Template for persistent VMs

Community Support
1

Hi,

Is there some way to create templates to instantiate persistent VM’s?

Thank you,

Juanjo.

2

juanjose_fuentes forum@opennebula.org writes:

Hi,

Hello,

Is there some way to create templates to instantiate persistent VM’s?

Just make the image persistent[1] and use it in a template.

Regards.

Footnotes:
[1] Managing Images — OpenNebula 4.12.1 documentation
signature.asc (342 Bytes)

3

Sorry, I think I didn’t explained myself correctly. I mean if it could be possible to instantiate a persistent templante n-times.

4

Unfortunately no.
You could clone a persistent Image + Template and instantiate a new VM from this Template.

src:
http://lists.opennebula.org/pipermail/users-opennebula.org/2013-February/039465.html

5

Someone knows why is that? I mean philosophically Opennebula is against this behaviour? or just is not implemented yet? and in this case is planned for near-future versions?

6

I don`t think that this feature will be implemented. If you search the old Mailing List you will find Mails from 2013 or later where different people complained about this “feature”. And nothing was done.
Which is really sad, because this is the main reason, why we not use Opennebula.

7

The problem here is a consistency problem, two VMs cannot modify the same
disk without a synchronization layer. Typically this is done through a
shared/distributed FS.

Let say that you have two VMs using the same disk, and both VMs writes the
disk, which change should persists? what coherence is presented to the VMs?
So if you want to share a disk between VMs expose it through NFS, GlusterFS
or any other method.

Could you explain your use case?

8

@ruben
I think you want to reply to this thread Shareable disk image between VMs ?

Because what we want is a simple workflow, to create a new VM from an Template with a persistent disk.
The current Workflow for a new VM is:

  1. Clone the Template
  2. Create a new persistent image and attach it to the new Template.
  3. Instantiate a new VM from this Template.

This would be really annoying for us. We are now running an old VMware Installation with ~50 VMs. Every VM is based on an VMware Template but with different Settings, Services etc (a typical Snowflake Server). So in Opennebula we would need 50 different Templates.

9

Hi this is totally aligned with out roadmap. In fact the cloud view now
have a save VM feature which is basically what you are describing, this has
been generalized for 4.14 and exposed in the admin view.

The process is as follows.

1.- A running VM with the target configuration
2.- Clone VM, it will copy the disks and create a new template for it
3.- Instantiate the VM.

However if you want to instantiate a template and make the copy on the fly
it is slightly different and something we could implement. If you are
intetested we can reopen:

http://dev.opennebula.org/issues/2048

and evaluate its implementation for the next version.

Note also that we are including in 4.14 a flexible instantiate dialog,
where the user can select vnets and vm capacity without creating a new
template for the admin view; just as it is exposed in the cloud view.