"Karl E. Jorgensen" <k...@jorgensen.org.uk> writes:
> Hi
>
> On Wed, Nov 19, 2014 at 12:24:27AM +0100, lee wrote:
>> Hi,
>>
>> so far, I managed to pvmove a LV to my USB stick and from there to a
>> backup disk in another machine. Doing so, I found that I can split off
>> LVs from a volume group and that this inevitably creates a new VG. That
>> leaves you stuck because it's impossible to move a LV from one VG to
>> another, and it's also impossible to merge multiple VGs into one VG :(
>> How stupid is that??
>
> Well - you can merge VGs. and You and split VGs. so you could:
>
> - pvcreate /dev/${usbdevice}
> - use pvmove to move your LV of choice onto the USB stick.
> - use vgsplit to split /dev/${usbdevice} into its on VG
> - Sneakernet the USB stick to a new box
> - Use vgmerge to join the USB stick to the box's VG
> - Use pvmove to move the LV onto a local disk
> - Use vgsplit to make the USB its own VG again
> - Sneakernet the USB stick back to the original box
> - Rinse and repeat.
>
> But that's a fair number of steps... You could also just:
Oh! Thank you, that solves my problem! :) I looked for something like
vgmerge and didn't find it.
I've done one step already, and when I move another VM to the USB stick,
I should be able to move the whole remaining VG onto the stick. Three
steps isn't too bad.
> - Create a file system on the USB device. and mount it.
> - dd if=/dev/oldvg/vgname | gzip --best > /media/usbstick/somefile.gz
> - Unmount and sneakernet to the new box
Hmmm, how would I put the copy of the VG back? Once the copying is all
done, I'll remove the remaining two discs from the server and plug 6
discs in from which I'll make a RAID-5 which will have about 6TB. Then
I'll pvcreate the whole RAID volume and probably re-install dom0 in its
own LV. The next step is to create two VGs, one for the guest VMs and a
large one for data.
I don't want to re-install dom0, but apparently just copying it with 'cp
-a' into the new LV might not allow me to make it bootable without
trouble.
What does Debian do in regard to grub? Can I just 'cp -a' dom0 over,
boot into a rescue system and install grub? Dom0 is currently not in a
LV.
> etc.. I'm sure you get the idea. No need to make it more complicated
> than absolutely necessary.
Yes --- though I don't mind when it's a bit more complicated now and
easier later. I can simply go through the same procedure a couple times
and do it forth and back; it's not like I had hundreds of VMs :)
>> (Note to self: Do not partition LVs but create LVs for swap partitions
>> instead.)
>
> Sounds like a sensible note. Unfortunately, if you use virtualisation,
> you will often end up slicing off LVs to be presented to the virtual
> machines as disks. And the VMs then partition them and/or create PVs
> on them. Nested stuff galore.
Guess what :)
I found out that I accidentially had managed to give dom0 and a VM the
very same partition as swap partition. It even worked ...
--
Again we must be afraid of speaking of daemons for fear that daemons
might swallow us. Finally, this fear has become reasonable.
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