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Old 12-08-2010, 10:20 PM   #1
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Registered: Mar 2006
Posts: 8

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How to change disk size by editing disk information on the hard disk?

The question is how to change physical size of hard disk by software?

I am moving winxp to virtual .vdi disk. Correct way is to take image of the whole harddisk dd if=/dev/sda etc. Problem is that the disks are huge and I only need the first 10GB which is C: drive.

So how can I edit the disk information ( partition table? MBR? ) on the physical source hard drive so so that it looks like 10GB hard drive instead of 250GB? After editing the size information I will start windows which will most probably do chkdsk etc. After windows and whole system ( grub etc. ) thinks that the disk is 10GB I can take image of that 10GB and convert it to 10GB virtual .vdi disk.

I have tried take copy of first 10GB of the disk just ignoring the rest. I did something like
dd if=/dev/sda of=./cdrive.dd bs=1M count=10K
and then tested
mount -o loop,offset=32256 -t ntfs ./cdrive.dd ./cdisk
and I could read the files normally, so this partially works.

I have not managed to convert this cut image to a working virtual .vdi disk yet. I have been using VBoxmanage converfromraw tool which did not give errors but did not manage boot the .vdi yet.
Old 12-09-2010, 05:37 AM   #2
Registered: Apr 2007
Location: Carlisle, UK
Distribution: Debian
Posts: 73

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You can use the dd command to copy a single partition on the drive rather than the full drive itself. E.g. dd if=/dev/sda1 of=/*somepath*/partition1.img

Wikipedia has some helpful examples:
1 members found this post helpful.
Old 12-16-2010, 08:12 AM   #3
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Registered: Mar 2006
Posts: 8

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Whole disk need to be copied when making image for virtualbox.

"If making an image, DO NOT image just the partition, this will not work! "

Now I am looking for tools to create MBR manually and then copying only one partition to a image file.


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