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Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?
From: |
Andrea Bolognani |
Subject: |
Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images? |
Date: |
Thu, 07 Jun 2018 12:02:29 +0200 |
On Wed, 2018-06-06 at 17:32 +0100, Daniel P. Berrangé wrote:
> On Wed, Jun 06, 2018 at 10:36:20AM -0500, Eric Blake wrote:
> > But for the new config to be useful, you have to modify at least one tool in
> > the path. At which point, it is just as easy to say: "libvirt is now smart
> > enough to read the config file out of a .qcow2 to know that it should prefer
> > a q35 machine" as it is to say "libvirt is now smart enough to treat a .tar
> > file containing .qcow2 and a config file that states that it should prefer a
> > q35 machine", and either approach requires just a single file for the user
> > to download.
>
> Just to be clear, libvirt isn't going to do either of those things.
>
> Whether there is metadata stuffed inside qcow2, or in a metdata file
> inside a tar file, libvirt is not going to look inside either of them.
> The XML is the only place libvirt deals with the hardware config.
>
> Extracting machine type is always going to be a job for the layer above
> such as OpenStack/OVirt/Virt-manager/etc. They will then decide whether
> or not they want to honour that info, and if so, put it into the XML
> they give to libvirt.
>
> As mentioned elsewhere, IMHO, it is more friendly to those tools
> to use pre-existing formats, eg TAR and XML/JSON, for which
> their respective programming langauges already have APIs/parsers.
Something that I haven't seen mentioned in the thread - and this
looks like as good a point as any to jump in - is that for q35
guests using EFI as well as aarch64 guests the "one click import"
experience requires not only hints about the machine (and firmware!)
type, but also a copy of the EFI variable store:
$ virt-builder fedora-27 --arch aarch64 --notes
Fedora® 27 Server (aarch64)
[...]
You will need to use the associated UEFI NVRAM variables file:
http://libguestfs.org/download/builder/fedora-27-aarch64-nvram.xz
While hints might be considered a reasonable fit for qcow2, I think
it's pretty hard to argue for embedding the NVRAM file in there,
which to me signals quite clearly that an archive containing the
disk image(s) *and* the configuration hints *and* other ancillary
files such as the NVRAM is the only way to build a solution that's
not dead on arrival.
It's pretty easy then to imagine using something like
$ virt-builder \
fedora-27 \
--arch aarch64 \
--format qva \
--output f27-aarch64.qva
or download the equivalent from some website, followed by
$ virt-install \
--name f27-aarch64 \
--import \
--input f27-aarch.qva
or the equivalent pointy-clicky import step and having things
Just Work™, provided sufficient hints are included in the archive;
the user, or the management application, would of course be able
to override such hints at import time.
--
Andrea Bolognani / Red Hat / Virtualization
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, (continued)
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Max Reitz, 2018/06/06
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Dr. David Alan Gilbert, 2018/06/06
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Eric Blake, 2018/06/06
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Michal Suchánek, 2018/06/06
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Eric Blake, 2018/06/06
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Daniel P . Berrangé, 2018/06/06
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Dr. David Alan Gilbert, 2018/06/06
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?,
Andrea Bolognani <=
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Daniel P . Berrangé, 2018/06/07
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Andrea Bolognani, 2018/06/07
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Daniel P . Berrangé, 2018/06/07
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Dr. David Alan Gilbert, 2018/06/07
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Andrea Bolognani, 2018/06/07
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Dr. David Alan Gilbert, 2018/06/07
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Andrea Bolognani, 2018/06/07
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Dr. David Alan Gilbert, 2018/06/07
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Gerd Hoffmann, 2018/06/07
- Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?, Richard W.M. Jones, 2018/06/07