Re: [Xen-users] Re: How to Backup and Restore MBR within Logical Volumes?

[Sergey Vlasov <vsu@xxxxxxxxxxx>]

On Fri, Nov 13, 2009 at 12:57:22AM +0800, Mr. Teo En Ming (Zhang Enming) wrote:
[...]
> # VM 11: Rocks 5.1 x86_64 HPC Compute Cluster HVM domU
> 
> kpartx -av /dev/virtualmachines/rocks0001
> 
> dd if=/dev/virtualmachines/rocks0001 of=$DEST/rocks0001.mbr bs=512 count=1
> 
> partimage -d -M -b -z1 save /dev/mapper/virtualmachines-rocks0001p1
> $DEST/virtualmachines-rocks0001p1.img
> 
> partimage -d -M -b -z1 save /dev/mapper/virtualmachines-rocks0001p2
> $DEST/virtualmachines-rocks0001p2.img
> 
> partimage -d -M -b -z1 save /dev/mapper/virtualmachines-rocks0001p5
> $DEST/virtualmachines-rocks0001p5.img

Note that this VM (and some other VMs listed in your script) uses
logical partitions.  In this case just saving a copy of MBR will not
be enough to save partition layout - MBR describes only 4 primary
partitions, and restoring just MBR will not restore extended
partitions.

One way to backup the complete partition layout is by saving also
the output of "sfdisk -d $device"; the resulting file can be used as
input to sfdisk to restore all partitions, including logical ones.
Saving MBR is still needed together with sfdisk, because it saves
the boot code (used for HVM) and CHS geometry information (which can
be used during boot in some cases).

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