Re: Attached disk blockpull

[Peter Krempa]

This is a libvirt question, so asking it on the qemu-block might not get
you an answer that quick, ... or ever if I didn't notice your other
question also addressed incorrectly.

[adding libvirt-users@redhat.com to cc]

On Tue, Sep 01, 2020 at 10:57:34 -0400, Yoonho Park wrote:
> I am trying to perform a blockpull on an attached disk, but I cannot do
> this using "virsh attach-disk" specifying a new, empty overlay file created
> with "qemu-img create". The VM does not pick up the backing_file path from

Could you please elaborate on the exact steps? specifically the
arguments for qemu-img create.

My feeling is that you didn't specify the backing image format (-F) when
creating the overlay, but it's hard to tell from this very sparse
question.

> the qcow2 overlay file, and there seems to be no way to specify the backing
> path through the attach-disk command itself. Instead the backing path has

virsh attach-disk is a syntax-sugar wrapper which generates the XML
document which is in fact used to attach disk. You can use virsh
attach-disk --print-xml to see what would be used.


> to be specified in the xml file used to create the VM, which precludes
> attaching a new disk to a running VM. Is this a bug? Is it possible to

using virsh attach-device allows you to pass in a whole <devices>
subelement such as <disk> with any configuration you are able to specify
when defining the XML.

The virsh attach-disk is limited to just "basic" config options.

> attach a disk to a running VM, and specify its backing path, using qemu
> directly? This is with qemu 4.2.0 and libvirt 6.0.0.