Bug 1324591

Summary: RHEV documentation needs to describe template versioning and how to use it.
Product: Red Hat Enterprise Virtualization Manager Reporter: Greg Scott <gscott>
Component: DocumentationAssignee: Emma Heftman <eheftman>
Status: CLOSED CURRENTRELEASE QA Contact: Tahlia Richardson <trichard>
Severity: unspecified Docs Contact:
Priority: high    
Version: 3.6.3CC: ahadas, gklein, gscott, lbopf, lsurette, mgoldboi, rbalakri, srevivo, trichard, ylavi
Target Milestone: ovirt-4.0.7Flags: lsvaty: testing_plan_complete-
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Hardware: Unspecified   
OS: Unspecified   
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2017-02-19 12:33:08 UTC Type: Bug
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oVirt Team: Docs RHEL 7.3 requirements from Atomic Host:
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Description Greg Scott 2016-04-06 17:49:39 UTC
Description of problem:
Chapter 7 of the Virtual Machine Management Guide describes what templates are and how to set up and deploy.  But it has not one single word about template versioning or how to use it.  And I am unable to find any other documentation on template versioning.  

If template versioning allows me to apply a Windows Update to a template and then keep VMs in a pool up to date based on that template, I can save a significant amount of time and money using that capability.  But I need to know how to use it and it should be officially documented.  I may be able to help the documentation team put it together if they need a use case.

Version-Release number of selected component (if applicable):
3.6

How reproducible:
At will

Steps to Reproduce:
1. Look over the documentation.
2. Search KCS articles.
3. Try Google and other search engines.

Actual results:
There are a few KCS articles on pieces of template versioning but nothing I can find in the official documentation.

Expected results:
Rich how-to documentation on template versioning, complete with relevant examples.

Additional info:

Comment 1 Yaniv Lavi 2016-04-26 11:42:35 UTC
Can you please add a link to this topic?
Greg what words did you look for? Maybe we can add them to make is easier to find.

Comment 2 Lucy Bopf 2016-04-26 13:44:04 UTC
Template sub-versioning is mentioned in two places in the documentation:

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Virtualization/3.6/html-single/Virtual_Machine_Management_Guide/#Creating_a_template_from_an_existing_virtual_machine

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Virtualization/3.6/html-single/Virtual_Machine_Management_Guide/#Explanation_of_Settings_in_the_New_Template_and_Edit_Template_Windows

I can see, though, that these two mentions are somewhat removed from one another.

Greg, would it be helpful if this existing information was just presented differently, or do you think some additional context is still required?

Comment 3 Greg Scott 2016-04-26 14:03:46 UTC
Thanks for the references Lucy.

I just looked them over.  The first one, with the screen shot, says:

"Optionally, select the Create as a Sub Template version check box, select a Root Template, and enter a Sub Version Name to create the new template as a sub template of an existing template."

OK, cool, here are the boxes to click to set one up.  But why is a sub template of an existing template good?  What is it mean?  How do I use it?  Why would I want one?  What happens to VMs in a pool based on the original template?  Do new VMs in the pool get the subtemplate and existing VMs keep using the original?  Or do existing VMs change to the subtemplate when they reboot?  Or are there other buttons to click to regulate which template my VMs use?  Or what?  

The second reference has this:

"Specifies whether the template is created as a new version of an existing template. Select this check box to access the settings for configuring this option.
Root Template: The template under which the sub template is added.
Sub Version Name: The name of the template. This is the name by which the template is accessed when creating a new virtual machine based on the template."

Which suggests the only reason for the sub template is to reference something by a different name?  There's gotta be more to it.

So let's say I make a template.  Then I make, say 1000 VMs based on that template.  Microsoft Patch Tuesday comes along and I apply a bunch of patches to the template, seal it, and set it up in RHEV as a sub template.  Did I just patch 1000 VMs that way?  Which would be waaay cool. And if so, how do I propagate those patches from the subtemplate out to the VMs?  Or am I missing the whole point?  

thanks

- Greg

Comment 4 Yaniv Lavi 2016-05-09 11:04:17 UTC
oVirt 4.0 Alpha has been released, moving to oVirt 4.0 Beta target.

Comment 8 Lucy Bopf 2017-01-19 13:40:40 UTC
Assigning to Emma for review.

Emma, I'd suggest following up the questions in comment 3 with somebody from the engineering team to see if we can get some more context about where template versioning can be useful.

Comment 9 Emma Heftman 2017-01-24 17:00:02 UTC
Hi Arik
I have updated text in the Administration and Virtual Machine Management Guides according to the information you provided in our meeting.


1. Please check step 7 in this section of the VMM:
http://file.tlv.redhat.com/~eheftman/bz1324591/Virtual_Management_Guide/html-single/#Creating_a_template_from_an_existing_virtual_machine


2. Please check the first paragraph in Introduction to Virtual Machine Pools in the Administration Guide:
http://file.tlv.redhat.com/~eheftman/bz1324591/html-single/#Pools

Comment 10 Arik 2017-01-26 08:23:57 UTC
(In reply to emma heftman from comment #9)
The content is correct. Please consider the following things:
1. At step 7 in the create template you may want to replace the term 'pools' in "such is the case when working with pools" with 'pools of virtual machines' to distinguish this kind of pool from storage pool.
2. I'm not sure that the explanation of setting a pool to the latest version of the template should reside in the first paragraph of Virtual Machine Pools just because it is yet another feature related to pools, not a major part of its definition.