[one-users] Multiple VM instances using one persistent image

[Carlos Martín Sánchez]

Hi Robert,

Actually, persistent means the opposite to read-only.
A persistent Image saves the changes made during the VM life-cycle, thus
making those changes persistent.

Please take into account that a non-persistent Image does not mean it is
read-only. Any Images of a type different from CDROM are not read-only, and
you can decide if the changes made will be saved back in the repository with
the persistence flag.


I hope that helped,
Carlos.
--
Carlos Martín, MSc
Project Major Contributor
OpenNebula - The Open Source Toolkit for Cloud Computing
www.OpenNebula.org <http://www.opennebula.org/> | cmartin at opennebula.org


On Thu, Jun 16, 2011 at 2:51 PM, Robert Maier <maier at zib.de> wrote:

> Hi,
>
> I set up ONE on a small cluster and got in trouble as I tried to use one
> persistent (live-cd) image by several VMs. The image is marked to be of
> type CDROM and is the VM's only disk. As the first VM is created, it
> boots properly and runs fine. When I try to create another instance of
> the same VM (template) I get an error printed on the terminal:
>
> Error: [VirtualMachineAllocate] Error trying to CREATE VM Could not get
> disk image for VM.
>
> This problem does not occur, if I set the image to public instead of
> persistent, i.e. the image is copied to VM_DIR instead of a symbolic
> link is being created.
> Why is it not possible to use one persistent image by multiple VMs? I
> thought persistent means (in some way) read-only. Thus, there should be
> no need to lock the image when it is used by a VM.
>
> Thanks in advance.
> Robert
>
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