DD Rules

[Karl Larsen]

Matthew Saltzman wrote:
> On Mon, 2007-09-03 at 09:38 -0600, Karl Larsen wrote:
>   
>> Vivek J. Patankar wrote:
>>     
>>> Karl Larsen wrote:
>>>       
>>>>    Well let me help Andy. First it is not a document! It is an email 
>>>> on the Fedora List. 
	If you want to copy something big from one partition to another the old dd method is for you. You have to do it right. This means that:

1. The destination partition MUST be as large or larger than the source partition where the data is coming from. This is essential!

2. The dd copies everything including the file system. 

3. Be ready to check the file system of the copy with fsck.

4. If you are making a copy of an entire working Fedora system make sure you change all the entries in /etc/grub.conf and /etc/fstab files to the new partitions of the copy before you try to run it.

5. To copy a partition from the source, called /dev/source to a destination partition called /dev/destination use the standard dd form:

	# dd if=/dev/source of=/dev/destination

6. Make certain that all Hard Drives are registered in bios. Put the F7 Rescue CD in, or your F7 DVD in, and select Rescue. When it asks if you want to mount your fedora system do not just go to the Prompt. At the prompt do your dd transfer. 

7. Take your time doing all this. It will save you problems later. There are a lot of ways to make errors. 

8. Think of how dd works this way, dd see's the source partition as just a lot of bytes. It takes a few bytes each cycle and puts those bytes on the destination partition. When done dd reports how many bytes it found and how many it put on destination. They are the same large number.

9. The default number of bytes per Block is defaulted to 512. The info DD says this:
 `bs=BYTES'
     Set both input and output block sizes to BYTES.  This makes `dd'
     read and write BYTES per block, overriding any `ibs' and `obs'
     settings.
So if in a hurry you can use bs=15000 which will be a good thing because the IDE hard drive controllers are quite slow. So rather than sending just 512 bytes per change, you send 15,000. A transfer will look like:

	# dd bs=15000 if=/dev/sda6 of=/dev/sdb5

I have not tried this. No reason to think it will not work.



-- 

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