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Re: [fedora-virt] 'eject' on a KVM guest



On 19/10/09 14:38, Daniel P. Berrange wrote:
On Mon, Oct 19, 2009 at 09:35:04AM -0400, Cole Robinson wrote:
On 10/19/2009 05:47 AM, Matthew Booth wrote:
What does the eject (to eject a CD) command do to a KVM guest? It
succeeds, and the result is that the device can no longer be mounted.
However, looking at the domain XML reveals it hasn't disconnected the
backing file.

Matt

It should be the equivalent of ejecting a CD or floppy on a physical
machine.

If you do this through libvirt (with the attach-device command and
suitable XML string), then the change should be reflected in the XML.

If you managed to send a monitor command to the KVM guest that didn't go
through libvirt, the change wouldn't be reflected in the domain XML for
the majority of operations (media eject included).

I think the problem Matt sees is from running 'eject' inside the guest.
libvirt will not see that, because KVM has no way to notify us that the
guest ejected the media.

That's it. Re-reading, that wasn't clear from my original question.

Fortunately, the new KVM monitor control protocol includes support for
this notification, so we'll be able to address this limitation in the
future.

Sounds good. Any idea what the timeframe might be for that?

To put this in context, I was trying to think of an existing way a guest can modify its environment. I was thinking that if you configured a boot order of cdrom, hd, and attached a custom LiveCD, the LiveCD could do its thing and then eject itself, booting from hd next time with no administrative intervention. Could that ever work?

Matt
--
Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team

M:       +44 (0)7977 267231
GPG ID:  D33C3490
GPG FPR: 3733 612D 2D05 5458 8A8A 1600 3441 EA19 D33C 3490


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