[adding nbdkit readers]
On 10/13/18 1:39 PM, Eric Wheeler wrote:> Hello all,
>
> It might be neat to attach ISOs to KVM guests via websockets. 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.
Are you using qemu as the hypervisor? If you are using something else,
like vmware, then using the kernel NBD module as the NBD client to
expose the browser-as-server via /dev/nbd0 is reasonable since
practically any hypervisor will attach to a raw block device. But if
you are using qemu, I'd suggest that you use qemu directly as the NBD
client, rather than indirecting through the kernel module (for that
matter, qemu's NBD client knows how to efficiently handle sparse files
if the server is capable, while to date the kernel nbd module does not).
Since you are using virsh, the libvirt list is a better resource for
figuring out the command line and/or XML changes to direct qemu to
connect as an NBD client.
>
> Here's an HTML5 open file example:
>
https://stackoverflow.com/questions/3582671/how-to-open-a-local-disk-file-with-javascript
>
> and the NBD protocol looks simple enough to implement in javascript:
>
https://stackoverflow.com/questions/17295140/where-is-the-network-block-device-format-describled
>
> What do you think? Does anyone have an interest in doing this?
The nbdkit project (under the libguestfs umbrella) has already
implemented an NBD server that can bridge to an image served over http,
if you want to use that as a starting point.
Then the obvious question - do you really need to implement a solution
using websockets through your browser in order to serve up a file on
your desktop, or can you reuse existing solutions of a userspace NBD
server to directly serve the file without involving the browser in the
middle.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
