How to decouple an instance from a template?

[jl0815]

We want to run a large number of Windows VMs in CloudStack and would like to build monthly updated images using Packer.
These images will then replace the existing templates in ACS.

Is there a way to decouple the running VM instances from the template they were created from?
The VMs should have their own lifecycle, independent of the templates' lifecycle.

Regards,
JL

[jl0815]

Okay, I can delete the template using “force delete,” and that doesn't seem to be a problem for the running instances.
The name of the original template still appears in the overview of both the instance and the ROOT volume.
Could this cause problems later on if new templates with the same name are registered?

JL

[daviftorres]

Dear @jl0815 ,

I don't see any future issues if CloudStack (ACS) keeps a reference showing which templates the running VMs came from.

My past concern was simply that ACS defaults to linked volumes between instances and their templates. It uses a backing chain, meaning the VM disk relies on the original template.

If this link is a concern for you, there are a few ways to fix it. You can manually flatten the volumes using the CLI, or you can perform a backup and restore (the restored VM will be completely independent).

Hope this makes sense. Regards,

[chunkyen]

If I am not mistaken, we can also use a compute offering with a sparse provisioning disk type to not use a backing chain for the qcow2 disk.

[davift]

If I am not mistaken, we can also use a compute offering with a sparse provisioning disk type to not use a backing chain for the qcow2 disk.

you are correct. but what i mentioned is for existing i stances deoyed with the "thing" (linked) provision.

[bernardodemarco]

Hello, @jl0815 and @daviftorres

Okay, I can delete the template using “force delete,” and that doesn't seem to be a problem for the running instances.

Exactly, the running VMs will not be affected. The template will be kept in primary storage until the last VM that uses it is expunged.

The name of the original template still appears in the overview of both the instance and the ROOT volume. Could this cause problems later on if new templates with the same name are registered?

No, this will not cause any issues. The only downside is that the UI will display a link to the template and, when accessing it, since the template is removed, the user will be redirected to a 404 page.

As for new templates with the same name, this will not be an issue either. ACS currently supports different templates with the same name. The are identified/differentiated by their internal IDs and UUIDs.

[jl0815]

Hi everyone.

Thank you very much for your replies.
My next thought was whether there might be any orphaned volumes after all the child VMs were deleted.
But as you've already pointed out, that's not the case.

Best regards,
JL