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LINUX-L  2007

LINUX-L 2007

Subject:

Re: Better way to do it:

From:

"John H. Sawyer" <[log in to unmask]>

Reply-To:

Platform Independent Linux List! <[log in to unmask]>

Date:

Thu, 30 Aug 2007 15:51:44 -0400

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (56 lines)

Thanks. It wasn't clear what the desire was based on the text you  
included with your message.

Defining the block size definitely makes an impact on speed

dd if=/dev/cdrom of=file1 bs=4096 count=254592
VS
dd if=/dev/cdrom of=file1 bs=1 count=1042808832

-jhs

On Aug 30, 2007, at 12:28 PM, Raymond Page wrote:

> John,
>
> He wanted random data.  If I wanted to generate a large file, I would
> do it your way too.  However a random filled file seemed to be the
> goal.  Using an audio cd guarantees some pretty random data
> (relatively to the sorts of noise various music can have) and it costs
> nothing from /dev/random or /dev/urandom.
>
> On 8/29/07, John H. Sawyer <[log in to unmask]> wrote:
>> Ick. /dev/zero is so much quicker and even faster with a larger
>> block size.
>>
>> dd if=/dev/zero of=file1 bs=4096 count=254592
>> 254592+0 records in
>> 254592+0 records out
>> 1042808832 bytes (1.0 GB) copied, 21.6826 seconds, 48.1 MB/s
>>
>> -jhs
>>
>> On Wed Aug 29 20:57:25 EDT 2007, Raymond Page <[log in to unmask]>
>> wrote:
>>> What about just popping in your favorite music cd and pulling
>>> data from that?
>>>
>>> Personally I'd use dd to get the right file size (if block size
>>> will
>>> take you over, make it short and then append)
>>>
>>> On 8/6/07, Edward Allcutt <[log in to unmask]> wrote:
>>>> On Mon, 2007-08-06 at 08:51 -0400, Allen S. Rout wrote:
>>>>> So, for debugging purposes (long story) I want to create a
>>>> couple of
>>>>> files which are precisely
>>>>>
>>>>> 1042808832
>>>>>
>>>>> bytes long.  We were musing about optimal ways to do this.
>>
>
>
> -- 
> Raymond Page
>

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