[svlug] ext3 and dd disk cloning

Rafael raffi at ark.linwin.com
Fri Jan 25 11:45:01 PST 2002


On Fri, Jan 25, 2002 at 11:28:40AM -0500, Justin F. Knotzke wrote:
> 
> 	Hi,
> 
> 	It appears you can't "clone" a disk in ext3 because the journal has
> a unique identifier and the kernel will not allow you to mount a dd'd
> disk. I might have to create the partitions, create the filesystem and
> then tar or cpio the files over.
> 
> 	This is a bit of a pain as compared to just doing a dd from one hd
> to another (same disk, same geometry etc).
> 
> 	Does anyone know a way to dd a ext3 drive? I'm going to try
> recreating the journal after the dd but I'm not sure if that will work.

Using dd to clone large disk drives is a waste of time and not appropriate
IMO. In my experience it's faster to clone a partition table, mount
partitions and tar or cpio files from one drive to another. This method
would let you copy from a working disk even though that might not be
desirable in some cases.

Any other way is a waste of time on copying otherwise unused space. dd
preserves fragmentation and other undesirable effects (open files
issues,etc.) so other methods are preffered. dd is good to make exact copy
of the drive for forensic purposes.

> 
> 	Thanks
> 	Justin.
> 
> 
> -- 
> Justin F. Knotzke
> shampoo at cam.org
> pgp public key http://www.shampoo.ca/pubkey.html

-- 
Rafael




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