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_______0
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PostPosted: Sat May 25, 2013 6:08 pm    Post subject: problem restoring clonned image, other options? Reply with quote

hi,

I've cloned a disk but the partitions are messy. It's possible to make it better with ntfsclone. However this way the mbr is missing.

When I try to dd the mbr into the lvm 'drive' either offline or booted into a VM the volume brakes. I don't understand how windows installs itself without breaking lvm volume. Manually dd'ing the mbr brakes lvm somehow.

I am talking about this:

Code:
dd if=/dev/sdd of=/dev/lvm/windoze bs=512 count=1


I need the two original partitions of m$$.

I was doing this way since ntfsclone is mightly efficient. I can ntfsclone -r -O both partitions but without the mbr this is an excersise in vain.

Anyone have clues for a workaround?

Does LVM have any type of built-in tools to clone a disk directly into an LVM partition? Since this doesn't work either:

Code:
dd if=/dev/sdc of=/dev/lvm/windoze


By the way dd'ing into a hard drive works fine. The problem lies within LVM. Possibly it overwrites some metadata. Would be nice if LVM could store it's info outside the volume's device so as to treat an LVM device name, '/dev/lvm/volume', as a hard drive exclusively.

An alternative option is whether m$$ got tools with the repair disk to retreate the bootloader and partition layout.

If not, could grub boot into an m$$ partition directly?
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BradN
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PostPosted: Sun May 26, 2013 4:32 am    Post subject: Reply with quote

As far as I know, LVM isn't designed to store entire disk images, but rather individual partitions. There's no reason you *can't* use LVM like that, but I think you will have to use loop devices in order to make linux see partitions inside.

My advice, use ntfsclone for backup/restore of ntfs filesystems (it will faithfully preserve a filesystem at least!), dd the mbr manually (and include the whole area before the first partition, some copy protections and extra bootloaders need this), and keep in mind the partition table is only part of the MBR, so you can backup/restore it separately if you need to.

partprobe (part of parted package I think?) can tell the kernel to rescan partitions after you load a new mbr, useful for scripting.

LVM doesn't store metadata inside volumes, that would be insane. It's stored inside the host device.
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vaxbrat
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PostPosted: Sun May 26, 2013 5:06 am    Post subject: You are clobbering the partition table using 512 Reply with quote

The mbr actually has both the boot code and the partition table in it. See the following to get dd to just do the boot code:


http://www.cyberciti.biz/faq/howto-copy-mbr/
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NeddySeagoon
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PostPosted: Sun May 26, 2013 10:22 am    Post subject: Reply with quote

_______0,

Its not just the MBR you are missing, thats only LBA 0. Its all the other blocks outside of the filesystems and before the first partition, where parts of the bootloader live. These need to be restored too.

e.g. the grub stage1.5 goes into LBA 1..22 (approx) The windows boot loader does something similar, so you need that space too, if you want it to boot.

To recover the data, you can mount the partitions inside the image, once you know where they start. That can be recovered from the partition table which you are dding to sector 0.
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BradN
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PostPosted: Sun May 26, 2013 6:14 pm    Post subject: Reply with quote

Oh wow I didn't realize the windows bootloaders did stuff like that, maybe that explains why one system I tried to clone wouldn't boot...
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PostPosted: Sun May 26, 2013 7:23 pm    Post subject: Reply with quote

if metadata is stored outside the volume device file why dd'ing into it brakes it?

I didn't get a clear answer. Anyone curious try the experiment.

By lvm utility I meant that lvm could have a utility to clone a physical disk onto a volume adjusting whatever it needs automagically.

In certain scenarios it's useful to use an LVM as raw disk for VM's, mainly for speed.

There's also the problem that there isn't an easy way to make a one-to-one copy of a partition. It'd be nice this:

cp /dev/sda1 /dev/sdb1

Without having to worry about manually creating a partition on sdb in advance to fit the copy.

thanks
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NeddySeagoon
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PostPosted: Mon May 27, 2013 5:47 pm    Post subject: Reply with quote

_______0,

In what way does the logical volume break?

When you dd to logical block 0, you overwrite any partition table that might have been there, unless you take special care not to.
If you have a disk image, then restoring it to a logical volume should work as long as you treat that volume as a disk.

If you have partition images but missing the space outside of the partitions, it gets harder.
You need a suitable partition table to allocate the space to dd the partition images. You also need the boot loader that goes in the space before the first partition if you hope to boot the restored image.
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PostPosted: Sat Jun 08, 2013 5:19 pm    Post subject: Reply with quote

NeddySeagoon wrote:
In what way does the logical volume break?


kpartx is unable to map the lvm volume this way.

why?
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BradN
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PostPosted: Sat Jun 08, 2013 8:01 pm    Post subject: Reply with quote

You're not by chance trying to present two copies of the same LVM physical volume to linux at the same time? I don't think it would like that.
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PostPosted: Sun Jun 09, 2013 9:02 am    Post subject: Reply with quote

using dd to make a whole disk image works for me.

I've made an image of my work laptop, which is about to get 'upgraded' from XP to Win7.
I was surprised to find that XP boots as it was intstalled on an Intel CPU and now its on an AMD.
I guess WinXP was made for i586.
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