DD not working

Jacques B. jjrboucher at gmail.com
Thu Aug 30 18:10:43 UTC 2007


<snip>
> So DD copy must have ruined the file system I put on.
<snip>
>
>         Karl F. Larsen, AKA K5DI

You obviously misunderstood what dd does.  dd will overwrite
everything (so yes will overwrite the file system table at the
beginning of the partition in addition to everything else).  It is a
bit by bit copy.  You can use dd to copy a file to a new file which
will do so on an existing file system (must be on an existing file
system).  However when running dd against a physical device (i.e.
/dev/sda) or partition (i.e. /dev/sda5) with a destination of another
physical device or partition, then the destination device/partition
does not have to be formatted prior to doing this.  dd is copying
everything (and I mean everything - partition table, inode table, file
slack, unallocated space - everything) thus resulting in an exact bit
by bit duplicate of that device onto a new one (or partition onto a
new partition).  Hence why I said I didn't think it would work to only
grab 10 gig of a 30 gig partition using dd with if= being your
device/partition and your of= being a device/partition.

Now if your of= was a file name on a mounted file system, that would
be very different (wouldn't do what you want to do, just an aside to
this topic).  You can dd a thumb drive to a file on your system (i.e.
if=/dev/sda of=/home/myname/thumb.dd) and then using the loop back
option mount thumb.dd (image of a block device), make changes to it
(add/remove/modify the content), unmount it and then dd it back onto
your thumb drive and the thumb drive would now have all those changes.
 You can even use dd to create an empty thumb drive.  I've done this
in order to create a scenario for a class and then dd'ed it onto a
bunch of thumb drives to that everybody would be working from the
exact same thumb drive.  But I am really straying of topic now.  Your
issue was moving your Fedora 7 partition to a new partition - not
something directly on topic seeing achieving this has nothing to do
with Fedora but is generic to Linux, however nevertheless dealing with
a Fedora system so sufficiently on topic to be asked on this list.

Jacques B.




More information about the fedora-list mailing list