DD not working--SUCCESS!

[Karl Larsen]

Jacques B. wrote:
>> That is a lot of cpu use and I think those suggesting the use of the
>> Rescue disk I have this:
>> The Rescue disk does not have dd. It also lacks RAM and will NOT work. I
>> was getting email and doing things with my computer while dd was sending
>> it to the other Hard Drive.
>>
>> It worked just fine.
>>
>>
>>
>>         Karl F. Larsen, AKA K5DI
>>     
>
> What lacks RAM?  I'm assuming you mean your computer.  Anyhow, not
> important at this point.  On to more important issues.
>
> More accurately you should say "So far it is working just fine".
>
> Imagine photocopying a book.  You photocopy the front of the book, the
> foreword, the table of content with the list of chapters and headings,
> then start photocopying the chapters.  While you are doing this you
> continue to make changes to the book.  You are now at page 20 of 100
> photocopying away.  All at the same time you change the chapter name
> of the chapter on page 45 (now that doesn't match what you photocopied
> in the beginning).  You remove a paragraph on page 15 (but you already
> photocopied it so it's already in your copy).  You delete page 19 so
> now your book is from page 1-99 but you already copied that page so
> it's on the copy.  You update your alphabetical index at the end of
> the book when you are up to page 50.  So the index tells you that
> something is on page 20 but it's really page 21 in your copy because
> you deleted page 19 after photocopying that page so your updated copy
> has it on page 20 but it is on page 21 on the original revision.  And
> it goes on.
>
> Now dd is doing the exact same thing.  It's copying stuff over
> complete with pointers to where to find certain data and pointers to
> free space on the drive.  That is written at the beginning of the
> copying process because it resides there.  Yet you are still using the
> system so what was marked as unallocated space is in use by the time
> dd gets to it.  And what was marked as used disk space when dd copied
> over the index is now unallocated space because you deleted something.
>  It can make a real mess of things.  Problems may manifest themselves
> pretty quickly, later on, or apparently not at all if you are lucky
> (but that will not mean that stuff isn't misaligned with the index
> because it's impossible for that NOT to happen given your scenario).
>
> The choice is yours.  Run with it and keep your fingers crossed or
> exercise an once of prevention now to avoid a potential pound of
> headaches later on and redo the process using a live CD as previously
> explained.  Or pursue someone else's advice on how to ghost a drive
> onto another one (entirely different approach than dd and certainly
> more efficient if this is something you will be repeating somewhat
> regularly - but again you would not do that on a live system...).
>
> Jacques B.
>
>   
OK. I changed my little paper so 6. says this:


6. Always run dd in the source computer. If your worried about computer 
activity during the transfer get out of X windows by using Cont-Alt-F1 
and then run dd.


-- 

	Karl F. Larsen, AKA K5DI
	Linux User
	#450462   http://counter.li.org.