Questions about the dd command

elmo elmo at ne.rr.com
Sat Mar 1 01:28:44 UTC 2008


Karl Larsen wrote:
> elmo wrote:
>   
>> I've spent literally hours trying to find direct answers on the dozens 
>> of websites that discuss 'dd'
>> but the couldn't find what I wanted.
>>
>> A few questions about the ' dd ' command:
>>
>>   For example:     sudo dd if=/dev/sda2 of=/dev/sdb2 bs=1440
>>
>>   1. Which is preferrable;    execute the command from an installed
>>        ubuntu (/dev/sda2) or from a ubuntu CD?
>>   
>>     
>     There is no point to using dd from a CD-Rom. That is silly.
>
>
>   
>>   2. How do you  modify the example  to show the data as it is being 
>> copied? 
>>      Would this have a drastic effect on how long it takes to complete 
>> the copy
>>       compared to just watching a blinking cursor?
>>   
>>     
>     There is no way I know to see what is happening.
>   
>>   3.  What effect on the does the ' bs = ' number have on
>>       the time to complete the copy or the accuracy of the copy?  Is 
>> there a
>>       default number if the the bs=    is omitted from the command?
>>
>> 	If you do not use a bs= it uses the default which is dead slow. I use bs=10000 and it is much quicker.
>>   
>>     
>
>     Suggest you read man dd where all these things come from.
>
> Karl
>
>   
I've gone through ' man dd ' dozens of times. Perhaps the answers are 
there but I don't recognize them.

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