.
>> Could someone let me know if I have missed something..? Or is there a
>> problem with using /dev/random this way?
>>
>> if I have a count=10 it hangs forever (several hours).
>>
>> Changing to use /dev/urandom and it generates the file ok.
> 
> you already have the answer. /dev/random might blocked, /dev/urandom doesn't.

Is this a "feature" of /dev/random ? ..it does not seem very useful to 
have it able to block for so long.

Please include my email address in replies,  as I'm not a member of this 
list.

Best regards, Jon
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