Bug 1813948

Summary:	[doc] clarify - what we support in ignition
Product:	Red Hat Enterprise Virtualization Manager	Reporter:	Liran Rotenberg <lrotenbe>
Component:	Documentation	Assignee:	Eli Marcus <emarcus>
Status:	CLOSED CURRENTRELEASE	QA Contact:	rhev-docs <rhev-docs>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	4.4.0	CC:	adahms, cminkema, ctomasko, emarcus, lsurette, mtessun, pelauter, rgolan, srevivo
Target Milestone:	ovirt-4.4.5	Keywords:	Documentation, NoDocsQEReview
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
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Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-04-05 13:53:57 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	Virt	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Liran Rotenberg 2020-03-16 14:38:20 UTC

Description of problem:
We added RHCOS and ignition (bz 1726907 and bz 1797659).
There are differences between the user experience in 4.3 and 4.4. 
In 4.3, we have RHCOS OS, with nothing special about it, it will show cloud init in the initialization, as a normal linux VM.
In UI and API, we can add only custom script in order to activate ignition.
The custom script must provide a JSON (ignition file) and inside it, the ignition version, for example: "ignition": { "version": "2.3.0" }.
- Cloud-init with custom script containing ignition file with the version will trigger ignition handling.

In 4.4 the support is better, selecting RHCOS OS will show in the UI ignition initialization, showing only what is capable from the engine to consume. The same is supported from API (initialization object with host name, user+password and ssh-keys) of course custom script is available, and will be taken with priority. For example, setting host name both in the initialization object and in the custom script, then the latter will go in.

In bz 1797659 we let the user have compatibility between 4.3 to 4.4. If he selects RHCOS as OS type, then in 4.3 it will work as cloud init but in 4.4 it will be ignition.

We need to have it proper in the documentation for users.

Additional info:
bz 1797659 is a bit wider, letting the engine select the right initialization and dropping user forcefully select it.

Comment 1 Rolfe Dlugy-Hegwer 2020-03-16 14:57:31 UTC

(In reply to Liran Rotenberg from comment #0)

> There are differences between the user experience in 4.3 and 4.4.

Meaning "There are differences between the user experience in RHV 4.3 and oVirt 4.4. "
 
> In 4.3, we have RHCOS OS, with nothing special about it, it will show cloud

Meaning "In RHV 4.3, we have RHCOS OS, with nothing special about it, it will show cloud

> In oVirt 4.4 the support is better, selecting RHCOS OS will show in the UI

etc...

Comment 2 Rolfe Dlugy-Hegwer 2020-03-16 15:36:40 UTC

https://www.ovirt.org/develop/release-management/features/virt/coreos-ignition-support.html

Comment 3 Liran Rotenberg 2020-03-18 13:54:57 UTC

Just to be clear: We do support custom script in both 4.3 and 4.4.
In custom script you can insert an ignition file and it support everything that ignition support(for the specific ignition version).
For example: https://coreos.com/ignition/docs/latest/configuration-v2_3.html .

Comment 4 Roy Golan 2020-03-18 15:28:05 UTC

> In custom script you can insert an ignition file and it support everything that ignition support(for the specific ignition version).
It's not a file, it's the actual content.

Also, need to document;
 - on which cases there will be parts added to the custom script
 - on which cases custom_script will not be changed at all
 - special note on the ignition version attribute

Liran can you cover those?

Comment 5 Liran Rotenberg 2020-03-19 08:32:03 UTC

(In reply to Roy Golan from comment #4)
> > In custom script you can insert an ignition file and it support everything that ignition support(for the specific ignition version).
> It's not a file, it's the actual content.
> 
> Also, need to document;
>  - on which cases there will be parts added to the custom script

Only in 4.4 it is possible that parts will be added to the custom script.
The options we have (UI/API) - host name, and user are added to a custom script and create one if there is no custom script.
The version is added from osinfo(if the ignition in custom script is without it or if there is no custom script).

- If a user has been set in the custom script and the user set another one with UI/API, then the custom script will be changed and the ignition will be sent with 2 users configuration.

>  - on which cases custom_script will not be changed at all

In 4.3 - always.
In 4.4 - when only custom script is provided with the ignition version or when we have a duplicate.
A duplicate is:
- If we configured host name in the custom script and we configured it again via UI/API.
- If we configured the same user name in the custom script and in the UI/API.
In those cases, the ignition will be sent with the host name/user configured in the custom script.

>  - special note on the ignition version attribute

Each RedHat CoreOS comes with ignition. The ignition supports version/s of ignition configuration.
For each configuration there are differences on how the ignition file can be built in terms of what is supported or how to write the file.

As an example - Fedora CoreOS is ignition configuration 3.x while RedHat CoreOS is 2.x.
The docs for each version is available on ignition documentation such as - https://coreos.com/ignition/docs/latest/configuration-v2_3.html .