[openstack-dev] [ironic] Kernel parameters needed to boot from iscsi

Julia Kreger juliaashleykreger at gmail.com
Mon Oct 16 19:29:28 UTC 2017

Greetings Yolanda!

I guess I'm slightly not clear. In fact, I may be slightly even more
confused since we've discussed this directly. Thinking out loud, there are
two different scenarios of booting from iSCSI.

1) Human created/assigned/associated LUN off of a SAN which we want a node
to boot from, and that LUN lives onward as the "storage" for the node.

2) Cinder facilitated LUN off of $something that we want a node to boot
from. This largely would be the logic we added this past cycle to support
either booting via iPXE to iSCSI, or in the case of the iRMC driver, to set
the HBA to boot/attach from specific volumes.

I think your largely bringing up the first case when we speak of booting
from iSCSI. If not, then we technically haven't reached the point where we
are explicitly supporting hardware HBA use, but no time like the present!

Since there are many things here, I think we need to make sure we are
contextually on the same page. If any of this is wrong, please correct me:

* You deploying a partition/filesystem image.
* Ironic is partitioning and executing the installation of grub.
* The scenario where your operating requires the boot loader command line
to be updated with specific arguments.
* Part of the problem is the ramdisk initialization where it is only honors
arguments in your specific case.
* Ironic does not presently provide a mechanism to append standard kernel
arguments outside of netboot. Example from ages ago that many may remember,
having to add ``noapic`` in some cases with a SMP kernel is to be used.

I believe it makes sense to have some sort of mechanism to append to the
default list in this case. There is the ansible deploy driver, but it seems
like that might be overkill for setting boot loader parameters, and Ironic
is explicitly executing grub-isntall.

I think the only reason we've resisted in supporting updating the defaults
file the past is because it would mean explicitly writing data to the grub
defaults file on the filesystem, I suspect our comfort level with
supporting that now may be different. In hindsight, considering we
essentially already support this with netboot but not local boot with a
partition image, I think we should add support for appending default



On Mon, Oct 16, 2017 at 2:06 AM, Yolanda Robla Mota <yroblamo at redhat.com>

> Hi
> Recently i've been helping some customers in the boot from ISCSI feature.
> So far everything was working, but we had a problem when booting the
> deployment image.
> It needed specifically a flag rd.iscsi.ibft=1 rd.iscsi.firmware=1 in the
> grub commands. But as the generated deployment image doesn't contain these
> flags, ISCSI was not booting properly. For other hardware setups, different
> flags may be needed.
> The solution was to manually execute a virt-customize on the deployment
> image to hardcode these parameters.
> I wonder if we can add some feature in Ironic to support it. We have
> discussed about kernel parameters several times. But at this time, it
> affects ISCSI booting. Not having a way in Ironic to customize these
> parameters forces to manual workarounds.
> So can we reconsider the proposal to add kernel parameters there? It could
> be a settable argument (driver_info/kernel_args), and then the IPA could
> set the parameters properly on the image. Or any other option is welcome.
> What are your thoughts there?
> Thanks
> --
> Yolanda Robla Mota
> Principal Software Engineer, RHCE
> Red Hat
> <https://www.redhat.com>
> C/Avellana 213
> Urb Portugal
> yroblamo at redhat.com    M: +34605641639
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