[sclug] Copy drive problem

Paul Branston apbran at rannoch.demon.co.uk
Sat Mar 2 17:40:22 UTC 2013

Since the partitions are not the same size you would be better using something like tar to do the transfer. Moving stuff using dd is very low level block copying hence you have an image of the old partition with the same used and free space and 'lost' a load of space. 

On 2 Mar 2013, at 17:02, Neil Haughton <haughtonomous at googlemail.com> wrote:

> On 1 March 2013 18:35, Alex Butcher <lug at assursys.co.uk> wrote:
>> On Fri, 1 Mar 2013, Neil Haughton wrote:
>> On Mar 1, 2013 5:02 PM, "Alex Butcher" <lug at assursys.co.uk> wrote:
>>>> On Fri, 1 Mar 2013, Neil Haughton wrote:
>>>>> Then I tried as root to 'dd' the sdb1 partition (/var)  to its new
>>> home:
>>>>> dd if=/dev/sdb1 of=/dev/sdc1
>>>>> After a long pause the message 'read error' appeared and dd bombed out,
>>>>> with only a couple of MB transferred.  Why would this be? Have I done
>>>>> anything wrong or missed out a vital step?
>>>> Sounds like /dev/sdb has developed a bad block or two. You'll need to
>>> write
>>>> to the block(s) in question to force the drive's firmware to reallocate
>>> them
>>>> if it's a hard error.
>> ...and obviously, the implication is that whatever data once occupied the
>> block(s) in question is gone now. Hopefully, it was nothing important.
>>> Alternatively, restore from backups onto /dev/sdc1. You do have backups,
>>>> right?!? ;-)
>>> Not of  this partition, which contains /var only.
>> HTH,
>> Alex
> I've managed to fdisk both partitions and fixed the two bad blocks (in
> sdb1), and dd'd them to their new counterparts. Here's a puzzle: sdb is
> only a 40GB drive whereas the new sdc is 320GB. Both have a 3GB first
> partition, but having dd'd the second partition across I find that sdc2
> (approx 327GB) is now being shown in gparted as 76% used! How is that? Why
> does the new partition apparently have over 200GB of data when the source
> partition had only 37GB at most (actually a lot less)?
> The command I used was
> dd iflag=nofollow if=/dev/sdb2 of=/dev/sdc2
> I used the iflag argument because I didn't want symlinks to my external
> drive to be followed. What is occupying all the extra space?
> Neil

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