6 p.m.
On Thu, 28 May 2020, Richard W.M. Jones wrote:
On Thu, May 28, 2020 at 12:24:22AM +0000, Eric Wheeler wrote:
> On Mon, 15 Oct 2018, Nir Soffer wrote:
> > On Sat, Oct 13, 2018 at 9:45 PM Eric Wheeler <nbd(a)lists.ewheeler.net>
wrote:
> > Hello all,
> >
> > It might be neat to attach ISOs to KVM guests via websockets.Â
Basically
> > the browser would be the NBD "server" and an NBD client would
run on the
> > hypervisor, then use `virsh change-media vm1 hdc --insert /dev/nbd0`
could
> > use an ISO from my desk to boot from.
> >
> > Here's an HTML5 open file example:
> >
https://stackoverflow.com/questions/3582671/how-to-open-a-local-disk-file...
> >
> > and the NBD protocol looks simple enough to implement in javascript:
> >
https://stackoverflow.com/questions/17295140/where-is-the-network-block-d...
> >
> > What do you think? Does anyone have an interest in doing this?
> >
> >
> > HTML File API is very limited:
> > - you cannot access any file except file provided by the user interactively
> > - no support for sparseness or underlying disk block size
> >
> > So it will be a pretty bad backend for NBD server.
> >
> > What are you trying to do?
>
> Hi Nir and Eric,
>
> I hope you are well!
>
> (I'm resurecting this old thread, not sure how I missed the replies.)
>
> We are interested in attaching a local ISO to a remote VM over http (maybe
> .qcow's, but ISO is the primary interest).
So this bit is simple, and something we do regularly. Assuming the
"remote VM" is using qemu as a hypervisor, then qemu has a curl driver
integrated so you can mount remote http:// or https:// resources as
disks on the VM directly. eg:
$ qemu-system-x86_64 -m 2048 -cdrom
https://download.fedoraproject.org/pub/fedora/linux/releases/32/Server/x8...
(A more realistic example would use libvirt, see the https protocol
in: https://libvirt.org/formatdomain.html#elementsDisks )
Cool feature, I hadn't realized this was an option.
You can also bounce the connection through nbdkit-curl-plugin which
gives you a bit more flexibility, eg the ability to transparently
uncompress the remote ISO. You would be using the NBD client in qemu
to connect (eg. over a Unix domain socket) to a local nbdkit, and
nbdkit's curl plugin to connect to the remote ISO. More info and a
worked example in these pages:
http://libguestfs.org/nbdkit-curl-plugin.1.html
https://rwmj.wordpress.com/2018/11/23/nbdkit-xz-curl/
Looks neat, perhaps we would write a plugin to integrate with a
webserver (cgi, php, etc) for the JS client instead of implementing the
whole protocol over websockets.
> This is common for remote KVM (iDRAC/iLO/iKVM/CIMC), so
wondering about
> an http front-end for qemu to do the same.
> Combining that with a spice JS client or noVNC for VM console access would
> be neat.
I'm a bit confused by what you mean by "http front-end for qemu".
When qemu is running headless using a VNC or Spice display we can access
the display of https+websockets using things like noVNC---which is out of
scope to this converstation---but I'm just saying that such an existing
web front-end for the display could be extended to have an "Insert CDROM"
button and use the javascript file IO for the user to reference a local
file and pass it to qemu over nbd, perhaps via nbdkit.
> I also like Eric Blake's idea of direct NBD client
integration with qemu
> instead of using /dev/nbd0.
You shouldn't need to use a loop device for this scenario, assuming
I've understood what you want.
True.
-Eric
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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