[arch-general] restore hdd image to a bigger disk

Mauro Santos registo.mailling at gmail.com
Tue Aug 24 18:02:40 EDT 2010

On 08/24/2010 10:20 PM, Marek Otahal wrote:
> On Tuesday 24 of August 2010 23:03:23 Mauro Santos wrote:
>> On 08/24/2010 08:14 PM, Marek Otahal wrote:
>>> Hi all,
>>> I use dd command to make an image of entire /dev/sda (160GB) and back up
>>> it as netobook.hdd to an external storage. The disk contains both
>>> encrypted(dmcrypt/luks) and normal linux/win partitions.
>>> My question is, if my netbook died and I needed to recover from backup,
>>> can I just dd-copy the image to a new larger disk? Does it matter?
>>> 1/ it will do, but the size will remain 160gb ..is ok.
>>> 2/ will do & possibility to resize partitions later ..even better! :)
>>> I've searched the net, but I'd like someone to confirm it 100% works
>>> (just dd and reboot).
>>> Thanks in advance, Marek
>> Most probably you don't even need to copy the image back to a disk to
>> get the files you need. I don't know about the encrypted(dmcrypt/luks)
>> partitions but the "normal" linux/win partitions can be accessed
>> directly from the image.
> Is that so? I like the restore to a functional computer ability, so copying 
> seems useful. But I was wondering how to mount a specific partition from an 
> image? (i make the image of whole /dev/sda, so sda1,2,..are hidden inside) 
> greetings, Marek

Usually I do it like this:
- mount (?) the image to a loop device
losetup /dev/loop0 /path/to/image/file

- get the start of partitions
parted /dev/loop0 unit B print

take notice of the starting bytes for the partition you want to mount
mount /dev/loop0 mnt_point -o offset=start_bytes

and thats it, you should be able to access at least the "normal"
partitions (read and write). I have never tried with encrypted
partitions, I guess you would have to pass some extra options to mount.

To unmount everything cleanly do:
umount mnt_point
losetup -d /dev/loop0

Mauro Santos

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