[linux-lvm] Backuping "special" snapshots

[Bryn M. Reeves]

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Marc Patino Gómez wrote:
> Hi  list,
> 
> I am searching a way to backup a "special" logical volume. This special
> lv doesn't contains a filesystem, it contains a hole image disk of a
> running server (MBR,Partition Table, Partitions and filesystems), in
> fact it is a VBD (Virtual Block Device) of a HVM Xen Guest.
> 
> I want to be able to make the backup without shutting down the Virtual
> Machine, but the traditional way :
> 
> - make a snapshot
> - mount snapshot
> - backup the snapshots
> - umount snapshot
> - remove snapshot
> 
> is not suitable for this kind of logical volumes.
> 
> I search some information about it, but the only clue is:
> 
> fdisk -l -u /dev/vg00/lv00

Hi Marc,

You can use the kpartx tool for this. It was originally written as part
of multipath-tools and it allows you to map the partitions on a
device-mapper device like an LVM2 logical volume.

E.g. you would run:

# kpartx -a /dev/vg00/lv00

And that will scan lv00 for partitions and create new devices in
/dev/mapper named lv00p1, lv00p2, ... that you can then use to access
the content of the partitions.

When you're done, run:

# kpartx -d /dev/vg00/lv00

To remove the temporary kpartx maps.

Regards,
Bryn.

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