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Re: [linux-lvm] How to 'copy' a volume?



Erich Weiler wrote:
Greetings all-

I have a problem I'm trying to solve, was hoping someone would know how to get around it...

I have a 2TB volume group, and one 500GB volume in it. There is a Xen VM in that volume group. What I'd like to do is 'copy' the volume and name it something else so I can use it as a 'template' for other VMs.

I know that LVM has the 'snapshot' capability. But this doesn't look like it's what I need, as I don't want my duplicate volume to have any affiliation with the original at all. I actually want to duplicate VM to take up just as much space as the first and be completely independent of any changes on the first. Is there a way of achieving this? Could I maybe simply make sure the volume is unmounted and not in use, then copy the /dev/mapper/myvolume file to something else? I bet it's more involved than that... :)

I find 'dd' is the simplest way of doing this. Unmount the volume, create a new logical volume of equal or greater size, then 'dd' from one to the other:

lvcreate -L 500G -n clone volgroup00
dd if=/dev/volgroup00/original of=/dev/volgroup/clone

Rather than copying VMs I snapshot them. I create a template system, create a snapshot of it, then modify the VMs config so it uses the snapshot as its disk (so the original is unmodified). If I need another copy of the VM its only a matter of creating another snapshot of the template LV, then copying and modifying the config. I usually set the extent size low so that modifications within the VMs don't chew up lots of space too.

--Dave


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