[CentOS] Question about dd (fill a hard disks' unused space with blanks)

Kevin Krieser k_krieser at sbcglobal.net
Sun Jun 7 22:05:03 UTC 2009

On Jun 7, 2009, at 2:59 PM, Les Mikesell wrote:

> Kevin Krieser wrote:
>>> I'll second the recommendation for clonezilla.  It knows enough  
>>> about
>>> most filesystems (including windows ntfs) to only store the used
>>> blocks
>>> and it can use network storage over nfs, smb, or sshfs if you use  
>>> the
>>> bootable CD clonezilla-live version.   If you do a lot of cloning,  
>>> you
>>> can also use the network-booting drbl version on a server that will
>>> PXE
>>> boot a client into clonezilla with the image storage directory  
>>> already
>>> NFS-mounted.  There is an rpm for Centos to install this.
>> The problem I had with clonezilla I had when I tried it once was I  
>> was
>> attempting to clone a hard drive (windows) that had some bad sectors.
>> Clonezilla didn't handle that well at all.
> That doesn't sound like a clonezilla-specific problem. Have you found
> some other tool that magically reads bad sector?
>> Either in duplicating the
>> drive from one drive to another, or when I tried to back it up to a
>> file on another USB drive failed verify.  Luckily, I had done a  
>> recent
>> windows backup, so I went through the recovery DVD route on the new
>> drive, removed programs I had previously removed from the factory
>> install, then restored over itself.  I spent a lot of effort trying  
>> to
>> avoid that.
> But - how often are you planning to clone bad drives?  I'd try to use
> something like ddrescue to try to recover first.  In the normal case,
> clonezilla does a good job.

In my case, I was hoping it would avoid the bad sector since the bad  
sectors were in free space.  So the hope was that it would skip it.   
Bad disks are a difficult case, and not a reason to avoid a tool  
unless it claims to be able to handle it.

Even ignoring the feature of Clonezilla where it can be used to  
install cloned images on many systems with lower overhead, there is  
the advantage that it doesn't have to be installed on the system you  
are cloning, like more recent versions of Ghost.  If I had known about  
it a year ago when I wanted to clone a hard drive before sending a  
computer out for repair, I would have used it.  Instead, I used  
knoppix, dd, and gzip to backup a system.  Took forever, having to go  
backup all the unused sectors on the disk.

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