clone linux VM with virtual LVM disk

M

m.ardito

Famous Member
Feb 17, 2010
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Torino, Italy
If I create a KVM template of a VM (say, ubuntu server) which has its virtual disk configured as (internal) LVM and than convert it to a template, then I can clone it to get several other VMs based on this machine.

Of course VM template internal LVM PVs/VGs/LVs all have their names and UUID like

Code: 
  --- Physical volume ---
  PV Name               /dev/vda5
  VG Name               ubuntu-webserver
  ...
  PV UUID               UHqIVU-BKta-3R5x-9HvP-CSNG-r6gH-w87UIi

  --- Volume group ---
  VG Name               ubuntu-webserver
  System ID
  ...
  Free  PE / Size       0 / 0
  VG UUID               pfg6xD-nhx7-ZkJR-D003-mNEz-vg0o-a2w9Vf

  --- Logical volume ---
  LV Name                /dev/ubuntu-webserver/swap_1
  VG Name                ubuntu-webserver
  LV UUID                YngPz7-dFCj-hGNN-6RyY-fxH3-VNHV-HczVbO
  ...

now, If I clone other VM from this tempate, all will get the same PVs/VGs/LVs names/UUID.
since their disks would be an exact clone.

The same would happen if one would restore a VM backup to another VMID and then changing its ssh keys/ip/hostname, etc.
The disk LVM would remain the one of the original VM from which the backup was taken.

Now, would this fact be a problem for the pve nodes hosting them?
Would "reused" PVs/VGs/LVs names/UUID inside several VMs conflict in some way?

I always thought that what's inside a VM (kvm) disk is completely unknown to the host and other VMs/CTs, but I got this hint from another thread, based on another issue.

Then, if troubles could arise from this names/UUID "reuse", what is suggested to do?
vgrename/lvrename and vgchange/lvchange, other?

Thanks,
Marco
 
Hello MArco

m.ardito said:
Now, would this fact be a problem for the pve nodes hosting them?
Would "reused" PVs/VGs/LVs names/UUID inside several VMs conflict in some way?
Click to expand...

No! Recently I made 10 (linked) clones from a debian using (same) LVMs. Works fine. The only one thing I had to adapt (but it´s neither a problem for/frompve nor related to LVM) was the certificate for ssl, because other connected machines in the networked complained that they used the same key.

m.ardito said:
I always thought that what's inside a VM (kvm) disk is completely unknown to the host and other VMs/CTs, but I got this hint from another thread, based on another issue.
Click to expand...

That´s also my understanding (at least for VMs, for CTs it may be different but this has no relevance here) - but I am curios about the thread you mentioned, do you have the link to it?

Kind regards

Mr.Holmes
 
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